Organic Chemistry Laboratory CHE 327 

Cornell College Term 7, 2007/2008

Addison Ault, Andrea Pionek, Jeff Cardon, Charley Liberko

 

Laboratory Information

 

Required:

Text: Addison Ault, Techniques and Experiments for Organic Chemistry, 6th Edition. You should have the textbook with you in the lab at all times.

Goggles may be purchased from the stockroom for $5.00.

Carbonless notebooks may be purchased from the stockroom for $9.

 

Daily Schedule

            Each day we will meet at 9:00 AM in West Science 100 to review the previous day’s results and to discuss the experiments for the day.   It is expected that all equipment be set up and ready to go by 12:30.  All experimental work must be carried out between 12:30 and 3:00 PM.  Any other time from 8:00 to11:30 and 12:30 to 5:00, the lab may be used for setting up equipment, cleaning glassware, weighing products, and taking melting points.   On Fridays, we will meet at 9:00 AM for review, discussion, and a quiz.  Friday afternoons are available for makeup; make arrangements with your instructor beforehand if you need to complete or make up a lab.

 

Preparation

            Before coming into the lab each day, each student must be adequately prepared in order that the lab time is spent safely and efficiently.  Proper preparation includes reading the lab procedure and relevant background material (you may need to do this several times in order to understand it), and preparation of the notebook with all necessary physical data (relevant melting points, boiling points, densities, and solubilities).

 

Notebooks and reports

All data and observations will be recorded directly in the notebook.   The carbonless copy from your notebook is due as you leave the laboratory each day or as soon as you have finished collecting data for that experiment.  Staple a copy of the Laboratory Notebook Grading Rubric to your pages.  Lab reports, products, and extra credit questions are due at 3:30 PM the day after the lab was scheduled to be completed. 

 

Point Breakdown                                Points                          Approx. %     

Notebook                                  130                                           19

Write-ups                                  260                                           37

Products                                     33                                              5

Quizzes                                     120                                           17

Final Exam                                100                                           14

Technique                                   35                                             5

Other                                         22                                              3      

            Total                                         700                                           100

 

As a general guide for grading, the following cut -offs will be used:

 

90%                 A-                                            80%                 B-

70%                 C-                                            60%                 D-


Schedule

 

Day

Experiment

Reference

(pages)

Techniques / Reactions

M   3 / 3

1. Isolation of Acetylsalicylic Acid from Aspirin Tablets

43-54, 150-159, 332-333

heating, filtration, crystallization, melting points

Tu   3 / 4

2. Distillation of  a

methanol / water mixture

62-72; 75-80, 305

Distillation

 

W   3 / 5

3. Separation of malachite green and phenolphthalein

92-109

Acid base extraction

Th  3 / 6

4.  Preparation of 2,4-Dinitrodiphenylamine

475-476

116-119

Nucleophilic aromatic substitution, recrystallization, TLC

F    3 / 7

Quiz 1

 

 

M   3 / 10

5.  Prep. of Cyclohexene from Cyclohexanol

376-380

122-128

acid catalyzed dehydration

GC analysis

Tu  3 / 11

6. Prep. of Cyclohexanone from cyclohexanol

387-389

87-90

182-199

oxidation, steam distillation, IR

W   3 / 12

7.  Preparation of

 “banana oil”

417-426

Fischer esterification,

SN2 substitution

Th  3 / 13

8. Unknowns

169-181

239-272

Solubility, chemical tests for functional groups

F    3 / 14

Quiz 2

 

Proposals due for Expt. 12:  9:00AM

M  3 / 17

 

9.  Preparation of tetraphenylcyclopentadieneone

595-597

Aldol reaction

Tu 3 / 18

 

10. Preparation of a photochromic compound

564-566

electrophilic aromatic substitution, nitration

W 3 / 19

 

11. Preparation of Malachite Green, Crystal Violet

439-440

 

Grignard reaction, preparation of dyes

Th  3 / 20

12. Student's Choice

 

Proposals due:  Friday, March 14 at 9:00AM

F    3 / 21

Quiz 3

 

 

M  3 / 24

13.  Preparation of norbornene-2,3-dicarboxylic anhydride

507,

510-514

Diels-Alder reaction

Tu 3 / 25

Review, Check out

Pizza Frenzy

 

 

W   3 / 26

Final Exam  9:00 - Noon

 

 


Safety

            Keeping the lab safe is the number one priority and it is everyone’s responsibility.  Before you begin, read Section 1 in your lab book.  Several rules are worth repeating:

 

Eye protection must be worn at all times in the lab. 

 

Appropriate attire must be worn in the lab. Clothing must cover all parts except the head, hands, and forearms.  Long hair should be tied back.

 

Memorize the location of all exits, showers, eye-washes, fire extinguishers, and fire blankets.

 

No food or beverages are allowed in the lab. Leave backpacks and coats in the hallway.

 

Be certain that there are no flammables in the area when lighting a flame. (Warning: artificial fingernails are extremely flammable.)

 

Be alert for hazards in the lab.  Do not proceed with any experiment until you understand the hazards involved.

 

Report all injuries to your instructor, even if they appear to be minor.

 

Do not come into contact with any of the solvents or reagents used in this lab other than soap and water.  Remove gloves and wash hands before leaving lab.

 

Clean up all chemical spills immediately, this includes drips on bottles.

 

Do not leave any bottle uncapped.  

 

Dispose of all wastes as directed.  (Ask before you dump.)

 

Come to the lab prepared. 

 

Material Safety Data Sheets (MSDS)

            You have a right to be informed as to all the known hazards and potential hazards of the materials you will work with.  MSDSs are provided by chemical suppliers which describe risks and proper handling of the reagents you will use.  Copies of these forms are available from the stockroom.

             As an example, consider the MSDS for acetone.  Pay particular attention to the “Precautionary Labeling” section.  Each compound is rated for its health, flammability, reactivity, and contact hazards. The rating is on a scale of 0 (very low or nonexistent hazard) to 4 (extreme hazard).  Acetone poses a low health and contact hazard (rating of 1), it has a very low reactivity (rating of 0), but severe flammability (rating of 3).  Keep in mind that you may already be familiar with acetone as it is commonly used as a “nail polish remover”. 

            A few danger words that you should get to know include:

Toxic - poisonous

Mutagen / carcinogen – causing mutations or cancer respectively

Teratogen – (literally “monster-forming”) causing birth defects

Lacrymator – causing watering of eyes irritation to mucus membranes

Caustic – causing chemical burns


Grading Guidelines

 

Notebooks

            Each student must keep a notebook with all data recorded immediately in ink.  For each experiment, your notebook will be graded on a 10-point scale.  The work should include the following, be in the order listed, and have the headings in bold.

 

Pre-lab: To be done prior to 9:00 AM

1    Descriptive title and date - This is also the title that you should enter in your Table of Contents along with the page numbers that the experiment is on.

2    Chemical structures / balanced chemical equations -Draw the structures for all organic reagents used including solvents.  Write a balanced chemical equation for each reaction including acid/base reactions.  Also include moles, masses, and/or volumes required to perform the experiment and theoretical yield in a well organized way.  Refer to p. 30 in your text book.  Note:  Equations in this manual are not balanced.

2    Data table of reagents - Fill in a table with information for all chemicals required in that particular experiment and their properties. (see Appendix 2-4 in this manual)

1    Procedure reference - Write a bibliographic reference or references to where the procedure can be found.  Be specific.  Be sure you are including all important parts of the procedure from the text and the Cornell lab manual.  If you prefer to write out procedure, you may.

 

During lab

1    Procedure summary as performed - Give a brief summary of the experiment including chemicals used, lab techniques, and product analysis.  Record anything that you performed differently from the referenced procedure and all things unique to only your experiment.  If nothing was changed, make a statement to that effect.  This should only be a couple of sentences or less and may be very similar to something required in your formal report.  (A good way to refine your writing is to have to write something more than once.)

1    Qualitative observations during procedure - What do you see, smell, hear during the experiment?

 

Post-lab

2    Results - This is a well-organized, brief presentation of the results of your experiment.  A table would work.  When reporting measured physical data, include the literature value with reference for comparison.  Include physical appearance, melting point or  boiling point, amount obtained in grams and moles, theoretical yield and percent yield in grams and moles with units and how they were calculated, limiting reagent, and anything else specific to the final results of you experiment.

10   Total

 

Odds and ends- the following may influence your technique points.

A copy of all spectra should be stapled into the notebook behind that experiment.  Spectra may be photocopied and reduced or trimmed down to size if necessary to fit into your report.  Be sure to include a caption.

            Notebooks will be collected Friday mornings and at the final exam to be checked for table of contents and spectra.

            Don’t forget to staple a grading rubric to your notebook pages before you turn them in (See Appendix 5).

 


Reports

After the lab has been completed you will prepare a short but formal report.  These reports should be word processed (hand drawing of structures is allowable if they are done neatly) and are limited to two pages, excluding graphs and spectra.  Text sections should be double spaced with one inch margins and 12 point font.  The reports are due at 3:30 PM the day after the lab work was scheduled to be completed.  Each report will be graded on a 20-point scale.  The report should include the following, be in the order listed, and have the headings in bold.  The approximate weight of importance of each section is given.

 

 

            Experiment Number and Title

 

10%     Claim – This statement should lay claim to the results that you think you got (not what you were supposed to have gotten).  The claim is essentially a conclusion and should typically include qualitative information on yield, quality, and purity of product.  

 

20%     Evidence – This section must support the claim and will be a concise listing of what you did and observed.  All data (for example number of grams and mmoles of reagents used, melting or boiling points of products etc.) should be included here. 

 

50%     Discussion – This section will convince the grader of the reasonableness of the claim in light of the evidence.  For maximum points, be sure to include the any/all of the following when applicable:

a.  A concise discussion of any new technique and how  this technique relates to the particulars of the experiment.

b.  A discussion of yield (or recovery), including discussion of systematic losses due to the limitations of the technique.

c.  A balanced chemical equation and a mechanism for any reactions carried out in the labs.

d.  Structures for all reagents.

e.  Spectra or graphs with proper meaningful captions.

 

10%     Visual Presentation – For maximum points, the report needs to follow the required format, including title, section headings, and appropriate length, be well organized and neatly presented.

 

10%     Stylistic Presentation – For maximum points, the report needs to be written using correct spelling, grammar, and references.  There needs to be appropriate use of significant figures.  (Be warned:  Good writing style will not make up for poor or nonexistent content.)

 

Refer to the sample write-ups below.  The samples are not shown with double spaces text.  Your reports should have double spaced text.  For the fun of it, what grade would you give the first report?  What grade would you give the second?  Has the student forgotten anything in the first report?

 


__________________________________________

[Preferred Write-up]

Experiment 15

Isolation of caffeine from tea

Ben der Dunthat

 

Claim:  A relatively pure sample of caffeine was recovered from black tea by extraction into hot water.

 

Evidence: The procedure was carried out as described by Ault[1] using 4 Lipton brand tea bags (11.6g), 120mL water, and 12.0 g CaCO3.  The mixture was heated to boiling for 21 minutes and filtered by suction. After cooling the filtrate, the product was extracted into chloroform.  Evaporation of the chloroform gave a white semisolid (0.47g) that was recrystallized from 95% ethanol (~3 mL) giving small colorless needles. 0.23g, 1.2 mmol, 1.8% isolated recovery, Mp 229-232, (235-236 lit.[2])

 

Discussion:  Caffeine is an organic compound with a high degree of polarity and it is quite soluble in both hot water and chloroform.   The high solubility in hot water (0.67g/ml) allows caffeine to be extracted from the tea leaves.  The tannic acid in tea, however, is also water soluble and is extracted along with the caffeine.  Since calcium salts of carboxylic acids are insoluble, the calcium carbonate acts to de-protonate the tannic acid and to precipitate it as the calcium salt making it possible to remove it by filtration.  As the aqueous solution cools, the solubility of caffeine is greatly decreased allowing most of it to be extracted into the chloroform layer.  Since caffeine is soluble in the cold water (0.02g/ml), the extraction will not remove all of the caffeine and some will remain in the aqueous layer.  Caffeine has a reasonable solubility in cold ethanol (0.02 g/ml) and a fair amount would have remained in the ethanol solution after the recrystallization.  The recovered yield is 1.8%, which compares to the reported range of caffeine in tea of 2-5%.  The isolated compound melts over a three-degree range close to the reported value for caffeine showing it to be reasonably pure.

____________________________________________________________________________

[Less-than-desirable Write-up]

Isolation of caffeen from tee

Sara N. Dipity

 

Claim:  We made caffine from tea.  We got it from the bags using isolation.  The melting point was good.

 

First, we followed the proceedure and got  caffene crystals.  Then we preformed a recrystallization on our crystals.   Then we dried our crystals. Then we weighed our crystals.  They weighed .0032.   A melting point was run on the crystals.  The melting point on the crystals was 128o. This is not to bad.

 

We got cafeine from tea....  I don’t like tea unless its iced when its hot out and then it’s ok if you use lots of suger but not that pink stuff. We heated the water to make it more soluble.   During the extraxion caffein was on  top because its is organic. The sepertory funnell seperated the caffin because it is more poler.   The calcium carbonate crystals looked like a white powder and their was some chunks in they’re: but I could have spilled some on the bench maybe.  When I suction filtrated the crystals it took to long so more may have been lost. The calcium crystals were used because it is a base and it protonated the tannic so it is less soluble and it didn’t dissolve.   I think that when I dried my stuff I let it dry two long so I lost some because some of it may have evaperated away.  It is yellow and sticks to the vile and smelled like a keytone.  It is mostly impure but more pure then my last product.  My percent thearetical yeild was 4.27452% wich is not very good do to error.  I wonder what would happen if we used instent tea instead.  I think it would be more.

 

(Did you spot any errors?  This could be worse.  It could be hand scribbled and it could be three pages in length!  Please don’t make us read anything like this.)

_________________________________________________


Answers to questions

            Questions are presented for each experiment to stimulate thinking about important concepts and should be considered before writing your discussion.  The questions may serve as fodder for quizzes and exams.  Answers to questions may be written on a separate piece of paper and turned in for extra credit. Be sure to include your name and the experiment number.  Bonus points will be given for answers to the questions as follows:

 

            2          thoughtful, correct answers

            1          reasonable answers

            0          poor or no answers

 

Extra bonus points for exceptional work may be awarded at the discretion of the instructor. 

 

Product Labels

            Each product should be properly labeled and placed on the appropriate lab table with an accompanying information card.  The product vial should contain a meaningful identification number containing the student’s initials and notebook page number (i.e. CAL-43).  The accompanying card should contain the student’s name, product ID number (matching the vial), product name, product amount (in grams), percent yield (or percent recovery if appropriate) and measured physical data such as melting or boiling point range.  If a spectrum was obtained, a labeled copy should be stapled to the card. 

 

Product Quality

            The quality of your products will be graded on a three-point scale as given below:

 

            3          High yield, good quality

            2          average yield, average quality

            1          poor yield, poor quality

            0          no product

 

Technique

            Your technique will be evaluated at the end of the term and will be worth five percent of your overall grade.  Technique points will be awarded at the discretion of the instructors.  The maximum number of points will be awarded to students who:

 

- Show up on time and are properly dressed

- Are fully prepared for lab

- Follow all safety rules

- Perform laboratory functions safely and efficiently

- Work carefully in the lab to avoid breakage, spills, contamination, and fire

- Properly dispose of waste

- Clean up their bench and common work areas daily

- Overall quality and completeness of notebook

 

Time Management

            It is expected that students will come to lab fully prepared with major glassware setup in advance and will work at a reasonable pace when in lab.  All of our experiments have been designed and tested so that they may be completed in less than two and one-half hours if the student is adequately prepared.  If for some unforeseen circumstance a fully prepared student who works efficiently is unable to complete an experiment by 3:00 PM, the student may make arrangements to complete the experiment on Friday afternoon at no penalty.  This option is available at the discretion of the instructor. 

 

Describing your products

            Science begins with observation.   Communicating science must always include descriptions of your observations.  In the organic lab, we must not only say that we obtained a product, but we must be able to describe it.  The most fundamental distinction will be the phase of matter of your product; is it a solid, liquid, or a gas?  But that is only the beginning; you should also describe its physical appearance and properties.  For example, if it is a liquid, you should describe whether it is clear or cloudy (opaque).  You should describe whether it is colored or colorless.  Note that clear and colorless are two different properties.  If you obtain a solid you should describe its crystalline form; are the crystals needle-like, platy, or prismatic?  If the crystals are too small to be observed they could be described as powdery.  Smell is also an important distinguishing characteristic; is the smell pleasant or pungent?  Words to describe smells might include sweet, fruity (esters), sour (carboxylic acids), fishy (amines), balsamic (cinnamon, cocoa, vanilla etc.), camphoric, citrus (lemon or lime), floral or earthy to name just a few. 

 

Science is worthless without good communication.  When communicating, it is important to spell and use words correctly.  The following are lists of words commonly misspelled or misused in this course.  Learn to use these words properly.

 

Commonly misspelled words

Dye / dyed

Ketone

Perform

Precipitate

Separated

Separatory funnel

Summary

Theoretical

Vial

Yield

 

Commonly misused words

Data (a noun, plural)

Distillate (the object; a noun)

Filter (the action; a verb), Filter (the object; a noun)

Filtrate (the material, a noun), (“Filtrated” will not be recognized in this course)

Precipitate (the action, a verb), Precipitate (the material, a noun)

To (a preposition), Two (a number), Too (an adverb)

Then (for order in time), than (for comparison)

Their (possessive form of they), There (a place), They’re (contraction of they are)


Experiment 1

Isolation of Acetylsalicylic Acid from Aspirin Tablets

 

Read pp. 43-54, 150-159, 332-333

 

            Aspirin is an analgesic, an antipyretic, and an anti-inflammatory agent.  It was first produced synthetically by Felix Hoffmann in 1893 and marketed by Bayer as a wonder-drug.  Recently, aspirin has been marketed for its ability to thin the blood and prevent or lessen the severity of heart attacks and strokes.   In this experiment, we will isolate the acetylsalicylic acid from aspirin tablets. 

            Aspirin tablets contain acetylsalicylic acid (the active ingredient) as well as “inert” binders to hold the tablet together.  We will take advantage of the fact that acetylsalicylic acid is quite soluble in hot ethanol while the binders are insoluble and can be removed by filtration. The solubility of acetylsalicylic acid will be reduced by the addition of water to the solution, allowing the acetylsalicylic acid to crystallize out.             

            Follow the procedure in the text for isolating acetyl salicylic acid.  After allowing your product to dry overnight, determine its mass and melting point range. 

 

Report

Discuss the chemical principles used in this lab.  Be sure to record the amount of product you obtained (recovered yield) as well as calculate the percent recovery.  The amount of acetylsalicylic acid in each tablet is reported on the product label.  In your discussion, include the theory of purification by crystallization.

The following information may be helpful for this experiment: Acetyl salicylic acid, M.W. 180.15 g / mol, pKa 3.49, m.p 135 oC.  Solubility: 1 g acetylsalicylic acid dissolves in 300 ml water at 25 oC or 100 ml water at 37oC, 5 ml ethanol, or 17 ml CHCl3. 

 

Balances:  Use only the top loading balances in this course (not the analytical balances). If you spill on a balance, consult with the instructor on how to clean it up. Never leave a spill!

Water hoses:  Keep your water hoses for the entire term. 

Melting points: Never leave the melting point apparatus “on” unless it is in use.  It could overheat and blowup the thermometer.

Broken glassware:  Put all broken glassware in the bucket beside the waste basket.  Remove and save any stoppers, stopcocks, or plastic parts.

Clean-up:  If detergent and water are not sufficient to clean your glassware try rinsing with a small amount of acetone. If that doesn’t work, try rinsing with dilute acid or base.

 

         Substance

          Amount

          Properties

sol.

    

mmoles

grams

   mL.

 M.W.

  dens. 

 m.p.  

 b.p.

w

o

Acetylsalicylic acid

    18

   3.25

 

    180

 

  140

 

N

Y

Ethanol

 

   0.79

    10

    46

   0.79

-130

   78

Y

Y

Water

 

    50

    50

    18

   1.00

    0

  100

Y

N


Experiment 2

Simple vs. Fractional Distillation of a Methanol / Water Mixture. 

 

Read pp. 62-72; 75-80, 305

 

In this experiment you will perform both a simple and a fractional distillation on a mixture of methanol and water and compare the two techniques based on the composition of the distillate as a function of the volume collected. While the goal of most distillations is to separate a mixture of volatile substances by collecting them in separate containers, the goal of these particular distillations is to compare the mole fractions of the distillate as a function of volume collected for the two techniques.  We will do this by monitoring the temperature of the distillate and using the vapor diagram to relate temperature to composition. 

 

You will work with a partner, one will perform the distillation and the other will record the data.  You will trade duties for the second distillation. 

 

Prepare a 0.5 mole fraction methanol/water mixture by combining 40 ml methanol with 18 ml water.  You will use this mixture for both distillations.  After the first distillation, make the necessary modifications in the glassware setup and pour the distillate back into the boiling flask.

 

 

Fractional distillation

For this experiment, we will modify a fractional distillation apparatus in order to help us understand the role of the fractionating column. (All future fractional distillations will use the standard glassware set-up.) We will use two thermometers, one below the fractionating column and the other in the standard place above the column in the still head (connecting adapter).  This will allow us to monitor the difference in vapor composition in the two regions of the apparatus.  The lower thermometer will be placed in the straight neck of a Claisen adaptor and adjusted so that the bulb is just above the boiling liquid.  The fractionating column will be placed on the other neck of the Claisen adaptor.  When carrying out your distillation, record the volume collected and temperature of both thermometers every 3-4 ml. Note whether or not any mixing lines are observed as the distillate is being collected. Continue the distillation until at least 50 ml distillate has been collected being sure to stop before the pot runs dry. 

On the same graph, plot the temperature of the distillate (upper thermometer) (vertical-axis) vs. the volume collected (horizontal axis) and the temperature of the vapor in the distillation pot (lower thermometer). vs. the volume collected  You will be plotting the data from the next trial here too.  Be sure to create a legend that distinguishes between the three data sets.  Be sure to label the axes and give your graphs a meaningful title. 

 

Simple Distillation

Set up a simple distillation apparatus as shown on page 66 with a flame used as the source of heat as shown on page 375.  Collect the distillate in a graduated cylinder.  When carrying out your distillation, record the volume collected and temperature every 3-4 ml. The entire bulb of the thermometer must be in contact with the vapors when taking a reading of the thermometer or the value will not be accurate; only take a reading when liquid is being collected.  Note whether or not any mixing lines are observed as the distillate is being collected. Continue the distillation until at least 50 ml distillate has been collected being sure to stop before the pot runs dry. 

On the same graph as above, plot the temperature of the distillate (vertical-axis) vs. the volume collected (horizontal-axis). For each recorded temperature, use the boiling point diagram p.73 to estimate the mole fraction of methanol in the mixture being collected at each point.  Plot the mole fraction of methanol vs. volume amount collected.  Be sure to keep the scale of the volume axes the same from one graph to the next. How do the two graphs compare?  Is it reasonable to simply use the boiling temperature of the distillate to monitor how well the components have been separated?

 

Helpful hints:  1) Do not use plastic clips or rubber coated clamps on any parts of the distillation which will be heated with a flame.  2) Be sure that all ground glass joints are clean and properly fitted or the vapors may escape and catch fire.  3) Don’t forget boiling stones. 4) Never distill to dryness. 

 

Report

            Discuss the theory of distillation using your results as an example.  Plot your graphs side by side for easy comparison.  Explain the significance of your graphs, the temperature differences between the two thermometers, and any other observations you made.        

 

Questions:  see question 1 a-e in the text on p.79 (consider the worst case scenario for each)

 

 

Glassware: Glassware is very expensive so be careful when handling it.  When setting up your apparatus, never leave a piece of glassware hanging unsupported.  Never leave a piece where it can roll off the counter.

 

Thermometers: Thermometers should be returned to the stockroom and stored in an upright position to prevent separation of the alcohol column.

 
Experiment 3

Separation of malachite green and phenolphthalein by acid base extraction

 

Read pp. 92-109

In this experiment you will be given a mixture of the indicator dyes malachite green and phenolphthalein.  We will take advantage of their acid/base properties to separate the mixture.  Phenolphthalein is commonly used in acid/base titrations and has the pink color in basic solution familiar to many chemistry students.  The compound is also a cathartic and was once the active ingredient in “Ex-Lax” brand laxative.  Malachite green in its solid form has a color similar to the mineral known as malachite, CuCO3.Cu(OH)2.  In strongly basic solutions a hydroxide ion adds to malachite green giving a colorless (neutral) carbinol form.  Malachite green is used to dye silk, wool, leather, jute, and will dye cotton if a mordant is used.  It has been used as a biological stain and as a fungicide and parasiticide in fish. 

            Malachite green and phenolphthalein are acid / base indicators and were chosen for this experiment so that it would be possible to use the observed colors to keep track of what species are in each layer.  This is a fairly new experiment and the procedure has not been optimized.  You will work with a partner and explore the effect of one variable on the amount and purity of the products.  You and your partner should work side by side performing each operation the same way and choose one variable to change in the procedure.  Have the instructor okay your idea before you begin.  Together, you will write one report.

 

Possible variations:

Use cresolphthalein instead of phenolphthalein

Use Victoria Blue B instead of malachite green

Vary the amount of oxalic acid used to precipitate malachite green

Use different drying agents in the ether prior to isolating the malachite green.

 

___________________________________________________________

Phenolphthalein micro-extraction

 

This is a short exercise to demonstrate the effectiveness of a base extraction procedure.

 

The question you are intended to answer from the mini-experiment is: how many base extractions need to be done on an ether solution of phenolphthalein before the color is no longer detectable?

 

Place two milliliters phenolphthalein solution (0.1% in ether) in a test tube.  Using a Pasteur pipette, extract the solution with a 2 mL portion of 5% NaOH solution.  Be sure to mix the two layers thoroughly and allow them to completely separate.  Using the pipette, remove the aqueous layer and place it in a separate test tube.  Repeat until the pink color is no longer detectable in the aqueous layer. 

 

Compare the colors of each of the successive aqueous extracts.  What do they tell us about the effectiveness of the procedure?

____________________________________________________________________

 

Procedure

            Be sure to note the observed colors during the procedure and estimate the intensity of each color.  Add 0.5 g of the dye mixture (0.3 g of phenolphthalein and 0.2 g of Malachite Green) to 30 ml 3M NaOH in a separatory funnel with mixing.  Add 20 mL of diethyl ether to the separatory funnel and mix the solvents slowly and thoroughly.  Be sure to vent the separatory funnel frequently.  Drain off the aqueous layer through the stopcock and decant the ether layer into a flask.  Return the aqueous layer to the separatory funnel and wash with two more 20 ml portions of ether combining all three ether layers.

 

Phenolphthalein

            The aqueous layer from above should be filtered by gravity if any solid is present. Any remaining ether should be removed with a pipette.   Acidify the aqueous layer by slowly adding 6M HCl (about 15 ml total will be needed).  How will you know when the mixture is acidic?  Set the mixture aside to allow the solid to form for at least 30 minutes preferably overnight. Collect the solid by suction filtration using a Hirsch funnel, washing with a small amount of water.  

             

Isolation Malachite Green Oxalate

            If the ether layer is not a single phase (uniform and clear), be sure to remove any remaining water using a pipette or a drying agent.  Dissolve 0.16g oxalic acid in 10 mL of ether and add to the combined ether layers from above (dissolution is slow so do this ahead of time).  Note any color changes.  Allow the mixture to precipitate for at least 30 minutes, preferably overnight.  Collect the product by suction filtration using a Hirsch funnel, and wash with a small amount of ether.

 

Caution: Malachite green will stain your skin and clothing.

 

Helpful hints: 1) Label all flasks containing solutions.   2) Do not throw anything away until you have the final products in hand.  3) Emulsions may sometimes be broken by gently stirring with a glass stir rod or by sitting for a few minutes.  If the emulsion is not easily broken in a few minutes just leave it in the separatory funnel and go on.

 

 

 

 

Report

Discuss the principles of acid base extraction.  Be sure to explain your observations for each step.  Relate colors to species present and intensities to amounts of species present.

 

Questions

1) Calculate the pH of each aqueous solution in this experiment.

a. 30 ml 3M NaOH

b. The original aqueous layer after 16 ml 6M HCl was added.

 

2)  a.  A student proposed to separate this mixture by using 20 ml 3M HCl and ether in the first step instead of the NaOH.  How would this change the separation?  What would be in each layer? 

b. Assuming that the student was successful above, what would the second step need to be to complete the separation? (hint: what pH would the student need to obtain?)

 

Separatory funnels: Be sure to loosen the nut on the stopcock when storing your separatory funnel or the Teflon will become distorted.

 

Pipettes: Pasteur pipettes are disposable and should be put with the glass waste.  The bulbs are reusable.


Experiment 4

Preparation of 2,4-Dinitrodiphenylamine

 

Read pp. 92-109, 116-119, 475-476

 

 

Caution:  Dinitrobromobenzene is an irritant, contact with skin should be avoided.

 

            In this experiment, we will prepare dinitrodiphenylamine via nucleophilic aromatic substitution.  We will perform the experiment on one-half scale of that in the text.  Continue to use a 125 mL Erlenmeyer flask fit with a condenser for the recrystallization. Two equivalents of the amine are needed to get the reaction to go; one does the substitution and the other acts as a base.  As the reaction proceeds, the mixture will be set aside for one hour to crystallize.  During this crystallization time, we will use thin layer chromatography to determine if the reaction has gone to completion.  After isolating our product, we will purify it further by recrystallization. 

 

Thin Layer Chromatography (TLC)

We will use thin layer chromatography to follow the progress of this reaction.   We will compare the TLC behavior of our product mixture with that of our two starting materials.  The visible disappearance of one of the starting materials (limiting reagent) from the reaction mixture will be taken as evidence that the reaction has gone to completion.  In addition, we will explore the effect of solvent polarity on Rf values.  

 

The procedure for thin layer chromatography is detailed in your text (pp-116-119) and is summarized for this experiment below. 

1) Prepare at least 3 micropipettes by heating capillary pipettes in a flame and drawing them out. 

2) Prepare at least three TLC plates by marking them with a soft pencil as shown in the figure below. 

3) Spot each plate with each starting materials and the product mixture.

4) Elute one plate in hexane (non-polar), one in acetone (most polar of the three), and one in toluene (intermediate polarity).

5) Use UV light to visualize each plate and mark the location of the spots with a pencil.  After they have been marked, expose the plates to iodine vapors and note any changes. 

            6) Using the eluting solvent that gives the best separation of spots, run another TLC plate with the product mixture after it has sat for an hour and note if there any differences from the plate spotted with the fresh reaction mixture. 

 

Make a scale drawing of each plate in your notebook and record the measured Rf values.

 


Report

            Discuss the chemical principles used in this lab.  Be sure to include a mechanism for the reaction.  In your discussion, explain how the eluting solvent polarity affects the Rf values for the substances.  Also, make a correlation between the relative Rf values of each compound and their relative affinities to the mobile and stationary phases.  A second part of your discussion should include the theory behind recrystallization. 

 

 

 

Marking plates for Thin Layer Chromatography

 

 

 

Rf = distance traveled by substance / distance traveled by solvent front.

 

Note: avoid spotting compounds too close to the edge of the plate.  Be sure that the spots are above the level of the eluting solvent in the chamber. 

 

 

Questions

            1)  In previous years, the waste bottle from this lab developed a large mass of long orange needles.  What does this tell us about our procedure? (be specific)  How could we fix this problem?

 

2)  A student ran out of bromodinitrobenzene and substituted chlorodinitrobenzene in the reaction and found that the reaction with the chlorodinitrobenzene went faster.  Explain. 

 

3)                            After developing a TLC plate, a student observed that the plate had dark spots running from the origin to the solvent front.  What did the student do wrong?

 

 

Appendix 1 of this manual provides useful suggestions for drawing reaction mechanisms.
Experiment 5

Dehydration of Cyclohexanol to Cyclohexene

 

Read pp. 376-380, 122-128

 

Use caution when handling the phosphoric acid.

 

            We will use a strong acid to dehydrate an alcohol to obtain an alkene.  Le Chatelier’s principle will be used to explain why we were able to drive the unfavorable reaction to completion. We will analyze both the crude and the distilled products by gas chromatography.  In order to save time we will do our analyses as a group (by lab benches) on mixed batches prepared by combining one drop from each student at your bench.  This will provide us with a picture of the average purity for each bench.  If time permits, individual samples may be run after that.   Prepare a 1% sample of your crude cyclohexene in diethyl ether by combining one drop from each student (6 drops total) and diluting that mixture down with 10 mL ether.  Do the same for the purified cyclohexene.  Your instructor will make the injections into the GC.  Compare the amount of cyclohexene in the sample to the amount of cyclohexanol.   The amount of ether in the sample is not a controlled amount and we will ignore the height of this peak. Note that the peak areas reported from GC run represent the amount of signal from the detector not the number of molecules detected.  (The peak ratio between the ether signal and the cyclohexene signal does not accurately reflect the mole ratio of the two.)  We are assuming that molecules like cyclohexene and the cyclohexanol are similar enough to have similar response factors. 

 

Helpful hints: 1) Remember that it takes time to reach equilibrium so do not rush the first distillation.  2) The collection flask should be kept on ice.  3) Be sure to save at least one drop of your crude material for GC analysis.  4) Before your final distillation, be sure that your entire apparatus is clean and dry (and free from acetone residue).  5) Collect your purified product from your final distillation into a tared vial. 6) If your final product becomes cloudy by picking up water, a small amount of drying agent can be used to dry it (be sure to remove it before turning in your product).

 

Report

Discuss the chemical principles used in this lab.  Be sure to include a mechanism for the reaction in your report.  Your discussion should comment on the purity of your product as determined by GC, the equilibrium of the reaction, and how the reaction was brought to completion. 

 

Questions

1)  Two “distillations” were done during this lab.  What was the purpose of each?

2) Why was it critical to have the cyclohexene dry and acid free before performing the second distillation?

3) If 2-methyl cyclohexanol were dehydrated, what products would be expected?  Which one would be the major product?  What technique could be used to identify the products? Be specific.


Experiment 6

Cyclohexanone from Cyclohexanol

 

Read pp. 387-389, 87-90, 182-199. 

 

 

Caution:  Before you begin, check the actual concentration of bleach on the bottle's label and adjust your amounts accordingly.

 

Oxidations are very important reactions in organic chemistry.  While oxidations may look relatively simple to perform on paper, in the lab they may become more complicated due to the need to ensure the reaction has gone to completion and that the product is adequately isolated.  There are several interesting features to this lab.  Pay attention to the purpose of each step as you read the lab.  First, you will need to add the oxidizing agent over a period of time in order to avoid having too large of a concentration of poisonous chlorine gas at any one time.  Our goal will be to maintain a steady state concentration of our oxidant in order to avoid losing it as chlorine gas.  Also, you will need to control the reaction temperature to minimize the loss of Cl2 gas.  As the reaction proceeds, the concentration of cyclohexanol will decrease slowing the rate of the reaction while the concentration of chloride will increase, increasing the rate of formation of chlorine gas.  You will need to check the reaction mixture to ensure that excess oxidizing agent is present to ensure that reaction has gone to completion.  After the reaction has been completed, the remaining oxidizing agent will have to be destroyed to avoid over-oxidizing the product. Finally, the product is insoluble in water and will be isolated by steam distillation before being purified by regular distillation.  Obtain an IR spectrum of your product. 

 

Helpful hints: 1) It may be difficult to keep the reaction temperature under 35 oC as stated in the lab text; use a water bath to keep the temperature at about 40 oC during the oxidation.  2) After your final addition, be sure to give the reaction a few minutes to come to completion before testing for excess chlorine.  4) It is much easier to purify your product if the reaction has gone to completion.

 

Report

Comment on the purity of your product based on its IR spectrum and its boiling range.  Be sure to include a mechanism for the reaction.  Discuss the chemical principles used in this lab including the importance of each step in the procedure in obtaining the maximum amount of product. 

 

Questions

See question 1 and 2 p.389. 

3) After you isolate the product, why is it necessary to neutralize the remaining acetic acid?  Be specific. 


Experiment 7

Preparation of Isoamyl Acetate

 

Read pp. 417-426

            Esters are an important functional group, particularly for their flavor and fragrance properties.  In this lab isoamyl acetate, a component of banana oil (as well as an alarm pheromone of the honey bee) will be prepared by two methods.  One is an acid catalyzed Fischer esterification, and the other is an SN2 substitution in a polar aprotic solvent. 

 

            You will work in pairs for this lab.  One person will carry out the esterification by the Fischer method (procedure 58.1) while the other person will carry out the nucleophilic substitution (procedure 58.2).  Pay attention to any color changes or precipitate formation in these reactions.  Be sure to obtain an IR spectrum of your purified product in order to determine its purity.  Note that ~50 g ice is the amount of ice chips that will fill a 100 mL beaker.  Do not weight the ice on the balance.

 

Report

Discuss the chemical principles used in this lab.  Be sure to include a mechanism for your reaction.  Propose what the most likely impurities are in the sample based on your IR spectrum. In your discussion compare the two methods used to prepare the ester.

 

 

 

Questions

1) Consider equilibrium.  Is one esterification method more likely to bring the reaction to completion than the other?  Explain.

 

2) Given that NaBr is much more soluble (>5X) in DMF than KBr explain why potassium was a good choice for a counter ion in this reaction.  How ill it affect the yield?

 

3) A company wished to produce isopentenyl acetate, (3-methyl-2-pentenyl acetate), the flavor known as “juicy fruit”. What would be the starting materials in each reaction and what would be the likely products?  Which esterification method would be better suited to produce the desired product? (Hint: consider possible side reactions) Explain.

 


Experiment 8

Identification of an unknown substance

 

Read pp. 169-181, 239-272, appendix

In this lab, you will use solubility and chemical reactivity to determine the identity of two unknown compounds.   You will be given two vials containing unknown substances.  These are the only amounts that you will receive so guard them carefully.  Be sure to protect them from spills and losses due to evaporation. You will also want to make sure that you do not squander your unknowns by using too much for any test or by running unnecessary tests.

For the first unknown, you will be given the same compound as your partner and you should compare results at every step.  Repeat any tests for which your results do not match.  Once you have made a short list of candidate compounds, you will report your results orally to one of the instructors.  The instructor will inform you as to the actual identity of this unknown and give you advice on how to proceed with your second unknown.

For your second unknown you will work alone and write a formal report proposing a short list of possible matches for your unknown and a way to distinguish between those if a derivative were to be made. 

 

Solubility

            The solubility of a compound is an excellent way to rapidly narrow down the number of possible functional groups that it might contain.  Using Section 23 of your book as a guide, test the solubility of several known compounds as well as each of your unknowns.  Combine a few mg of the compound (one drop of liquid) with a 3-5 mL solvent and note whether or not the compound dissolved.   Remember not to use too much compound as you may saturate the solution or waste your unknown; but you do need enough to be able to see it in the test tube.  Check the solubility of the compound in water.  If the compound is soluble in water check the pH of the aqueous solution.  If the compound is insoluble in water, check the solubility of your compound in 5% HCl, and 5% NaOH.   Remember that the term soluble means that the solute and solvent form a single phase; a single phase solution may be colored but must not be cloudy or contain any precipitate or oily droplets.  Sometimes a compound is soluble but may go into solution slowly.  Be sure that you allow enough time for each to go into solution.   The flow chart below will help you make sense of your results.  Keep in mind that this chart is limited to the functional groups that we will be testing in this lab. 

 

Classification tests

            Chemical classification tests take advantage of the fact that different compounds that contain the same functional group have similar reactivity.  You will compare the reactivity of your unknown functional groups with compounds that have known functional groups.  The key to success here is to always run a blank and a control and to carefully record your observations.  Also, as with any test, the results should not be trusted if they are not reproducible.  Be sure to repeat your tests if there is any ambiguity. 

            Run a blank – run each test side by side with a compound that will give a negative result.

            Run a control – run each test side by side with a compound that will give a positive test.  By always having a positive and a negative test alongside an unknown, the interpretation of the results will be more straightforward. 

            Carefully record your observations .  When conflicting data is obtained, you must decide what evidence should carry more weight.  This is easier to do when you have observations rather than just your interpretation.  For example, it is more helpful, and more correct to report that the Tollens test produced a gray precipitate on heating for 15 minutes than to write down that the Tollens test was positive.  Simply writing a ‘+’ sign in your notebook may be misleading.

            Before attempting any classification tests on your unknowns, practice each test on known compounds to get a sense of what positive and negative tests look like.  Results will inevitably vary each time the tests are run.  Your observations may be different from those reported in the book.  Pay attention.

 

 

The recommended functional group tests are summarized below not necessarily in the order that they should be run.

 

Helpful hints: 1) Run a control and a blank side by side for each of the tests.  These will help you interpret your results.  2) If a result from a classification test is ambiguous, it is usually quicker to repeat the test than to try to interpret poor data. 

 

Acetyl chloride test for alcohols and amines (do this in the hood)

Cautiously add 3-5 drops of acetyl chloride to a dry test tube containing a few mg unknown.  Evolution of heat and/or HCl gas indicates a positive test.  It may difficult to determine the production of a small amount of heat with a small amount of reactant. If your unknown is less reactive it may a slightly larger amount of unknown to determine if a reaction has occurred.  Amines and alcohols give positive tests but with noticeable differences.  When the reaction mixture is carefully diluted with water, a precipitate may form.  Alcohols often give a solid acyl ester and 1o and 2o amines often give a solid acetaminde derivative; 3o amines do not. 

 

 

Test

 

Reference

Controls

Hinsberg (Be sure to consult your instructor before attempting this test)

 

29.2

Amines; 1o, 2o, 3o, (be sure to test an aromatic amine as well)

2,4-dinitrophenyhydrazine

 

29.5

Aldehydes and ketones

Chromic anhydride  (run on alcohols and aldehydes/ ketones)

 

29.4

Alcohols; (1o, 2o, 3o),

aldehydes

Acetyl chloride

 

Procedure above

Alcohols and amines

 

 

Amines

If solubility indicates that the unknown is an amine:

            Confirm the presence of an amine by running the acetyl chloride test.

            If an amine is present, consult your instructor before attempting the Hinsberg test to distinguish 1o, 2o, and 3o amines.

                        1o amines will be soluble after step 1 and insoluble after step 2 of Hinsberg.

                        2o amines will be insoluble after both steps 1 and 2 of Hinsberg.

                        3o amine will not react and observations will reflect the solubility behavior of the amine. 

 

Aldehydes, Ketones and Alcohols

If solubility indicates that the unknown is an alcohol, aldehyde or ketone:

Test for the presence of an alcohol using acetyl chloride.

If and alcohol is indicated, run chromic anhydride test to distinguish 1o and 2o, from 3o

            1o and 2o alcohols will react quickly

3o alcohols give no visible reaction.

            If alcohol is not present run the 2,4-dinitrophenyl hydrazine test (+ for aldehydes and ketones).

            If and aldehyde or ketone is present, run chromic anhydride test (+ for aldehydes)

 

Carboxylic Acids

We will not use a positive test to confirm the presence of a carboxylic acid.

 

Determine the physical characteristics.

            There are clues to the compound’s identity in its physical characteristics.  Is it a solid or a liquid?  Does it have a distinct color?  Does it have a characteristic odor? 

 

Determine a melting or boiling point range

            If your unknown is a liquid determine its boiling point by placing a small amount it in a Pyrex test tube with a thermometer suspended a few centimeters above the liquid level.    Using a flame and a wire screen gently heat the tube until the reflux ring completely covers the bulb of the thermometer.  Be sure not to heat the sides of the test tube above the liquid or you will superheat your vapor.  Wait until the thermometer reaches a constant temperature before taking a reading.  We recommend practicing this technique on one of the known compounds so that you can look up the reported boiling point and check the accuracy of your result. 

 

Choose a derivative

            With the information obtained above, you should be able to go to the appropriate table in the appendix of your textbook and make a short list of possible compounds.  For example, if you have an ester with a boiling range of 190-194 oC you could go to the table of esters and choose esters that have a boiling point within a 5 -10 o range of the observed value.  Remember that your value is a measured quantity and will have some error associated with it.  In the table, there are three esters which fall into that range: heptyl acetate, phenyl acetate and methyl benzoate.  Since you cannot distinguish between these based on your boiling point, you will need to consider a derivative.  Note that of the three possible derivatives, the DNB derivative is the best choice because the three possible compounds have drastically different melting points with this derivative.  The NBz derivative for two of the compounds has the same melting point and it will not be helpful in distinguishing between the two.   The Acid derivative is not even listed for two of the possible compounds so it is also not helpful in this case.   Due to time constraints, you will not actually prepare these derivatives. Note that not all of the unknowns are necessarily listed in the back of your text.

 

First unknown Oral Reports. 

            After you have completed your work on your first unknown, you will report your results orally to your instructor.  These reports will be graded on a 10 point scale (3 points for being correct, 3 points for organization, and 4 points for logic).  For your report, you may only use your notebook as a reference.  Start by giving the unknown number and describing its physical characteristics including melting or boiling point.  Give the results of the solubility tests and your conclusions based on solubility.  State the results of any functional group tests you performed and conclude with the identity of your unknown functional group and a short list of candidate compounds.  State what derivative could be prepared and how the results of that experiment would allow you to determine the identity of the unknown compound.

 

Identification of second unknown

            For your unknown compound you will work alone and follow the same procedure that you used to identify the first unknown. 

 

Report

            Your report should include the unknown number and the identity of the unknown functional group and a short list of candidate compounds with all relevant data.

 

 Leave the remainder of your unknown out on the bench-top so that we can double-check it. 


Experiment 9

Preparation of Tetraphenylcyclopentadienone

 

Read pp. 595-597

 

This lab utilizes a pair of aldol condensations between dibenzylketone and benzil to produce tetraphenylcyclopentadienone.  The product is unique for two reasons.  First, the product is a deep purple color.  It is quite unusual for a compound with such a short conjugation length to be so highly colored.  Due to sterics, the phenyl groups are not in the same plane as the cyclopentadienone ring and are not fully conjugated with it.   While cyclopentadienone is quite reactive with itself toward Diels Alder reactions and it cannot be isolated on its own, the bulky phenyl groups in the tetraphenylcyclopentadienone protect the molecule from reacting with itself. This reaction is catalyzed by base.  The base used in this reaction will be trimethylbenzylammonium hydroxide because it has a higher solubility in our solvent than sodium hydroxide.  Prepare the compound on ½ scale as described in the text noting all color changes observed during the procedure.

 

TLC

We will use thin layer chromatography as an indicator of the purity of our product.  Dissolve a small amount of your product in dichloromethane and spot it on a TLC plate along with each of the two starting materials.  Elute the plate with toluene.  Determine if either of the starting materials is present in the product.

 

Solid phase IR

Obtain an IR spectrum of your dried product by grinding ~10 mg compound with 10 mg KBr with a mortar and pestle into a fine powder.  Fill the sample compartment of the specular reflectance attachment, level it smooth, and insert the sample holder into the chamber.

 

Report

Discuss the chemical principles used in this lab.  Explain the color changes observed.  Also, be sure to include a complete mechanism for the reaction.  (Since two identical aldol reactions occur, you only need to show one complete reaction.)  Discuss your results from the TLC and your IR spectrum.

 

Questions

1)  What did you observe that would support the idea that the trimethylbenzylammonium hydroxide is a catalyst in this reaction?  Explain

2)  How does your mechanism suggest that the hydroxide is a catalyst? (Start with the definition of a catalyst.)

3)  What is the driving force for the removal of the water in this reaction?


Experiment 10

Preparation of a Photochromic Compound

 

Read pp. 564-566

 

 

Caution: nitric and sulfuric acid can cause severe burns.  Handle with care.

 

            Follow the beginning procedures in the book but increase the amount of nitric acid to 2.25 mL of conc nitric acid (density 1.42 g/mL; 0.036 mole HNO3) as two equivalents of the nitronium ion are needed for the complete conversion. 

           

One of the goals of the experiment is to obtain your product as a single crystal. In order to give yourself the best chance of doing this you must modify the last part of the procedure. Here is the suggested modification: 

            First, filter the dried solution into a perfectly clean 125 mL, ground glass jointed, Erlenmeyer flask. Add one or two boiling stones. Clamp the flask by its neck in position on top of the rings of a steam bath that is supported above the base of the ring stand by a cork ring. The point is to make it possible to remove the steam bath without disturbing the Erlenmeyer flask. Complete a set-up for distillation of ether from the Erlenmeyer flask. 

Now, using the steam bath, distill slowly to reduce the volume of the dried ethereal solution to 30 to 35 mL.

At the point when 30 to 35 mL of solution remains, keep the Erlenmeyer flask clamped in position while removing the condenser and distillation adapter. Then slide the cork ring to the  side so that you can lower and remove the water bath. Don’t even think of removing the boiling stones. Cover the neck of the flask with a piece of aluminum foil and then allow the remaining solution to stand undisturbed until crystallization is complete. If you are lucky it will take several hours to crystallize, and if you are extremely fortunate you will obtain your product as a single crystal. You then become a member of the 2-(2,4-dinitrobenzyl)pyridine Hall of Fame.

 

 

Helpful hints:  1) Calculate out the number of moles of all reactants and be sure that there is a slight excess of nitric acid.  2) It may be easier to do the extraction in several smaller batches rather than one large batch.  3) When distilling off the ether, reduce its volume to 25 ml not 50 ml as it says in the book. 

 

The source of the photochromism in this compound has been the topic of debate.  Here are the latest ideas on structures.

 

“Apparently, while exposure of the ‘CH’ substance to light produces both the ‘OH’ and ‘NH’ substances, it is the ‘NH”’material that is responsible for the blue color.

 

                                 

                                     CH                                                  OH                                                  NH

                       brown sugar brown                                                                                 blue jeans blue

 

We could speculate that the deep blue color is a result of the effective resonance delocalization that is present in the NH form:

 

                     

 

                                                                                       NH form”

 

Journal of Chemical Education 2001, 78, 1596

 

Report

            Discuss the chemical principles used in this lab.

 

Questions

1) Explain the regioselectivity of the nitration.  Why was only the one ring nitrated and why were those two positions nitrated?

 

2) After the nitration, why was it necessary to add the base? What would have happened in the end if we didn’t add the base?

 

 

                      2-(2,4-dinitrobenzyl)-pyridine Hall of Fame.

 

The Hall of Fame includes those students who have obtained their product primarily as a single crystal with a mass of 750 mg or more.

 

Current members are:

 


Craig Kouba; 1974

Heather Parham; 1999

Graham Pumphrey; 2000

Rhonda Reisdorff; 2000

Ashley Meyer; 2004

Andrew Jeffrey; 2006

Sara Marsteller; 2006

Tina Pontarelli; 2007

Lindsey Wilson; 2007


 


Experiment 11

Preparation of Malachite Green and Crystal Violet

 

Reference: Tabor, D.F., Meagley, R.P, Supplee, D.; J. Chem. Ed. 1996, 73, 259.

 

 

 

Caution:    Malachite Green and Crystal Violet are biological stains and will readily stain skin and clothing.   Be sure dyed clothing is washed (separate from other clothing) before wearing. 

 

 

Helpful hints:  1) If the Grignard reaction does not appear to be proceeding, consult your instructor. 2) Before heating, be sure that the ground glass joint in your reflux apparatus is clean or it may lock up. 

 

Procedure

  An oven dried dry, 125 mL Erlenmeyer flask with ground glass joint is charged with a magnetic stir bar, magnesium turnings (0.40 g), dry THF (20 mL), 4-bromo-N,N-dimethyl aniline (2.5 g).  A dry glass stirring rod is used to gently crush several of the magnesium turnings to expose a fresh surface.  The flask is equipped with a reflux condenser and heated to gentle reflux for 30 minutes on a stirring hot plate (low setting).  During heating, the magnesium should be partially consumed and the color should change to a  cloudy “dishwater” gray.  After cooling to room temperature, methyl benzoate (0.42g) or dimethyl carbonate (0.24g) is added in one portion.  The mixture is returned to reflux for an additional 5 minutes.  After cooling to room temperature, HCl (8 mL, 10%) is slowly added. 

 

Dying

 A sample of cotton fabric is placed in the solution and soaked for several minutes.  After removing the sample, the cloth is thoroughly rinsed in cold running water.  Be sure that the cloth is thoroughly rinsed before touching it with your bare hands.  You are free to use the remaining dye to experiment with dying your own samples.  When you are finished, pour the extra dye mixtures into the waste container in the hood. 

 

Note:  You will not isolate your product from this experiment but you should still calculate a theoretical yield.  This will give you an idea about the amount of coverage you get from your dye.

 

 

Report 

Discuss the chemical principles used in this lab. 

 

Questions

 

1) When producing the dye, explain why the color of the dye does not appear until addition of the acid in the final step. 

 


Experiment 12

Choose your own experiment

 

You will plan and carry out a lab experiment of your own choosing.  You may choose an experiment from the list below or, with the instructor's approval, from another source.  You will be responsible for checking to make sure that the necessary reagents and glassware are available.  You will also be responsible for making sure that all safety precautions are followed. 

 

Proposal

You will type a short proposal for the experiment that you will carry out.  Be sure to include the following:  an informative title, an introduction telling why you are doing what you are proposing (why is this interesting?), a procedure with reference and any proposed modifications, a description of the chemistry, and balanced equations.  Some of the procedures can take a long time.  Be sure to make arrangements to start any long procedures in advance.  On a separate sheet of paper, type a list of materials you will need and any special equipment or needs.  Turn this list in to Andrea.

 

 

Lab

Reference page

Preparation of Adamantane

364

N,N-DiethylToluamide ("Off")

461

Reactions of Vanillin

485

Preparation of Diazonium Dyes

498

p-Acetamidophenol ("Tylenol")

529

Coconut Aldehyde

543

Thermochromic compounds

559

Chemiluminescence : Luminol

567

Solvatochromic Dyes:  MOED

627

Liquid Crystals:  MBBA

Handout

Isolation of Cholesterol from Gallstones

327-329

Biodeisel from vegetable oil

Handout

 

 


EXPERIMENT 13

Preparation of Norbornene-2,3-dicarboxylic Anhydride

 

Read pp. 507, 510-514

            Your instructor will “crack” the cyclopentadiene for you but you are still responsible for understanding the chemistry involved. 

 

 Perform the Diels Alder addition as described in the text.  The expected product of the reaction is the endo product shown, which melts at 165o C.  In the literature, the product is also known as “carbic anhydride” or “nadic anhydride”. 

 

 

 

Note that it is very important to keep this reaction dry.  Be sure that the joint in your glassware is tightly sealed to prevent water from the steam bath from getting into your reaction.  Be sure to dry the outside of the joint before removing the reflux condenser.

           

Report

Discuss the chemical principles used in this lab.

 

Questions

 

See Questions 1-3 pp. 513-514.

 

  1. What will happen if water gets into the reaction mixture?  Be specific. 

 


Appendix 1

                              Writing Mechanisms

 

General considerations

 

1.   Divide the transformation into steps. Starting material to first intermediate is the first step; first intermediate to second intermediate is the second step; ... final intermediate to product is the last step.

 

2.   For each step, represent all the reactants and all the products of the step.

 

3.   Use arrows to show the movement of electrons. For a proton transfer step, show a pair of electrons of the proton acceptor (the base) moving to accept the proton from the proton donor. For an alkyl transfer step, show a pair of electrons of the alkyl acceptor (the nucleophile) moving to accept the alkyl group from the alkyl donor. In general, use arrows to indicate the movement of pairs of electrons from their source to their destination.

 

4.   Use an arrow with a two barb head to show the movement of a pair of electrons; use an arrow with a single barb to show the movement of a single electron.

 

5.   Draw the arrow with the butt end of the arrow next to the electrons that move, and the point of the arrow at the destination of the electrons.

 

Pay attention to pH

 

In an acidic aqueous solution hydronium ion will be the only kinetically important proton donor. (Specific acid catalysis)

 

In a basic aqueous solution hydroxide ion will be the only kinetically important proton acceptor. (Specific base catalysis)

 

6.   a.   When the pH is near 0, hydronium ion will be the proton donor, and water will be the proton acceptor.

 

      b.   When the pH is near 14, water will be the proton donor, and hydroxide ion will be the proton acceptor.

 

      c.   It will always be a mistake to invoke both hydronium ion and hydroxide ion in the same reaction.


Appendix 2

Inorganics

 

     

 

 

 

 

Solubility

      Substance

   M.W.

   Dens.

    M.P.

    B.P.

H2O

Org.

 

 

 

 

 

 

 

Aluminum chloride

133

 

dec

 

dec.

some

Ammonium hydroxide

35

 

 

 

sol

 

Bromine

160

3.12

-7

59

sol

sol

Calcium carbonate, anh.

100

 

 

 

sl

ins

Calcium chloride, anh.

111

 

 

 

sol

 

Decolorizing carbon

 

 

 

 

ins

ins

Hydrogen bromide

81

 

-89

-57

sol

sol

Hydrogen chloride

37

 

-115

-85

sol

sol

Iodine

254

 

114

184

sl

sol

Iodine monochloride

162

3.18

27

87

dec

sol

Magnesium metal

24

 

1400

 

 

 

Magnesium sulfate, anh.

120

 

 

 

sol

ins

Nitric acid

63

1.50

-42

83

sol

 

Phosphoric acid

98

1.83

 

 

sol

 

Potassium acetate

98

 

292

 

sol

sl

Potassium carbonate, anh

138

 

891

 

sol

ins

Potassium hydroxide

56

 

360

1320

sol

 

Sodium acetate

82

 

324

 

sol

 

Sodium bicarbonate

84

 

 

 

sl

 

Sodium bisulfite

120

 

 

 

sol

 

Sodium borohydride

38

 

 

 

sol

sol

Sodium bromide

103

 

747

1390

sol

 

Sodium carbonate, anh.

106

 

851

 

sol

 

Sodium chlorate

106

 

248

 

sol

 

Sodium chloride

58

 

801

1413

sol

 

Sodium hypochlorite

74

 

 

 

sol

 

Sodium nitrate

85

 

307

dec

sol

 

Sodium nitrite

69

 

271

dec

sol

 

Sodium sulfate, anh.

142

 

884

 

sol

ins

Sulfuric acid

98

1.81

10

330

sol

 

Zinc metal

65

 

419

907

ins

ins

 

Appendix 3

 

Organics

 

 

 

 

 

 

Solubility

 

      Substance

   M.W.

   Dens.

    M.P.

    B.P.

H2O

Org.

 

 

 

 

 

 

 

Acetylsalicylic acid

180

 

140

 

ins

sol

Aniline

93

1.02

-6

184

ins

sol

Benzil

210

 

95

 

ins

sol

2-Benzylpyridine

169

1.05

10

276

ins

sol

p-Bromodimethylaniline

200

 

55

264

ins

sol

Cyclohexanol

100

0.963

22

161

sl

sol

Cyclohexanone

98

0.947

-47

155

sl

sol

Cyclohexene

82

0.811

-104

83

ins

sol

Cyclopentadiene

66

0.802

-89

42

ins

sol

Dimethyl carbonate

90

1.069

4

90

sl

sol

2,4-Dinitrobromobenzene

247

 

75

 

ins

sol

2,4-Dinitrodiphenylamine

259

 

161

 

ins

sl

2-(2,4-dinitrobenzyl)pyridine

259

 

 

 

ins

sol

1,3-Diphenylacetone

210

1.04

34

330

ins

sol

Isoamyl alcohol

88

0.809

-117

130

sl

sol

Isoamyl acetate

130

0.876

-78

142

ins

yes

Isoamyl bromide

151

1.261

-112

121

ins

sol

Malachite Green oxalate

927

 

164

 

sol

ins

Maleic Anhydride

98

 

56

200

dec

sol

p-Methoxyaniline

123

 

60

243

ins

sol

Methyl benzoate

136

1.094

-12

189

ins

sol

Oxalic acid  · 2 H2O

126

 

106

 

ins

sol

p-Phenetidine

137

 

4

250

ins

sol

Phenolphthalein

319

 

263

 

ins

sol

p-Toluidine

107

0.963

47

200

ins

sol

Tetracyclone

384

 

220

 

ins

ins

Triethyleneglycol

150

1.125

-7

285

sol

sol

Victoria Blue

506

 

206 (dec)

 

 

 

 

 


Appendix 4

 

Solvents

 

 

     

 

 

 

 

Solubility

      Substance

   M.W.

   Dens.

    M.P.

    B.P.

H2O

Org.

 

 

 

 

 

 

 

Acetic Acid

60

1.05

16

118

yes

yes

Acetone

58

0.78

-94

57

yes

yes

2-Butanone

72

0.81

-89

80

yes

yes

Carbon Tetrachloride

154

1.59

-23

77

no

yes

Chloroform

119

1.49

-63

62

no

yes

Cyclohexane

84

0.78

7

81

no

yes

Dichloromethane

85

1.33

-97

40

no

yes

Dimethylformamide

73

0.94

-61

153

yes

yes

Dimethylsulfoxide

78

1.10

18

189

yes

yes

Ethanol

46

0.79

-130

78

yes

yes

Ethyl acetate

88

0.90

-84

78

sl.

yes

Ethyl ether

74

0.71

-116

35

sl.

yes

Hexane

86

0.66

-95

69

no

yes

Methanol

33

0.81

-98

65

yes

yes

Methylene Chloride

85

1.33

-97

40

no

yes

1-Propanol

60

0.80

-127

97

yes

yes

2-Propanol

60

0.79

-89

82

yes

yes

Toluene

92

0.865

-93

111

no

yes

Water

18

1.00

0

100

yes

no

 

 



Appendix 5

 

Organic Chemistry Laboratory Notebook Rubric

 

Name: ________________________________

Title of Experiment: ___________________________

 

Pre-lab

Descriptive title and date

0  1

 

Chemical structures / balanced chemical equations

0  1  2

 

Data table of reagents

0  1  2

 

Procedure reference

0  1

During lab

Procedure summary

0  1

 

Qualitative observations

0  1

Post-lab

Results

0  1  2

Total

 

___/10

 

 

Organic Chemistry Laboratory Notebook Rubric

 

Name: ________________________________

Title of Experiment: ___________________________

 

Pre-lab

Descriptive title and date

0  1

 

Chemical structures / balanced chemical equations

0  1  2

 

Data table of reagents

0  1  2

 

Procedure reference

0  1

During lab

Procedure summary

0  1

 

Qualitative observations

0  1

Post-lab

Results

0  1  2

Total

 

___/10

 

 

Organic Chemistry Laboratory Notebook Rubric

 

Name: ________________________________

Title of Experiment: ___________________________

 

Pre-lab

Descriptive title and date

0  1

 

Chemical structures / balanced chemical equations

0  1  2

 

Data table of reagents

0  1  2

 

Procedure reference

0  1

During lab

Procedure summary

0  1

 

Qualitative observations

0  1

Post-lab

Results

0  1  2

Total

 

___/10

 

 

Organic Chemistry Laboratory Notebook Rubric

 

Name: ________________________________

Title of Experiment: ___________________________

 

Pre-lab

Descriptive title and date

0  1

 

Chemical structures / balanced chemical equations

0  1  2

 

Data table of reagents

0  1  2

 

Procedure reference

0  1

During lab

Procedure summary

0  1

 

Qualitative observations

0  1

Post-lab

Results

0  1  2

Total

 

___/10

 

 



[1] Ault, A.; Techniques and Experiments for Organic Chemistry, 6th ed. University Science Books, pp 337-340.

[2] Literature value from Aldrich Catalog, 1996-1997.