Identify the most and the least acidic compound in each of the following sets. Leave the remaining answer in each set blank. a) difluoroacetic acid: fluoroacetic acid: trifluoroacetic acid: b) 2-chlorobutanoic acid: 4-chlorobutanoic acid: 3-chlorobutanoic acid: c) cyclohexanol: phenol: benzoic acid:

Explanation:

The given set of options are:

a) difluoroacetic acid: _______ fluoroacetic acid: _______ trifluoroacetic acid: _______

b) 2-chlorobutanoic acid: _______ 4-chlorobutanoic acid: _______ 3-chlorobutanoic acid: _______

c)cyclohexanol: _______ phenol: _______ benzoic acid:

A strong acid is one whose conjugate base is stabilized either by resonance or -I effect.

a) If -I groups are present on the carboxylic acid group then they stabilize the carboxylate anion (the conjugate base of the carboxylic acid) and give more strength to the carboxylic acid group. More the number of -I groups then more will be the strength of the carboxylic acid.

Among the given options,

Trifluoroacetic acid has three fluorine atoms in its structure thus it is a strong acid.

Fluoroacetic acid has only one fluorine atom in its structure. Hence it is the weak acid among the given options.

b) The -I groups should be nearer to the carboxylic acid group then it attains more stability.

If the distance of the -I group increases from the -COOH group then, the strength of the carboxylic acid group decreases.

So, the strongest acid is 2-chlorobutanoic acid.

The weak acid among them is 4-chlorobutanoic acid.

c) Among the given options benzoic acid is the strongest acid because due to resonance benzoate anion is stabilized more.

Here resonance exists in both phenyl group and group.

The weak acid is cyclohexanol.

Because cyclohexanolate anion is not stabilized by resonance.