Gas-Phase Detection of HSOH: Synthesis by Flash Vacuum Pyrolysis of Di-tert-butyl Sulfoxide and Rotational-Torsional Spectrum
Abstract
Gas-phase oxadisulfane (HSOH), the missing link between the well-known molecules hydrogen peroxide (HOOH) and disulfane (HSSH), was synthesized by flash vacuum pyrolysis of di-tert-butyl sulfoxide. Using mass spectrometry, the pyrolysis conditions have been optimized towards formation of HSOH. Microwave spectroscopic investigation of the pyrolysis products allowed - assisted by high-level quantum-chemical calculations - the first measurement of the rotational-torsional spectrum of HSOH. In total, we have measured approximately 600 lines of the rotational-torsional spectrum in the frequency range from 64 GHz to 1.9 THz and assigned some 470 of these to the rotational-torsional spectrum of HSOH in its ground torsional state. Some 120 out of the 600 lines arise from the isotopomer H34SOH. The HSOH molecule displays strong c-type and somewhat weaker b-type transitions, indicating a nonplanar skew chain structure, similar to the analogous molecules HOOH and HSSH. The rotational constants (MHz) of the main isotopomer (A=202 069, B=15 282, C=14 840), determined by applying a least-squares analysis to the presently available data set, are in excellent agreement with those predicted by quantum-chemical calculations (A=202 136, B=15 279, C=14 840). Our theoretical treatment also derived the following barrier heights against internal rotation in HSOH (when in the cis and trans configurations) to be Vcis=2216 cm-1 and Vtrans=1579 cm-1. The internal rotational motion results in detectable torsional splittings that are dependent on the angular momentum quantum numbers J and Ka.
- Publication:
-
Chemistry A European Journal
- Pub Date:
- November 2003
- Bibcode:
- 2003CEJ.....9.5501W
- Keywords:
-
- ab initio calculations;
- flash vacuum pyrolysis;
- mass spectrometry;
- oxasulfanes;
- rotational spectroscopy