What is the product when glucose reacts with bromine water ?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Gluconic acid
Glucose has an aldehyde group (–CHO). Bromine water is a mild oxidising agent: it oxidises only the –CHO group to –COOH and gives the six-carbon carboxylic acid, gluconic acid. This reaction shows that the carbonyl group of glucose is an aldehyde group.
\( \displaystyle \ce{CHO-(CHOH)4-CH2OH} \xrightarrow{\ce{Br2}\ \text{water}} \ce{COOH-(CHOH)4-CH2OH} \)
Why the other options are incorrect
Option (2) Glyceraldehyde — Incorrect. It is a three-carbon sugar; bromine water does not break the carbon chain of glucose.
Option (3) Saccharic acid — Incorrect. It is formed with a strong oxidising agent, nitric acid, which oxidises both the –CHO and the –\( \ce{CH2OH} \) groups to –COOH.
Option (4) Oxime — Incorrect. It is formed with hydroxylamine (\( \ce{NH2OH} \)), which reacts with the carbonyl group.
NCERT (2026-27 edition):
Structure of Glucose – “… 4. Glucose gets oxidised to six carbon carboxylic acid (gluconic acid) on reaction with a mild oxidising agent like bromine water. This indicates that the carbonyl group is present as an aldehydic group.”