Which of the following statement is not true for glucose?
Biomolecules · Class 12 · JEE Main Previous Year Question
Which of the following statement is not true for glucose?
- a
Glucose exists in two crystalline forms and
- b✓
Glucose gives test for aldehyde
- c
Glucose reacts with hydroxylamine to form oxime
- d
The pentaacetate of glucose does not react with hydroxylamine to give oxime
Glucose gives test for aldehyde
Step 1: Glucose Anomers — Glucose is known to exist in two crystalline forms, and , which differ at the anomeric carbon (C1).
Step 2: Chemical Reactivity — Glucose reacts with hydroxylamine to give an oxime, but its pentaacetate does not because the hemiacetal is locked.
Step 3: Not-True Statement — Despite being an aldohexose, glucose fails the standard for aldehydes. This is because the aldehyde group is only present in a tiny fraction of the open-chain form in equilibrium.
Remember: Schiff's test failure is one of the key pieces of evidence for the cyclic structure of glucose.
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