Force constant calculations of the LAM-1 modes ofn-alkanes and their substituted ?-Monohalo- and ?,?-dihalo- species in their extended zig-zag planar configurations as found in urea inclusion compounds

Force constants were determined for the C8, C10, C12 and C14 series ofn-alkanes C n H2n + 2 using an approximate SVFF calculation and observed LAM = 1 wave numbers. 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 α-Cn H2n + 1 X and α,ω-Cn H2nX2 species, where X = C1, Br or I were calculated. For α-chloroalkanes and α,ω-dichloroalkanes, them = 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 them = 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.