Chapter 19: Q18. (page 748)

Question: Rank the compounds in each group in order of increasing acidity.
a.
b.

Short Answer

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Step by step solution

Step-by-Step SolutionStep 1: Benzoic acid

Benzoic acid comes under the category of aromatic carboxylic acid. Several organic substances like phenol can be prepared by using benzoic acid.

Acidity of benzoic acids

The conjugate base is destabilized if there is an electron-donating group in a particular compound. This makes the acid less acidic in nature.

The presence of electron-withdrawing groups leads the conjugate base to be more stabilized, making the acid acidic.

Arrangement of compounds in the increasing order of acidity

a. In the second compound, the chloro group functions as an electron-withdrawing group resulting in the high acidic strength of the particular compound.

The methyl group present in the third compound is an electron releasing group that destabilizes the conjugate base making it less acidic. The first compound is more acidic than the third compound as it does not have an electron-donating group.

The order of acidity can be given as:

Increasing order of the acidity of the different compounds in question a

b. The carbonyl group in the second compound is an electron-donating group that stabilizes the conjugate base of the compound. Hence this compound is more acidic.

The first compound is more acidic than the third compound as the group is an electron-donating group. The increasing order of acidity can be given as: