Question

Which following reagent is used to detect presence of five hydroxyl groups in a glucose molecule?

Options

• Acetic anhydride

• Dilute nitric acid

• Br₂ water

• Hydroxyl amine

Answer 1

Acetic anhydride

Explanation:

\[\begin{array}{cc}
\ce{CHO}\phantom{...............}\ce{CHO}\phantom{......}\ce{O}\phantom{......................}\\
|\phantom{....................}|\phantom{..........}||\phantom{......................}\\
\ce{(CHOH)_4 ->[(CH3CO)_2O] (CH - O - C - CH3)_4 + CH3COOH}\\
|\phantom{....................}|\phantom{................................}\\
\ce{\underset{Glucose}{CH2OH}}\phantom{.............}\ce{CH2 - O - C - CH3}\phantom{...........}\phantom{....}\\
\phantom{...........}||\\
\phantom{...........}\ce{\underset{Glucose pentacetate}{O}}
\end{array}\]

The production of pentacetate is detected, indicating that glucose has five hydroxyl groups.