ROTATIONAL SPECTRA OF CH2DCCH AND CH3CCD - EXPERIMENTAL AND AB-INITIO EQUILIBRIUM STRUCTURES OF PROPYNE

The ground state rotational spectra of CH2DCCH and CH3CCD (main species and 13C-substituted species) have been measured up to 470 GHz. Accurate rotational and centrifugal distortion constants have been determined. r0, rs, rε{lunate}, I, and rρm, structures of propyne have been calculated. The ab initio structure has also been calculated using three different methods (SCF, MP2, and QCISD) and two basis sets (DZP and TZ2P). Offsets have been derived empirically using molecules containing structural units present in propyne and whose equilibrium structures have been determined previously. A near-equilibrium structure has been estimated to be acetylenic r(CH) = 1.061 (1) Å, r(CC) = 1.204 (1) Å, r(CC) = l.458 (2) Å, methyl r(CH) = 1.089 (1) Å, and ∠(CCH) = 110.7 (5)°. © 1993 Academic Press, Inc.