The Detection of tert-Butylthiosulfoxylic Acid, t-BuSSOH, and 1-Oxatrisulfane, HSSOH, in the Gas Phase – Experimental Results and Ab Initio Calculations
✍ Scribed by Andreas Königshofen; Markus Behnke; Mario Hoverath; Josef Hahn
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- German
- Weight
- 145 KB
- Volume
- 625
- Category
- Article
- ISSN
- 0372-7874
No coin nor oath required. For personal study only.
✦ Synopsis
Flash vacuum pyrolysis (FVP) of tert-butylthiosulfinic acid S-tert-butylester, t-BuS(O)St-Bu, at a temperature of 500 °C and a pressure of 0.07 hPa leads to the formation of tert-butylthiosulfoxylic acid, t-BuSSOH (1), and 2-methylpropene as byproduct. 1 has been identified in the gas phase by its IR absorption bands at m(OH) = 3598 cm ±1 , d(SOH) = 1149 cm ±1 and m(SO) = 718 cm ±1 . At higher temperatures (700 °C) the elimination of a second mole of 2-methylpropene and the shift of m(SO) to higher wavenumbers (750 cm ±1 ) indicate the formation of 1-oxatrisulfane, HSSOH. Different sulfenic acids RSOH (R = Me, i-Pr, t-Bu) were synthesized by FVP in order to study the influence of the substituent R on the vibrational wavenumbers m(OH), m(SO) and d(SOH) observed in the gas phase. The strongest effect results for d(SOH) leading to a decrease by 6 wavenumbers if the methyl group is substituted by a tert-butyl group. The assignment of the experimental wavenumbers has been supported by theoretical values obtained from ab initio calculations at the MP2(fc)/6-311G** level. Further-more, the theoretical studies show that of all compounds RS 2 OR' (R = R' = H, Me; R = Me (H), R' = H (Me)) the unbranched chain isomers RSSOR' are energetically favored over the branched chain isomers. Relaxed potential energy surface scans at the MP2(fc)/6-311G** level have been carried out to study the rotational isomers of the branched molecules RS(Y)XR' (R = R' = H, Me; R = Me (H), R' = H (Me); X = O (S), Y = S (O)). Of the three conformations (+)syn-clinal, (±)syn-clinal, and anti-periplanar resulting from molecular model considerations only the two latter ones correspond to local minima on the calculated potential curve. The (±)syn-clinal conformation is slightly favored for all other constitutional isomers except for HS(O)SH and MeS(O)SH, which prefer the anti-periplanar conformation.