FORCE-CONSTANT CALCULATIONS OF THE LAM-1 MODES OF N-ALKANES AND THEIR SUBSTITUTED ALPHA-MONOHALO-SPECIES AND ALPHA,OMEGA-DIHALO-SPECIES IN THEIR EXTENDED ZIGZAG PLANAR CONFIGURATIONS AS FOUND IN UREA INCLUSION-COMPOUNDS

Force constants were determined for the C-8, C-10, C-12 and C-14 series of n-alkanes CnH-2n+2 using an approximate SVFF calculation and observed LAM = 1 wavenumbers. In this calculation the hydrogen atoms were neglected and only the carbon backbone chain and terminal atoms were considered; this was valid since only low-frequency vibrations were under consideration. Using force constant transfer, the wavenumbers of the LAM = 1 accordion modes for the analogous alpha-CnH-2n+1X and alpha,omega-CnH-2nX2 species, where X = Cl, Br or I were calculated. For alpha-chloroalkanes and alpha,omega-dichloroalkanes, the m = 1 accordion modes are calculated to be in the 220-130 cm-1 and 200-120 cm-1 regions, respectively. For the bromo- and iodo-analogues the m = 1 accordion modes are calculated to be in the 200-100 cm-1, 150-90 cm-1 and in the 170-100, 135-80 cm-1 regions, respectively.