Concept explainers
(a)
Interpretation:
The
Concept introduction:
The compounds which have the same molecular formula but have different arrangements of atoms are known as isomers. The phenomenon is called isomerism. The isomers are generally classified as structural isomers and stereoisomers. Stereoisomers are further divided into two categories diastereomers and enantiomers.
Answer to Problem 9.44AP
The isomers of C6H13Br that can exist as enantiomers are 3-bromo-2-methylpentane and 2-bromo-3-methylpentane.
Explanation of Solution
The structures of C6H13Br isomers are shown below.
Figure 1
The compounds that have chiral centers can exist as enantiomers. The compound 3-bromo-2-methylpentane and 2-bromo-3-methylpentane have chiral centers in them. The chiral centers of 3-bromo-2-methylpentane and 2-bromo-3-methylpentane are indicated with star mark as shown below.
Figure 2
Therefore, 3-bromo-2-methylpentane and 2-bromo-3-methylpentane can exist as enantiomers.
The compounds 3-bromo-2-methylpentane and 2-bromo-3-methylpentane can exist as enantiomers.
(b)
Interpretation:
The alkyl halides among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can exist as diastereomers are to be identified.
Concept introduction:
The compounds which have the same molecular formula but have different arrangements of atoms are known as isomers. The phenomenon is called isomerism. The isomers are generally classified as structural isomers and stereoisomers. Stereoisomers are further divided into two categories diastereomers and enantiomers.
Answer to Problem 9.44AP
The isomer of C6H13Br that can exist as diastereomers is 2-bromo-3-methylpentane.
Explanation of Solution
The structures of C6H13Br isomers are shown below.
Figure 1
The compounds that have two chiral centers can exist as enantiomers. The compound 3-bromo-2-methylpentane and 2-bromo-3-methylpentane have chiral centers in them. The chiral centers of 2-bromo-3-methylpentane are indicated with star mark as shown below.
Figure 3
Therefore, 2-bromo-3-methylpentane can exist as diastereomers.
The compound 2-bromo-3-methylpentane can exist as diastereomers.
(c)
Interpretation:
The alkyl halides among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can give the fastest SN2 reaction with sodium methoxide are to be identified.
Concept introduction:
The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as a substitution reaction. In a nucleophilic substitution reaction, nucleophile takes the position of leaving the group by attacking on the electron-deficient carbon atom.
Answer to Problem 9.44AP
The fastest SN2 reaction with sodium methoxide is of 1-bromohexane among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane.
Explanation of Solution
The structures of C6H13Br isomers are shown below.
Figure 1
The rate of SN2 reaction primary halide is greater than that of secondary halides. The rate of SN2 reaction secondary halide is greater than that of tertiary halides. The reason for this trend is the steric hindrance. The steric hindrance is very less than in the case of primary halide than secondary and tertiary halides.
The compound 1-bromohexane is primary halide with lowest steric hindrance. Therefore, 1-bromohexane undergoes the fastest SN2 reaction with sodium methoxide among the isomer of C6H13Br.
The compound 1-bromohexane has fastest rate of SN2 reaction.
(d)
Interpretation:
The alkyl halides among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can is least reactive to sodium methoxide in methanol are to be identified.
Concept introduction:
The replacement or substitution of one
Answer to Problem 9.44AP
The isomer of C6H13Br which has least reactivity towards sodium methoxide in methanol is 1-bromo-2, 2-dimethy1butane.
Explanation of Solution
The structures of C6H13Br isomers are shown below.
Figure 1
The compound 1-bromo-2, 2-dimethy1butane has preferred to undergo an elimination reaction to form
The compound, 1-bromo-2, 2-dimethy1butane, has the least reactivity towards sodium methoxide in methanol.
(e)
Interpretation:
The alkyl halides among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can give only one alkene in the E2 reaction with K+−OtBu are to be identified.
Concept introduction:
The elimination reaction of alkyl halide involves removal of the halogen atom and hydrogen atom from the adjacent carbon atoms, which leads to the formation of the alkene. A bulky base increases the chance of elimination reaction of substitution reaction.
Answer to Problem 9.44AP
The compound 1-bromohexane will give only one alkene after E2 reaction with K+−OtBu.
Explanation of Solution
The structures of C6H13Br isomers are shown below.
Figure 1
The compound 1-bromohexane will give only one alkene after E2 reaction with K+−OtBu because the halide is attached to the terminal carbon atom. The possibilities of rearrangement in the E2 reaction are least for this compound.
The E2 reaction of 1-bromohexane with K+−OtBu will produce only one alkene.
(f)
Interpretation:
The alkyl halides among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can that give an E2 but no SN2 reaction with sodium methoxide in methanol are to be identified.
Concept introduction:
The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as a substitution reaction. In a nucleophilic substitution reaction, nucleophile takes the position of leaving the group by attacking on the electron-deficient carbon atom.
Answer to Problem 9.44AP
The alkyl halide among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can that give an E2 but no SN2 reaction with sodium methoxide in methanol is 3-bromo-3-methylpentane.
Explanation of Solution
The structures of C6H13Br isomers are shown below.
Figure 1
The rate of SN2 reaction varies primary halide greater than secondary halides. The rate of SN2 reaction varies secondary halide greater than tertiary halides. The reason for this trend is the steric hindrance. The steric hindrance is very less than in case of primary halide than secondary and tertiary halides.
The steric hindrance in case of 3-bromo-3-methylpentane is maximum. Therefore, it will not undergo SN2. The compound, 3-bromo-3-methylpentane, can easily undergoes E2 reaction to form alkene.
The isomer of C6H13Br among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can that give an E2 but no SN2 reaction with sodium methoxide in methanol is 3-bromo-3-methylpentane.
(g)
Interpretation:
The alkyl halides among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can undergo an SN1 reaction to give rearranged products are to be identified.
Concept introduction:
The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as a substitution reaction. In a nucleophilic substitution reaction, nucleophile takes the position of leaving the group by attacking on the electron-deficient carbon atom.
Answer to Problem 9.44AP
The alkyl halides among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can undergo an SN1 reaction to give rearranged products are 3-bromo-2-methylpentane and 2-bromo-3-methylpentane.
Explanation of Solution
The structures of C6H13Br isomers are shown below.
Figure 1
The stability of tertiary carbocation is more than the stability of secondary carbocation. Therefore, in case of 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane, the secondary carbocation formed will undergo rearrangement to form a more stable tertiary carbocation.
The isomer of C6H13Br among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can undergo an SN1 reaction to give rearranged products are 3-bromo-2-methylpentane and 2-bromo-3-methylpentane.
(h)
Interpretation:
The alkyl halide among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can gives the fastest SN1 reaction is to be identified.
Concept introduction:
The replacement or substitution of one functional group with another different functional group in any chemical reaction is termed as a substitution reaction. In a nucleophilic substitution reaction, nucleophile takes the position of leaving the group by attacking on the electron-deficient carbon atom.
Answer to Problem 9.44AP
The alkyl halide among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can gives the fastest SN1 reaction is 3-bromo-3-methylpentane.
Explanation of Solution
The structures of C6H13Br isomers are shown below.
Figure 1
The rate of SN1 reaction primary halide is lower than that of secondary halide. The rate of SN1 reaction secondary halide is lower than that of tertiary halides. The reason for this trend is the formation of a stable carbocation. The compound 3-bromo-3-methylpentane a stable tertiary carbocation.
Therefore, 3-bromo-3-methylpentane undergoes the fastest SN1 reaction among the isomer of C6H13Br.
The isomer of C6H13Br among 1-bromohexane, 3-bromo-3-methylpentane, 1-bromo-2, 2-dimethy1butane, 3-bromo-2-methylpentane, and 2-bromo-3-methylpentane that can gives the fastest SN1 reaction is 3-bromo-3-methylpentane.
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Chapter 9 Solutions
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