Properties of Nitrophenols:

 O-Nitrophenol is a yellow in colour crystalline compound, whereas m- and p-isomers are colourless crystalline compounds.

Isomer             ortho                meta                para

m.pt. (°C)         45                    97                    114

The lowest melting point of o-isomer is due to intra-molecular hydrogen bonding while meta and para isomers possess intermolecular hydrogen bonding and so, they comprise higher melting points.

They are stronger acids as compared to phenol. The order is:

p-isomer > o-isomer > m-isomer > phenol

while reduced, they form corresponding p-Nitrophenols and aminophenols. o- react along with bromine water to form 2, 4, 6-tribromophenol through transfer of nitro group.