Carbohydrates

Step 1: Nature of glucose.
Glucose is an aldohexose and contains an aldehyde group (–CHO). Bromine water is a mild oxidising agent. Step 2: Reaction.
Bromine water oxidises the –CHO group of glucose to –COOH, forming gluconic acid. Step 3: Observation.
The reddish-brown colour of bromine water disappears, confirming the presence of the aldehyde group in glucose. Conclusion:
Glucose reacts with bromine water to form gluconic acid, showing that glucose contains an aldehyde group.

Step 1: Structure of glucose.
Glucose is an aldohexose with the molecular formula C H O . Its open-chain structure is:
Step 2: Identify alcoholic groups.
- The four middle carbons each have a hydroxyl (–OH) group, making them secondary alcohols.
- The terminal –CH OH group at C-6 is a primary alcoholic group.

Step 3: Conclusion.
Thus, glucose has only one primary alcoholic group (at carbon-6).

Final Answer:

(i) Reaction of glucose with hydroxylamine:
Glucose reacts with hydroxylamine ( ) to form an oxime by reacting with the aldehyde group (-CHO) of glucose. (ii) Reaction of glucose with bromine water:
Glucose undergoes mild oxidation with bromine water, converting the aldehyde group (-CHO) into a carboxylic acid (-COOH), giving gluconic acid. Conclusion:
- With hydroxylamine, glucose forms an oxime derivative.
- With bromine water, glucose is oxidized to gluconic acid.

Step 1: Structural formula.
The open-chain form of D-glucose: It has 6 carbons, 5 hydroxyl groups, and 1 aldehyde group.
Step 2: IUPAC name.
As an aldohexose, the correct name is
2,3,4,5,6-pentahydroxyhexanal. In stereochemical form, it is (2R,3S,4R,5R).
Step 3: Test for aldehyde group.
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Fehling’s Test: On heating with Fehling’s solution, glucose reduces Cu to red precipitate of Cu O. -
Tollen’s Test: On heating with ammoniacal silver nitrate, glucose reduces Ag to metallic silver (silver mirror).
Step 4: Conclusion.
Thus, D-glucose contains an aldehyde group confirmed by positive Fehling’s and Tollen’s tests.