DEAR GOLU,

One which is more acidic will have less PKa value...

So the order goes like:

1)CH3(NO2)>(NO2)2-CH2>(NO2)3-CH

2)m-nitrophenol > p-nitrophenol>2,4,6 trinitrophenol>phenol

3)(N02)-CH2-COOH>CH3-C0-CH2-COOH>CH3COOH

In orthonitrophenol the hydrogen of the -OH group satisfies the conditions for intramolecular hydrogen bonding and should in theory be bound to the nitrogen of the nitro substituent making difficult its loss as H+.

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Sagar Singh

B.Tech IIT Delhi