Question

$ - OH$ group present in alcohols is neutral while it is acidic in carboxylic acid because
(A) In carboxylic acid $ - OH$group is attached to electron withdrawing carbonyl group
(B) In alcohols $ - OH$group is attached to alkyl group which is electron withdrawing
(C) Carboxylic group is an electron releasing group
(D) Alcoholic group is an electron withdrawing group

Answer 1

Hint:Alkyl group on alcohol is electron donating while carbonyl group on carboxylic acid is electron withdrawing. Electron donating groups are known to decrease acidity while electron withdrawing groups are known to increase acidity.

Complete answer:Acidic strength of any compound depends on the ease with which the hydrogen is lost. After the loss of the proton,the more stable the ion is,the more acidic it will be. This is how the acidic character of any compound is determined.
In the case of alcohols,the attached group is the alkyl group which is electron donating in nature. After the loss of the proton the ethoxide ion is formed.This ion is not resonance stabilised.
While in case of carboxylic acid ,the ion formed is carboxylate ion and it is resonance stabilised because of the presence of carbonyl group. The stability of resonance ions is more. The carbonyl group withdraws the electron density from oxygen making it negatively charged.The negative charge on electronegative atoms is stable and hence the ion. Hence,the presence of electron withdrawing carbonyl group in carboxylic acid makes the $ - OH$ acidic while this does not happen in case of alcohols.

Hence, the correct option is A.

Note:We need to keep in mind the key point: the more stable the ion after the loss of proton is formed, the more acidic the compound will be. Acidic strength also depends upon the group attached with the compound.