Question

The melting point of o-nitrophenol is 44°C while that of the para-isomer is 114°C. Explain.​

Answer 1

Answer:

Due to intramolecular hydrogen bonding in ortho-isomer, it has least melting point. Due to effective intermolecular hydrogen bonding and close packed structure in para-isomer, it has highest melting point among the isomers. So, the order is para

Answer 2

The melting point of o-nitrophenol is 44°C while that of the para-isomer is 114°C. The explanation to the above statement are given below -

• For the ortho nitrophenol, the nitro group and alcohol group will be in close alignment.
• The close alignment of these groups will cause the intrahydrogen bonding.
• These bonding will make the compound more stable. Thus the melting point of ortho nitrophenol will be less.
• For the para nitrophenol, the nitro group and alcohol group are apart, and they form the interhydrogen bonds. This makes the compound more stable in comparison to the ortho isomer. Thus the melting point of para isomer is more than that of ortho isomer.