Question

Glucose gives silver mirror with Tollen's reagent, which shows the presence of:

• A. a ketonic group
• B. an aldehydic group
• C. an alcoholic group
• D. an acidic group

Answer 1

The correct option is B an aldehydic group

Glucose gives silver mirror test with Tollen's reagent. It is due to the presence of an aldehydic group $(-CHO)$. Tollen's reagent is silver ammonia complex. It is mild oxidisng agent and oxidises aldehyde group to carboxylate ion. Tollen's reagent itself is reduced to metallic silver.

$\underset{Glucose}{C_5{H}_{11}{O}_{5}CHO}+\underset{\left(Tolle{n}^{\prime }sreagent\right)}{2Ag{\left(N{H}_3\right)}_{2}OH}⟶\underset{Gluconicacid}{C_5{H}_{11}{O}_{5}COOH}+\underset{Silvermirror}{2Ag}+2H_{2}O+4N{H}_3$