NONLINEAR HYDROGEN-BONDS O-CENTER-DOT-CENTER-DOT-CENTER-DOT-H-C AND THE ROLE OF SECONDARY INTERACTIONS - THE ROTATIONAL SPECTRUM OF THE OXIRANE-CENTER-DOT-CENTER-DOT-CENTER-DOT-ACETYLENE COMPLEX

Rotational constants (A(O), B-O, C-O) and quartic centrifugal distortion constants (Delta(J), Delta(JK), delta(J)) of five isotopomers of a complex (CH2)(2)O ... HCCH of oxirane and acetylene were determined by using pulsed-nozzle, Fourier-transform microwave spectroscopy. The complex has C-5 symmetry, with the HCCH subunit lying in the plane perpendicular to that of the COC nuclei of oxirane and acting as proton donor in forming a hydrogen bond to the oxygen atom. A weak secondary inferaction between the CH2 groups of oxirane and the acetylene pi-bond causes a significant nonlinearity of the primary hydrogen bond. This behaviour is compared with that in related complexes.