Dissolving monosaccharaides in aqueous base causes them to undergo

Options

A. enolization
B. tautomerization
C. isomerization
D. all of these

Answer

D

Explanation

If a solution of `D-` glucose containing calcium hydroxide is allowed to stand for several days, then several products can be isolated, including `D-` fructose and `D-` mannose. Thus, monosaccharides undergo isomerization via enolate ions and enediols (e.g., `D-` glucose isomerizes to `D-` mannose and to `D-` furctose) when placed in aqueous base.
This type of reaction is called the Lobry de Bruyn-van Ekenstein rearrangement. When carrying out reaction with monosaccharides it is usually important to prevent these isomerizations and thereby the stereochemistry at all of the stercocentres.
One way to do this is to convert the monosaccharide to the methyl glycoside first. We can then safely carry out reaction in basic media because the aldehyde group has been converted to tan actual are stable in aqueous base.