(a) What is a homologous series? Explain with an example.(b) Define the following terms giving one example of each.(i) Esterification(ii) Addition reaction

(a) Homologous series is a group of organic compounds having similar structures and similar chemical properties in which the successive compounds differ by CHgroup.

Example: All the alkanes have similar structures with single covalent bonds and show similar chemical properties, so they can be grouped together in the form of a homologous series.

(b) (i) Esterification: An ester is formed when ethanol (alcohol) reacts with ethanoic acid, on heating, in the presence of a few drops of concentrated sulphuric acid by the process of esterification.
For example in an esterification reaction, butyl acetate can be made from acetic acid and 1-butanol.

The chemical equation involved in the formation of the ester is given below:

$CH_3COOH + C_2H_5OH \xrightarrow {Conc. H_2SO_4}  CH_3COOC_2H_5 + H_2O$

Esters are biological materials, that have a pleasant characteristic, fruity odour. 

(ii)  Addition reaction: (a) The reactions in which an unsaturated hydrocarbon combines with another substance to give a single product is called an addition reaction.
Example: Ethene reacts with hydrogen when heated in the presence of nickel catalyst to form ethane:
$CH_2-CH_2 + H_2 \xrightarrow{Ni catalyst; heat} CH_3-CH_3$


Simply Easy Learning

Updated on: 13-Mar-2023


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