Question

Explain addition reaction with example.

Answer 1

In an
addition reaction, two atoms or groups add across a
multiple bond (C=C or C≡C) of an
unsaturated compound to form a
single product with fewer multiple bonds.

Hydrogenation of ethene:
\[ \mathrm{CH_2{=}CH_2 \;+\; H_2 \xrightarrow[\;473\text{–}523\,K\;]{Ni/Pt} \; CH_3{-}CH_3} \] Ethene (unsaturated) adds hydrogen to give ethane (saturated).

Addition of bromine to ethene (decolourisation of Br\(_2\) water):
\[ \mathrm{CH_2{=}CH_2 \;+\; Br_2 \;\longrightarrow\; BrCH_2{-}CH_2Br} \] (1,2-dibromoethane is formed; brown colour of bromine disappears.)