Chapter 21, Problem 21.35P

Interpretation Introduction

(a)

Interpretation: The lactol formed from intramolecular cyclization of given hydroxyl aldehyde is to be predicted.

Concept introduction: Aldehydes or ketones on reaction with one equivalent of alcohol form hemiacetal and on reaction with two equivalents of alcohol it forms acetals. This is nucleophilic addition reaction. These reactions takes place in presence of acids, commonly $p\text{-toluenesulfonicacid}$.

Cyclic hemiacetals containing five or six-membered rings are generally stable and can be isolated.

Interpretation Introduction

(b)

Interpretation: The lactol formed from intramolecular cyclization of given hydroxyl aldehyde is to be predicted.

Concept introduction: Aldehydes or ketones on reaction with one equivalent of alcohol form hemiacetal and on reaction with two equivalents of alcohol it forms acetals. This is nucleophilic addition reaction. These reactions takes place in presence of acids, commonly $p\text{-toluenesulfonicacid}$.

Cyclic hemiacetals containing five or six-membered rings are generally stable and can be isolated.