3
$\begingroup$

I know that intermolecular forces increase the boiling and melting point of a compound, but what is the effect of intramolecular forces on boiling and melting points?

I found contradicting answers while searching on the web.

Improve this question
$\endgroup$
7
  • 3
    $\begingroup$ Why would there be an effect? There is none. $\endgroup$ – Ivan Neretin Apr 3 '19 at 13:40
  • $\begingroup$ @IshanJawale As Ivan says, there shouldn't be an effect of intramolecular forces. Changing from gas to liquid to solid is only affected by the interactions between molecules, not within them. $\endgroup$ – Tyberius Apr 3 '19 at 16:07
  • $\begingroup$ @WilliamR.Ebenezer There is a general problem with these unspecific, short titles. They will almost always lead to confusion and sometimes would appear to be not fitting at all. The mix-up in the other post did not make this better. If you are suggesting these kind of edits, please double check if it (partially) invalidates an answer (as was the case in the linked one). $\endgroup$ – Martin - マーチン♦ Apr 4 '19 at 14:26
  • $\begingroup$ @Martin-マーチン, yes, I did notice that earlier, before you pointed out, but my edit had already been petitioned. But I judged that it would be better, as a question with a contradicting title is worse than a few edits made to the answers mentioning the inadvertent error(the site must edge towards the perfection!). The point being, this question would not be posted had this error been non-existent, as the same question had been addressed satisfactorily earlier, under the same title. $\endgroup$ – William R. Ebenezer Apr 4 '19 at 14:50
  • $\begingroup$ @Tyberius I agree with that, too close. $\endgroup$ – William R. Ebenezer Apr 4 '19 at 15:05
5
$\begingroup$

The effect of intramolecular forces versus intermolecular forces on boiling and melting points is sometimes seen when we compare the boiling points of ortho- and para-nitrophenol (or similar compounds).

Para-nitrophenol shows intermolecular hydrogen bonding, which causes an increase in boiling point as different molecules bond better with each other, as compared to ortho-nitrophenol, where there is intramolecular hydrogen bonding, which does not help in increasing the boiling point, hence p-nitrophenol has a higher boiling point than o-nitrophenol.

However, while comparing intramolecular bonding with no hydrogen bonding, no difference can be expected unless the intramolecular bonding affects the intermolecular bonding in some way, for instance by changing size and thus packing.

Improve this answer
$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.