Question

The following isomerization reaction, drawn using D-glucose as starting material, occurs with all aldohexoses in the presence of base. Draw a stepwise mechanism that illustrates how each compound is formed.

Short answer

Answer

Step-by-step solution

Isomerization reaction

Isomerization constitutes a process that modifies a particular molecule into its isomer. The isomerism is termed a rearrangement reaction if the process happens intramolecularly. An example of an isomerization reaction is enolization.

Reaction mechanism

A reaction mechanism comprises several species termed reaction intermediates. These species constitute free radicals or ions that are short-lived and not stable.

Stepwise mechanism showing the formation of compounds

The protonation of D-glucose generates two products. Protonation of the second structure, enolate, can happen from two directions. The protonation on O of the third structure creates an enediol. The mechanism can be given as follows:

Protonation products of D-glucose and the resulting enediol formed in the reaction

A new enolate is created due to the deprotonation of the OH at the second carbon of the enediol. The enolate further forms the ketohexose. The reaction can be given as:

Formation of the enolate that further converts to ketohexose