Millimeter-Wave Rotational Spectrum of HSSH and DSSD. I. Q Branches

Abstract

The Q-branch rotational lines of H2S2 have been measured in the frequency range 80-200 Gc/sec, those of D 2 S2, in the range from 60 to 220 Gc/sec. For HSSH, measurements were made on the torsional vibrational state Vt= 1, and the S-S bond-stretching vibrational state "11,= 1 as well as on the ground state. The molecules are the most nearly accidentally symmetric tops of any so far reported. Wang's asymmetry parameter bp = (C-B) / (2A -B -C) for the ground vibrational state of H32S32SH is found to have the value bp = -1.10X 10-5 ; fOL H32S84SH, bp = -1.07XlO-5 ; for D32S32SD, bp = -2.10XIQ-6. The asymmetry increases markedly with the torsional oscillation: for H32S32SH when "IIt=l, bp = -4.055XlO-5; it decreases with the S-S stretching: for H32S32SH when "11.= 1, bp = -7.72XlO-o. The molecule is found to have the nonplanar chain structure HSSH, with the structural parameters having the values: daR = 1.327 A, daB = 2.055 A, L HSS = 91.32°, and the dihedral angle '1=90°36'. The barrier to relative internal rotation of the two SH groups is evidently very high, much higher than in H20 2• The internal rotational splitting of the ground vibrational state is too small to be resolved. In the torsional vibrational state Vt= 1 it was found to be 2Av= 15.99 Mc/sec. The near orthogonality of the bond angles, the S-S length, and the high barrier to internal rotation indicate significant 7T" bonding through the mechanism of hyperconjugation.

Submillimeter Wave Spectrum of HS34SH

“…In the present paper we report the spectrum of HS34SH in the frequency range between 60 and 420 GHz, greatly extending the earlier rQ0-branch measurements of Winnewisser et al [1]. The values of the rotational and centrifugal distortion parameters of this molecule in the ground state have been signifi cantly improved.…”

“…In a previous series of papers describing the rota tional spectrum of HSSH [1][2][3][4][5][6] in the millimeter and submillimeter wave region, only the rQ0-branch of HS34SH was reported. The outstanding spectral char acteristics for the symmetric species HS34SH are the perpendicular type spectrum of the molecule with a typical intensity alternation of 3:1 for adjacent J rotational lines (see Figure 1).…”

“…The rotational spectrum of disulfane, HSSH has been studied in a series of papers [1][2][3][4][5][6] and recently work has been resumed with the aim of understanding some of the subtle details of the HSSH spectrum, its barrier to internal rotation and its isotopic species [7], [8]. In addition it is now highly desirable and possible to have a full substitution structure of disulfane avail able, which can be compared with the ongoing theo retical chemistry ab-initio structural calculations.…”

Conformational consequences of intramolecular hydrogen bonding by OH to the directional lone-pair of sulfur in derivatives of methyl phenyl sulfide, diphenyl sulfide, and diphenyl disulfide

“…90" and the HSS angle is also near 90" (44). The filled 3p lone pair electrons minimize their mutal repulsion by a twist of 90" to give the observed conformation.…”

A quantum chemical study of H2S2: Intramolecular torsional mode and intermolecular interactions with rare gases

“…[36][37][38], and in contrast with that of Winnewisser et al that underestimated the HSS angles at around 91°. 39 Generally these data are assessed on the basis that the microwave derived geometries rely on the uncertainty of the value of the HSS angle, which serves as reference. In fact, the localization of hydrogen atoms in the presence of heavy atoms is often problematic by diffraction techniques.…”