Question

Define the following giving one example of each: [5 MARKS]
1. Esterification
2. Addition reaction

Answer 1

Each point: 2.5 Mark

(i) Esterification- Esters are most commonly formed by reaction of an acid and an alcohol. Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to give an ester. Esters are sweet-smelling substances. These are used in making perfumes and as flavouring agents.

${\text{CH}}_3\text{COOH}+{\text{CH}}_3{\text{CH}}_2\text{OH}\stackrel{{\text{Conc. H}}_2{\text{SO}}_4}{\to }{\text{CH}}_3{\text{COOC}}_2{\text{H}}_5+{\text{H}}_2\text{O}$

(ii) Addition reaction- An addition reaction is where two or more molecules combine to form a larger one. Addition reactions are limited to chemical compounds that have multiple bonds, such as molecules with carbon-carbon double bonds (alkenes), with triple bonds (alkynes) or with carbonyl ($\text{-C=O}$) groups. Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons. This reaction is commonly used in the hydrogenation of vegetable oils using a nickel catalyst.