IR-Active and inactive A polar bond is usually IR-active A nonpolar bond in a symmetrical molecule will absorb weakly or not at all force on in direction of field force on+ +)y in direction of field E molecule compressed molecule stretched dipole moment decreased electric electric X→ dipole moment increased force on field field opposite direction of field ⊙ force on opposite direction of field Chapter 12Chapter 12 11 IR-Active and Inactive • A polar bond is usually IR-active. • A nonpolar bond in a symmetrical molecule will absorb weakly or not at all. =>