Hydrogen Bonding: Why p-Nitrophenol Is Less Volatile Than o-Nitrophenol

Same formula (C6H5NO3), same functional groups, yet o-nitrophenol melts at about 45 °C and p-nitrophenol at about 114 °C. Why is the para isomer so much harder to vaporise?

Intermolecular and intramolecular hydrogen bonding, the six-membered chelate ring in ortho, the chain in para, and how one cause decides melting point, volatility and solubility.

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In this video

• 0:00The puzzle: two nitrophenols
• 0:30What is a hydrogen bond?
• 1:00Two kinds of hydrogen bond
• 1:26Why it controls volatility
• 2:05Ortho: the six-membered ring
• 2:53Para: a chain forms
• 3:30Side by side