Bromine induced dipole moment

An electrostatic potential map showing the temporary induced dipole moment of molecular bromine when it is in the vicinity of a nucleophile. 

Molecular bromine is a nonpolar compound, because the Br—Br bond is covalent. Nevertheless, the molecule is polarizable, and the proximity of a nucleophile can cause a temporary, induced dipole moment (Figure 9.9). 

As a molecule of Br2 gets close to the pi bond of an alkene, the electron density of the pi bond begins to repel the electron cloud around Br2- This effect gives the Br2 molecule an induced dipole moment (this is a temporary interaction—it only happens while the bromine molecule is near the alkene) ... 

In this chapter, we will explore both of these scenarios. For now, let us start by trying to make the electrophile a better electrophile. How do we make Bt2 a better electrophile Let s remember why Br2 is an electrophile in the first place. Just a few moments ago, we saw that an induced dipole moment is formed when Br2 gets close to an alkene. This creates a partial positive charge on one of the bromine atoms. Clearly, if we had Br+ instead of Br2, then that would be an even better electrophile. We would not have to wait around for Br2 to become slightly polarized. 

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