Vibrational spectra, conformations, and intramolecular interactions of R(CH2)(2)-O-PCl2 molecules (R = Et, OMe).

IR and Raman spectroscopy, normal coordinate analysis, and molecular mechan ics were used to study the conformations of R(CH2)(2)-O-PCl2 molecules (R = Et, OMe). It is shown that in the case of R = Et, that the molecules prefe r to exist in more or less extended conformations, R and PCl2 groups being spatially far apart. In contrast, the convoluted conformations are preferre d in the case of R = OMe. In these conformations the intramolecular distanc es between nonbonded P1 and O5 atoms are comparable with the sums of the co rresponding van der Waal's radii. The substantial energetical preference of the convoluted conformations in the liquid state is assigned to certain at tractive intramolecular 1-5 interactions between the phosphorus and the oxy gen atoms. The energy of the interaction may amount to similar to 2-4.5 kca l mol(-1). (C) 1999 Elsevier Science B.V. All rights reserved.