Question

4. An alcoholic compound was found to have molecular mass of 90 u. It was acetylated. Molecular
mass of the acetyl derivative was found to be 174 u. How many alcoholic (-OH) groups must be
present in the original compound?​

Answer 1

lAcetylation of an alcohol takes place in the following manner:

R−OH

→

Acetylation

R−OAc

Thus, it is clear that each −OH group is replaced by a −OAc group. Now, the weight of an acetyl group (Ac) is 43 and the weight of the lost Hydrogen atom is 1. Upon completion of reaction, for each −OH group present in a molecule, there is an increase of 43−1=42 units of weight.

Now, net increase in weight of the given molecule (390−180)=210

Thus, total number of −OH groups in the original molecule is

42

210

=5

Answer 2

Explanation:

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