Question

Explain the terms Inductive and Electromeric effects. Which electron displacement effect explains the following correct orders of acidity of the carboxylic acids?

$C{H}_{3}C{H}_{2}COOH>(C{H}_3{)}_{2}CHCOOH>(C{H}_3{)}_{3}CCOOH$

Answer 1

Inductive effect is the displacement of sigma electrons towards more electronegative species. It is transmuted though a chain of C atoms. It is classified into +I effect and -I effect.
Electron releasing groups such as alkyl groups show +I effect. -I effect is shown by electron withdrawing groups such as nitro, cyano, halo, amino etc.

Electromeric effect is temporary effect and involves transfer of pi electrons by the demand of attacking reagents towards more electronegative species.It is more powerful than inductive effect and is shown by compounds having C=C, C=N or N≡NN≡N groups. It is classified into + E effect and -E effect.
In +E effect, pi electrons are transferred towards the attacking reagent whereas in -E effect, pi electrons are transferred away from the attacking reagent.

The decreasing order of the acidity $C{H}_{3}C{H}_{2}COOH>(C{H}_3{)}_{2}CHCOOH>(C{H}_3{)}_{3}CCOOH$ is explained on the following basis. Electron releasing groups such as methyl groups , intensify the negative charge and decreases stability and acidic nature. Hence, more is the number of electron releasing groups, less is the acidic nature.