Get your chemical equations right

Class 12 Chemistry is not too tough to crack if you master tricky questions like these.

1.An organic compound contains 69.77% carbon, 11.63 % hydrogen and rest oxygen. The molecular mass of the compound is 86. It does not reduce Tollen’s reagent but forms an addition compound with sodium hydrogen sulphite and gives positive iodoform test. On vigorous oxidation, it gives ethanoic acid and propanoic acid. Write the possible structure of the compound.
Sol.

C = 69.77%, H = 11.67%

Therefore, O= 100 – (69.77 + 11.63)%

= 18.6 %

1

The empirical formula of the given compound = f9

Empirical formula mass = 5 × 12 + 10 × 1 + 1 × 16 = 86

Molar mass = 86 (given)

Therefore, Molecular formula =f9

Since the compound form sodium hydrogen sulphite addition product, therefore, it must be either an aldehyde or methyl ketone. Since the compound does not reduce Tollen’s reagent therefore, it cannot be an aldehyde and hence it must be a methyl ketone. Since the compound gives positive iodoform test, therefore, the given compound is a methyl ketone. Since the given compound on vigorous oxidation gives a mixture of ethanoic acid and propanoic acid, therefore, the methyl ketone is

2

 

Published in Hindustan Times, New Delhi, January 28, 2015

(The set of questions and answers have been compiled by subject experts of chemistry department at Studymate)