Chapter 5 Ochem

Your task is to convert 2-bromobutane to 1-butene in highest yield. Which reagents would you use?

(CH3), 3COK/(CH3)3COH

Your task is to convert 2-bromobutane to 1-butene in highest yield. Which reagents would you use?

(CHa)COK/(CHa),COH

20. If a solution of a compound (30.0 g/100 mL of solution) has a measured rotation of +15° in a 2.0 dm tube, the specific rotation is:

+25°

The p orbital of a methyl cation, CH,', contains how many electrons?

0

Which alkyl halide would you expect to undergo an Sw2 reaction most slowly? Br

1-bromo-2,2-dimethylbutane

How many different alkenes are formed by E2 elimination from 2-bromo-2,3-dimethylhexane using a strong base such as sodium ethoxide?

3

An alkane which can exhibit optical activity is: A. 2,2-dimethylpropane- B. 2-methylbutane C. 3-Methylpentane D. 3-Methylhexane E. 2,3-Dimethylbutane

3-Methylhexane

The correct IUPAC name for the following compound is:

4-Bromo-2-ethyl-1-pentene

Which of the following would most readily undergo an Sn2 reaction?

4-bromo-1-butene

What is the total number of possible stereoisomers for the following molecule?

8

Which alkene is the least stable?

A

Which structure represents (E)-1-bromo-2-methylhex-2-ene?

A

Which of the following molecules is(are) chiral?

A. II, II

Which of the following statements is true?

Achiral molecules usually contain a plane of symmetry.

What is the rate-determining step of an SN1 reaction mechanism?

Breaking the bond between the carbon and the leaving group to generate a carbocation.

What is the major product for the following reaction?

C

Which is a polar aprotic solvent?

CH,CH2CH2OCH;CH2CH3

What is the relationship between the following two compounds?

Constitutional isomers

The compounds whose molecules are shown below would have: A. the same melting point. B. different melting points. C. equal but opposite optical rotations. D. More than one of these choices.

D. More than one of these choices.

Which of the following statements about stereoisomers is not true? A. Stereoisomers have identical IUPAC names except for a prefix like cis or trans. B. Stereoisomers differ in enfiguration. C. Stereoisomers always have the same functional groups. D. Stereoisomers differ only in their structural formula.

D. Stereoisomers differ only in their structural formula.

Which compound would show optical activity? A. cis-1,4-Dimethyleyclohexane B. trans-1,4-Dimethylcyclohexane C. cis-1,4-Dimethylcycloheptane D. trans-1,4-Dimethylcycloheptane

D. trans-1,4-Dimethylcycloheptane

Identify the leaving group in the following reaction.

H20

Select the potential energy diagram that represents a single-step endothermic (endergonic) reaction.

I

What are the major product(s) formed when cis-1-bromo-2-methylcyclohexane reacts with sodium isopropoxide in isopropyl alcohol?

I

What is the major elimination product obtained from the following reaction?

I

Which of the following alkenes is the most stable?

I

Humulene is a natural product found in plants ranging from pine trees to tobacco to ginseng. Classify each double bond in humulene labeled I, II, III according to its substitution pattern.

I = Disubstituted; II = trisubstituted; III = trisubstituted.

Identify the leaving group in the following reaction.

I-

Rank the following carbocations in order of decreasing stability, putting the most stable first.

I>||> III

The major product of the following reaction would be:

II

Which of the following molecules has a plane of symmetry?

II

Rank the alkyl halides in order of decreasing SN2 reactivity, putting the most reactive first.

II > I > II

trans-1,2-Dibromocyclohexane is represented by structure(s):

II and III

Which of the following compounds are chiral?

II only

Identify the pair(s) of enantiomers among the following.

III & IV

Which alkyl halide would be most reactive in an SN1 reaction?

IV

Which of the following alkyl halides would give the indicated product upon reaction with sodium methoxide (NaOCH,)?

IV

Which of the following compounds can have a meso stereoisomer?

IV

What is the relationship between the following compounds?

Identical

Which of the following is true about any (R)-enantiomer?

It is the mirror image of the (S)-enantiomer

The reaction of what nucleophile and alkyl halide is represented by the following transition

Methoxide with 2-bromopropane

What is (are) the starting material(s) in the reaction below?

Only I

What is the product of the nucleophilic substitution reaction shown below?

Only II

The rate equation for a nucleophilic substitution reaction of a tertiary alkyl bromide (R-Br) with l-ion would be:

Rate = k [RBr]

Identify the mechanism of the following reaction.

SN2

What is the relationship between the following two compounds?

Stereoisomers

Which of the following statements is true?

Stereoisomers that are mirror images but are not superimposable are enantiomers.

What can be said with certainty if a compound has [a] = -9.25 ?

The compound is not a meso form.

Why does E2 elimination occur more rapidly in cis-2-chloro-1,1,3-trimethylcyclohexane than in the trans isomer?

The leaving group and the a-hydrogen are boch axial in the cis isomer.

The reaction of bromoethane with sodium hydroxide produces the substitution product ethanol. What is the effect of doubling the concentration of sodium hydroxide on the rate of the reaction?

The rate increases by a factor of 2

Which of the following statements about E2 elimination from an alkyl halide using ethoxide as a base is false? A. The rate of the reaction = k[alkyl halide][sodium ethoxide] B. The reactivity order for the alkyl halide is 3* > 2" > 1°. C. The rate is independent of the leaving group. D. The reaction occurs in a single step.

The rate is independent of the leaving group.

Given the following substitution reaction, what would the effect be of changing the solvent from CH;OH to DMSO? CH3(CH2)sBr + NaOH → CHa(CH2)sOH + Br

The rate would increase because SN2 reactions are favored by polar aprotic solvents

Consider the substitution reaction that takes place when (R)-3-bromo-3-methylhexane is treated with methanol. Which of the following would be true?

The reaction would take place with racemization.

Consider the substitution'Yeaction that takes place when (R)-3-bromo-3-methylhexane is treated with methanol. Which of the following would be true?

The reaction would take place with racemization.

A true statement about the transition state(s) of an Sy2 reaction is:

The single transition state represents the point of maximum free energy of the reaction

Which of the statements about the properties of the carbon-carbon double bond is not true? A. There is restricted rotation around the carbon-carbon double bond. B. Whenever the two groups on each end of a carbon-carbon double bond are the same, two diastereomers are possible. C. Trans alkenes are generally D. The stability of the carbon-carbon double bond more stable than cis alkenes. substituent groups increases. increases as the number of

Whenever the two groups on each end of a carbon-carbon double bond are the same, two diastereomers are possible.

I and II are:

identical

A reaction that produces one stereoisomer predominantly or exclusively over other possible isomeric products

is stereoselective

How many chiral centers are in the following compound?

none of the above

The reaction shown happens in a single step. The rate law for this reaction is: CH3CH2Br + OH -> CH3CH2OH + Br

rate = k[CH,CH,Br][OH]

The hybridization of the charged carbon in a carbocation is

sp2

Which structure represents (E)-1-bromo-2-methyl-2-hexene?

А