Question

The presence of carbonyl group in glucose is confirmed by its reaction with hydroxylamine. Identify the type of carbonyl group present and its position. Give a chemical reaction in support of your answer.

Answer 1

The carbonyl group is present in glucose aldehyde at the C₁ atom. Glucose on oxidation with a mild oxidising agent like Br₂ water gives gluconic acid containing the same number of C atoms (six) as are present in glucose.

\[\begin{array}{cc}
\ce{CHO}\phantom{.............}\ce{COOH}\\
|\phantom{..................}|\phantom{......}\\
\ce{(CHOH)4 ->[Br2 water](CHOH)4}\\
|\phantom{..................}|\phantom{......}\\
\phantom{..}\ce{CH2OH}\phantom{..........}\ce{\underset{Gluconic acid}{CH2OH}}
\end{array}\]

This indicates that the carbonyl group is present in an aldehydic \[\ce{(-CHO)}\] group.