Chapter 4 CHM132

What is the general mechanism of nucleophilic acyl substitution?

• One-step SN1-type mechanism

• Two-step: nucleophilic attack followed by leaving group departure

• Acid–base neutralization

• Rearrangement reaction

Which of the following is the best leaving group among carboxylic acid derivatives?

• NH₂⁻

• OH⁻

• OR⁻

• Cl⁻

Arrange the following leaving groups from poorest to best in nucleophilic acyl substitution:

• OH⁻ < NH₂⁻ < RCOO⁻ < OR⁻ < Cl⁻

• NH₂⁻ < OH⁻ < OR⁻ < RCOO⁻ < Cl⁻

• Cl⁻ < RCOO⁻ < OR⁻ < OH⁻ < NH₂⁻

• RCOO⁻ < Cl⁻ < OH⁻ < NH₂⁻ < OR⁻

Why is a carboxylic acid (R–COOH) less reactive than an acid chloride (R–COCl)?

• Cl⁻ is more electronegative than OH⁻

• OH⁻ is a weaker acid

• OH⁻ is a poor leaving group compared to Cl⁻

• Carboxylic acids do not contain a carbonyl group

What is the product when an ester reacts with ammonia (NH₃)?

• Carboxylic acid

• Amide

• Ketone

• Aldehyde

Why are amides generally the least reactive among carboxylic acid derivatives?

• Amides do not contain a leaving group

• The carbonyl group in amides is unstable

• NH₂⁻ is a poor leaving group due to its strong basicity

• Amides are charged species and unreactive in water

What is the product of this hydrolysis reaction: R–COCl + H₂O → ?

• R–CH₃

• R–COOH

• R–OH

• R–COOR

Which of the following carboxylic acid derivatives reacts fastest with water?

• Ester

• Acid chloride

• Amide

• Anhydride

True or False: The reactivity of acid derivatives increases with increasing basicity of the leaving group.

• True

• False

True or False: Nucleophilic acyl substitution occurs via a two-step mechanism involving a tetrahedral intermediate.

• True

• False