Thursday, June 12, 2014

Carboxylic acids have higher b.p than alcohols having comparable molcular weight for e.g propanic acid have much higher b.p (141 degree celcius) than  n-butyl alcohol (118), although both of them have same molecular weight.
A pair of alcohol (n-butyl alcohol) molecule are held toghter by only one hydrogen bond but a pair of  carboxalic acid (propionic acid) molecular are held toghter not by one but by two hydrogen bonds. More the number of hydrogen bonds between the molecules, more heat should be supplied to break them and the substance. So, b.p of carboxylic acid is higher than that of alcohol of comparable molecular weight.

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Thank you !