DIPOLE MOMENT
The dipole moment is a property of the molecule that results from charge separations like those discussed above. However, it is not possible to measure the dipole moment of an individual bond within a molecule; we can measure only the total moment of the molecule, which is the vectorial sum of the individual bond moments.34 These individual moments are roughly the same from molecule to molecule,35 but this constancy is by no means universal. Thus, from the dipole moments of toluene and nitrobenzene (Fig. 1.10)36 we should expect the moment of p-nitrotoluene to be 4.36 D.