Reinvestigation of Microwave Spectrum of Ethylsilane: I. Structure and Dipole Moment

✍ Scribed by Yuzuru Niide; Michiro Hayashi

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 131 KB
• Volume: 216
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.2002.8650

✦ Synopsis

Microwave spectra of ethylsilane and its 19 isotopic species have been measured. A least-squares analysis of the observed frequencies gave rotational constants and three quartic centrifugal distortion constants. The r s structure has been well established from the moments of inertia calculated from the observed rotational constants. The structure has also been obtained from the differences of the observed moments of inertia between the isotopic and normal species by the diagnostic leastsquares method. The structure of trans-propylsilane has been established from the reported and newly observed rotational constants for the isotopically substituted species of this molecule by application of the so-called diagnostic least-squares method. The structual parameters of ethylsilane were compared with those of analogous molecules. Special attention was paid to the C-C bond length. The newly obtained bond length is r (C-C) = 1.541 ± 0.001 Å. The dipole moment and its direction in the molecule were determined from Stark-effect measurements of several low-J transitions by the usual perturbation method; µ a = 0.733 ± 0.001 D, µ b = 0.349 ± 0.003 D, and µ total = 0.812 ± 0.002 D were obtained for the normal species. The angle between the dipole moment and the Si-C bond was 36 toward the inside of the molecule. These values were compared with those of analogous molecules. C 2002 Elsevier Science (USA)

EXPERIMENTAL DETAILS

Samples of the normal and isotopically substituted species of ethylsilane were prepared by the following reactions.