What happens in a nucleophilic acyl substitution reaction?

Nucleophilic acyl substitution (acyl transfer reaction) occurs by a two-step mechanism. First, attack of the carbonyl carbon atom of an acyl derivative by a nucleophile yields a tetrahedral intermediate. The tetrahedral intermediate can then eject a leaving group. The net result is a substitution reaction.

What is the difference between nucleophilic acyl substitution and nucleophilic addition?

The mechanisms for nucleophilic acyl addition or substitution begin with the same first step in which a nucleophile adds to C=O (Figure 16.001). Figure 16.004 In contrast, nucleophilic acyl substitution leads to loss of a Z group from the Nu-C-O- intermediate. The result is that Z is replaced or substituted by Nu.

Is acyl substitution endothermic?

The first step of nucleophilic acyl substitution is the endothermic attack of the nucleophile. The second step is highly exothermic, and this is where the leaving group (i.e. alkoxide) is expelled from the tetrahedral intermediate.

Why are acyl halides the most reactive for nucleophilic acyl substitution reactions?

Acid halides are the most reactive towards nucleophiles, followed by anhydrides, esters, and amides. Carboxylate ions are essentially unreactive towards nucleophilic substitution, since they possess no leaving group.

Which is an example of an acyl substitution?

Exercise 4 Saponification of esters is a specific example of a more general reaction type called nucleophilic acyl substitution. It is typical of derivatives of carboxylic acids- esters, acyl halides, amides, and anhydrides- and may be summarized in general terms by the following scheme:

How does a nucleophilic acyl substitution reaction occur?

Nucleophilic acyl substitution (acyl transfer reaction) occurs by a two-step mechanism. First, attack of the carbonyl carbon atom of an acyl derivative by a nucleophile yields a tetrahedral intermediate. The tetrahedral intermediate can then eject a leaving group. The net result is a substitution reaction. The first step is rate determining.

What happens to a carbonyl compound in a substitution reaction?

Carbonyl Condensation Reactions In an a-substitution reaction, the carbonyl compound behaves as a nucleophile after being converted into an enol or enolate ion. Carbonyl compounds can behave as either electrophiles or nucleophiles. In a nucleophilic addition reaction or a nucleophilic acyl substitution reaction, the carbonyl group

How does a carbonyl compound behave in a condensation reaction?

Carbonyl compounds can behave as either electrophiles or nucleophiles. In a nucleophilic addition reaction or a nucleophilic acyl substitution reaction, the carbonyl group behaves as an electrophile by accepting electrons from an attacking nucleophile. Carbonyl condensation reactions involve both kinds of reactivity of carbonyl compounds.