High School

Glucose is an aldose. Which one of the following reactions is not expected with glucose?

A. It does not form oxime.
B. It does not react with Grignard reagent.
C. It does not form osazones.
D. It does not reduce Tollens' reagent.

Answer :

Final answer:

Glucose, as a reducing sugar, does undergo reactions with Tollens' reagent, forms osazones, and does not form Schiff's bases with amines as expected, but the reaction it does not undergo is with Grignard reagent. The correct option is c.

Explanation:

The student asked which reaction is not expected with glucose, which is an aldose. Glucose is a reducing sugar, meaning it can be oxidized by reagents like Tollens' reagent, Benedict's reagent, and Fehling's solution. These reagents will in turn be reduced during the reaction, typically with formation of a silver mirror in the case of Tollens', or precipitation of cuprous oxide with Fehling's solution.

Glucose forms osazones when reacted with phenylhydrazine, and although it reacts with amines, the expected Schiff's bases are not usually isolated because they rapidly cyclize to form glucosylamine. However, glucose will not react to form a hydrogen sulfite addition compound or react with Grignard reagents to form the expected alcohols, as is typically seen with free aldehydes or ketones.

Considering the reactions of glucose provided, the correct answer is that glucose does not react with Grignard reagent; all other options listed are reactions that glucose will undergo.