Benzoic acid-boiling point-strength-more acidic than acetic acid.

Benzoic  acid boiling point explanation.

Oxygen is more electronegative than hydrogen. So, O – H bond of benzoic acid is polar in nature .

As a result, benzoic acid forms inter-molecular hydrogen bond. To break this large number of inter-molecular hydrogen bond , a great amount energy is required.

Consequently, the boiling point of benzoic acid is high, that is, the boiling point of benzoic acid is 249ᵒC .

Another explanation of high boiling point of benzoic acid is molecular mass. The molecular mass of benzoic acid is 122.04.

With increasing molecular mass , the Vander waal’s force of attraction among the molecules increases .Hence the boiling point of benzoic acid becomes high.

Benzoic acid strength explanation

In case of benzoic acid,the carboxylic acid group ( –COOH ) is directly attached to the sp2 hybridized carbon atom of aromatic benzene ring that is, attached with phenyl group.

Now, +R  effect of phenyl group is greater than –I effect ( +R > –I ) . As a result of this , the O–H bond of benzoic acid becomes less polar than its expected value.

Consequently, the tendency of benzoic acid to donate proton in aqueous medium decreases. For this reason benzoic acid behave as a weak acid. 

But ,the presence of electron withdrawing group with benzene ring increase the acidic strength and presence of electron repulsive group decrease the acidic strength of benzoic acid.

For example, p-nitro benzoic acid is more acidic than benzoic acid while p-methoxy benzoic acid is less acidic than benzoic acid.

Why benzoic acid is more acidic than acetic acid?

In case of benzoic acid, the carboxylic acid group ( –COOH ) is directly attached to the sp2 hybridized carbon atom of aromatic benzene ring , that is, attached with phenyl group.

Now, +R effect of phenyl group is greater than –I effect ( +R > –I ). As a result of 

this, the O–H bond of benzoic acid becomes less polar than its expected value.

Consequently, the tendency of benzoic acid to donate proton in aqueous medium decreases.For the above reason benzoic acid behave as a weak acid.

Although benzoic acid is more acidic than acetic acid. Because, in case of acetic, the carboxylic acid group (–COOH ) is directly attached to the methyl group ( –CH₃ ) which have +I effect.

Now, the +I effect of methyl group is more effective than the combined effect due to +R and –I effect of phenyl group .Therefore, benzoic acid becomes more acidic than acetic acid.

Which is more acidic fluoro acetic acid or chloro acetic acid?

The  strength of any acid depends on the stability of conjugate base of that acid .

Now, on ionization of both fluoro acetic acid and chloro acetic acid in aqueous 

solution, gives  the conjugate base , fluoro acetate and chloro acetate anion respectively.

Both the anion have two equivalent resonating structure . But,fluoro acetate anion  becomes more stable than chloro acetate anion.

Because , fluorine is more electronegative than chlorine atom . That is why fluorine have  greater – I effect than that of chlorine.

Since, fluoro acetate anion  is more stable than chloro acetate anion , hence fluoro acetic acid is more stronger acid than chloro acetic acid.

Summary:

Benzoic acid boiling point explanation.
Benzoic acid strength explanation
Which is more acidic fluoro acetic acid or chloro acetic acid?
Why benzoic acid is more acidic than acetic acid?

Benzoic acid definition in chemistry