Chapter 24, Problem 26P

Interpretation Introduction

Interpretation:

The structural formulas for the given compounds are to be provided.

Concept Introduction:

In Fischer projection formula, the horizontal and vertical line represents the bonds that are present above and below the plane, respectively.

The verticals bonds are represented as dashed wedge and horizontal bonds as dark wedge.

Answer to Problem 26P

Solution:

a) The structural formula of $(-)\text{-Xylose}$ is ${\text{C}}_5{\text{H}}_{10}{\text{O}}_5$ and the Fischer projection is shown below.

b) The structural formula for the xylitol is ${\text{C}}_5{\text{H}}_{12}{\text{O}}_5$ and Fischer projection is shown below.

c) The structural formula of $\text{β-D-Xylopyranose}$ is shown below.

d) The structural formula of $\text{α-L-Xylofuranose}$ is shown below.

e) The structure of $\text{Methyl}\text{α-L-xylofuranoside}$ is shown below.

f) The Fischer projection formula for the given compound is shown below.

g) The structure of the given compound is shown below.

h) The structure of the given compound is shown below.

i) The Fischer projection formula for the given compound is shown below.

Explanation of Solution

a) The given structure of $(+)\text{-D-xylose}$ is shown below.

In, $(+)\text{-D-xylose}$, hydroxyl group present on the fourth carbon is in right side.

L and D indicate the absolute configuration of a compound. If hydroxy group attached with chiral centre is to the right side and present on the bottom, then the carbohydrate is in D form but if hydroxy group is present to the left side then the carbohydrate is in L-form.

The name of the given compound is $(-)\text{-Xylose}$. The Fischer projection of $(-)\text{-Xylose}$ is shown below.

b) The given compound is xylitol.

The alcohol derivative of xylose is xylitol in which the reduction of aldehyde group to alcohol takes place. Thus, the Fischer projection formula for the xylitol is shown below.

c) The given compound is $\text{β-D-Xylopyranose}$.

Sugar molecule that has six-membered-ring is known as pyranose and sugar molecule that has five-membered-ring is called furanose.

The given compound is formed when $\text{C1}$ and $\text{C5}$ carbon unit of $\text{D-Xylose}$ reacts with each other. The formation of $\text{β-D-Xylopyranose}$ from $\text{D-Xylose}$ is shown below.

Thus, the structural formula of $\text{β-D-Xylopyranose}$ is shown below.

d) The given compound is $\text{α-L-Xylofuranose}$.

L and D indicate the absolute configuration of a compound. If hydroxy group attached with chiral centre is to the right side and present on the bottom, then the carbohydrate is in D form but if hydroxy group is present to the left side then the carbohydrate is in L-form.

The given compound is formed when $\text{C1}$ and $\text{C4}$ carbon unit of $\text{L-Xylose}$ reacts with each other. The formation of $\text{α-L-Xylofuranose}$ from $\text{L-Xylose}$ is shown below.

Thus, the structural formula of $\text{α-L-Xylofuranose}$ is shown below.

e) The given compound is $\text{Methyl}\text{α-L-xylofuranoside}$.

The given compound is formed when hydroxyl group is replaced by methoxy group as shown below.

Thus, the structure of $\text{Methyl}\text{α-L-xylofuranoside}$ is shown below.

f) The given compound is $\text{D-Xylonic}\text{acid}$.

The oxidation of $\text{D-xylose}$ into acid results in the formation of $\text{D-Xylonic}\text{acid}$. Thus, the Fischer projection formula for the given compound is shown below.

g) The given compound is $\text{δ-Lactone}$.

Lactones are class of organic compound which contain $\text{-OCO-}$ as part of the ring. The formation of $\text{δ-Lactone}$ takes place from $\text{D-Xylonic}\text{acid}$. When hydroxyl group that is present on $\text{C1}$ and $\text{C5}$ carbon unit of $\text{D-Xylonic}\text{acid}$ combine together results in the formation of $\text{δ-Lactone}$ as shown below.

Thus, the structure of the given compound is shown below.

h) The given compound is $\text{γ-Lactone}$.

Lactones are class of organic compound which contain $\text{-OCO-}$ as part of the ring. The formation of $\text{γ-Lactone}$ takes place from $\text{D-Xylonic}\text{acid}$. When hydroxyl group that is present on $\text{C1}$ and $\text{C4}$ carbon unit of $\text{D-Xylonic}\text{acid}$ combine together results in the formation of $\text{γ-Lactone}$ as shown below.

Thus, the structure of the given compound is shown below.

i) The given compound is Xylaric acid.

The oxidation of $\text{D-xylose}$ into acid results in the formation of Xylaric acid. To form Xylaric acid, the oxidation of aldehyde group and hydroxyl group of $\text{D-xylose}$ into acid take place Thus, the Fischer projection formula for the given compound is shown below.