CHEMISTRY

Topics: Chlorine, Stereochemistry, Hydrogen Pages: 73 (5330 words) Published: October 28, 2013
Keghan
Chapter 8

MULTIPLE CHOICE QUESTIONS
Topic: Structure Elucidation
1. An alkene adds hydrogen in the presence of a catalyst to give 3,4-dimethylhexane. Ozonolysis of the alkene followed by treatment with zinc and acetic acid gives a single organic product. The structure of the alkene is:

CH3
A)

CH3CH=C-CHCH2CH3

(cis or trans)

CH3
CH3

B)

CH3CH2C=CCH3

(cis or trans)

CH2CH3
C)

CH3
CH2=CCH2CHCH2CH3
CH3
CH2

D)

CH3CH2CCHCH2CH3
CH3
CH3

E)

CH3CH2CHCHCH=CH2
CH3

Ans: B

241

Keghan
Chapter 8

Topic: Structure Elucidation
2. Ozonolysis of compound Z yields the products shown below. What is the structure of Z? O

Z

1) O3
2) Zn, HOAc

O

2HCH + CH3CCH2CH

O

I

II

III

O
H

IV
A)
B)
C)
D)
E)

O

V

I
II
III
IV
V
Ans: B

242

Keghan
Chapter 8

Topic: Structure Elucidation
3. Compound C has the molecular formula C7H12. On catalytic hydrogenation, 1 mol of C absorbs 1 mol of hydrogen and yields a compound with the molecular formula C7H14. On ozonolysis and subsequent treatment with zinc and acetic acid, C yields only: O

O

The structure of C is:

I

II

IV
A)
B)
C)
D)
E)

III

V

I
II
III
IV
V
Ans: E

Topic: Structure Elucidation

4. Compound X has the molecular formula C6H10. X decolorizes bromine in carbon tetrachloride. X also shows IR absorption at about 3300 cm-1. When treated with excess hydrogen and a nickel catalyst, X yields 2-methylpentane. The most likely structure for X is:

A)
B)
C)
D)
E)
Ans: D

243

Keghan
Chapter 8

Topic: Structure Elucidation
5. An unknown compound, A, has the molecular formula C7H12. On oxidation with hot aqueous potassium permanganate, A yields CH3CH2COOH and (CH3)2CHCOOH. Which of the following structures best represents A?

A)
B)
C)
D)
E)
Ans: C

244

Keghan
Chapter 8

Topic: Structure Elucidation
6. Determine a possible structure for an alkene, X, formula C9H14, on the basis of the following information: X adds one mole of hydrogen on catalytic hydrogenation. On treatment with hot basic KMnO4 followed by acidification, X yields the following dicarboxylic acid.

O

HO

OH

O

A possible structure for X might be:

I

II

IV
A)
B)
C)
D)
E)

III

V

I
II
III
IV
V
Ans: C

Topic: Structure Elucidation
7. An optically active compound, Y, with the molecular formula C7H12 gives a positive test with cold dilute KMnO4 and shows IR absorption at about 3300 cm-1. On catalytic hydrogenation, Y yields Z(C7H16) and Z is also optically active. Which is a possible structure for Y?

A) CH3CH2CH2CH2CH2CCH
B) (CH3)2CHCH2CH2CCH
C) CH3CH2CH(CH3)CH2CCH
D) CH3CH2CH(CH3)CCCH3
E) CH2=CHCH(CH3)CH2CH=CH2
Ans: C

245

Keghan
Chapter 8

Topic: Structure Elucidation
8. One mole of an optically active compound, X, with the molecular formula C6H8 reacts with three moles of hydrogen in the presence of a catalyst to yield an optically inactive product that cannot be resolved. X also exhibits IR absorption at approximately 3300 cm-1. Which is a possible structure for X?

A) (E)-4-hexen-1-yne
B) (Z)-4-hexen-1-yne
C) (E)-2-hexen-4-yne
D) 2-methyl-1-penten-3-yne
E) 3-methyl-1-penten-4-yne
Ans: E
Topic: Structure Elucidation
9. An alkene with the molecular formula C10H18 is treated with ozone and then with zinc and acetic acid. The product isolated from these reactions is: O

O

What is the structure of the alkene?

I

II

III

IV
A)
B)
C)
D)
E)

V

I
II
III
IV
V
Ans: C

246

Keghan
Chapter 8

Topic: Structure Elucidation
10. An optically active compound, A, with the molecular formula C7H12 reacts with cold dilute KMnO4 and gives IR absorption at about 3300 cm-1. On catalytic hydrogenation, A is converted to B (C7H16) and B is also optically active. Which is a possible structure for A?

I

II

III

IV
A)
B)
C)
D)
E)

V

I
II
III
IV
V
Ans: E

Topic:...
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