Question

Write the product obtained when D-glucose reacts with \( H_2N - OH \).

Hint:

Hydroxylamine reacts with aldehydes and ketones to form oximes, which are useful intermediates in organic synthesis.

Answer 1

When D-glucose reacts with hydroxylamine (\( H_2N - OH \)), the product obtained is D-glucose oxime. The reaction involves the formation of an oxime by the condensation of the aldehyde group (at C-1) of D-glucose with hydroxylamine, eliminating a molecule of water (\( H_2O \)).

Reaction:
\[ \text{D-Glucose} + H_2N-OH \rightarrow \text{D-Glucose Oxime} + H_2O \]

Structure of D-Glucose Oxime:
The oxime forms at the C-1 position of D-glucose, replacing the aldehyde group (\( -CHO \)) with the oxime group (\( C=N-OH \)). The rest of the glucose structure remains unchanged.

Key Points:

• The reaction is specific to the open-chain form of D-glucose, which contains an aldehyde group.
• In aqueous solutions, D-glucose exists predominantly in the cyclic hemiacetal form, but a small equilibrium amount of the open-chain form allows this reaction to proceed.
• Oximes are stable compounds and can be used for characterization or protection of carbonyl groups in organic synthesis.

Final Answer:
The product is D-glucose oxime (\( C_6H_{12}O_5N-OH \)), formed at the C-1 position.