Vibrational IR‐Multiphoton Excitation of Thiirane‐1‐oxide (C₂H₄SO) and d‐Thiirane‐1‐oxide (C₂H₃DSO)

Abstract

We report the IR‐laser‐induced dissociation of C2H4SO and of C2H3DSO, which was synthesized for the first time. After multiphoton excitation in the frequency range of the SO chromophore (with a large band strength of G = 2.4 pm2 for C2H4SO and 2.8 pm2 for C2H3DSO) in the 1060‐1090 cm−1 range of the CO2 laser the product analysis was carried out by static yield measurements using quantitative IR‐spectroscopy of ethylene (C2H3D, C2H4). Effective laser chemical rate constants k1(st) = (0.70±0.38) cm2 J−1 for C2H3DSO with excitation at v̄(R28) = 1083.48 cm−1 and (0.52±0.14) cm2 J−1 for C2H4SO were obtained from a fit to the fluence dependence of the photochemical primary yields. A nonlinear intensity dependence of the apparent product yield (Papp) was found by using different temporal pulse profiles (singlemode, mode‐locked and multimode pulses) at 1083.48 cm−1 (9R28) for C2H4SO and at 1082.30 cm−1 (9R26) for C2H3DSO in static yield measurements and time‐resolved experiments. FTIR measurements were performed to assign the fundamentals of C2H3DSO, which are compared with the harmonic frequencies calculated using GAUSSIAN 92 at MP2 level with different basis sets.

The Synthesis of [2-2H1]Thiirane-1-oxide and [2,2-2H2]Thiirane-1-oxide and the Diastereoselective Infrared Laser Chemistry of [2-2H1]Thiirane-1-oxide

“…The fundamentals are n 4 1114 cm À1 for the cis and n 4 1116 cm À1 for the trans isomer, which are visible as two close-lying but well-separated Q branches in Figure 6. Because of the small wavenumber separation of the two bands, we have chosen two laser lines on the low wavenumber side of the laser chemical yield spectrum, [3] where the yield starts to drop steeply to low values (line 9 R 22 at 1079.85 cm À1 and line 9 R 26 at 1082.30 cm…”

“…Table 1 provides a summary of the vibrational data for all isotopomers investigated here, compared with ab initio calculations for CH 2 CD 2 SO (see also ref. [3] for related calculations of C 2 H 4 SO and C 2 H 3 DSO). The experimental fundamental wavenumbers n give rough band positions from overall band shape, except for those cases where in ref.…”

“…[15] On the other hand, a low-resolution investigation of the infrared spectra of the undeuterated compound was reported quite some time ago [20] and we have already presented a preliminary analysis of somewhat improved data from our work on C 2 H 4 SO and C 2 H 3 DSO. [3] In the present paper we shall provide a survey of data at modest resolution and summarize their analysis for all three isotopomers. Until high-resolution analyses are available for all bands, a project that will need quite some time to complete, if it can be completed at all within the current state of the art, the assignments must remain preliminary, but should nevertheless provide good initial insights.…”

“…The harmonic wavenumbers (w e ) are calculated ab initio (MP2) with a 6-311G** basis set (GAUSSIAN 92). n Ä i are measured fundamental wavenumbers, G are integrated band strengths, [28] calculated ab initio (MP2) for CH 2 CD 2 SO or from experiment [3] for C 2 H 4 SO. have based our assignment upon a combination of frequency ordering and intensity predictions from ab initio calculations.…”

Infrared diode laser spectroscopic investigation of four C–H stretching vibrational modes of propylene oxide

“…Quack and co-workers described the first high resolution IR study of a chiral molecule CHBrClF using a Fourier transform (FT) IR spectrometer [4]. They also determined the rotational and centrifugal distortion constants of the ground and several first excited vibrational states of a few other relatively simple chiral molecules such as fluorooxirane [5] and thiirane-1-oxide [6,7] in the related studies. There are a number of noticeable challenges in studying midsized organic molecules using high resolution IR spectroscopy.…”