Count the stereocentres (chiral carbons) in each of: alpha-D-glucopyranose (ring form), open-chain D-fructose, and beta-D-fructofuranose (ring form, ring closure between C-2 and C-5). The total of the three counts is

Answer: A

alpha-D-glucopyranose: C-1 to C-5 are all stereogenic = 5. Open-chain D-fructose: C-3, C-4, C-5 = 3. beta-D-fructofuranose: the ring closure makes C-2 a stereocentre, so C-2, C-3, C-4, C-5 = 4. Total = 5 + 3 + 4 = 12.

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Count the stereocentres (chiral carbons) in each of: alpha-D-glucopyranose (ring form), open-chain D-fructose, and beta-D-fructofuranose (ring form, ring closure between C-2 and C-5). The total of the three counts is

Answer: A

More questions on Carbohydrates: classification, glucose structure, reactions