Boiling point of cycloalkanes and alkanes. Which one is higher? And why?

Answer 1

The boiling point depends on the interaction between the molecules: the stronger the interaction the higher the boiling point.

For saturated hydrocarbons the only forces between the molecules are Van der Waals dispersion force (There isn't much electronegativity difference between carbon and hydrogen, so there is hardly any bond polarity. The molecules themselves also have very little polarity).

Thus the more "open" and "straight" molecules will have bigger surface of interaction, meaning stronger interaction and higher boiling point. Cycloalkanes are not planar but still can have more expanded conformations than alkanes. Therefore cycloalkanes will have higher bp than alkanes. Also branched alkanes have for the same reason even lower bp than their non-branched isomers.

Answer 2

Boiling point of cycloalkanes is higher, but I don't agree with Kunnu - boiling isn't involved with bond energy. unless hydrogen bond. But there is no hydrogen bond in alkanes.

I don't agree with Lim, because molecular mass of alkane is higher than cycloalkane,
e.g. heksane - C6H14 M=86
cycloheksane - C6H12 M=84.

Answer 3

cycloalkane has higher boiling point than alkane because their relative molecular mass is higher than alkane.

Answer 4

boiling point of cycloalkanes are more than alkanes...........
becoz the bond energy required for breaking bonds of cycloalkanes is more than alkanes........

Answer 5

if we consider 2 different molecules of hexane and cyclohexane we will find that both has the same number of carbons but different number of hydrogen and as we know there are some attraction force between molecules in the compound and this force will effect the boiling point of each compound. cyclohexan more higher than normal hexan