Intermolecular Forces

Between two molecules of acetic acid there are 3 forces of attraction that affect them. These being the London dispersion force, the dipole-dipole force and hydrogen bonding.

The first force of attraction is the london dispersion force. Its a force of attraction that affects all molecules. Its the creation of temporary opposite poles at the ends of a molecule caused by the movement of electrons around the atoms. As the electrons move around the molecule one side may temporaryily have more electrons than the other side. Creating a negative end to the molecule. Since one side is now more negative the opposite end becomes more positively charged. Creating a weak temporary attraction between the charged ends.

The second force that affects the molecule is Dipole-Dipole. This is an electrostatic attraction between the positive end of one molecule and the negative end of another molecule. The unshared electron pairs on the oxygen atoms make them more negatively charged than the other ends of the molecule. Making the ends with hydrogens more negatively charged. So two molecules of Acetic acid would have a dipole-dipole bond here.

The last force of attraction is hydrogen bonding. Hydrogen bonding is a special case of dipole-dipole attraction. It causes a temporary covalent bond between the hydrogen of one molecule and the nitrogen, oxygen, or flourine of another molecule. In acetic acid this occurs between the oxygen of one molecule and any of the hydrogens of the other acetic acid molecule.

The oxygen atoms are more negatively charged than the hydrogen atoms.
The solid line indicates a dipole-dipole bond.
The dotted line indicates a hydrogen bond.