Transition dipole—dipole coupling interactions in the B form of stearic acid single crystals

Raman spectra of the B form of stearic acid single crystals CH₃(CH₂)₁₆COOH have been recorded for various polarization geometries. Infrared spectra were obtained for the B powder form. A normal coordinate treatment of the crystal has been performed. The group coordinate force field describing the intramolecular potential, a hydroen-bond potential and intermolecular non-bonded atom—atom interactions were used. In addition transition dipole—dipole coupling interactions between the CO bonds in the unit cell were needed in order to explain the observed infrared and Raman bands, contrary to some previous observations concerning the existence of two different conformations of this dimeric carboxylic acid.