Practice Final a Solutions

You should allow yourself exactly three hoursto take this exam.

Last Name:

First Name:

Section TF:

Important Notes:

1. This exam consists of 16 problems on 16 pages, plus this cover sheet, and two pages for scratch workat the end of the exam.

2. All answers must be written in the spaces provided. Do not write anything in red ink. Answerswritten on the back of a page will not be graded. Anything written on the scratch page will not be graded.

3. You are allowed to use a set of molecular models for this exam.

SOLUTIONS

1 Name:1. Each of the following transformations can be carried out in three or fewer steps. Fill in the reagentsrequired for each step. If a step is not needed, please put an "X" next to that number. Be sure to consider thestereochemistry (if relevant)!

a)

b)

c)

d)

2.

3.

1.

2.

3.

1.

2.

3.

1.

2.

3.

1.

Br

OO

Cl

OMe

(+/-)

CN

(+/-)

Mg0, Et2Oor

Li (2 equiv.)NaSH

H2O

X

Raney Ni

X

MgBr

H+ workup

CrO3

MeOH,

X

X

NBS, CCl4

NaCN

X

also: 1. KOtBu, tBuOH2. H2, Pd/C

2 Name:1. Each of the following transformations can be carried out in three or fewer steps. Fill in the reagentsrequired for each step. If a step is not needed, please put an "X" next to that number. Be sure to consider thestereochemistry (if relevant)!

a)

b)

c)

d)

2.

3.

1.

2.

3.

1.

2.

3.

1.

2.

3.

1.

CH3 CH3

(+/-)

Br

Br

O

O

O

O

OO

OHO

HO

O

(+/-)

Na0, NH3

CH2I2, Zn/Cu

X

Br2

X

HBr

KOtBu,tBuOH

Br2

H3O+conc.H2SO4

conc.H2SO4

Br2

O,

OsO4

NaHSO4, H2O

NBS, CCl4

KOtBu, tBuOH

mCPBA

3 Name:3. Fill in each box with the major organic product of the indicated transformation. Be sure to give thestereochemistry of each if it is relevant (e.g., whether it is racemic / single enantiomer)! Any chiral startingmaterials are pure, single enantiomers unless otherwise specified.

a)

b)

c)

d)

OH1. SOCl2, pyridine

2. KI

OTs

KOtBu

tBuOH

D2O

cat. D2SO450 C

D2O

cat. D2SO478 C

I

DOD

D

OD

(+/-)

4 Name:4. Fill in each box with the starting material of the indicated transformation. Be sure to give thestereochemistry of each if it is relevant (e.g., whether it is racemic / single enantiomer)! Any chiral productsare pure, single enantiomers unless otherwise specified.

a)

b)

c)

d)

1. BH3, THF

2. NaOH, H2O2

1. NaNH2, NH3

2.3. Na0, NH3

Br

(1 equiv.)

conc. H2SO4 O

O

O

CH3

H OH

CH2CH3

HH3C

H3C

O

O

HOOH

or

HO

5 Name:

5. Consider the alkene below.

a. Provide the best possible systematic name for this alkene in the box below. You may ignore R/Sdesignations.

c. Assign R/S configurations or hybridizations, as appropriate, to each of the atoms circled in the moleculebelow.

N

O

H3C

H

O

O

Ph

OH

b. In the box below, provide the best possible systematic name of a compound that would be adiastereomer of the alkene shown above. You may ignore R/S designations.

(circle one)R S

(circle one)R S

(circle one)

sp sp2 sp3

(circle one)

sp sp2 sp3

(E)-4-isopropyl-5,6,6-trimethyl-3-heptene

(Z)-4-isopropyl-5,6,6-trimethyl-3-heptene

6 Name:6. Carefully consider the structures of each of the compounds depicted below.

(a) Draw this compound in its most stable conformation.

OH

(b) Draw this compound in its most stable conformation.

H

H

H H

(c) Draw this compound using a clear 3-D representation.

O O

O

O

OH

H

OCH3

CH3

O

O

O

7 Name:

7. Consider the following synthetic transformation:

Two E-2a students proposed different synthetic routes to the indicated product:

b. Briefly explain why only that synthetic route worked. Your explanation must include both chairconformation drawings and "cartoon" orbital sketches for full credit. You do not need to draw any curved-arrow mechanisms.

HOH

H H

H

Barney suggested: 1. TsCl, pyridine; 2. KOtBu, tBuOH

Phil suggested: 1. SOCl2, pyridine; 2. KOtBu, tBuOH

a. Only one of these proposals gave the desired product. Which student was successful?

(circle one)

Barney Phil

Barney: TsCl gives a leaving group with retention of stereochemistry, which allows the idealorbital overlap for an E2 elimination.

OTsH

H

H

H

OTs

H

OTs*CO

CH

Phil: SOCl2, pyridine gives a leaving group with inversion of stereochemistry, and thus it cannotpossess any antiperiplanar orbital overlap!

ClH

H

H

H

Cl No periplanar orbitals!

8 Name:

8a. Provide a complete curved-arrow mechanism for the following transformation.

b. For the molecules shown below, draw a "cartoon" orbital sketch of the indicated frontier molecularorbitals (HOMO and LUMO) in the boxes provided.

O

ONO2O2N

NO2

NO2

LUMO LUMO

HOMO HOMO

For adiene: For a

dienophile:

+ CO2

O

O

NO2

NO2

O NO2

NO2

O

9 Name:

9. In the presence of a secondary amine, the reagent N-iodosuccinimide (NIS), is observed to react withalkenes as shown below:

a. Provide a complete curved-arrow mechanism for this transformation and, for every step, identify all thefrontier molecular orbital (donor/acceptor) interactions involved. Note that you only need to name theorbitals; you do not need to draw either energy-level diagrams or "cartoon" orbital sketches. Keep in mindthat this reaction is observed to be both stereospecific (giving only anti addition) and regiospecific (givingonly the product with the iodine on the secondary carbon); the mechanism you propose must be consistentwith these observations.

b. Based on your answer above, provide a complete curved-arrow mechanism for the followingtransformation. You need not identify the frontier molecular orbital interactions for this part.

+ NI

O

O

HN(CH3)2

I

N(CH3)2+ N H

O

ON-iodosuccinimide

(NIS)

(as a racemic mixture)

HO

H

NI

O

O

N H

O

OO

I+ +

NI

O

O

I

(+/-)

HN(CH3)2

I

N(CH3)2

(+/-)

H

Products

:N

O

O

Donor1: CCAcceptor1: *NIDonor2: nIAcceptor2: *CC

Donor: nNAcceptor: *CI

Donor: nN-Acceptor: *NH

HO

IO

I

H

:N

O

O

10 Name:

10. The following transformation should look at least somewhat familiar to you.

a. Provide a complete curved-arrow mechanism for this transformation. You may invoke solvent ("Sol:") fordeprotonations where necessary.

b. Draw the product of the following analogous reaction in the box below in its most stable conformation.You do not need to draw a curved-arrow mechanism.

Hg(OAc)2, H2SO4

HOOH

O

O

CH3

H3CHO OH

Hg(OAc)2, H2SO4

Hg

OAc

OAc

Hg

OAc

HOOH

HOO

H

PhH

HgOAc

:sol

HOO

PhH

HgOAc

H+HOO

PhH

HgOAcPh

O

HO

H+

O

PhOHO

O

CH3 H :solO

O

CH3

OO

11. You have just synthesized a new compound, and the following spectroscopic data is obtained: From the mass spectrum, you deduce that the molecular formula is: C15H24

The proton NMR spectrum (with expansions) is:

The infrared spectrum is:

Draw your best choice for the structure of this molecule in the box below.

From the infrared spectrum, circle the functionalgroups that are definitely present:

From the infrared spectrum, circle the functionalgroups that are definitely absent:

O H C O C C C N/C O C C

11 Name:

C CC N/C C/N H O H/N H

ppm

0540060080001002100410061008100020022004200620082000300230043006300830004WAVENUMBERS

0

10

20

30

40

50

60

70

80

90

100

%TRANSMITTANCE

12 11 10 9 8 7 6 5 4 3 2 1 0

1H

1H

6H

2.86 1.25

12. You have just synthesized a new compound, and the following spectroscopic data is obtained: From the mass spectrum, you deduce that the molecular formula is: C6H11NO2







12 Name:

C CHC N/C C/N H O H/N H

ppm

0540060080001002100410061008100020022004200620082000300230043006300830004WAVENUMBERS

0

10

20

30

40

50

60

70

80

90

100

%TRANSMITTANCE

12 11 10 9 8 7 6 5 4 3 2 1 0

1H 2H2H

6H

4.45 2.41 1.94

OCH3

H3CO CN

13. You have just synthesized a new compound, and the following spectroscopic data is obtained: From the mass spectrum, you deduce that the molecular formula is: C4H6O2







13 Name:

C CHC N/C C/N H O H/N H

ppm12 11 10 9 8 7 6 5 4 3 2 1 0

1H

1H

1H

4.2 2.5 2.3

0540060080001002100410061008100020022004200620082000300230043006300830004WAVENUMBERS

0

10

20

30

40

50

60

70

80

90

100

%TRANSMITTANCE

O

O

14

Starting Materials:

Name:

14. Provide a complete synthesis of the following desired product from the indicated starting material,cyclopropanol, plus any alkynes with four or fewer carbons. You may use any inorganic reagents you wish.The correct answer will require six or fewer total steps.

Desired Product

OH

cyclopropanol

O

Cl


plus any hydrocarbonswith four or fewer carbons

HC CHH2

Lindlar cat.H2C CH2

HBrBr

Compound A

1. NaNH2, NH3

2. Cmpd. A

H2

Lindlar cat.

OH

Cl2,

15

Starting Material:

Name:

15. Provide a complete synthesis of the following desired product from the indicated starting material, plusany inorganic and organic reagents you wish, but all carbons from the starting material must end up in theproduct. You may ignore stereochemistry. The best answer will require five or fewer total steps.

Desired Product

OEt

EtO

1. O3

2. Me2S

CHO

CHO

NaBH4

MeOH

OH

OH

1. NaH (xs or 2 equiv.)2. EtBr (xs or 2 equiv.)

PBr3 (or otherleaving groups

are OK)

Br

Br

NaOEt,EtOH

16

Starting Material:

Name:

16. Provide a complete synthesis of the following desired product from the indicated starting material,fumaric acid. You may use any organic or inorganic reagents you wish. The correct answer will require threeor fewer total steps.

Desired Product


HOOH

O

Ofumaric acid

OHHO

O

OOHO

OHO

CO2H

CO2H

(+/-)

1. O32. H2O2

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Practice Final a Solutions

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