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. H represented as ④y0000⊙ force on+ in direction of field force on in direction of field E molecule compressed molecule stretched dipole moment decreased dipole moment increased electric electric field force on- field opposite direction of field force on- opposite direction of field 11 Copyright 2005 Pearson Prentice Hall,Inc Chapter 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. =>