Microwave spectrum, structure and dipole moment of phenylacetylene

Abstract

The microwave spectra of phenylacetylene, C6H5CCH, the deuterated species, CGHSCCD, and carbon-13 species at positions C(2), C(3), C(4), C(7) and C(8) have been measured and analysed. Inertial defects confirm the expected planarity of the molecule, and pronounced nuclear spin effects in the ground-state and vibrationally excited spectra confirm the C2, symmetry. The detailed structure is determined to be: 208, and C(8) 3) C(4) = 119.9" and C(3)C(4)C(5) = 119.9'. The dipole moment has been accurately determined using a new Stark-effect technique to be p = pa = 0.656+0.005 D and is found to be smaller for the deuterated species by 0.010 k 0.003 D.

The electronic spectra of aryl olefins: A theoretical study of phenylacetylene

“…See Table II͒. Experimental estimates of the dipole moment in the ground and the 1 L b states amount to 0.66 18 and 0.86 D. 36 The second vertical electronic absorption computed at the ground state geometry corresponds to the 2 1 A 1 excited state at 5.19 eV. The related transition has a →* character and a calculated oscillator strength of 0.460.…”

Coupled electron pair calculations for R-C  E molecules (E = N, P, As or Sb)

“…It is plausible that the electronic structure and the geometric parameters of the C-C=E fragment (C = ipso carbon atom) are only weakly influenced by the accurate ring geometry. Alterations of the ring (compared with benzene) affect mainly the angle E (C2-C-C6) and the bond length a (C-C2; C-C6), and are relatively small: (i) The measured ring geometries of benzonitrile (H,C, -C=N) [47,48] and of ethynylbenzene (H,C,-CCC-H) [49] deviate from those of benzene by less than 0.01 A or 2'.…”

The millimetre-wave rotational spectrum of phenylacetylene

“…The rotational spectrum of phenylacetylene was first studied by Zeil et al [9], and their survey investigation was followed by a much more detailed study of Cox et al [10]. Rotational constants were obtained for seven different isotopic species leading to a determination of the molecular structure.…”