Question

Question 12.6 Draw formulas for the first five members of each homologous series beginning with the following compounds.

(a) H–COOH

(b) CH3COCH3

(c) H–CH=CH2

Class XI Organic Chemistry : Some Basic Principles and Techniques Page 362

Answer 1

homogenous series :-All the members of a series can be represented by a general formula . The difference between two successive members of a series is -CH2 by molecular formula and 14 amu by molecular weight.
$ex:-\text{Alkane}=C_nH_{2n+2}$
(a) H-COOH, this belongs carboxylic acid group .
hence , homogeneous series of it is
H-COOH , methanoic acid
CH3-COOH, ethanoic acid
CH3CH2-COOH , propanoic acid
CH3CH2CH2-COOH,butanoic acid
CH3CH2CH2CH2-COOH,pentanoic acid.

(b) it belongs to Ketones .
CH3COCH3, propanone
CH3CH2COCH3, butan-2-one
CH3CH2COCH2CH3,pentan-3-one
CH3CH2CH2COCH2CH3,Haxan-3-one
CH3CH2CH2CH2COCH2CH3, Heptane-3-one

(c) it belongs to alkene group.
CH2=CH2,Ethene
CH3CH=CH2,propene
CH3CH2CH=CH2,but-1-ene
CH3CH2CH2CH=CH2,pent-1-ene
CH3CH2CH2CH2CH=CH2,Hex-1-ene