The electric dipole moment of tetrahydropyran-water

Using Stark-effect Fourier-transform microwave spectroscopy, the electric d ipole moment components of tetrahydropyran-H2O were measured to be /mu(a)/ = 1.6034(3) D and /mu(c)/ = 0.9881(11) D. The a- and c-type spectra of the complex were observed. No b-type spectrum was found, consistent with ab ini tio geometries, which have a plane of symmetry in this hetero-dimer. Suppor ted by these findings the mu(b) component of the dipole moment was fixed to zero. Adjusting the two remaining components, the Stark splittings can be reproduced within the experimental uncertainty. The ab initio dipole calcul ation, performed using the MP2/Spackman basis, shows that the measured dipo le moment is only consistent with an axial-anti-configuration of the comple x. (C) 1998 Elsevier Science B.V. All rights reserved.