Chapter 6, Problem 6.59AP

a.

Summary Introduction

To determine:

Whether the given carbohydrate (a.) is the alpha or beta anomer.

Introduction:

Diastereomers are those stereoisomers who differ in orientation of two chiral centers due to which the isomers are not the mirror images of each other. The cyclic forms of diastereoisomeric sugars which differ at the anomeric carbon (carbonyl carbon which reacts to form hemiacetal) are known as anomers. Hemiacetal is formed when the carbonyl carbon (partially positive) and oxygen of hydroxyl group (partially negative) forms a bond. The hemiacetal anomers exist in alpha and beta forms based on the site of substituent at anomeric carbon.

b.

Summary Introduction

To determine:

Whether the given carbohydrate (b.) is the alpha or beta anomer.

Introduction:

Diastereomers are those stereoisomers who differ in orientation of two chiral centers due to which the isomers are not the mirror images of each other. The cyclic forms of diastereoisomeric sugars which differ at the anomeric carbon (carbonyl carbon which reacts to form hemiacetal) are known as anomers. Hemiacetal is formed when the carbonyl carbon (partially positive) and oxygen of hydroxyl group (partially negative) forms a bond. The hemiacetal anomers exist in alpha and beta forms based on the site of substituent at anomeric carbon.