mcmp 204 exam #final

MCMP 204 / Final Exam / Fall 2009 Last Name______________________________________

Final Examination

1. (20 points) (a) Fill in the approximate pKa values of the following acids. Choose from

among the following, some of which may be used more than once or not be used at all.

–5 –2 3 10 16 25 32 55

CH3CH2OH2

+CH3CH2OH

H3O

+

HF CH3CH2SH

CH3CH2NH2 HBr

CH3C C H

(b) Compute the Keq for the following reaction. The pKa of HCN is 9.4.

H CN C2H5O C2H5OH CN

Keq = ______________

2. (25 points) Each of the following situations reflect errors found on student exam papers

during the semester. In each case, tell what is wrong and why.

(a) Circle the ONE structure that contains an error. Explain the error BRIEFLY.

H

H

C C

H

H3C

H

C CH

(b) Circle the ONE structure that contains an error. Explain the error BRIEFLY.

CH3

H3CCH3

CH3

CH3

(CH3)2CH CH2CH3

CH3


(c) What is wrong with the following mechanism? Explain BRIEFLY.

C OH

CH3

H3C

CH3

OH2H

+C OH2

CH3

H3C

CH3

+OH2

C

CH3

H3C

CH3

+ OH2

(d) What is wrong with the following transformation as written? Explain BRIEFLY.

CH3CH2CH2 BrMg, ether

CH3CH2CH2 MgBr

O

, H3O+

CH3CH2CH2 CH2CH2OH

(e) What is wrong with the following transformation? Explain BRIEFLY.

CH3CH2 MgBr H3C OH CH3CH2CH3 OH MgBr+


3. (43 points) (a) Circle the ONE compound that has an enantiomer.

Br

CH3HO

CH2CH3

Br

CH3

OH

H3C

Br

CH3

Br

H3C

Br

CH3

(b) Give the structures of ALL enols that would spontaneously revert to the following

ketone: O

HH3C

(c) Which ONE of the following compounds would have UV absorption at the highest

wavelength?

H2C C CHCH2CH3CH3

CH3

CH3

CH3

CH3

CH3

C C CH

CH3H3C

CH3

(d) How many moles of K+ MnO4– are required to convert one mole of

tetrahydrothiophene into sulfolane? A by-product of the reaction is MnO2.

S S

O O

tetrahydrothiophene sulfolane

Answer


(e) Circle the compound that has an NMR spectrum which consists entirely of one singlet

and two triplets.

CH3O

CH3O

CHCH2CH

OCH3

OCH3

CH3CH2 O C O CH2CH3

H3C

CH3

C C

H

H3COCH2

CH2OCH3

H

C(OCH2CH2Cl)4

(f) Circle the ONE compound that could be a product of the following reaction sequence.

CH3

1) B2H6

2) H2O2, OH

(a single enantiomer)

OH

H

H3C

H

CH3

HOH

H

CH3

OH

OH

HH3C

H

(g) Circle the approximate ratio of the C'C stretching frequency to the CAC stretching

frequency in the IR.

3 1 1/3 2/3 2/3 3/2 3/2 1/3

(h) How many p molecular orbitals (bonding plus antibonding) does 1,3,5-hexatriene

have?

H2C CH CH CH CH CH2

1,3,5-hexatriene


(i) Consider the enantiomeric resolution of racemic hydratropic acid, A.

CH

CH3

CO2H

hydratropic acid

A

CH2NH2

benzylamine

CH

NH2

CHCH3

OH

3-amino-3-phenyl-2-propanol

B

C

CH

CH3

CHCH3

OH

3-phenyl-2-butanol

D

A satisfactory resolving agent for enantiomeric resolution of A by the method of

diastereomeric salts would likely be (circle ONE)—

(i) benzylamine B

(ii) the racemate of either diastereomer of C.

(iii) either diastereomer of D, as long as it is enantiomerically pure.

(iv) either diastereomer of C, as long as it is enantiomerically pure.

(v) a 50:50 mixture of enantiomerically pure diastereomers of C.

(vi) none of the above

(j) The compound that has an sp-hybridized carbon (circle ONE):

C CH2

H3C

H3C

H2C C CH2 CH3CHCH2CH3

+H2C C

HC CH3

CH3

+

(k) The carbocation that would undergo rearrangement (circle ONE):

CH3+

+ CH3

CHCH3+

CH(CH3)2+

CH3CHCH2CH2CH3+


(l) Give the name of the compound shown in one of its conformations in the Newman

projection below.

H

CH(CH3)2H

CH2CH3

OH

H3C(the name)

4. (13 points) Consider the molecule taxol (otherwise known as paclitaxel), which is a

naturally derived anti-cancer drug that has been relatively successful in treating breast,

ovarian and lung cancers.

O

O

O

OO

H

OH

OHO O

O

O

OH

NHO

O

AB

Taxol

(a) How many asymmetric carbons does taxol have? _________

(b) Give the stereochemical configurations of carbons A and B in the structure above.

Configuration of carbon A: ________

Configuration of carbon B: ________

(c) Complete the following formula of taxol, given that is has an unsaturation number of

23. (Note that taxol contains one N. Count the Hs if you want, but there is a much

quicker way.)

C47H___________NO13


5. (27 points) Complete the following “chemical crossword” by supplying the structures of the

missing organic compounds or reagents.

H2C CHCH2CH2CH2CH3

1) B2H6

2) H2O2, –OH

alkaline KMnO4, then H3O+

HBr, peroxides

HBr, H2SO4

Mg, ether

D CH2CH2CH2CH2CH2CH3

1) Hg(OAc)2, H2O (solvent)

2) NaBH4

PCC (Cr(VI), anhydrous)

1) OsO4

2) H2O, NaHSO3

H2, Lindlar catalyst


6. (15 points) Outline a multi-step synthesis of (Z)-3-heptenoic acid from 1-pentyne. This

means that you should show all reagents and the organic products of each step (NOT

mechanisms!); no by-products are necessary.

C C

CH3CH2CH2

H

CH2C

H

CH3CH2CH2C CH

OH

O

1-pentyne

(Z)-3-heptenoic acid


7. (15 points) (a) Give a curved-arrow mechanism, and show the stereochemistry of the

product epoxide that forms, when enantiomerically pure (2S,3R)-3-bromo-2-butanol

reacts with hydroxide ion. Make sure that each mechanistic step is shown separately.

C CH3C

H

HO

H

CH3

Br

(2S,3R)-3-bromo-2-butanol

OH (an epoxide A)

(1 molar

equivalent)

(b) An epoxide is also formed when optically pure (2S,3S)-3-bromo-2-butanol, a

diastereomer of the above starting material, is subjected to the same reaction. Give the

structure and stereochemistry of this epoxide. (No mechanism necessary.)

(c) Is the product of (b) optically active? Explain.

mcmp 204 exam #final

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