Question

Which of the following is a homologue of $ C{H_3}NHC{H_2}C{H_2}C{H_3} $ ?
(A) $ C{H_3}C{H_2}NHC{H_2}C{H_3} $
(B) $ C{H_3}C{H_2}C{H_2}N{H_2} $
(C) $ C{H_3}CH(C{H_3})N{H_2} $
(D) $ C{H_3}C{H_2}NHC{H_3} $

Answer 1

Hint: Homologous series is the series of alkanes, alkenes or alkynes in which the molecular formula of two compounds differ by one mole of $ C{H_2} $ group only. For example: methane and ethane belong to the same homologous family and are adjacent to each other.

Complete step by step solution:
First of all we will talk about the alkanes, alkenes and alkynes.
Alkanes: The compounds which are formed by carbon and hydrogen and have only a single bond between the carbon-carbon atoms, are known as alkanes. For example: The first member of the alkane family is ethane $ ({H_3}C - C{H_3}) $ . The general formula of the alkane group is $ {C_n}{H_{(2n + 2)}} $ .
Alkenes: The compounds which are formed by carbon and hydrogen and have at least one double bond along with a single bond between the carbon-carbon atoms, are known as alkenes. For example: The first member of the alkene family is ethene $ ({H_2}C = C{H_2}) $ . The general formula of the alkene group is $ {C_n}{H_{2n}} $ .
Alkynes: The compounds which are formed by carbon and hydrogen and have at least one triple bond along with a single bond between the carbon-carbon atoms, are known as alkynes. For example: The first member of the alkyne family is ethyne $ (HC \equiv CH) $ . The general formula of the alkyne group is $ {C_n}{H_{(2n - 2)}} $ .
Homologous series is the series of alkanes, alkenes or alkynes in which the molecular formula of two compounds differ by one mole of $ C{H_2} $ group only.
Here we are given with the compound $ C{H_3}NHC{H_2}C{H_2}C{H_3} $ the general formula is $ {C_4}N{H_{11}} $ so the homologue of this compound will be either $ {C_3}N{H_9} $ or $ {C_5}N{H_{13}} $ so the compound in option d i.e. $ C{H_3}C{H_2}NHC{H_3} $ has the general formula $ {C_3}N{H_9} $ .
So option D is correct.

Note:
Primary alkyl group: Those alkyl groups in which carbon is attached with three hydrogen atoms and carbon atoms.
Secondary alkyl group: Those alkyl groups in which carbon is attached with two hydrogen atoms and two carbon atoms.
Tertiary alkyl group: Those alkyl groups in which carbon with one hydrogen and three carbon atoms.