Which acid of each pair shown here would you expect to be stronger?
(i) `CH_(3)CO_(2)H or CH_(2)FCO_(2)H`
(ii) `CH_(2)FCO_(2)H or CH_2ClCO_(2)H`
(iii) `CH_(2)FCH_(2)CH_(2)CO_(2)H or CH_(3)CHFCH_(2)CO_(2)H`
(iv)

Explanation

(i) `CH_(2)FCOOH`

The +I effect of `CH_3` group increases the electron density on the `O-H` bond. Therefore, release of proton becomes difficult. On the other hand, the -I effect of `F` decreases the electron density on the `O-H` bond. Therefore, proton can be released easily. Hence, `CH_2FCOOH` is a stronger acid than `CH_3COOH`.

(ii) `CH_(2)FCOOH`

`F` has stronger -I effect than `Cl`. Therefore, `CH_(2)FCOOH` can release proton more easily than `CH_(2)ClCOOH`. Hence, `CH_(2)FCOOH` is stronger acid than `CH_2ClCOOH`
(iii) `CH_(3)CHFCH_(2)COOH`

Inductive effect decreases with increase in distance. Hence, the +I effect of F in `CH_3CHFCH_2COOH` is more than it is in `CH_(2)FCH_2CH_2COOH`. Hence, `CH_(3)CHFCH_2COOH` is stronger acid than `CH_2FCH_2CH_2COOH`.


(iv)


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