Simone Esser

Publications (2)5.93 Total impact

• Article: Low-pressure pyrolysis of tBu2SO: synthesis and IR spectroscopic detection of HSOH.

  Helmut Beckers, Simone Esser, Thorsten Metzroth, Markus Behnke, Helge Willner, Jürgen Gauss, Josef Hahn
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  ABSTRACT: Sulfenic acid (HSOH, 1) has been synthesized in the gas-phase by low-pressure high-temperature (1150 degrees C) pyrolysis of di-tert-butyl sulfoxide (tBu(2)SO, 2) and characterized by means of matrix isolation and gas-phase IR spectroscopy. High-level coupled-cluster (CC) calculations (CCSD(T)/cc-pVTZ and CCSD(T)/cc-pVQZ) support the first identification of the gas-phase IR spectrum of 1 and enable its spectral characterization. Five of the six vibrational fundamentals of matrix-isolated 1 have been assigned, and its rotational-resolved gas-phase IR spectrum provides additional information on the O-H and S-H stretching fundamentals. Investigations of the pyrolysis reaction by mass spectrometry, matrix isolation, and gas-phase FT-IR spectroscopy reveal that, up to 500 degrees C, 2 decomposes selectively into tert-butylsulfenic acid, (tBuSOH, 3), and 2-methylpropene. The formation of the isomeric sulfoxide (tBu(H)SO, 3 a) has been excluded. Transient 3 has been characterized by a comprehensive matrix and gas-phase vibrational IR study guided by the predicted vibrational spectrum calculated at the density functional theory (DFT) level (B3LYP/6-311+G(2d,p)). At higher temperatures, the intramolecular decomposition of 3, monitored by matrix IR spectroscopy, yields short-lived 1 along with 2-methylpropene, but also H(2)O, and most probably sulfur atoms. In addition, HSSOH (6), H(2), and S(2)O are found among the final pyrolysis products observed at 1150 degrees C in the gas phase owing to competing intra- and intermolecular decomposition routes of 3. The decomposition routes of the starting compound 2 and of the primary intermediate 3 are discussed on the basis of experimental results and a computational study performed at the B3LYP/6-311G* and second-order Møller-Plesset (MP2/6-311G* and RI-MP2/QZVPP) levels of theory.
  Chemistry 02/2006; 12(3):832-44. · 5.93 Impact Factor
• Source

  Available from: Sandra Brünken

  Article: Gas-phase detection of HSOD and empirical equilibrium structure of oxadisulfane

  Oliver Baum, Simone Esser, Niels Gierse, Sandra Brünken, Frank Lewen, Josef Hahn, Jürgen Gauss, Stephan Schlemmer, Thomas F. Giesen
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  ABSTRACT: We present the first gas phase spectra of singly deuterated oxadisulfane, HSOD, in its vibrational ground state. More than 100 transitions have been recorded with highest frequency accuracy using the Cologne Terahertz Spectrometer. The molecular parameters derived from a least squares fit analysis proof HSOD to be an almost accidental symmetric prolate top molecule with an asymmetry parameter κ=−0.9985. Spectra of c-type and weaker b-type transitions have been recorded in the range from 716 to 772 GHz. The ratio of the dipole moments μc/μb=2.4(3) has been derived from measured line intensities. The c-type transitions are split by the tunneling motion of a hindered internal rotation, whereas b-type transitions show no splitting within the Doppler limited line profiles. We derived the equilibrium molecular structure of oxadisulfane, HSOH, from experimental values of the rotational constants A0, B0, and C0 of HSOH, H34SOH, DSOD, and HSOD. The equilibrium rotational constants Ae, Be, and Ce were derived by taking vibration–rotation interaction constants αr obtained from high-level ab initio calculations into account.
  Journal of Molecular Structure.