Microwave Spectra, Molecular Structure, and Electric Dipole Moment of 1,2-Dithiin

✍ Scribed by J.Z. Gillies; C.W. Gillies; E.A. Cotter; E. Block; R. DeOrazio

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 179 KB
• Volume: 180
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1996.0232

✦ Synopsis

A pulsed-beam Fourier transform microwave spectrometer was used to investigate the rotational spectrum of 1,2dithia-3,5-cyclohexadiene in the range 8 to 18 GHz. The observed a-type transitions were fit to a Watson asymmetric top Hamiltonian, giving the following rotational constants for the normal isotopomer: A Å 3326.362(2) MHz, B Å 3102.842(2) MHz, C Å 1756.0026(7) MHz. An electric dipole moment of m total Å m a Å 1.850(1) D was determined from Stark effect measurements. Observed nuclear spin statistical weights, an inertial defect of D Å I c 0 I a 0 I b Å 027.00685 uA ˚2, and zero m b and m c electric dipole components show the molecule has C 2 symmetry which corresponds to a twisted conformation about the S{S bond. Spectral assignments were obtained for the singly substituted 34 S and two 13 C isotopomers in natural abundance. The moments of inertia of the four isotopomers were used to determine the following r s structural ring parameters: r(S{S) Å 2.051(3) A ˚, r(C{S) Å 1.759(4) A ˚, r(C|C) Å 1.353(3) A ˚, r(C{C) Å 1.451(1) A ˚, u(SSC) Å 98.7(2)Њ, u(SCC) Å 121.4(2)Њ, u(CCC) Å 124.2(2)Њ, f(SSCC) Å 41.2Њ, f(SSCC) Å 41.2Њ, f(SCCC) Å 00.3Њ, f(CCCC) Å 29.0Њ, and f(CSSC) Å 53.9Њ.