Dipole-Induced Dipole Interactions (College Board AP® Chemistry): Revision Note

Dipole-Induced Dipole Interactions

• Dipole-induced dipole interactions are attractions between a polar molecule and a nonpolar molecule

• These forces are always attractive

• The polar molecule induces, or causes, a temporary dipole in the nonpolar molecule by distorting its electron distribution

• For example, in the interaction between polar water molecules and nonpolar iodine molecules:

  • There is a partial negative charge on the oxygen atom of the polar O—H bond in water

  • This causes a distortion in the electron cloud distribution in the iodine molecules

  • This distortion creates an induced dipole in the iodine molecule

• This induced dipole is then weakly attracted to the negative oxygen atom, allowing some degree of iodine dissolution in water

• However, because this force is weak, the iodine molecules are not very soluble in water

  • Iodine dissolves only slightly because the hydrogen bonds between water molecules are much stronger than the attractions between water and I₂, so I₂ cannot break into water's hydrogen-bonded network

Dipole-induced dipole interactions

Dipole-induced dipole interaction between polar water molecules and iodine molecules

• The strength of this interaction is dependent on two factors:

  • The magnitude of the dipole moment in the polar molecule

  • The polarizability of the nonpolar molecule

• London dispersion forces also act between the polar and nonpolar molecules, in addition to the dipole-induced dipole attraction