Answer:
(a) The most acidic compound - oxalic acid
The least acidic compound - acetic acid
(b) The most acidic compound - 2,4-dinitrobenzoic acid
The least acidic compound - p-bromobenzoic acid
(c) The most acidic compound - benzoic acid
The least acidic compound - cyclohexanol
Explanation:
(a) Presence of electron donating group decreases the acidity of carboxylic acid. Therefore , acetic acid is least acidic due to methyl group on carbon of -COOH group.
Oxalic acid is the most acidic compound due to presence of 2 -COOH group.
(b) Presence of electron withdrawing group increases the acidity of benzoic acid. 2,4-dinitrobenzoic acid will be more acidic as it has two strong electronegative substituents ([tex]-NO_2[/tex] group).
p-bromobenzoic acid will be less acidic than p-nitrobenzoic acid beacuse Br is weaker electron withdrawing group than [tex]NO_2[/tex]
(c) pKa value of benzoic acid(4.45) is more than other compounds and cyclohexanol has least pKa value (16).(Since , higher the pKa value , least acidic the compound is )
