Q. 13. 26 - An Introduction to General, Organic, and Biological Chemistry

Question

Draw the Fischer projections for $D$-fructose and $L$-fructose.

Step-by-Step Solution

Answer

$D$-Fructose and $L$-Fructose must be drawn in Fischer projections.

Introduction

• The penultimate carbon of $D$sugars is displayed in a Fischer projection with hydrogen on the left and hydroxyl on the right.
• The $L$sugars will be represented similarly, with hydrogen on the right and hydroxyl on the left.
• $D$-Fructose and $L$-Fructose must be drawn in Fischer projections in this problem.

Explanation of D -Fructose and L -Fructose in Fischer projections.

• Enantiomers are mirror images of each other, hence $D$ and L-Fructose are mirror images of each other. 
• D-fructose is a ketohexose, which means it has six carbons and a keto group on the right side, as well as the penultimate hydroxy group.

Structure of D -Fructose and L -Fructose in Fischer projections.

Knowing the structure of $D$-Fructose, we can simply swap out each stereogenic centre to create$L$-Fructose, as shown in the diagram below.