Chapter 18, Problem 18.70EP

(a)

Interpretation Introduction

Interpretation: The number of carbons in $\text{D}-\text{glucose}$ which do not have a hydroxyl group directly attached to it has to be stated.

Concept introduction: Open chain structures of monosaccharides which contain five or more carbon atoms exist in equilibrium with two cyclic structures.  These cyclic structures are the dominating forms at equilibrium.  The carbonyl group in the open-chain structure of monosaccharide reacts intramolecularly with a hydroxyl group which results in the formation of cyclic forms.  These cyclic compounds are called cyclic hemiacetals.

(b)

Interpretation Introduction

Interpretation: The number of carbons in $\text{D}-\text{galactose}$ which do not have a hydroxyl group directly attached to it has to be stated.

Concept introduction: Open chain structures of monosaccharides which contain five or more carbon atoms exist in equilibrium with two cyclic structures.  These cyclic structures are the dominating forms at equilibrium.  The carbonyl group in the open-chain structure of monosaccharide reacts intramolecularly with a hydroxyl group which results in the formation of cyclic forms.  These cyclic compounds are called cyclic hemiacetals.

(c)

Interpretation Introduction

Interpretation: The number of carbons in $\text{D}-\text{fructose}$ which do not have a hydroxyl group directly attached to it has to be stated.

Concept introduction: Open chain structures of monosaccharides which contain five or more carbon atoms exist in equilibrium with two cyclic structures.  These cyclic structures are the dominating forms at equilibrium.  The carbonyl group in the open-chain structure of monosaccharide reacts intramolecularly with a hydroxyl group which results in the formation of cyclic forms.  These cyclic compounds are called cyclic hemiacetals.

(d)

Interpretation Introduction

Interpretation: The number of carbons in $\text{D}-\text{ribose}$ which do not have a hydroxyl group directly attached to it has to be stated.

Concept introduction: Open chain structures of monosaccharides which contain five or more carbon atoms exist in equilibrium with two cyclic structures.  These cyclic structures are the dominating forms at equilibrium.  The carbonyl group in the open-chain structure of monosaccharide reacts intramolecularly with a hydroxyl group which results in the formation of cyclic forms.  These cyclic compounds are called cyclic hemiacetals.