Chapter 17, Problem 42P

Interpretation Introduction

Interpretation:

The given conditions in the synthesis of $(-)$ malic acid are to be discussed.

Concept introduction:

Electrophiles are electron deficient species that have positive or partially positive charge. Lewis acids are electrophiles that accept electron pair.

Nucleophiles are electron rich species that have negative or partially negative charge. Lewis bases are nucleophiles that donate electron pair.

Substitution reaction: A reaction in which one of the hydrogen atoms of a hydrocarbon or a functional group is substituted by any other functional group is called substitution reaction.

Nucleophilic substitution reaction is a reaction in which an electron rich nucleophile attacks the positive or partial positive charge of an atom or a group of atoms to replace a leaving group.

${\text{S}}_{\text{N}}\text{2}$ reaction is the nucleophilic substitution reaction in which the two components are involved in the rate determining step.

The ${\text{S}}_{\text{N}}\text{2}$mechanism of substitution reaction occurs in secondary alkyl halides with an inversion of configuration.

The ${\text{S}}_{\text{N}}\text{2}$reaction takes place in one step. The nucleophile attacks the alkyl halide from the side opposite to the leaving group, resulting in an inversion of configuration.

An ${\text{S}}_{\text{N}}1$ reaction is a nucleophilic substitution reaction in which only one component is involved in the rate-determining step.

The nucleophilic substitutions in which a nucleophile replaces a leaving group are known as ${\text{S}}_{\text{N}}1$ reactions.

${\text{S}}_{\text{N}}1$ reactions are unimolecular as the rate of reaction is dependent on the concentration of a single reactant.

When the order of progression from the group of highest priority to that of the next highest priority is clockwise, it is said to be the $\left(R\right)$ configuration

When the order of progression from the group of highest priority to that of the next highest priority is anticlockwise, then it is said to be the $\left(S\right)$ configuration.

A racemic mixture or racemic form is an equimolar mixture of two enantiomers. The racemic form causes no net rotation of plane-polarised light.

$(R)-(+)$ Glyceraldehyde is converted to $(-)$ malic acid that starts when $(R)-(+)$ Glyceraldehyde is converted to $(-)$ tartaric acid.

The $(-)$ tartaric acid reacts with phosphorus tribromide so that one alcoholic $-\text{OH}$ group is replaced by $-\text{Br}$ group.

The product of the reaction is then treated with dimethyl sulfide, which results in the formation of $(-)$ malic acid.