Chapter 9, Problem 1P

(a)

Interpretation Introduction

Interpretation:

The Haworth projections for

  

in a-furanose form should be identified along with the name of the sugar.

Concept introduction:

A Haworth projection is common way to represent the cyclic structure of monosaccharides.

Five and six membered hemiacetals are represented as planar pentagons or hexagons.

  $\text{α}$ -form of the Haworth projection indicates, the exocyclic O group at the anomeric centre is on the opposite face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

  $\text{β}$ -form of the Haworth projection, the exocyclic O group at the anomeric centre is on the same face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

In the Haworth projection ${\text{- CH}}_{\text{2}}\text{OH}$ group is present in the RIGHT side of the ring is called D- form.

In the Haworth projection ${\text{- CH}}_{\text{2}}\text{OH}$ group is present in the LEFT side of the ring is called L- form.

For example:

Haworth projections of glucose:

  

Pictorial representation:

  $\text{α-D-Xylofuranose}$

  

Explanation of Solution

The given structure is as follows.

  

Above structure has 5 carbons and on 3rd carbon $\text{–OH}$ group is present in the left side of the carbon chain. Therefore, the name of the sugar is $\text{α-D-Xylofuranose}$ .

Let’s draw the Haworth projection of $\text{α-D-Xylofuranose}$ .

In the D form of Haworth projection, the exocyclic O group at the anomeric centre is on the opposite face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

  

(b)

Interpretation Introduction

Interpretation:

The Haworth projections for L isomer of (a) should be drawn.

Concept introduction:

A Haworth projection is common way to represent the cyclic structure of monosaccharides.

Five and six membered hemiacetals are represented as planar pentagons or hexagons.

  $\text{α}$ form of the Haworth projection indicates, the exocyclic O group at the anomeric centre is on the opposite face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

  $\text{β}$ form of the Haworth projection, the exocyclic O group at the anomeric centre is on the same face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

In the Haworth projection ${\text{- CH}}_{\text{2}}\text{OH}$ group is present in the RIGHT side of the ring is called D- form.

In the Haworth projection ${\text{- CH}}_{\text{2}}\text{OH}$ group is present in the LEFT side of the ring is called L- form.

For example:

Haworth projections of glucose:

  

Pictorial representation:

  $\text{β - L - Xylofuranose}$

  

Explanation of Solution

In L form of Haworth projection, the exocyclic O group at the anomeric centre is on the same face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

  

(c)

Interpretation Introduction

Interpretation:

The Haworth projections for a-D-Glc-NAc should be drawn.

Concept introduction:

A Haworth projection is common way to represent the cyclic structure of monosaccharides.

Five and six membered hemiacetals are represented as planar pentagons or hexagons.

  $\text{α}$ form of the Haworth projection indicates, the exocyclic O group at the anomeric centre is on the opposite face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

  $\text{β}$ form of the Haworth projection, the exocyclic O group at the anomeric centre is on the same face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

In the Haworth projection ${\text{- CH}}_{\text{2}}\text{OH}$ group is present in the RIGHT side of the ring is called D- form.

In the Haworth projection ${\text{- CH}}_{\text{2}}\text{OH}$ group is present in the LEFT side of the ring is called L- form.

For example:

Haworth projections of glucose:

  

Pictorial representation:

  $\text{α-D-GlcNAC}$

  $\text{(N-acetyl-α -D-Glucoseaminide)}$

  

Explanation of Solution

  $\text{α-D-GlcNAC}$

  $\text{(N-acetyl-α -D-Glucoseaminide)}$

In this compound, $\text{ α-D-Glucose}$ has acetanilide group at the 3^rd carbon. The structure is as follows.

  

(d)

Interpretation Introduction

Interpretation:

The Haworth projections for a-D-Fructofuranose should be drawn.

Concept introduction:

A Haworth projection is common way to represent the cyclic structure of monosaccharides.

Five and six membered hemiacetals are represented as planar pentagons or hexagons.

  $\text{α}$ form of the Haworth projection indicates, the exocyclic O group at the anomeric centre is on the opposite face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

  $\text{β}$ form of the Haworth projection, the exocyclic O group at the anomeric centre is on the same face as to the ${\text{CH}}_{\text{2}}\text{OH}$ group.

In the Haworth projection ${\text{- CH}}_{\text{2}}\text{OH}$ group is present in the RIGHT side of the ring is called D- form.

In the Haworth projection ${\text{- CH}}_{\text{2}}\text{OH}$ group is present in the LEFT side of the ring is called L- form.

For example:

Haworth projections of glucose:

  

Pictorial representation:

  $\text{α - D - Fructofuranose}$

  

Explanation of Solution

  $\text{α - D - Fructofuranose}$

It has 5 member furanose ring. The structure is as follows.