Q3 of 60 Page 1

What is meant by homologous series of carbon compounds? Write the general formula of (i) alkenes, and (ii) alkynes. Draw the structures of the first member of each series to show the bonding between the two carbon atoms.

The series which consists of similar structures and similar chemical properties in which the successive compounds differs by a CH2 group is termed as homologues series.

The two characteristics of homologues series are as follows:


1. The members of the homologues series consists of same general formula such as Alkanes have general formula CnH2n+2


2. The two adjacent homologues have a difference of molecular mass of 14 u.


The general formula for alkenes and alkynes are as follows:


(i) Alkenes, CnH2n


(ii) Alkynes, CnH2n-2


The first member of the series of alkenes is : Ethane which has formula CH4 and the first member of series of Alkynes is: Ethne and have formula C2H2 the structure is as follows:


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