Question

An unknown compound of carbon, hydrogen and oxygen contains 69.77% C and 11.63% H and has a molecular weight of 86. It does not reduce Fehling solution, but forms a bisulphite addition compound and gives a positive iodoform test. What is the possible structure ?

Answer 1

(i) For empirical formula

Element	Percentage	Relative number of atoms	Simplest ratio
C	69.77	69.77/12 = 5.81	5
H	11.63	11.63/1 = 11.63	10
O	18.6	18.6/16 = 1.16	1

Thus, ratio of C, H and O in the compound is 5 : 10 : 1 

.'. Empirical formula of compound = C₅H₁₀O For molecular formula :

Empirical formula wt. = (12 x 5) + (10 x 1) + 16 = 86

Molecular wt. of compound = 86

n = molecular wt./empirical formula wt.

= 86/86 = 1

:. Molecular formula =  (empirical formula)_n

= C₅H₁₀O

(ii) Compound forms bisulphite addition compound and thus, has carbonyl group,

ie, aldehyde or ketone.

(iii) It does not reduce Fehling solution and thus, it is not aldehyde but it is ketone.

(iv) It gives positive iodoform test and thus, it has

(v) Above facts reveals that compound is :