Textbook Question
Show how you would accomplish the following syntheses. Some of these conversions may require more than one step.
(a) isopentyl alcohol → isopentyl acetate (banana oil)
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22. Carboxylic Acid Derivatives: NAS
Nucleophilic Acyl Substitution
Multiple Choice
In nucleophilic acyl substitution, which of the following best describes the key mechanistic step that distinguishes it from nucleophilic substitution at alkyl halides?
A
Direct displacement of the leaving group without any intermediate
B
A concerted mechanism involving simultaneous bond making and breaking
C
The formation and collapse of a intermediate
D
The involvement of a intermediate
Verified step by step guidance1
Understand that nucleophilic acyl substitution involves a nucleophile attacking a carbonyl carbon, which is electrophilic due to the polarization of the C=O bond.
Recognize that unlike nucleophilic substitution at alkyl halides, which often proceeds via direct displacement (SN2) or carbocation intermediates (SN1), nucleophilic acyl substitution proceeds through a distinct intermediate.
Identify that the key mechanistic step is the nucleophile adding to the carbonyl carbon, breaking the double bond and forming a tetrahedral intermediate where the carbon is bonded to four groups.
Note that this tetrahedral intermediate is unstable and subsequently collapses, expelling the leaving group and restoring the carbonyl functionality.
Conclude that the formation and collapse of the tetrahedral intermediate is the hallmark step that differentiates nucleophilic acyl substitution from nucleophilic substitution at alkyl halides.
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