Chapter 29.7, Problem 12P

Interpretation Introduction

Interpretation:

The pro-R or pro-S hydrogen removed from citrate during the dehydration in step 2 of the citric acid cycle.

Concept introduction:

A molecule is said to be pro chiral, if it can be converted from achiral to chiral a single chemical step.

For instance, an unsymmetrical ketone like 2-butanone is pro chiral because it can be converted to the chiral alcohol 2-butanol, by the addition of hydrogen.

Which enantiomer of 2-butanol is produced depends on which face of the planar carbonyl undergoes reaction to distinguish between the possibilities, the stereo chemical description Re and Si (announced ‘ray’ and ‘sigh’) are used.

The concept of this designation is as follows: Rank the three groups attached to the trigonal, sp² hybridized carbon according to the conventional Cahn-In gold-Prelog (CIP) system and imagine curved among from the highest to second highest, to third highest ranked substituents.