15min:

MAUSUMI GOSWAMI, L. NARASIMHAN, S. T. MANJU AND E. ARUNAN, Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India.

Rotational Spectra of phenylacetylene-water complex and its HDO and D₂O isotopomers have been measured. The spectra resemble an asymmetric top with =-0.73 for the parent isotopomer. Both `a' and `b' dipole transitions have been observed. All the transitions are split into two resulting from a possible internal rotation of H₂O in the complex. The measured rotational constants are A = 2672.0931(31) MHz, B = 996.3581(8) MHz, C = 731.7056(4) MHz for the stronger series and A = 2673.1331(44) MHz, B = 996.3926(10) MHz, C = 731.5737(6) MHz for the weaker series. Spectra for HDO isotopomer agree with a structure where water is in the plane of phenylacetylene by donating one of its hydrogen to the acetylene cloud and the oxygen is involved in a secondary interaction forming C-H---O hydrogen bond with the ring hydrogen ortho to the acetylenic group. The experiments for D₂O isotopomer are in progress. The structure agrees with the one proposed from Fluorescence Dip Infrared Spectroscopy studies [1].

\bigskip 1. G. N. Patwari and co-workers, Private Communication.