CHEM 281 – Prectice for Final Exam

Spring semester – XXXX

Instructor: Dr. Peggy Paduraru

Student Signature

Please, READ THE QUESTIONS COMPLETELY AND CAREFULLY

Clearly mark the answers in the multiple choice sets: ý or þ Your exam consists of 12

printed pages including this one. The final page of this exam includes a bonus question and

you are permitted to use molecular models.

Question

1 (18)

2 (16)

3 (4)

4 (10)

5 (19)

6 (3)

7 (12)

8 (8)

9 (10)

10 (5) - BONUS

Total (100)

Mark

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

Total

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1. Clearly indicate the right answer for the following multiple choice questions (A to I). (2 marks

each)

A. What is the activation energy for the reaction B ? A in the following diagram?

B. Which one of the following alkyl halides undergoes E1 reactions with the fastest rate?

CH3CHCH3

F

CH3CHCH3

Cl

CH3CHCH3

Br

CH3CHCH3

I

CH3I

C. Which of the following is the best method for preparing CH3Br?

CH3OH + Br

CH3OH + HBr

CH3OH + Br2

CH3OH + NaBr

CH3OH + Br+

D. Which of the following is the most stable cation?

H3CC CH2 C CH3

CH3

H3C CH3C

CH3

CH3

E. What is the name of the major organic product of the following reaction?

CH2=CHC(CH3)3H+, H2O

3,3-dimethyl-1-butanol 3,3-dimethyl-2-butanol 2,3-dimethyl-2-butanol

2,3-dimethyl-1-butanol 4-methyl-2-pentanol F. Which of the following is not a nucleophile?

Br FeBr3 NH3 CH3OCH3

A B C D E

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G. Which of the following is the best nucleophile in water?

I CH3SCH3 CH3OCH3 Cl Br

H. How many proton NMR single ts will 2-bromo-3-methyl-2-butene exhibit?

1 2 3 4 5 G. What are the major products from the following reaction?

HIOH2C

I CH2OH OH CH2I

OCH2I OH I OCH2OH

+ +

+ +

H. Which of the following is the best reaction sequence to use if one wants to accomplish a

Markovnikov addition of water to an alkene with minimal skeletal rearrangement?

water + dilute acid

water + concentrated acid

oxymercuration-reduction

hydroboration-oxidation

I. Which of the following statements about propene, CH3CH=CH2 is correct?

all nine atoms lie in the same plane

the compound has a cis and a trans isomer

all the atoms are sp2 hybridized

it generally acts as a Lewis acid

there is a total of eight sigma bonds

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2. Predict the major products of the following reactions. Include stereochemistry where

appropriate. (2 marks each)

HCl

Br2

CCl4

PhCO3H

H2O

H+

1. Hg(OAc) 2, H2O

2. NaBH4

Br2

CH3OH

H2

Pt

(g)

(a)

(b)

(c)1. BH3, THF

2. H2O2, -OH

(d)

(e)

(f)

(h)

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3. Provide a detailed, step-by-step mechanism for the reaction shown below. (4 marks)

HO Br2O

Br

+ HBr

4. Consider the reaction shown below. CH2CH3

Cl

CH3

H3C CH3

NaOCH2CH3

CH3CH2OH

A

a) Will it proceed by substitution of elimination? What factors determine the most likely

mechanism? (2 marks)

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Stereoisomer 1 Stereoisomer 2

b) Give the systematic name for the starting material (A). (3 marks)

Name:

c) Draw two stereoisomers of compound A and specify their relationship to compound A. (2

marks)

d) Write the expected product and the mechanism by which it forms. (3 marks)

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5. For the following questions (a to e) consider the scheme below as well as the additional

facts.

OH H2SO4

heat+

A

B C

HCl

D EH2O

Facts:

- the 1H NMR of compounds B and C is provided below:

B: 1.01 (d, 6H), 1.71 (d, 3H), 1.87 (m, 1H), 1.92 (m, 2H), 5.48 (m, 1H), 5.52 (m, 1H)

C: 1.06 (t, 3H), 1.11 (d, 6H), 2.0 (m, 2H), 2.52 (m, 1H), 5.47 (m, 1H), 5.50 (m, 1H)

- compounds A and E are constitutional isomers

a. Identify structures B to E in the boxes below. (6 marks: 1.5 marks each)

B C

D E

b. Draw two stereoisomers of compound B and name one of them. (2 marks)

stereoisomer 1 stereoisomer 2

Name

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c. Write a detailed mechanism to account for the transformation below: (4 marks)

d. Draw a reaction coordinate diagram for the transformation above (D → E). Please label

transition state(s) as TS, the rate determining step as RDS and indicate what intermediates (if

any) are involved. Also, on the diagram indicate ∆G‡ and ∆G0. (4 marks)

Progress of reaction

Energy

D EH2O

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e. Starting with compound C identified from the scheme above, synthesize 3 alcohols which

are structural isomers. (Fill in the structure of compound C, the three reaction conditions and

the structure of the three alcohols) (3 marks)

6. Rank the following compounds according to their acidity (3 marks)

H3CCH3

CH3

CH3

OHHO

CO2H

A B C D

Most Acidic Least acidic

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7. In the box above each reaction arrow, please fill in the reagents that would be required to

effect the desired transformation. (12 marks: 2 marks each box)

OH

O

OH

Br

a)

b)

c)

d)

8. Please provide the necessary reagents and conditions to effect the following

transformations (more than one step is necessary for each transformation). (8 marks)

Br

a) HC CH

OH

Hb)

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9. Answer the following questions considering the structures A, B and C below.

O

OH

OCH3

OH

OCH3

A B C a) Show the reagents/conditions for the transformations. (4 marks)

A → B and A → C

b) Is an equimolar mixture of B and C chiral? (circle the one that applies) (2 marks)

YES NO

c) Draw the enantiomer or compound A. (2 marks)

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d) Compare the boiling points of compounds A and C? Explain (2 marks)

10. BONUS QUESTION (5 marks)

How would you accomplish the following transformation (more than one step might be

necessary). Br

Br