APSC Legal Metrology: Chiral C atoms Paper 2

The number of chiral C atoms present in glucose molecule is
(A) 2
(B) 3
(C) 4
(D) 6

The correct answer is: (C) 4

Explanation:

Glucose is an aldohexose sugar with the molecular formula C₆H₁₂O₆. Its open-chain structure is:

HOCH₂–(CHOH)₄–CHO

The carbon atoms in glucose are numbered as follows:

1. C-1: Aldehyde group – not chiral
2. C-2 to C-5: Each is attached to four different groups – chiral
3. C-6: CH₂OH – not chiral

Therefore:

• C-2, C-3, C-4, and C-5 are chiral centers
• Total chiral carbon atoms = 4

✅ Answer: (C) 4