Question

Rank the compounds in order of increasing vapor pressure at 298 degrees celcius: Cyclopropane, Cyclobutane, and Cyclopentane.

Answer 1

There is not much difference in electronegativity of Carbon and hydrogen and so there is not much polarity difference among the given cylcoalkanes, however the molecules are held together by weak Vander wall forces.

so higher the number of carbons higher the moelcular weight higher the ineraction.

The order of van der wall inteaction will be

Cyclopentane > cyclobutane> cyclopentane

So due to this the vapours will be formed easily in cyclopentane as compared to cyclobutane and then cyclopentane.

So vapour pressue order will be:

cyclopropane < cyclobutane < cyclopetane.