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I read it from a book but don't know the reason. Please explain...

Boiling point orders are -

Ethanamide > Ethanoic Anhydride > Ethanoic Acid

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Ethanamide has a higher boiling point than ethanoic acid since amide has two hydogen atoms it can form more Hydrogen bonds than ethanoic acid and their molar masses are 45gmol-1 and 60gmol-1 which makes the difference brought by the London forces somewhat negligible . you may suppose Ethanoic anhydride should be having a lower boiling point than ethanoic acid and ethanamide since it only has London forces and dipole dipole attractions.But ehanoic anhydride(molar mass-106gmol-1) has a higher molar mass than Ethanoic acid(molar mass-60gmol-1) making the London forces in ehatnoic anhydride more significant. Hence we have ethanamide(222 °C)>Ethanoic anhydride(140°C)>Ethanoic acid(118°C).

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  • $\begingroup$ My book says, Ethanoic Anhydride molecular mass is much more than Ethanoic Acid, that's why Ethanoic Anhydride have higher boiling point than Ethanoic Acid. I have rather more confusion that why ethanamide have higher boiling point than Ethanoic Anhydride. $\endgroup$ – HelenaWilliams Apr 29 at 5:08
  • $\begingroup$ Yes Helena your book is correct and I have revised my answer.Hope it helps. $\endgroup$ – AfiJaabb Apr 29 at 5:16

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