Chloromethane, bond length dipole moment

Chloromethane. bond length of, 335 bond strength of, 335 dipole moment of, 335 dissociation enthalpy of, 195 electrostatic potential map of, 38, 143.335... 

It s relatively easy to measure dipole moments, and values for some common substances are given in Table 2,1. Once the dipole moment is known, it s then possible to calculate the amount of charge separation in a molecule. In chloromethane, for example, the measured dipole moment is p = 1.S7 D. If we assume that the contributions of the nonpolar C-H bonds are small, then most of the chloromethane dipole moment is due to the C-Cl bond. Since the C-Cl bond length is 178 pm, the dipole moment of chloromethane would be 1.78 x 4.8 D = 8.5 D if a full negative charge on chlorine were separated from a full positive charge on carbon by a distance of 178 pm (that is, if the C-C bond were ionic, C Cl"). But because the actual dipole moment of chloromethane is only 1.87 D, the C-Cl bond is only about ( )(100%) = 22% ionic. Thus, the chlorine atom in chloromethane has an excess of about 0.2 electron, and the carbon atom has a deficiency of about 0.2 electron (Figure 2.3, p. 40). 

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