Question

When glucose (Problem 19-52) is treated with NaBH₄ , reaction occurs to yield sorbitol, a polyalcohol commonly used as a food additive. Show how this reduction occurs.

Short answer

Reduction followed as:

Step-by-step solution

Reduction with sodium borohydride

Sodium borohydride NaBH₄ is the mild reducing agent which is used to reduce the aldehyde and ketone carbonyl group to the alcohol. It reduces aldehyde to primary alcohol and ketone to secondary alcohol it do not reduce the higher carbonyl like carboxylic acid and ether so, it is a mild reagent.

Reduction of glucose with sodium borohydride

As glucose contain the aldehyde group and sodium borohydride is the basic reducing agent so it abstracts the proton of the aldehyde followed by hydrolysis convert the carbonyl into the hydroxyl group as the primary alcohol is formed in sorbitol as shown below:

Reduction of Glucose

Reduction of glucose

Reduction of glucose to form sorbitol is followed by hydrolysis by converting the open aldehyde to alcohol group.

Compound Formation