Why phenol is stronger acid than alcohol and salicylic acid is a stronger acid than p-hydroxy benzoic acid ?
Why phenol is stronger acid than aliphatic alcohol ?
With aliphatic alcohols there is no factor stabilizing group which stabilize the alkoxide anion RO – relative to the alcohol itself.
On the other hand, with phenols there is possibility of relative stabilization of the anion by delocalization of its negative charge through interaction with the pi orbitals of the aromatic nucleus.
Delocalization also occurs in the undissociated phenol molecules. For this reason phenols are stronger acids than aliphatic alcohols.
Why aliphatic alcohol is less acidic than aliphatic carboxylic acid ?
In case of aliphatic alcohol there is no factor stabilizing group which stabilize the alkoxideanion, RO – relative to the alcohol itself.
On the other hand, delocalization of the negative charge in the carboxylate anion involves structure of identical energy content and their centres involved two highly electronegative oxygen atoms.
That is why, aliphatic alcohols are very less acidic than
carboxylic acid.
Why salicylic acid is a stronger acid than p-hydroxy benzoic acid ?
The conjugate of salicylic acid that is salicylate ion getsstabilized by the intra ionic hydrogen bonding.
But the conjugate base of p-hydroxy benzoic acid that is p-hydroxy benzoate ion does not stabilized by such type H-bonding.
Hence, it is clear that salicylate ion is a weaker base than
the p-hydroxy benzoate ion , that is, salicylic acid is a stronger acid than
p-hydroxy benzoic acid.
Why dimethyl amine is a stronger base than trimethyl amine in aqueous medium ?
Dimethylamine is a stronger base than trimethyl amine in aqueous medium because the conjugate acid of the former is more stable than that of the later compound due to formation of H-bonding .The stability order of the conjugate acids due to salvation effect are as follows,
Summary
- Why phenol is stronger acid than aliphatic alcohol ?
- Why dimethyamine is more basic than trimethylamine in aqueous medium ?
- Why salicylic acid is stronger acid than p-hydroxy benzoic acid ?
No comments