This results in a molecule where the center of positive charge (defined by the nuclei) does not coincide with the center of negative charge(defined by the electron orbitals).

which is very very weak, and short range forces of this nature are collectively known as van der Waals interactions

cohesive force attracting the molecules together.

Johannes Diderik van der Waals 

when the temperature is low enough.

Eα−α1α2r6(11.4.1)(11.4.1)Eα−α1α2r6 E\: \alpha \: \dfrac{-\alpha_1\alpha_2}{r^6} \tag{11.4.1} Dipole Induced - Dipole: The Intermolecular forces between a polar and non-polar molecule.

Why is pentane's boiling point so much lower than the other two?  Why does butan-1-ol have a higher boiling point than 2-methylpropan-1-ol? 

The the term InterMolecular Force (IMF) literally means the forces between molecules, and as such, is often a misnomer, as simply speaking, not all matter is composed of molecules.  Yet this term is used pervasively, and so we will use it, but first lets compare it to the so called "intramolecular forces", the forces within the proverbial "molecule.

Ion-Dipole Forces (these may not be true IMF, but we will call them IMFs) Dipole-Dipole Forces (between two polar molecules) Hydrogen Bonding (special type of dipole-dipole) Dipole-Induced Dipole (between polar and nonpolar molecules) Instantaneous Dipole-Induced Diploe (between two nonpolar molecules, often called London Dispersion Forces)

 The second major shortcoming is that not all covalently bonding molecules have a discrete formula, like diamond, which is a covalent network, and so even though it is a covalently bonded entity, it does not fit the paradigm of a molecule with a unique molecular formula.

E∝−|q1|μ2r2

Equation 11.2.411.2.4\ref{11.2.2}. E∝−|q1|μ2r2(11.2.4)