ch 4 alkanes

Chapter 4 1. What is the IUPAC name for the following compound?

A) 7,7 diethyl-5-isopropyl-3,4-dimethyldecane B) 7,7-diethyl-5-isopropyl-2,3-dimethyldecane C) 7,7-diethyl-4-isopropyl-2,3-dimethyldecane

Ans: B

2. Give the IUPAC name for the following compound.

A) 7,7-diethyl-2,4,5-trimethylnonane C) 6-ethyl-2,4,5-trimethyloctane B) 7-ethyl-2,4,5-trimethyloctane

Ans: A


A) 4,4-diethyl-2,3,6-trimethylnonane C) 5,5-diethyl-2,3,6-trimethylnonane B) 5,5-diethyl-4,7,8-trimethylnonane

Ans: C


A) 2,5-dimethyl-3-t-butylheptane C) 2,5-dimethyl-4-t-butylheptane B) 2,5-dimethyl-4-t-butylhexane

Ans: C


A) 7-ethyl-6-isobutyl-3-methylundecane C) 7-ethyl-6-isobutyl-3-methyldecane B) 7-ethyl-6-isobutyl-3-methylnonane

Ans: C


A) 5-sec-butyl-2,4-dimethylnonane C) 6-sec-butyl-3,5-dimethyldecane B) 6-sec-butyl-2,4-dimethyldecane

Ans: C


H

HH

CH3H3C

A) 2-methyl-4-isopropylheptane C) 3-methyl-5-isopropylhexane B) 2-methyl-4-isopropyloctane

Ans: A


A) 1-sec-butyl-4-isopropyl-2-methylcycloheptane B) 1-sec-butyl-4-isopropyl-2-methylcyclohexane C) 1-sec-butyl-3-isopropyl-3-methylcyclohexane

Ans: B


HH

H

A) 4-ethyl-5-isopropylnonane C) 5-ethyl-4-isopropylnonane B) 5-ethyl-4-isopropyloctane

Ans: C


A) 5-sec-butyl-7,7-diethyl-2,3-dimethyldecane B) 4-sec-butyl-6,6-diethyl-2,3-dimethyldecane C) 5-sec-butyl-7,7-diethyl-2,3-dimethylundedecane

Ans: A


A) 6-isobutyl-3,7-dimethyl-7-propyluncedecane B) 4-isobutyl-2,5-dimethyl-5-propylnonane C) 5-isobutyl-2,6-dimethyl-6-propyldecane

Ans: C


A) 4-isobutylyl-2-methylhexane C) 4-isopropyl-2-methylheptane B) 4-isopropyl-3-methylheptane

Ans: B


A) 5,5-diethyl-2,3,6-trimethyldecane C) 4,4-diethyl-2,3,6-trimethylnonane B) 5,5-diethyl-2,3,6-trimethylnonane

Ans: B


A) 3,6-diethyl-4,4,5-trimethylnonane C) 2,5-diethyl-3,3,4-trimethyloctane B) 2,5-diethyl-3,3,4-trimethylnonane

Ans: A

15. The preferred conformation of cis-3-t-butyl-1-methyl-cyclohexane is one in which: A) the t-butyl group is axial and the methyl is equatorial. B) the methyl group is axial and the t-butyl group is equatorial. C) both groups are axial. D) both groups are equatorial. E) None of the choices are correct.

Ans: D

16. Which represents the ring-flipped conformer of a?

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

17. Consider the molecule cis-1-ethyl-3-isopropylcyclohexane. Which is the overall most-stable conformer?

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

18. Which of the following structures represents the most stable form of 1-isopropyl-2-methylcyclohexane?

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

19. Select the most stable conformer of cis-1, 3-cyclohexane diol.

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

20. Rank the indicated conformations in order of decreasing stability.

A) A

22. Which of the following conformations of 1,2-dibromoethane is the most stable?

A B C D

H Br

H

H

H Br

H Br

H

H

Br H

Br

HHH

H

Br

Br

HHH

Br

H

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

23. Given the three Newman projections drawn below, rank them in order of increasing stability.

A) B

25. Assuming that the size of substituents is H

27. The graph below shows the energy changes that occur during rotation around the CC bond indicated in compound a. Which letter(s) on the graph correspond(s) to this Newman Projection?

A) A and G B) B and F C) C and E D) D Ans: D

28. Consider rotation about the indicated bond in the molecule below. Which Newman Projection best represents the most stable conformer of the molecule during rotation about the indicated bond?

A) A B) B C) C Ans: A

29. Which statement about the following conformers of the same compound is true?

A) B is the most stable and A is the least stable. B) A is the most stable and B is the least stable. C) C is the most stable and A is the least stable. D) B is the most stable and C is the least stable. E) A is the most stable and C is the least stable.

Ans: E

30. How are the molecules below related to each other?

A) They are constitutional isomers. B) They are identical. C) They are resonance structures. D) They are not isomers; they are different compounds. E) They are stereoisomers.

Ans: C



Ans: A



Ans: B



Ans: A



Ans: D



Ans: C

36. Which of the following statements is (are) true about the following compound?

A) Ca and Cd are 1 carbons. B) Cb and Cc are 3 carbons. C) Ce and Ca are 2 carbons. D) (Ca and Cd are 1 carbons) and (Cb and Cc are 3 carbons). E) (Cb and Cc are 3 carbons) and (Ce and Ca are 2 carbons).

Ans: E

37. Which of the following statements is (are) true about compound B below?

Ca

Cb

Cc

B

A) Ca and Cb are quaternary. B) Cc is primary. C) Ca is quaternary. D) Cb is tertiary. E) Cc is primary, Ca is quaternary, and Cb is tertiary.

Ans: E

38. Predict the most stable conformation of cis-1-isopropyl-4-ethylcyclohexane. A) The isopropyl group is axial and the ethyl group is equatorial. B) Both groups are axial. C) Both groups are equatorial. D) The isopropyl group is equatorial and the ethyl group is axial. E) There is no way to predict for this molecule.

Ans: D

39. Which of the following equations is correct for the combustion of cyclohexane? A)

B)

C)

D)

E)

Ans: B

40. What is the relative position of the substituents A and B to each other in the following conformation?

A) Anti B) Eclipsed C) Syn D) Gauche Ans: D

41. Which of the following Newman projections represents the most stable conformation of 2,3-dimethylbutane?

A B C D

H3C CH3

CH3

H

H3C H

H CH3

CH3

CH3

H CH3

H3C H

CH3

CH3

H CH3

H H

CH3

CH3

H3C CH3

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

42. Which of the following statements best explains the reason for the relative stabilities of the two conformers shown below?

CH3

H CH3CH3

HHH3C

H3CH

CH3

HH

A. B.

A) A has more torsional strain; B has more steric strain. B) A has more steric strain; B has more torsional strain. C) A and B have the same torsional strain. D) A and B have the same steric strain. E) A and B have similar steric strain; B has more torsional strain.

Ans: E

Challenge Questions


H

H HH

HH

A) 4-isobutyl-2-ethyl-1-isopropylcyclohexane B) 4-sec-butyl-2-ethyl-1-isopropylsyclobutane C) 4-sec-butyl-2-ethyl-1-isopropylcyclohexane D) 2-ethyl-4-isobutyl-1-isopropylcyclohexane E) 1-isopropyl-2-ethyl-4-secbutylcyclobutane

Ans: C

44. Which of the following cyclohexane derivatives is most stable?

A B C D

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

45. (3Z)-Dactomeleyne has been isolated from the digestive glands of the sea hare Aplysia dactylomela. In the 1995 synthesis by E. Lee and co-workers, the compound below undergoes a reduction reaction to produce one of the late stage intermediates. Identify a possible product from this reaction.

O

OCl

OH

CO2CH3

Br ?

O

OCl

OH

COCl

Br O

OCl

O

CO2CH3

Br O

OCl

OH

BrO

OCl

OH

CO2CH3

Br

OH

A B C D

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

46. Cryptophycin C is a marine natural product with anti-cancer activity. An intermediate in its synthesis is shown below. Identify the most stable Newman projection looking down the C2-C3 bond.

O NHBoc

OOHO 12

3

45

(intermediate for Cryptophycin C)

H

H

H

OHO

O

OH

BocHN

H

HHOHO

O

OH

BocHN

A B C

H

H

H

OHO

O

OH

BocHN

A) A B) B C) C Ans: A

47. How is each molecule (i-iv) related to compound A?

O OH

OH

MeO

OMe

NH2Compound A

O OH

OH

MeO

OMe NH2

ii iii iv

OHO

OH

OMe

OMe

NH2

iO H

MeO

OH

OMe

OHNH2

O HMeO

OMe

OHNH2HO

A) i) Constitutional isomer, ii) stereoisomer, iii) identical, iv) stereoisomer B) i) Stereoisomer, ii) constitutional isomer, iii) identical, iv) stereoisomer C) i) identical, ii) constitutional isomer, iii) identical, iv) stereoisomer D) i) stereoisomer, ii) identical, iii) constitutional isomer, iv) identical

Ans: C

ch 4 alkanes

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