Q. 13.17 - An Introduction to General, Organic, and Biological Chemistry

Question

Identify each of the following as D or L:

Step-by-Step Solution

Answer

(a) The structure is an a$D$-isomer 

(b) The structure is a $D$isomer is

(c) The structure is $L$ isomer

Step 1 : Given information (a)

The structure is 

We have to find that the isomer.

Step 2: Explanation for (a)

In this problem, we have to identify given structures as D or L.

The difference between $D$ and $L$ isomers is in the position of the -$OH$group in the penultimate carbon atom. The $OH$ group in the $D$ isomer of the penultimate carbon is on the right side, and in $L$isomer is on the left side. In the Figure below, we can see examples of $D$ and $L$ isomers on glyceraldehyde.

In this example the numbering starts from the top carbon atom (with the hydroxy group), which means that the penultimate carbon has the $OH$ group on the right side, which means that this structure is a $D$ isomer.

Step 3 : Given information (b)

The structure is 

We have to find the isomer

Step 4 : Explanation for (b)

In this problem, we have to identify given structures as $L$or $D$.

The difference between $L$ and $D$ isomers is in the position of the $-OH$group in the penultimate carbon atom. The $OH$ in the $D$ isomer of the penultimate carbon is on the right side, and in $L$ isomer is on the left side. In the Figure below, we can see examples of $D$ and $L$ isomers on glyceraldehyde.

In this example, the $OH$ group is on the right side, which means that this structure is a $D$ isomer.

Step 5: Given information (c)

The structure is 

We have to find the isomer. 

Step 6 : Explanation for (c)

In this problem, we have to identify given structures as $D$ or $L$.

The difference between $L$ and $D$ isomers is in the position of the - $OH$group in the penultimate carbon atom. The $OH$ group in the $D$ isomer of the penultimate carbon is on the right side, and in $L$ isomer is on the left side. In the Figure below, we can see examples of $D$ and $L$ isomers on glyceraldehyde.

In this example, the $OH$ group is on the left side, which means that this structure is a $L$ isomer.