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Chemistry 2312-003

Organic Chemistry I

Midterm Examination II

11:00 am 12:20 pm

Answer Key

November 1, 2012

J. Jeon

Name: _______________Key_________________ Total /110

please print

ID #: ______________________________________

There are 105 points on this exam and the sevenexam pages. For the multiple choice questions 1-14, select the best answerand darken completelywith

a pencilthe space corresponding to that answer in scantron (form # 882-E).

You are free to use molecular models during the exam. For questions15and 16, I will not reconsider grades for answers written in pencil.

Have fun!

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1-2. (10 pts) These problems are about the IUPAC (International Union of Pure and Applied Chemistry)

nomenclature of organic compounds.

1.(5 pts) Select the best name for the following molecule.

Cl

a) (S)-5-Chloro-2,2-dimethylhexane

b) (R)-2,2-Dimethy-5-chlorolhexanec) (2S,5R)-2,2-Dimethy-5-chlorolhexane

d) (2R,5S)-2-Chloro-5,5-dimethylhexane

e) (R)-5-Chloro-2,2-dimethylhexane

2.(5 pts) Select the best name for the following molecule.

F

a) (E)-3-Ethyl-5-fluorohept-5-ene

b) (Z)-5-Ethyl-3-fluorohept-2-ene

c) (E)-5-Ethyl-3-fluorohept-2-ene

d) (Z)-3-Ethyl-5-fluorohept-5-ene

e) (E)-3-Fluoro-5-ethylhept-5-ene

3-6. (20 pts) Label each of the following pairs of structures as constitutional isomers (C), diastereomers (D),

enantiomers (E), or superimposable (S).

3.(5 pts)

EtO2C

Cl

Cl

CO2EtCO2Et

Cl

Cl

EtO2C

a) C b) D c) E d) S

4.(5 pts)

Me

NH2

Me

Br

Me

NH2

Br

Me

a) C b) D c) E d) S

5. (5 pts)

OH

Me NH2

MeH

Me

H2N OH

a) C b) D c) E d) S

6.(5 pts)

O O

a) C b) D c) E d) S

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7. (5 pts) Designate Ror Sconfiguration for each of the chirality centers (A, B, and C).

A

B

C

N

OH

Me MeH

A B C

a) R S S

b) S S R

c) S R S

d) R R S

e) S R R

8. (5 pts) Which of the following compound(s) is (are) meso?

H

Ph

OH

PhH

OH

same as H

Ph

OH

HPh

OH

A A

H

Cl CH3

HCl

CH3

B

a) A

b)B

c)All

d)none

9. (5 pts) Rank the following carbocations in order of stability. (1= most stable, 4= least stable)

A B C D

A B C D

a) 4 1 3 2

b) 3 4 1 2

c) 1 3 4 2

d) 1 4 3 2

e) 3 4 2 1

10. (5 pts) Rank the following alkenes in order of stability. (1= most stable, 4= least stable)

A B C D

A B C D

a) 2 4 3 1

b) 1 2 3 4

c) 2 1 3 4

d) 1 4 2 3

e) 3 1 2 4

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11-12. (5 pts) Consider the following reaction:

Br

Me

HH

+ O

Me

HH

HOH Br+

!H (bonds broken) = 285 kJ/mol !H (bonds formed) = 381 kJ/mol The following rate equation has been experimentally established for this transformation:

rate = k[HO][CH3CH2Br]

The energy diagram for this transformation is shown below:

E

Reaction Coordinate

Br

Me

H

H+OH

O

Me

H

HH Br+

11.Which of the following statements is nottrue?

a) !G, !H, !S, and Keqare thermodynamic factors.

b) The position of equilibrium will be significantly affected by an increase in temperature.

c) The reaction is exothermic.

d) The entropy of system is approximately zero.

e) The reaction is spontaneous.

12.Which of the following statements is nottrue?

a) Activation energy and temperature are kinetic factors.

b) The rate will be faster by an increase in temperature.

c) If the concentration of hydroxide is doubled, the rate will be doubled.

d) The transition state is close in structure to the products.

e) The reaction follows the second order kinetics.

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15.(15 pts) Draw theMajorproduct and a detailed arrow-pushingmechanism (step by step, draw all the

intermediates)for the following reactions in the boxes provided. Specify the correct stereochemistry where

appropriate.

Br

Me NaOMe

MeOH

Br

Me

thermodynamically

more stable conformaiton

kinetically active

"reactive conformer"

NaOMe

Br

MeH

Me

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16.(15 pts) Draw theMajorproduct and a detailed arrow-pushingmechanism (step by step, draw all the

intermediates)for the following reactions in the boxes provided. Specify the correct stereochemistry where

appropriate.

Br

Me NaOMe

MeOH

Et

Br

Me

H

Me

Et

BrH

Me

Et

H Me

BrH

Me

Br

Me

180C

NaOMe

Et

Me

H

Me

MeEt

H Me

Zaitsev

product

Br

MeH

H

Hofmann

product

***** End of Exam *****

You may pick up your exam on Thursday, November 8 (in class). Thank you!