Chapter 18, Problem 18.94EP

(a)

Interpretation Introduction

Interpretation: The Haworth projection formula for the given monosaccharide has to be drawn.

Concept introduction: The Haworth projection formula can be drawn by using the following rules.

• Ø For $\alpha$ and $\beta$ configurations, if hydroxyl group is drawn at the right position in Fischer projection formula then in the cyclic form of Haworth projection, the same $\text{OH}$ group should be drawn below the ring.
• Ø If hydroxyl group is drawn at the left position in Fischer projection formula then in the cyclic form of Haworth projection, the same $\text{OH}$ group should be drawn above the ring.
• Ø For $\beta$ configuration, the position of $\text{OH}$ group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group always remains in the same direction.
• Ø For $\alpha$. configuration, the position of $\text{OH}$ group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group always remains in the opposite direction.
• Ø The hydroxyl group that is obtained from the carbonyl group can be placed above or below the ring which is dependent upon the ring closure of the cyclic form.
• Ø For D configuration, ${\text{CH}}_{\text{2}}\text{OH}$ group is always placed above the cyclic ring.
• Ø For L configuration, ${\text{CH}}_{\text{2}}\text{OH}$ group is always placed below the cyclic ring.

Answer to Problem 18.94EP

The Haworth projection formula for the given monosaccharide is,

Explanation of Solution

The given monosaccharide is $\alpha -\text{D}-\text{mannose}$. The open-chain structure of $\alpha -\text{D}-\text{mannose}$ is,

The Haworth projection formula for the given monosaccharide, $\alpha -\text{D}-\text{mannose}$ is shown as,

Thus, in this Haworth projection formula of the given monosaccharide, ${\text{CH}}_{\text{2}}\text{OH}$ group is placed above the cyclic ring.  The position of $\text{OH}$ group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group is in the opposite direction.  Thus, this Haworth projection formula is a $\alpha -\text{D}-\text{monosaccharide}$.

(b)

Interpretation Introduction

Interpretation: The Haworth projection formula for the given monosaccharide has to be drawn.

Concept introduction: The Haworth projection formula can be drawn by using the following rules.

• Ø For $\alpha$ and $\beta$ configurations, if hydroxyl group is drawn at the right position in Fischer projection formula then in the cyclic form of Haworth projection, the same $\text{OH}$ group should be drawn below the ring.
• Ø If hydroxyl group is drawn at the left position in Fischer projection formula then in the cyclic form of Haworth projection, the same $\text{OH}$ group should be drawn above the ring.
• Ø For $\beta$ configuration, the position of $\text{OH}$ group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group always remains in the same direction.
• Ø For $\alpha$. configuration, the position of $\text{OH}$ group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group always remains in the opposite direction.
• Ø The hydroxyl group that is obtained from the carbonyl group can be placed above or below the ring which is dependent upon the ring closure of the cyclic form.
• Ø For D configuration, ${\text{CH}}_{\text{2}}\text{OH}$ group is always placed above the cyclic ring.
• Ø For L configuration, ${\text{CH}}_{\text{2}}\text{OH}$ group is always placed below the cyclic ring.

Answer to Problem 18.94EP

The Haworth projection formula for the given monosaccharide is,

Explanation of Solution

The given monosaccharide is $\beta -\text{D}-\text{mannose}$. The open-chain structure of $\beta -\text{D}-\text{mannose}$ is,

The Haworth projection formula for the given monosaccharide, $\beta -\text{D}-\text{mannose}$ is shown as,

Thus, in this Haworth projection formula of the given monosaccharide, ${\text{CH}}_{\text{2}}\text{OH}$ group is placed above the cyclic ring.  The position of $\text{OH}$ group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group is in the same direction.  Thus, this Haworth projection formula is a $\beta -\text{D}-\text{monosaccharide}$.

(c)

Interpretation Introduction

Interpretation: The Haworth projection formula for the given monosaccharide has to be drawn.

Concept introduction: The simplest hydrolyzed form that is obtained from the carbohydrates is known as monosaccharide.

Haworth projection is a method that is used to provide the three-dimensional cyclic form of a monosaccharide.

Answer to Problem 18.94EP

The Haworth projection formula for the given monosaccharide is,

Explanation of Solution

The given monosaccharide is $\alpha -\text{L}-\text{mannose}$. The open-chain structure of $\alpha -\text{L}-\text{mannose}$ is,

The Haworth projection formula for the given monosaccharide, $\alpha -\text{L}-\text{mannose}$ is shown as,

Thus, in this Haworth projection formula of the given monosaccharide, ${\text{CH}}_{\text{2}}\text{OH}$ group is placed below the cyclic ring.  The position of $\text{OH}$. group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group is in the opposite direction.  Thus, this Haworth projection formula is a $\alpha -\text{L}-\text{monosaccharide}$.

(d)

Interpretation Introduction

Interpretation: The Haworth projection formula for the given monosaccharide has to be drawn.

Concept introduction: The Haworth projection formula can be drawn by using the following rules.

• Ø For $\alpha$ and $\beta$ configurations, if hydroxyl group is drawn at the right position in Fischer projection formula then in the cyclic form of Haworth projection, the same $\text{OH}$ group should be drawn below the ring.
• Ø If hydroxyl group is drawn at the left position in Fischer projection formula then in the cyclic form of Haworth projection, the same $\text{OH}$ group should be drawn above the ring.
• Ø For $\beta$ configuration, the position of $\text{OH}$ group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group always remains in the same direction.
• Ø For $\alpha$. configuration, the position of $\text{OH}$ group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group always remains in the opposite direction.
• Ø The hydroxyl group that is obtained from the carbonyl group can be placed above or below the ring which is dependent upon the ring closure of the cyclic form.
• Ø For D configuration, ${\text{CH}}_{\text{2}}\text{OH}$ group is always placed above the cyclic ring.
• Ø For L configuration, ${\text{CH}}_{\text{2}}\text{OH}$ group is always placed below the cyclic ring.

Answer to Problem 18.94EP

The Haworth projection formula for the given monosaccharide is,

Explanation of Solution

The given monosaccharide is $\beta -\text{L}-\text{mannose}$. The open-chain structure of $\beta -\text{L}-\text{mannose}$ is,

The Haworth projection formula for the given monosaccharide, $\beta -\text{L}-\text{mannose}$ is shown as,

Thus, in this Haworth projection formula of the given monosaccharide, ${\text{CH}}_{\text{2}}\text{OH}$ group is placed below the cyclic ring.  The position of $\text{OH}$ group at the first carbon with respect to ${\text{CH}}_{\text{2}}\text{OH}$ group is in the same direction.  Thus, this Haworth projection formula is a $\beta -\text{L}-\text{monosaccharide}$.