Per acetic acid( CH3COOO-H) is a weaker acid than acetic acid as acetate ion is stabilised by resonance.
Acidic strength of aromatic acids The parent member of the family benzoic acid which is a weaker acid( Ka = 6.3 x 10-5) than acid( Ka = 17.7 x 10-5) but stronger than acetic acid.
Some order of acidity are
( b) Similarly, Ka values of methyl substituted( toluic acids) at 298 K are as follows:
From the Ka values, it is evident that with the exception of o-isomer, both p and m-toluic acids are weaker acids than benzoic acid whereas the three isomeric nitro benzoic acids are stronger acids than benzoic acid.
( ii) Reactions involving cleavage of C-O-H bond( a) Formation of anhydride