Dipole moments of organophosphorus compounds. 15. Polarities and polarizabilities of some acetylenic compounds

Dipole moments for the acetylenic organophosphorus compounds have already been obtained through an additive scheme based on m(P § O) = 1.2D [3]. The mean value m(P + C) resulting from that earlier work was ~0.4D. Later, the additive bond-polarity scheme (including polarities of C atom in various hybridizations) was analyzed in light of experimentally determined DM values for molecules whose polarity was~independent of free rotation, and an effective diethylphosphonium group conformation established. This same additive scheme was used in the DM analysis of the present work. Interest also attaches to a study of the conformations of acetylenic organophosphorus compounds with internal rotation. Although rotation affects the DM of compounds with an irregular ethoxy group substituted at the P atom, hydrocarbon radical rotation has no effect on either the magnitude or direction of the DM, at least in the additive scheme approximation. In the latter case, the spatial orientation can be established from the molar Kerr constant [4]. This can be measured, or calculated for the various conformations, in the case of compounds (I) and (II). Valence angles and bond moments required in the present calculations were taken from