PRELAB ASSIGNMENTS AND

LABORATORY HANDOUTS

CHEMISTRY 221B

ORGANIC CHEMISTRY LABORATORY I

FALL 2011

OH

O

water

ether

Handouts to accompany:

Organic Chemistry Laboratory: A Microscale Approach, 4th

ed. Pavia/Lampman/Kriz/Engel

1 Lab Schedule: see laboratory handouts for prelaboratory (prelab) assignments, lab sheets, and augmented experiments

Dates Experiment What’s Due

Week 1: Sept 22, 23, 27

Laboratory check in; Safety scavenger hunt; Computer lab orientation

Nothing

Week 2: Sept 29, 30 Oct 4

Experiment 1, Lab Ex 1, option A Experiment 2A-D: Solubility

Prelab for week 2 Handout from week 1

Week 3: Oct 6, 7, 11

Experiment 4 A, B, &D (including optional D): Extraction

Prelab for week 3; Lab report for Experiment 2 A-D and Experiment 1

Week 4: Oct 13, 14, 18

Continue Experiment 4 Prelab for week 4

Week 5: October 20, 21, 25

Experiment 3: Crystalizaiton and melting points

Prelab for week 5 Report to Experiment 4

Week 6: Oct 27, 28, Nov. 1

Conformational Analysis (models and computers) Bring models

Prelab for week 6 Report for Experiment 3

Week 7: Nov 3, 4, 8

Experiment 15 Chirality/Carvone Prelab for week 7 Report for Conformational Analysis

Week 8: Nov 10, 15, 18*

Experiment 6 Simple and Fractional Distillation

Prelab for week 8 Report for Experiment 15

Week 9: Nov 17, 22, Dec 2*

GC analysis of terpenes and functional group tests (addition reactions)

Prelab for week 9 Report for Experiment 6

Week 10: Nov 29, Dec 1, 5*

Lab final and check-out Report for GC analysis of terpenes

*Friday’s lab falls behind schedule due to Veteran’s day holiday, November 11 (campus closed). The labfinal/checkout day will be the last day of classes (Monday, December 5, 2011) unless prior arrangements have been made with your instructor. Notes:

a. Lab final will include questions from all labs and prelabs that have been returned. b. You must obtain instructor's signature on each worksheet before leaving lab. c. When IR or GC data is obtained, one partner should turn in the printout, and the other a

photocopy. All peaks should be labeled. d. Labs are due in the first ten minutes of the indicated period. 1 point will be deducted for

each weekday late. e. Prelab questions (at the top of each worksheet or online) are due at the beginning of each

period, and are not accepted late. If the prelab is online, it must be completed prior to the beginning of the laboratory period.

f. You will be required to submit a hand written procedure for each week’s experiment at the BEGINING of class

Safety is the number one priority in the laboratory. A student who does not wear laboratory goggle or who commits another serious safety violation will receive one verbal warning, and will then be asked to leave the lab.

2

3 Name: Lab day/time

Chemistry 221A, Fall 2011 Handout for Laboratory, Week 1:

Experiment 1: Introduction to Microscale Laboratory

PRELAB: Read the following sections in the Pavia et al. laboratory text: Technique 1*: Safety (Chapt 31 Signature), Technique 3: Glassware (chapt 33 Signature), Technique 4: Finding Laboratory Data (Chapt 34 Signature) No prelab questions or procedure for this week only! *The Techniques are in the back of your lab manual. For example, if you are using the 4th Edition text, Technique 1 is on pages 542-558; in the Signature text this technique is on pages 243-260.

Safety Scavenger Hunt and quiz Find each piece of equipment in the lab room or building, and indicate its location:

a. Eyewash

b. Safety shower

c. First aid kit

d. Material Safety Data Sheets (MSDSs)

e. Fire extinguisher

f. Nearest exit(s) from room

g. Three staircases in building

h. Waste container

i. Safety goggles

j. Chemicals for 221b

Questions:

1. When is it appropriate to wear your safety goggles in lab? What are the consequences for failing to do so?

2. What are the three main points of entry for chemicals into your body, and how can you minimize each?

3. What are the two potential consequences of pouring chemicals back into the reagent bottle?

4. What does NFPA stand for and what does each color diamond represent?

5. v. What does a "3" in the red box indicate of the NFPA symbol mean? A "2" in the blue box?

4 Introduction to the computer lab:

Proceed to the chemistry computer lab (CS-333). Fill out a computer lab account sheet. Your instructor will tell you whether accounts have been created yet, and how to log in. You may use the lab for chemistry related work throughout the year. Be advised that inappropriate use of the lab, and/or excessive printing may result in the termination of this privilege.

The computers in the chemistry computer lab should be configured to allow you to complete the assignments below, and other chemistry-related assignments. In some cases you will be able to configure your home computer with specific plugins (like Java, Shockwave, and Flash for OWL) for chemistry use. Directions for installing plugins are linked to the OWL introductory exercises. Other computer labs on campus may not have this support. Be aware that the Firefox browser in CS-330 has been tested and should work for your class; other browsers (such as Internet Explorer) may not.

The following exercises will walk you through some of the key features of the Blackboard and OWL sites for the lecture and laboratory courses. If you require additional assistance, please consult the instructor, or the Student Technology Support Center, PL-1108; acmlabs@csusb.edu 909-537-3395 (x73395) for Blackboard help, or the OWL support (owl.cengage.com) for the homework only. 1. Go to the Blackboard site (http://blackboard.csusb.edu). You should already be enrolled in

the lecture and lab courses: your login name is your CoyoteID number, and you should be able to log in the same way you do for “mycoyote.csusb.edu”.

2. It is a good idea to, change your password. On the left hand menu choose personal information, then change password. You should use a password that is meaningful to you, and should not share this with anyone.

3. Next, go to the lecture course (Chemistry 221a). Look at the announcements. Go to the "Course Documents". What folders exist, and what is in each folder?

4. Look at each of the other course buttons, and what is presently on those pages. Ask questions if you have difficulty navigating the site.

5. Return to the Blackboard window (it is a different browser window). From “External Links”, follow the link to the OWL registration page, and sign up. You must have an OWL account login and password to use this site. If you bought your book new from the CSUSB Bookstore, OWL access instructions should have been bundled with the text. If you bought your text elsewhere, you will need to purchase OWL access separately from the http://owl.cengage.com. Choose "student registration", then "Organic Chemistry I: Cousins", then complete the "Self-Registration" form. View the current assignments. How many assignments are there, and when are they due

6. Return to the Blackboard window. Click on the small blue underlined word CSUSB online at the top left of the page to return to the course page, then proceed to the laboratory web site, CHEM 221b (sections 01-07). Try out the buttons to look at all the pages. Where is prelab quiz for week 2 located?

7. When you are done, make sure you log out of your OWL account, your Blackboard account, and your Chemistry computer account. You are responsible to malicious conduct in your account, should you fail to log of the chemistry lab computer.

5 Name____________________________ Lab day/time________________________

Handout for Laboratory, Week 2: Experiment 1 and Experiment 2 A-D, Solubility Chemistry 221B, Fall 2011

Prelab: Read the following in your lab text: The introduction to Experiments 1 and 2; Techniques 5: (Measurement) and 10 (Solubility); Laboratory Exercise 1 (option A) in Experiment 1, and Experiment 2: Solubility in the laboratory text, and sections on polarity in your lecture text. Complete the online prelab (on Blackboard) before lab, and turn in your laboratory procedure at the beginning of the period.

PROCEDURE

Safety: Methylene chloride (CH2Cl2, or dichloromethane) is a suspected carcinogen. Avoid leaving open flasks and breathing its fumes. Dispose of methylene chloride in the halogenated organic waste bottle. Diethyl ether, hexanes, and organic alcohols are highly flammable, and all sources of heat, sparks, and flames should be avoided when it is in use. You should avoid breathing the vapors. 6.0 M HCl and 6.0 M NaOH are caustic, and contact with skin and clothes should be avoided. If contact does occur, flush the skin or fabric with copious amounts of water. All non-chlorinated organic materials should be disposed of in the regular organic waste bucket. Aqueous layers should be combined, neutralized (use a drop of phenolthalein and add acid or base as needed until an endpoint is reached), and poured down the sink.

Laboratory Exercise 1, Option A: Using an Automatic Pipette,

Safety/Waste disposal: Dispose of extra hexane in the non-halogenated organic waste container found in the main hood. All tap water free of hexane can go down the sink. Any tap water contaminated with hexane should also be placed in the non-halogenated organic waste container.

Mass of Empty vial: Mass of vial with H2O:

Mass of H2O dispensed:

Volume of H2O dispensed: (check the pipette to make sure!)

Calculated density of H2O (= mass/vol.): g/mL (lit = 0.997)

Show your calculations:

Mass of Empty vial: Mass of vial with hexane:

Mass of hexane dispensed:

Volume of hexane dispensed: (check the pipette to make sure!)

Calculated density of hexane (= mass/vol.): g/mL (lit = 0.660) Show your calculations:

6 Experiment 2: Solubility,

Follow the procedure in the text for parts A-D, Experiment 2. Fill in the charts below as you go. Be sure to mix completely and consistently before noting solubilities. Do NOT answer yes/no or use check marks/X’s; use the words “soluble” “insoluble” “partially soluble” (Parts A & D) or “miscible,” “immicible,” or “partially miscible” for Parts B & C. Part A. Solubility of Solid Compounds

Part B. Solubility of Different Alcohols

Solvents

Alcohols Water Hexane

Methyl Alcohol

CH3OH

1-Butanol

CH3CH2CH2CH2OH

1-Octanol

CH3(CH2)6CH2OH

C

O

HO

C

CH2

C

OH

O O

Benzophenone

Malonic Acid

Biphenyl

Organic Compounds Water(highly polar)

Methyl alcohol(intermed. polarity)

Hexane(non-polar)

Solvents

7 Part C. Miscible or immicible pairs:

Water and ethyl alcohol Water and diethyl ether Water and methylene chloride Water and hexane Hexane and methylene chloride

Part D. Solubility of Organic Acids and Bases

Additional Questions

1. Compare your calculated densities (part 1) to literature densities (lit.). What source(s) of error contributed to differences in these values?

2. Water and hexane don't mix; that is, they form two layers when placed in the same container. Which compound would comprise the top layer?

3. Why is it necessary to keep the pipettes separate, that is to use the H2O pipette only for H2O, and hexane pipette for hexane only?

C

O

OH

C

O

O CH2CH3H2N

Benzoic Acid

Ethyl 4-aminobenzoate

Solvents

Water 1.0 M NaOH 1.0 M HCl

Add 6.0M HCl

Add 6.0M NaOH

8 4. Explain the observed solubilities for part 2A for all three compounds. Consider polarity of the

solvent and solute, and the possibility of hydrogen bonding.

5. How does the solubility of alcohols in water and hexane vary, with number of carbon atoms in the alcohol molecule? (Hint: count the number of carbon atoms and number of OH’s in each type of alcohol. Now calculate a carbon to OH ratio for each).

6. What would you predict for the solubility of 1,5-hexanediol in water? In hexane? Explain, considering your answer to question 5, above. (hint: what is the carbon to OH ratio in 1,5-hexanediol?)

7. Complete the four chemical equations below to explain the solubility observations in part D, including what happened when 1.0 M HCl was added to ethyl 4-amino benzoate, then 6.0 M NaOH, as well as 1.0 M NaOH to benzoic acid, then 6.0 M HCl.

NH2C6H4CO2CH2CH3 + HCl(aq) + NaOH(aq)

C6H5CO2H + NaOH(aq) + HCl(aq)

9 Prelab Week 4 worksheet. Complete and bring to lab with you. This is part of your prelab grade, and can be filled out by following the purification scheme in your book, as well as the online prelab.

componentsupper layer

lower layer

a.

b.

c.

d.

upper layer

lower layer

d.

e.

f.

g.

Procedure for the Experiment 4, Part D Optional Exercise: Isolating a Neutral Compound from a Mixture containing a Base Impurity

1. Measure out ____ g of an unknown mixture containing a compound and a neutral compound.

2. Add this solid and mL of to a screw top centrifuge tube. Mix completely.

3. Add mL of to the tube and mix thoroughly. Removed the layer with a pipette to a labeled test tube.

4. Repeat step 3. 5. Add M to the removed layers in the test tube dropwise until a ppt.

forms. The identity of the ppt. is . 6. To the remaining in the centrifuge tube, add mL of and

mix thoroughly. Remove the layer to a labeled “holding” test tube for later disposal.

7. Transfer the layer, remaining in the centrifuge tube, to a clean, dry test tube. Add to remove the remaining water, wait minutes.

8. Remove the liquid, containing dissolved to a clean, tared container. Evaporate the solvent in the hood (don’t overheat). Determine the mass and melting point of the solid remaining.

10

11 Name____________________________ Lab day/time________________________

Handout for Laboratory, Weeks 3&4: Experiment 4, Extraction Chemistry 221B, Fall 2011

PRELAB Read the following in your lab text: The procedure for Experiment 4, parts A, B and D; Technique 12 (Extraction, Separations and Drying Agents); Technique 8.3, Technique 8, Section 8.3 (Vacuum Filtration); Technique 9, (Physical Constants of Solids: The Melting Point), Week 3 Prelab: Complete the online prelab prior to attending lab and turn in procedure at the beginning of lab. Week 4 Prelab: Complete the proceeding prelab sheet (p. 10 in this book) while doing the online prelab for week 4. This must be done prior to lab. Bring your completed sheet to week 4 lab at the beginning of the period.

PROCEDURE Safety: Methylene chloride (CH2Cl2, or dichloromethane) is a suspected carcinogen. Avoid leaving open flasks and breathing its fumes. Evaporate excess methylene chloride on a water or sand bath in the fume hood. Dispose of methylene chloride in the halogenated organic waste bottle. Diethyl ether is highly flammable, and all sources of heat, sparks, and flames should be avoided when it is in use, as should breathing the vapors. All other organic materials should be disposed of in the regular organic waste bucket; aqueous layers should be combined, neutralized (use a drop of phenolthalein and add acid or base as needed until an endpoint is reached), and poured down the sink.

Follow the procedure in the text for parts A, B, D and D-optional Put your data for part B on the board during week 4, and be sure to obtain class average data on week 4. You should write up a procedure for part D-optional on the week 4 prelab worsheet (p. 10 in this packet), and show the instructor before proceeding. Turn in the extra prelab page stapled to your report. Part A. Extraction of Caffeine Amount of caffeine added:

Calculated theoretical recovery, total mass: —this is the result“Pre-Lab” calculation from the book; complete this calculation on a separate “calculates” paper, and attach to your lab report.

Amount of caffeine recovered (in g):

Percent caffeine recovered (in g): show calculations on the separate “calculations” page

Part B. Distribution Coefficient add your data to the table posted!! Identity compound used:

Amount used (in g):

Amount solid recovered from CH2Cl2 layer (in g):

Distribution Coefficient for this solute between dichloromethane and water: (show calculations on the separate “calculations” page) Class data for distribution coefficients:

12 Part D. Data Neutral component D MP range*_________ mg recovered _______ % recovery ______

Acidic impurity—is there precipitate visible in the first NaOH tube? ____ The second? ____

Neutral component D-optional MP range*_________ mg recovered _______ % recovery ______

Basic impurity-- is there precipitate visible in the first HCl tube? ____ The second? ____

*MP Range contains two values, spanning the temperature range from the point at which the first drop of liquid appears, to the point at which the last solid is converted to liquid

Instructor initials obtained after showing sample recovered

Show calculations for % recovery on calculations page: based on amount of unknown mixture used; you can assume that 0.100 g of neutral component was mixed with 0.050 g of either the acidic or basic impurity. Identity of Neutral component D, and lit MP: Identity of Neutral component D-optional, and lit MP:

Questions 1. Each of the solvents listed below are used in experiments in this course. Will the organic

phase be in the upper or lower layer when each of the solvents is mixed with water? Methylene chloride; pentane; toluene; diethyl ether.

2. Examine the class distribution coefficients calculated in part b. Draw structures for the three solids below, and label each with the average of the class distribution coefficients. Explain whether the average distribution coefficients are what are expected for the relative solubility of the solids in water vs. dichloromethane.

3. Suggest a qualitative test (based on solubility) that would differentiate a pure acidic organic compound from a neutral organic compound. Indicate clearly how the test would be done: steps to be taken, what result would be expected for an acidic compound vs. a neutral compounds. Hint: lab 2 contained a series of qualitative tests. Qualitative solubility tests give different (visible) results for different types of compounds. Answer on the calculations page, attached.

13 Procedure for determining melting points (keep this page for reference):

Your goal is to determine an accurate melting range for your compound. This accomplished in two steps, using two samples 1. Determine approximate melting point using the first sample by heating quickly to up to 200 oC 2. Determine an accurate melting range using the second sample while slowly heating through

the melting range. Step 1: approximate melting point.

a. Prepare two identical melting point samples as indicated in the lab book (1-2 mm, packed firmly)

b. Insert one sample tube into the MP apparatus and turn on the power. Make sure you can see the whole sample, and that the temperature of the apparatus (seen on the electronic meter) is well below the expected melting point of the unknown to avoid premature melting.

c. Set the heating dial to about 7 to heat quickly.

d. Observe the sample carefully and note the temperature at which the sample starts to melt. Quickly stop heating by turning the knob back to zero.

Step 2: melting range

1. Allow the apparatus to cool to 15 oC below the approximate melting temperature.

2. Insert the second melting-point tube, and check to make sure the sample is visible and that it has not begun to melt. Start heating to the set point by turning the knob to a lower number (2-3) and carefully watch your sample to see if it has begun to melt. If after 2 min. the temperature has not risen, turn the knob, one number at a time higher until the temperature begins to rise slowly.

3. The temperature should continue to rise at no more than a few degrees per minute while you observe your sample. When the first drop of liquid appears in the melting point capillary, record this as the initial temperature. Continue to watch your sample until it has completely liquefied. Record this as the final temperature. These two temperatures are the melting point range, often called improperly the "melting point."

4. Return the heating knob to zero, turn off the electronic thermometer, and remove your used melting point capillary. The melting point capillary should be placed into one of the glass waste containers on the bench near the melting point apparatus. You must wait until the temperature is below the desired set-point before you can begin examining a new sample.

Safety/Waste Disposal: Dispose of the melting point tube and unused sample in the indicated waste containers. And remember: the MP apparatuses get hot.

14

15 Week 5: Experiment 3A & D: Crystallization & Melting Points

Chemistry 221B, Fall 2011

Name: Lab day:

Read the experiment (3A and A optional, as well as 3D), and Technique 8, filtration (8.1, 8.2, 8.3, 8.5), Technique 11, crystallization (11.1, 11.2, 11.3) and Technique 9, melting points (9.2-9.5, 9.7)

PROCEDURE:

Perform the prelab calculations for Part A

Minimum amount of boiling ethanol needed: ml

Expected amount of sulfanilamide remaining at zero degrees: g

Show your calculations in the space below

Complete the steps for semi-microscale crystallization of impure sulfanilamide, including concentration of the mother liquor (the “optional” section). If the mother liquor has evaporated, use a small portion of hot ethanol to transfer the residue in the filter flask into a test tube, then concentrate to dryness. Make sure you record masses and melting point ranges for all three solids. The keys to a successful crystallization is to quickly but carefully add a minimum amount of boiling solvent to dissolve the solid, then letting it cool slowly to room temperture before cooling, without agitation.

MAKE SURE YOU OBTAIN AN INSTRUCTOR'S SIGNATURE NEXT TO THE DATA, AFTER OBTAINING YIELDS AND MELTING POINTS, BUT BEFORE YOU DISCARD YOUR SAMPLES IN THE WASTE BOTTLE!

Melting point exercise (Experiment 3D).

1. Pack two tubes with your assigned unknown. Make sure to record the number/letter of your unknown.

2. Determine the precise melting point range of your unknown in two trials.

16 3. Choose at least two likely identities for the unknown, from the samples

provided. 4. Carefully mix crushed samples of your unknown, and the suspected known in a

1:1 ratio. 5. Obtain an accurate “mixed melting point” for the mixture your prepared. 6. Repeat steps 4 & 5 for each known you picked and your assigned unknown, until

you are sure that you have assigned your unknown correctly. Record your assignment.

Safety/Waste Disposal: Dispose of the melting point tube and unused sample in the indicated waste containers.

DATA AND QUESTIONS:

CRYSTALLIZATION:

Mass of Sulfanilamide used: g

Mass of isolated sulfanilamide from crystallization: g Percent recovery (= [mass isolated (g) / mass used] * 100) % show calculations

Melting point range of the impure sulfanilamide: - oC

Melting point range of crystalline sulfanilamide: - oC

Literature melting point: (source of data: )

Mass of sulfanilamide obtained from mother liquor: g

Melting point range of sulfanilamide obtained from mother liquor: oC

ADDITIONAL QUESTIONS

1. Why is the recovery of the first crystals less than 100%? Is the amount of material from the crystals plus the mother liquor crystals 100%? Why or why not?

2. Which is purer, the original crystals, or the material isolated from the mother liquor? How can you tell?

17

3. Using what you know about polarities of ethanol and sulfanilamide (draw their structures), explain why ethanol is a good solvent for this crystallization.

4. Create a graphic representation of the steps you used to purify the sulfanilamide sample via crystallization. This may be in the form of a flow chart, to show steps and what’s removed at each step, or a series of diagrams.

Melting Point Data and Analysis for unknown

1. Unknown number/letter:

2. Approximate melting point of your sample:

3. Exact melting Range of your sample: - oC, e.g. start point-end point oC.

4. Mixed melting point with: , melting range: oC

18 5. Mixed melting point with: , melting range: oC

6. My unknown is: (chemical name)

7. Explain what effects each of the following improper packing techniques for the melting point tube would have on the observed melting point range: (a) too much sample; (b) sample packed too loosely.

8. What two effects does adding an impurity have on the melting point range of a compound?

19 Name: Lab day:

Laboratory, Week 6: Conformational Analysis Chemistry 221B, Fall, 2011 Prior to lab, complete the following reading: Read through this handout to the end; and read Sections 3.6, 3.7, 4.2, 4.4-4.8 in McMurry: Organic Chemistry with Biological Applications, 2e (lecture text); complete the online prelab for week 6. (http://blackboard.csusb.edu)..

BRING YOUR PLASTIC MODELS TO LAB WITH YOU, OR BORROW A SET.

Part 1. Butane

1. Make a plastic model of butane.

2. Look perpendicular to ("down") the 2,3-bond of your (plastic) butane molecule. Begin with the two methyl groups eclipsing one another (0° dihedral angle). Next, rotate your model around the 2,3 bond in 60° increments. Locate each unique conformation, staggered or eclipsed, gauche and anti.

3. Log in to a workstation in CS-333. You will work with your partner. Bring your plastic models and this handout. Open the application “Spartan ES”. Click on the “maximize” button on the upper right, so that the Spartan window fits properly on your screen.

To build a model of butane: 1. • Choose “File/new” 2. • Choose the sp3 hybridized carbon atom from the pallet 3. • Click anywhere on the drawing screen to draw the first carbon atom 4. • Click on one of the ends of the bonds to carbon to attach the second carbon atom 5. • Repeat twice to make butane 6. • Choose File/“Save as” to save molecule with an appropriate name To Minimize this molecular model 7. •Choose “Setup/calculation” 8. • Choose “Equilibrium Geometry”, then “Molecular Mechanics” and “MMFF” on the setup

box, then OK 9. • Choose Setup/“submit” (this submits the calculation, which should take a few seconds) 10. Examine the resulting model 11. • Choose different views from the Model menu 12. • Rotate, translate, and zoom the model using the right/left mouse keys with or without the

control key (try this) 13. • Measure the bond lengths, bond angles, and dihedral angle (to measure dihedral angle,

choose “Geometry”/“Measure dihedral” then click on the four carbon atoms in a row). 14. Record: the minimized dihedral angle:

Now you are ready to create the four conformers extreme conformers for butane (see p. 95, McMurry) You must “constrain the dihedral” angle of the model, at each of the indicated values (0, 60, 120, 180 deg), then minimize each model, by exactly following the steps below:

1. • Choose Geometry/”measure dihedral” Now click on the four carbons of butane in a row from one end of the molecule to the other.

2. • Type the desired dihedral angle value, in the box in the lower right corner of the screen, then choose “Enter”. The model will convert to the desired dihedral angle. Rotate the

20 molecule on the screen with your mouse, to view it from different angles.

3. • Choose “Geometry”/“Constrain dihedral” 4. • Click on the purple lock next to the box in the lower right of screen (Your model should

now show a purple line and lock picture across the central C-C bond.) 5. • Setup and submit the molecule as indicated above (“To Minimize . . .”) except that you

must check the “subject to constraints” box. You can view the energy of each resulting structure: “Display Properties” (given as molar heat of formation in kcal/mol). Record in the table below, the energies of each conformer, and measure dihedrals, and distances between end carbon atoms (with “measure distance”). Leave the final two columns of the table blank, for now.

RECORD DATA for each conformer in this table:

Dihedral angle Distance C1-C4 Energy calculated (kcal/mol)

Relative energy (calculated)

Relative energy from text

0

60

120

180

Calculate the relative energy (calculated) by taking the lowest energy from the “Energy Calculated” column, and subtracting it from each other energy in the column. If you do this calculation correctly, one of the conformers should have a “relative energy (calculated) of zero, and all others should have positive energies. Now, plot the relative energies (calculated) on the y-axis vs. dihedral angle (x-axis) for the four conformers.. Plot a second line in a different color or pattern, showing the energy values from the text (see p. 95 McMurry).

On the graph above, Label each minima and maximum on your graph (minima are "valleys", maxima are "hills"). Then Label each minimum or maximum as either eclipsed or staggered and include syn, gauche, anti etc at needed.

21

Questions:

1. Are the maximum/minimum values from your Spartan calculations the same as the values from the text? Why or why not?

2. Why do some minima have lower energies than others?

Close all files on the screen.

Part B: Cyclohexane chair and boat:

1. With your plastic models, attach 6 sp3 carbons in a ring. Arrange the ring into a puckered “chair”. Show to your instructor if you are unsure if you have a chair. One clue: three of the “H’s” (empty valences) should be “up”, the ring horizontal, three H’s should be “down”. These six up-down positions are called axial.

2. On the computer: To prepare the cyclohexane chair, clear the screen (File/New), then click on “rings” on the building pallet and choose the cyclohexane ring, then click on the main desktop. Setup and submit this calculation, as above.

Data for chair

a. Record the energy of the molecule (kcal/mol)

b. Read and record the C-C-C angles

c. Record the C-C-C-C dihedral angles

d. Record the H-H distances on adjacent carbons (closest H’s)

e. Are there any gauche interactions in your structure?

f. Sketch the model and label the axial and equatorial H’s.

3. Convert your plastic model chair to a boat, by bringing the “foot” of the chair up. Check with your instructor to make sure it is a boat.

22 4. Look down each bond in the boat cyclohexane. Record all eclipsing interactions you see. 5. Are there any significant steric repulsions in your boat model? 6. On the computer: Open the file “cyclohexane twist boat” that is on the desktop. DO NOT minimize this structure. Compare this structure with the boat you built with your plastic models. See if you can convert the boat you built with plastic models into a twist boat. Hint: it is a small movement. 7. Data for Twist Boat (on the SpartanES screen)

a. Record the energy of the molecule (kcal/mol)

b. C-C-C angles (are they all the same?)

c. C-C-C-C dihedral angles (are they all the same?)

d. H-H distances on adjacent carbons (closest H’s)

e. How is this twist boat minimum structure different than a boat?

f. Why did the computer minimized to a twist-boat, and not a boat?

Sketch the twist-boat below.

Close all files on the screen.

Part C. Substituted Cyclohexanes.

After completing part B, this should be easy. Clear the screen (file/new) and use the cyclohexane template to start. Add the diaxial, diequatorial, or equatorial/axial 1,3-dimethyl groups one set at a time, minimize each structure, and record the data below.

Data for disubstituted cyclohexanes

Two methyl groups Distance between methyl carbons

Cis or trans? Energy (kcal/mol)

Relative energy

1,3-diaxial

1,3-diequatorial

1,3-equatorial/axial

Complete this sentence based on your data in the table above:

The _ (more/fewer) _ axial methyl groups, the (greater/lesser) the energy of the molecule.

23

Sketch and label all three dimethylcyclohexane models in three dimensions below.

Close all files on the screen

16D. Cis and Trans-2-butene

File/New. To build 2-butene, choose the “sp2 carbon” atom. Click on the screen to draw the first alkenyl carbon. Then click on the double bonded end of this to add the second alkenyl carbon. Now, choose the “sp3/carbon” atom, and add a carbon to each end of the pi bond, in either cis or trans orientation as needed. 1-butene is prepared similarly, with the alkene on the end. Minimize each alkene structure, using the PM3 semi-empirical method (Setup calculation, semi-empirical, PM3; then Setup/submit), and record the data requested below.

Butene isomer Distance between methyl carbons

Calculated energy (kcal/mol)

Relative energy Relative energy from text

Cis-2-butene

Trans-2-butene

Suggest reasons why the two isomers have different relative energies (see Section 7.5, McMurry).

24

25 Name____________________________ Lab day/time________________________

Handout for Laboratory, Week 7: Experiment 15 Spearmint and Caraway Oil: (+)- and (-)-Carvones

Chemistry 221B, Fall 2011 PRELAB: Read the following before completing your report sheet to help you answer questions and interpret data. Read the Essay on the Stereochemical Theory of Odor (preceding Experiment 15) also read Experiment 15. Also read Technique 22 (Gas Chromatography); Technique 23 (Polarimetry), Technique 25 (IR Spectroscopy. Complete the online prelab, and print out your description of the steps you will do. PROCEDURE:

These samples are expensive. Use as little as possible, and do not contaminate with a dirty pipette or by pouring back sample.

Follow the procedure in the text. All students will perform the odor test for all samples. Each partner will run the IR, GC, and polarimetry for one of the two indicated samples, and make copies for their partners (who will analyze the complimentary sample). Omit boiling point determination. Also note that supervision will be required while using both the Polarimeter and the GC/FID. LABORATORY REPORT: DATA ODORS: 1. Compare the odors of both Spearmint and Caraway Oils. In your own words, describe these odors. Try to make your descriptions depict the characteristic differences and similarities. Spearmint oil: Caraway oil:

2. Now describe the odors of the pure (+) and (-) carvones. Which carvone corresponds to which oil? How are the odors of the pure carvones different from the odors of the oils?

GC DATA Obtain a GC scan for samples of both Spearmint and Caraway oils (not pure). Using the scans in Lab textbook, assign identities to as many peaks as possible. Attach copies of the labeled graphs for both isomers to your lab report

Retention time for major peak of spearmint oil:

Retention time for major peak of caraway oil:

Other likely component(s) of Other likely component(s) of

Spearmint oil: Caraway oil:

Indicate the similarities and differences between retention times and components in the two samples.

26 IR SPECTROSCOPY: Obtain IR spectra for both samples of pure (+)- and (-)-carvone. Include these spectra (clearly labeled as (+)- and (-)-carvone) with your report. Label each non-fingerprint peak with the corresponding bond stretch. (see Table IR. 25.1, in Pavia) -- List the major stretching frequencies in each spectrum in the table below. -- Are there any significant differences between these two spectra (ignoring intensity)? (+) Carvone: Wavenumber at center of stretch (cm-1)

(-) Carvone: Wavenumber at center of stretch (cm-1)

POLARIMETRY Obtain the observed rotation for the individual samples of both pure (+)- and (-)-carvone. Show calculations (+)-Carvone: (note the concentration is the density for carvone, obtained by reference)

Solution Concentration: ______________(g/ml) Cell Path Length: _______________(dm) Observed rotation [α]: _______________ Calculated Specific rotation [α]D

20: _______________

Show calculation of specific rotation: [α]D20= [α]/(conc., g/ml * length, dm)

(-)-Carvone: grams of (+) carvone: g diluted to 10 ml

Solution Concentration: _______________ Cell Path Length: _______________ Observed rotation [α]: _______________ Calculated Specific rotation [α]D20: _______________

Show calculation of specific rotation:

[α]D20= [α]/(conc., g/ml * length, dm)

Compare these two specific rotations [α]D20’s to one another. Be certain to comment on any similarities and differences.

27 ADDITIONAL QUESTIONS

1. Using the Cahn-Ingold-Prelog rules, assign priorities to the groups around the chirality center in carvone (see Chapter 5, McMurry). Draw the structural formulas for (+)- and (-)-carvone with the groups oriented in their correct positions to show the R and S configurations.

2. What measurements were made for the two oils? For the two pure carvone enantiomers?

3. Describe the differences between the four sample analyzed (two oils and two pure carvones), and the relationships between them. Be specific.

4. What measurements are the same for (+) and (-) carvone? Which ones are different?

5. Explain the differences between data (odors, GC scans) for spearmint and caraway oils.

6. Explain why the retention times for both carvone isomers are the same.

7. The toxicity of (+)-carvone in rats is about 400 times greater than that of (-)-carvone. How do you account for the difference in these toxicities?

28

29 Name___________________________________ Lab day/time________________________

Handout for Laboratory, Week 8, Experiment 6A: Simple and Fractional Distillation Chemistry 221B Fall 2011

PRELAB: Read the following in your lab text: Experiment 6A, Technique 13A (Boiling Points); Technique 14 (Simple Distillation); Technique 15A (Fractional Distillation). Complete the online prelab (http://blackboard.csusb.edu) prior to your laboratory period. Turn in your Prelab procedure at the beginning of the period.

Procedure: Follow the procedure for Experiment 6A in the text. We will not be collecting a samples at 1.0 & 4.5 ml for GC analysis. Be aware that we are using the macro glassware (14/20 long joints) with the exception of the 10 mL flask, and that the glassware must be assembled using Kemclamps, lying flat on the table. Obtain your instructor's permission prior to beginning heating. Follow all blue cautionary notes in the text, make sure you use a boiling stone, and discard the final organic material in the non-halogenated waste container. Record your data in the Data Table.

Data Table: Simple Distillation Fractional Distillation mL sample Temp (deg C) mL sample Temp (deg C) 0.5 0.5 1.0 1.0 1.5 1.5 2.0 2.0 2.5 2.5 3.0 3.0 3.5 3.5 4.0 4.0 4.5 4.5 5.0 5.0 5.5 5.5 6.0 6.0 6.5 6.5

Temperature, oC 125

115

105

95

85

75

65

55

ML distilled 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

30 On the grid on the previous page, plot the data obtained for the distillations (mL collected on the x-axis, and distillation temperature on the y-axis). Plot data for both simple and fractional distillation on the same graph, using different colors or symbols. Data Analysis and Questions:

1. Look critically at your data in the table, and on the graph. Record here, the approximate boiling point of the lower boiling component. oC

2. Record here, the approximate boiling point of the higher boiling component. oC

3. Identify which of the two compounds on p. 47 are in your mixture.

Compound 1: Compound 2:

4. What does your graph tell you about the efficiencies of the two distillation methods? (e.g. which would be better at completely separating your two components)?

5. What is the purpose of boiling stones?

6. What errors would be introduced in the data, if the thermometer bulb were placed too high in the distillation column?

7. Why is it dangerous to attempt to carry out a distillation in a completely closed apparatus, one with no vent to the atmosphere?

8. Under what conditions can a good separation be achieved with a simple distillation?

31 Laboratory Handout for Week 9: Gas Chromatographic Analysis of Citrus Oils

Chemistry 221B, Fall 2011 Prelab Read in Pavia, et al.: Technique 22 (Gas Chromatography); the Essay on Terpenes (starting on p 55, Signature and p. 108, hardbound); Technique 12, (Extraction) especially section 12.7 (using a separatory funnel); Read also the sections in Experiment 25, pertaining to unsaturation tests only. Also read the on-line handout identified as “Citrus paper” available on Blackboard, located in the Lab Handouts folder for Chem 221B, and review the notes below. Complete the online prelab quiz prior to your lab section meeting time. Turn in your Prelab procedure at the beginning of the period.

PROCEDURE: Gas Chromatography (GC) In this experiment you will select a citrus fruit from those provided, extract the essential oils (mainly terpenes and terpenoids) from the outer (colored) rind, and analyze the oil by Gas Chromatography (GC). You will need to refer to the standard (reference) chromatogram to complete your report, posted on the laboratory Blackboard page. The GC instruments are set up to obtain a good separation of the components in your citrus extract. It does not matter which you use: the primary difference is in the age of the oven, not in the order, number, or separation efficiency of the GC column. SAFETY: Pentane is very volatile and very flammable. No flames will be permitted in the lab, and evaporation should be completed in the hood. Extraction: Select a citrus fruit (Grapefruit, Lemon, Lime, Orange (Navel or Valencia), Tangerine, or Tangelo). Obtain a 4”x4” square of aluminum foil and record the mass of this sheet of foil. Transfer the citrus fruit onto the sheet of foil and then remove approximately 2.0 g of citrus peel using the cheese grater. Be sure that the rind is grated into very fine particles (use the smallest texture for the grating process, and do not damage the pulp of the fruit, as most of the essential oils will be found in oil sacks within the peel of the fruit). Once you have grated the citrus rind, obtain the mass of the rind. Place the rind in a separatory funnel along with 7.0 mL of pentane. Extract this mixture for approximately ten minutes (be certain to vent the separatory funnel frequently, as pentane is very volatile) and drain the pentane solution into a 50 mL Erlenmeyer flask. Repeat the extraction two more times using two additional 7.0 mL aliquots of pentane. Collect all of the pentane solutions together and then add approximately 1.0 g of sodium sulfate (Na2SO4) to the pentane solution. Cover the Erlenmeyer flask and allow this mixture to stand for approximately ten minutes with occasional swirling. After the solution has dried sufficiently (it no longer appears cloudy), carefully decant the pentane solution into a pre-weighed 60 mL beaker and evaporate the pentane in a sand bath using low heat and a gentle stream of air over the mouth of the beaker. (NOTE: You must use a low heat setting for this evaporation. If you use too much heat for this evaporation, you will decompose many of the essential oils contained in your extract. In addition, you must make sure that this evaporation is performed in the fume hood, as pentane is very flammable.) Once the evaporation is complete, allow the beaker to cool to room temperature and obtain the mass of the crude citrus fruit extract. It should appear as a viscous, amber oil. Dilute the sample with approximately 1.0 mL of dichloromethane (methylene chloride) and transfer the resulting solution into a 3.0 mL conical reaction vial (cap the vial until analysis). Inject approximately 0.25 �L of the dichloromethane solution into the GC or GC/MS and analyze the data. Functional group tests

32 While waiting for the GC (or after you run the GC test) you can test your sample for unsaturation using the bromine and potassium permanganate tests. First, check out a white spot plate from the stockroom. Next, perform the tests on known compounds that will give both positive and negative results: for example cyclohexene and cyclohexane (or whatever saturated, without pi bonds, and unsaturated, with pi bonds, samples are provided.)

To test: place 1 drop of pure, or 2 drops of a solution of your test sample in a single clean well. For the bromine test, add one drop of bromine/CH2Cl2 (0.5%) to the test sample and observe. If the orange color remains, stop adding bromine, and record “1 drop”. If the color is bleached in less than 30 seconds, add a second drop, and continue adding drops slowly until the orange color is no longer bleached. Record the total number of drops of bromine solution needed to keep the color from fading. More than 1-2 drops is a positive test for unsaturation (pi bonds). Record your results in the table below.

For the potassium permanganate test, place one drop of liquid or 2 drops of solution in a clean test well. Add 1-2 drops of potassium permanganate solution, and observe. If the purple color fades, and/or a brown ppt is observed, the test is positive. You may need to pipette away the solution to observe the brown precipitate. Record your results in the table below.

After testing both the known positive and known negative compounds in both tests, place two drops of your terpene/terpenoid solution in a clean well, and perform the bromine test. Then place two drops of your terpene/terpenoid solution in another clean well, and perform the potassium permanganate test.

Make sure you leave some terpene/terpenoid sample in the vial for GC analysis (even if it means omitting one or both unsaturation tests).

33 Name: Lab day:

LABORATORY REPORT: DATA Citrus Fruit Used: ______________________Mass of Citrus Peel Used: __________________

Mass of Citrus Oil Recovered: ____________________Percent Recovery: _________________

Unsaturation test results: Test compound/solution Number drops Br2 needed to color? Brown ppt KMnO4? (yes/no) Cyclohexane Cyclohexene Terpene solution

Make sure your GC scan (or a photocopy) is attached. LABEL YOUR SCAN with the fruit used, and each known peak identified. Identify all peaks you can by a retention time comparison to those compounds present in the standard sample, and write the identity of this peak directly above the peak in question. Each person in each group must turn in a copy of the GC. The compounds most often observed in citrus oils are listed in the table below. The standard retention times (second column of table) are available on the laboratory web site for the GC and GC/MS instruments. You should include in the third column your retention times only for those components in your sample. The largest peak in your spectrum should be limonene. All other assignments are made relative to this peak. It is important to note that not all of these compounds will be found in every citrus fruit extract. Complete the student sample column of the Table below. If you have peaks that don't correspond to any of the peaks in the standard, list them on your GC scan as "unknowns".

Component Standard Sample: Retention Time

Student Sample: Retention time

alpha Thugene alpha-Pinene

Sabinene beta-Pinene

beta-Myrcene p-Cymene

d-Limonene gamma-Terpinene

Terpinolene Linalool

Citronellal

alpha-Terpineol

Neral Geranial

Neryl Acetate Geranyl Acetate alpha-Farnesene beta-Bisabolene

34 The Structures of Common Essential Oils Observed Performing GC or GC/MS Analysis of

O

OH

OH

H

O

H

O

O

O

O

(Z and E isomers of citral)

O

H

Citronellal

alpha-Pinene beta-Pinene

beta-Myrcene D-Limonene gamma-Terpinene

Linalool

Neral*

alpha -Thujene Sabinene

Terpinolene alpha-Terpineol

Geranyl AcetateGeranial*

alpha-Farnesene

Neryl Acetate

beta-Bisabulene

p-Cymene

35 Questions:

1. Examine the structures of the eighteen compounds By labeling the previous page, indicate which of these terpenes and terpenoids are monoterpenes and which are sesquiterpenes. Label each of the compounds listed on the previous page as either a terpene or terpenoid.

2. alpha-Pinene has a boiling point of 155-156 °C, while beta-pinene has a boiling point of 165 - 166 °C. Compare these boiling points to the standard retention times presented in the table. Does the order of elution (value of the retention times) make sense relative to the boiling points? Explain.

3. Apply the isoprene rule to find the isoprene units in the following compounds: (label on

the previous page) (a) alpha-Farnesene; (b) gamma-Terpinene; (c) alpha Pinene 4. Examine the labeled gas chromatograms for a different citrus fruit. What peaks

(compounds) do these two different citrus fruits share in common? What are the differences? Does it appear that the compounds are present in the same relative (approximate) amounts?

5. What is the stationary phase of GC column? The mobile phase of the GC column?

6. Examine the results of your unsaturation tests. Based on the results of your tests, and in reference to the “known” compounds, does your terpene solution appear to be saturated or unsaturated? Is this what you expected, given the structures on the prior page?

7. Write equations below for the reaction of limonene with Br2, and separately with KMnO4. Show correct stereochemistry for the products.