Why is the density of cyclic hydrocarbons more than that of their acyclic counterparts?

For ex:

Cyclopentane: 751 kg/m³
Pentane: 626 kg/m³

Cyclohexane:779 kg/m³
Hexane:655 kg/m³

In fact, as you can see above, cyclopentane is even denser than hexane.

My reasoning so far is:

Attractions in hydrocarbons depend only on London forces, which increases with surface area. An alkane will have more surface area for bonding as compared to a cycloalkane (The inside of the ring cant be used), so it will have more forces, and hence will be packed closer (be denser).

But this contradicts the facts.


1 Answer 1


A simple explanation might be that the ratio of carbon to hydrogen is higher in the cyclic hydrocarbons, and carbon is a heavier element than hydrogen.


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