Question

Question: Indicate the type of catalysis that is occurring in the slow step in each of the following reaction sequences:

Short answer

The answer is,

a. Intramolecular nucleophilic catalysis

b. Intramolecular general- acid catalysis

Step-by-step solution

Catalysis

In order to carry out a reaction with a faster rate, substances called catalyst. This will increase the rate of a reaction by decreasing the activation energy of the reactant compound or by forming a stable transition state.

Subpart a

The mechanism for the given compound is shown below.

Hence this is an intramolecular nucleophilic catalysis reaction. The chlorine leaving group leaves from the compound as the lone pair of sulfur atom shifts.

Subpart b

The mechanism for the given compound is shown below.

The OH substituent is protonating the leaving group as it departs, causing it to be a weaker base and therefore, a better leaving group.

Hence this is an intramolecular general- acid catalysis reaction.