Question

Compound having a molecular formula $C_4{H}_8{O}_3$ on acetylation gives an acetyl derivative compound having a molecular weight 188. The number of $OH$ group(s) in the compound is:

Answer 1

$R-OH\stackrel{\text{Acetylation}}{\to }R-OAc$
From the reaction, it can be seen that $H$ is being replaced by $-CO-C{H}_3$ group.
There is an increase of 42 ,i.e., $(43-1)$ mass per hydroxy group.
Molecular formula of the given compound is $C_4{H}_8{O}_3$.
$\therefore$ Molecular mass will be $=12\times 4+1\times 8+16\times 3=104$
Net increase in weight of the given compound $=188-104=84$
Hence, two hydroxyl groups are present per molecule in the reactant.