Question

A compound with molecular formula `C_(4)H_(10)O_(4)` on acylation with acetic anhydride gives a compound with molecular formula `C_(12)H_(18)O_(8)`. How many hydroxyl groups are present in the compound?
A. 1
B. 2
C. 3
D. 4

Answer 1

Correct Answer - D
Mol. Mass of `C_(4)H_(10)O_(4)`
`= 12 xx 4 + 10 xx 1 + 4 xx 16 = 122`
Mol. Mass of acylated product `(C_(12)H_(18)O_(8))`
`= 12 xx 12 + 18 xx 1 + 4 xx 16 = 290`
Increase in mol. Mass `= 290 - 122 = 168`
The reaction involved is `-OH + CH_(3)COCl rarr - O.CO. CH_(3) + HCl`
Increase in mol mass due to one `-OH` group = (Mol. mass of `COCH_(3)`) - At. mass of H `= 2 xx 12 + 16 + 3 - 1 = 42`
`:.` No. of `-OH` groups `= (168)/(42) = 4`