An ester has a molecular mass of 102. On aqueous hydrolysis, it produces a monobasic acid and alcohol. If 0.185 g of the acid produced completely neutralises 25 mL of 0.1 N NaOH, find out the structural forulae of the alcohol produced and the ester with proper reasoning.

An ester has a molecular mass of 102. On aqueous hydrolysis, it produc

1.	An ester has a molecular mass of 102. On aqueous hydrolysis, it produces a monobasic acid and alcohol. If 0.185 g of the acid produced completely neutralises 25 mL of 0.1 N NaOH, find out the structural forulae of the alcohol produced and the ester with proper reasoning.
Answer» Solution :(i) From the AVAILABLE data, 25 ML of 0.1 N NaOH NEUTRALISE acid =0.185 g 1000 mL of 1.N NaOH will neutralise acid `=overset(0.185xx1000)underset(25xx0.1)=74.0g` 1000 mL of 1 N NaOH contain gram equivalent of it and it and it must react with gram equivalent of acid. `THEREFORE`Equivalent mass of monobasic acid =74.0 Molecular mass of monobasic acid =74.0 (ii) The monobasic acid is represented as RCOOH and the molecular mass from the molecular formula is `=RCOOH=R+12+32+1+R+45` `therefore Now R+45=74 or R=74-45=29`. This indicates that R is ethyl group `(CH_(3)CH_(2))` and the acid is `CH_(3)CH_(2)COOH.` (Propanoic acid). (iii) The molecular mass of ester `(CH_(3)CH_(2)COOR)` is 102. Mass of alkyl group (R-)=(102-73)=29 This indicates that the alkyl group R is also `C_(2)H_(5)` group and the ester is `CH_(3)CH_(2)COOC_(2)H_(5).` `underset("Ethyl propionate")underset()(CH_(3)CH_(2)COOC_(2)H_(5))+H_(2)Ooverset(H^(+))rarrunderset("Propionic acid")underset()(CH_(3)CH_(2)COOH)+underset("Ethyl alcohol")underset()(C_(2)H_(5)OH)`