Intermolecular forces

[Scienuk]

1. Why does CH3COOH have a higher boiling point than CH3CH2OH, don't they both form hydrogen bonding, what else is a determining factor? Is it the molar mass as the greater the molar mass the more electrons and the increased polarisability so the stronger the London dispersion forces?

2. What intermolecular forces does van der Waals' forces cover (I get different interpretations from different sources)?

[VeronicaG]

Van der Waals covers London forces, dipole-dipole, dipole-induced-dipole and hydrogen bonding.

[Msj Chem]

For the IB, van der Waals forces include London dispersion forces and dipole-dipole attractions, but not hydrogen bonding. 

There's a good explanation of the higher boiling point of carboxylic acids here:

http://www.chemguide.co.uk/organicprops/acids/background.html

In a pure carboxylic acid, hydrogen bonding can occur between two molecules of acid to produce a dimer.

This immediately doubles the size of the molecule and so increases the van der Waals dispersion forces between one of these dimers and its neighbours - resulting in a high boiling point.

Edited June 7, 2016 by Msj Chem