Explain this boiling point order please [closed]








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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**




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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