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 E in direction of field molecule compressed molecule stretched dipole moment decreased electric dipole moment increased electric field force on- feld opposite direction force on- of field opposite direction 二> of field Chapter 12 11Chapter 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. =>