Your name: ______________________________________

Chem 140B Winter 2013, Final Examination, Friday, 22 March, 2013, 8 11 AM Directions: Answer the questions contained in this examination to the best of your ability and according to the instructions for each question. Partial credit will be awarded where appropriate. Exams completed using pencil will not be eligible for regrade. If using ink, only black or blue ink is allowed. Using erasable ink will be treated as if pencil was used. Each question is presented on a different sheet of paper. Answers MUST be on the same page as the question they pertain to; otherwise no credit will be awarded. Use the back of each sheet of paper for scratch work. DO NOT detach any pages from your exam! Once you turn in your exam, you must leave the room. Below, give your name, ID number, and signature. By signing you agree to abide by UC San Diego policies, rules, and regulations regarding academic integrity and cheating. Name:_____________________________________ ID #_________________________ Signature:__________________________________ Policy on cheating: Molecular model kits are the only aids allowed during these examinations. Using notes, crib, or cheat sheets; using notes written or otherwise printed on clothes, skin, or personal belongs; conversing with other students during the exam; using any electricity-powered device; and/or using books or bound material of any sort are considered forms of cheating, and will be disciplined to the fullest extent of UCSD academic code and procedures. UCSD-issued student ID cards ARE REQUIRED DURING THE EXAMINATION and will be checked for validity DURING the exam. Failure to provide valid ID during an examination will result in a score of zero. By signing above, (1) you agree to abide by the terms and conditions set forth on this page and (2) acknowledge that you can read, write, and follow directions in English.

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Question 1. Predict the product of the following reactions. Disregard any possibility for lactone (cyclic ester formation) or internal hemiacetalization. (5 points each)

HO

O O O

OMe

excessMeMgBr

then HCl

HO

O O O

OMe

excessNaBH4

then HCl

HO

O O O

OMe

excessMeLi

then HCl

HO

O O O

OMe

excessiBu2AlH

then HCl

HO

O O O

OMe then HCl

excess NaNH2,

Ph3P CH3Br

HO

O O O

OMe

SHHS

TsOH

excess

Your name: ______________________________________

Question 2. Please select reactants and provide reagents to complete the following synthesis. You may use any reagent that you have ever seen in your entire life, but should not require anything NOT found in your textbook. (15 points)

Possible starting materials (you are NOT limited to these, but TWO of these are recommended.

OO

Me

MeOO

Me

Me

O

O MeMe Me Me

OO

O

O O

HOOH

O

O HO OH

Your name: ______________________________________

Question 3. Rank the following four molecules according to their reactivity as electrophiles (imagine water is the nucleophile), where 1 is most reactive and 4 is least reactive. (5 points)

A: 1>2>3>4 G: 2>3>4>1 M: 3>1>2>4 S: 4>1>2>3 B: 1>3>4>2 H: 2>4>1>3 N: 3>2>4>1 T: 4>2>3>1 C: 1>4>2>3 I: 2>1>3>4 O: 3>4>1>2 U: 4>3>1>2 D: 1>2>4>3 J: 2>3>1>4 P: 3>1>4>2 V: 4>1>3>2 E: 1>3>2>4 K: 2>4>3>1 Q: 3>2>1>4 W: 4>2>1>3 F: 1>4>3>2 L: 2>1>4>3 R: 3>4>2>1 X: 4>3>2>1

Question 4. Rank the following four molecules according to their reactivity in aromatic bromination using diatomic bromine and iron(III) bromide as a catalyst, where 1 is most reactive and 4 is least reactive. (5 points)

A: 1>2>3>4 G: 2>3>4>1 M: 3>1>2>4 S: 4>1>2>3 B: 1>3>4>2 H: 2>4>1>3 N: 3>2>4>1 T: 4>2>3>1 C: 1>4>2>3 I: 2>1>3>4 O: 3>4>1>2 U: 4>3>1>2 D: 1>2>4>3 J: 2>3>1>4 P: 3>1>4>2 V: 4>1>3>2 E: 1>3>2>4 K: 2>4>3>1 Q: 3>2>1>4 W: 4>2>1>3 F: 1>4>3>2 L: 2>1>4>3 R: 3>4>2>1 X: 4>3>2>1

O NH2 O OEt

O Cl O O

O

Me

1 2 3 4

Your answer:

OMe

MeO OMe

HN

O

Me O2N

NO2

NO2Me

Cl

1 2 3 4

Your answer:

Your name: ______________________________________

Question 5. Please supply reagents to complete the synthesis of racemic ibuprofen from isobutylbenzene according to the scheme below. You may use any reagents that you have seen in your entire life, but you should not need any reagent NOT found in your textbook. (25 points each step)

STEP ONE: STEP TWO: STEP THREE: STEP FOUR: STEP FIVE:

Me

Me

isobutylbenzeneMe

Me Me

O

Me

Me Me

OH

Me

Me Me

Cl

Me

Me Me

CN

Me

Me Me

COOH

racemic ibuprofen

STEPONE

STEPTWO

STEPTHREE

STEPFOUR

STEPFIVE

Your name: ______________________________________

Question 6. The following three reactions WILL NOT WORK as written (either no chemical reaction will take place OR the product drawn will not be generated). In each case identify the flaw in the reaction and then provide a solution (hint: the fix will usually involve replacing one reactant or reagent with another that will produce the desired product). NOTE: you may change EITHER the reactant(s) OR the reagent(s), but NOT BOTH. (10 points each for A, B, and C) A

Problem: Fix: B

Problem: Fix: C

Problem: Fix:

Me OH

OOOMeMgBr

MeOO

MeMe

OH

Me

OOOH

Jones oxidation

Me OH

OOO

Me OH

OOORaney nickel

Me OH

O

Your name: ______________________________________

Question 7. Please supply reagents to accomplish the following syntheses. You may use any reagents that you have ever seen in your entire life, but you should not need reagents NOT presented in your textbook. (10 points each for A, B, and C) A

step one: step two: B

step one: step two: C

step one: step two:

Me Br MeN

O

Me

Me

TWO STEPS ONLY

OH TWO STEPS ONLY

Me

Br BrBr

TWO STEPS ONLY

Your name: ______________________________________

Question 8. The following reaction is an example of a Favorskii ring contraction. Please provide a mechanism using the curved arrow formalism. Start by attacking the carbonyl with hydroxide ion. (15 points)

MeMe

OBr MeMe

CO2Haqueous NaOH

aqueous HClworkup

Your name: ______________________________________

Question 9. The invention and development of carbodiimide reagents was strongly motivated by the need to make new -lactam antibiotics related to penicillin. Below, diisopropyl-carbodiimide (DIC) was used to form an amide bond intramolecularly. Please provide a mechanism for this process using the curved arrow formalism. Do not abbreviate proton transfers. (15 points)

NH

HOOC

S MeMe

OO

RHN

N

S MeMe

OO

RHN

O

N C NiPr iPr

Your name: ______________________________________

Question 10. Please select reactants and provide reagents to complete the following synthesis. You may use any reagent that you have ever seen in your entire life, but should not require anything NOT found in your textbook. (15 points)

HOOH O

OMeOMeO

OMe

OO

MeO

O

OO

O

O

O

MeO

O

OMe

OO

O OHHO

OO

O OHHO

Possible starting materials (you are NOT limited to these, but TWO of these are recommended.

Your name: ______________________________________

Question 11. Propose a structure consistent with the following data. The integrals are given in the top left frame, which is also the expanded view of the entire 1H NMR spectrum. The other three frames are zoomed in. Note: the signal at 7.26 PPM is residual solvent for the sample. (10 points) Formula: C4H8O

Your answer:

8.2 to 0.2 ppm 7.0 to 6.0 ppm

4.4 to 3.5 ppm 1.8 to 0.8 ppm

11

1

2

3

J = 6.85, 14.3 Hz

J = 1.70,14.3 Hz

J = 1.70,6.85 Hz

J = 6.90 Hz

J = 6.90 Hz

Your name: ______________________________________

Question 12. Propose a structure consistent with the following data. (10 points) Formula: C6H4INO2 (each signal below integrates to 1)

Your answer:

J = 8.00 Hz

J = 8.00 Hz

J = 7.45 Hz

J = 7.45 Hz

Your name: ______________________________________

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