Gas-phase detection of HSOH: synthesis by flash vacuum pyrolysis of di-tert-butyl sulfoxide and rotational-torsional spectrum

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 H(34)SOH. 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 V(cis) approximately equal to 2216 cm(-1) and V(trans) approximately equal to 1579 cm(-1). The internal rotational motion results in detectable torsional splittings that are dependent on the angular momentum quantum numbers J and K(a).     

Cycloaddition of N-acylimines with cyclobutadienes

N-Acylimines (2) possess the characteristics of both hetero-1,3-dienes and dienophiles. They react with the kinetically stabilised cyclobutadienes 1 to form 4-aza-2-oxabicyclo[4.2.0]octa-3,7-dienes (3) and/or 2-azabicyclo[2.2.0]hex-5-enes (4). Compounds of the type 3 undergo acid-catalysed isomerisation to give compounds 4. Homocyclopropenylium intermediates of the type 5 are supposed to be involved in both processes (1 + 2 → 3 + 4 and 3 → 4).     

Spectroscopy among the stars

The space between the stars is not void, but filled with interstellar matter, mainly composed of dust and gas, which gather in large interstellar clouds. In our Galaxy these interstellar clouds are distributed along a thin, but extended layer which basically traces out the spiral distribution of matter: the stars, the gas, and the dust component. Up to the present time more than 100 different molecules have been identified in interstellar molecular clouds. The majority of the interstellar molecules constitute carbon containing organic substances. During the past years, overwhelming evidence has been gathered, mainly through spectroscopic observations, that interstellar molecular clouds provide the birthplaces for stars. In fact detailed high spectral and spatial resolution spectroscopic measurements reveal physical and chemical processes of the intricate star formation process.     

X-ray investigations of nebivolol and its isomers

The molecular and crystal structures of the hydrochlorides of d-nebivolol, dl-nebivolol, and seven nebivolol isomers have been determined by X-ray structure analysis. The absolute configuration of all the compounds could be determined unambiguously using anomal dispersion effects. Two compounds, dl-nebivolol (NEB-1d,l) and the (S,R,S,R) nebivolol isomer (NEB-6), crystallize as racemic mixtures in the centrosymmetric space group P-1. d-Nebivolol and six nebivolol isomers crystallize in space group P2₁2₁2₁. The d- and l-nebivolol molecules in NEB-1d and NEB-1d,l adopt a conformation which is significantly different compared with that of all nebivolol isomers. With the exception of dl-nebivolol (NEB-1d,l) numerous intermolecular hydrogen bonds connect the molecules forming molecular layers.     

A precise study of the rotational spectrum of formaldehyde H212C16O,H213C16O,H212C18O,H213C18O

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

     

207.

From Complex Natural Products to Simple Synthetic Mimetics by Computational De Novo Design          下载免费PDF全文

Lukas Friedrich  Dr. Tiago Rodrigues  Claudia S. Neuhaus  Dr. Petra Schneider  Prof. Dr. Gisbert Schneider 《Angewandte Chemie (International ed. in English)》2016,55(23):6789-6792

We present the computational de novo design of synthetically accessible chemical entities that mimic the complex sesquiterpene natural product (?)‐Englerin A. We synthesized lead‐like probes from commercially available building blocks and profiled them for activity against a computationally predicted panel of macromolecular targets. Both the design template (?)‐Englerin A and its low‐molecular weight mimetics presented nanomolar binding affinities and antagonized the transient receptor potential calcium channel TRPM8 in a cell‐based assay, without showing target promiscuity or frequent‐hitter properties. This proof‐of‐concept study outlines an expeditious solution to obtaining natural‐product‐inspired chemical matter with desirable properties.     

208.

Rotational Spectra of the Thiosulfeno Radical, HSS and DSS, between 0.3 and 0.9 THz     

Tanimoto M  Klaus T  Müller HS  Winnewisser G 《Journal of Molecular Spectroscopy》2000,199(1):73-80

The rotational spectra of the HSS and DSS radicals were studied in selected regions between 331 and 883 GHz. The radicals were produced by discharging a gaseous mixture of hydrogen (or deuterium) and hydrogen sulfide in the cell. The observation of the b-type Q-branch and R-branch lines with K(a) = 2-1 and 3-2 for HSS and DSS, respectively, as well as the a-type R-branch lines allowed the improvement and the determination of the molecular constants among them (in MHz) We have reevaluated the harmonic force field of HSS and the ground state average and approximate equilibrium structural parameters. For the latter, we obtained r(HS) = 135.23 pm, r(SS) = 196.03 pm, and angle = 101.74 degrees. These results are compared with those from previous and own quantum chemical calculations as well as with results of related molecules. Copyright 2000 Academic Press.     

209.

The Ground State Spectroscopic Constants of Formaldehyde     

Müller HS  Winnewisser G  Demaison J  Perrin A  Valentin A 《Journal of Molecular Spectroscopy》2000,200(1):143-144

     

210.

Absolute Line Intensities for the nu6 Band of H2O2     

Klee S  Winnewisser M  Perrin A  Flaud J 《Journal of Molecular Spectroscopy》1999,195(1):154-161

The purpose of this work was to obtain reliable absolute intensities for the nu6 band of H2O2. It was undertaken because strong discrepancies exist between the different nu6 band intensities which are presently available in the literature (A. Perrin, A. Valentin, J.-M. Flaud, C. Camy-Peyret, L. Schriver, A. Schriver, and P. Arcas, J. Mol. Spectrosc. 1995. 171, 358), (R. May, J. Quant. Radiat. Transfer 1991. 45, 267), and (R. L. Sams, personal communication). The method which was chosen in the present work was to measure simultaneously the far-infrared absorptions and the nu6 absorptions of H2O2. Consequently, Fourier transform spectra of H2O2 were recorded at Giessen in a spectral range (370-1270 cm-1) which covers both the R branch of the torsion-rotation band and the P branch of the nu6 band which appear at low and high wavenumbers, respectively. From the low wavenumber data, the partial pressure of H2O2 present in the cell during the recording of the spectra was determined by calibrating the observed absorptions in the torsion-rotation band with intensities computed using the permanent H2O2 dipole moment measured by Stark effect (A. Perrin, J.-M. Flaud, C. Camy-Peyret, R. Schermaul, M. Winnewisser, J.-Y. Mandin, V. Dana, M. Badaoui, and J. Koput, J. Mol. Spectrosc. 1996. 176, 287-296) and [E. A. Cohen and H. M. Pickett, J. Mol. Spectrosc. 1981. 87, 582-583). In the high frequency range, this value of the partial pressure of H2O2 was used to measure absolute line intensities in the nu6 band. Finally, the line intensities in the nu6 band were fitted using the theoretical methods described in detail in our previous works. Using these new results on line intensities together with the line position parameters that we obtained previously, a new synthetic spectra of the nu6 band was generated, leading to a total band intensity of 0.185 x 10(-16) cm-1/(molecule.cm-2) at 296 K. It has to be pointed out that the new line intensities agree to within the experimental uncertainties with the individual line intensity measurements performed previously by May and by Sams. Copyright 1999 Academic Press.     

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	H212C16O	H213C16O	H212C18O	H213C18O
A/MHz	281 970.572 (24)	281 993.258(135)	281 961.94 (39)	281 985.00 (93)
B/MHz	38 836.0456(13)	37 811.0887(25)	36 904.1693(66)	35 859.256(10)
C/MHz	34 002.2034(12)	33 213.9790(25)	32 511.5311(63)	31 697.868(10)

From Complex Natural Products to Simple Synthetic Mimetics by Computational De Novo Design

We present the computational de novo design of synthetically accessible chemical entities that mimic the complex sesquiterpene natural product (?)‐Englerin A. We synthesized lead‐like probes from commercially available building blocks and profiled them for activity against a computationally predicted panel of macromolecular targets. Both the design template (?)‐Englerin A and its low‐molecular weight mimetics presented nanomolar binding affinities and antagonized the transient receptor potential calcium channel TRPM8 in a cell‐based assay, without showing target promiscuity or frequent‐hitter properties. This proof‐of‐concept study outlines an expeditious solution to obtaining natural‐product‐inspired chemical matter with desirable properties.     

Rotational Spectra of the Thiosulfeno Radical, HSS and DSS, between 0.3 and 0.9 THz

The rotational spectra of the HSS and DSS radicals were studied in selected regions between 331 and 883 GHz. The radicals were produced by discharging a gaseous mixture of hydrogen (or deuterium) and hydrogen sulfide in the cell. The observation of the b-type Q-branch and R-branch lines with K(a) = 2-1 and 3-2 for HSS and DSS, respectively, as well as the a-type R-branch lines allowed the improvement and the determination of the molecular constants among them (in MHz) We have reevaluated the harmonic force field of HSS and the ground state average and approximate equilibrium structural parameters. For the latter, we obtained r(HS) = 135.23 pm, r(SS) = 196.03 pm, and angle = 101.74 degrees. These results are compared with those from previous and own quantum chemical calculations as well as with results of related molecules. Copyright 2000 Academic Press.     

Absolute Line Intensities for the nu6 Band of H2O2

The purpose of this work was to obtain reliable absolute intensities for the nu6 band of H2O2. It was undertaken because strong discrepancies exist between the different nu6 band intensities which are presently available in the literature (A. Perrin, A. Valentin, J.-M. Flaud, C. Camy-Peyret, L. Schriver, A. Schriver, and P. Arcas, J. Mol. Spectrosc. 1995. 171, 358), (R. May, J. Quant. Radiat. Transfer 1991. 45, 267), and (R. L. Sams, personal communication). The method which was chosen in the present work was to measure simultaneously the far-infrared absorptions and the nu6 absorptions of H2O2. Consequently, Fourier transform spectra of H2O2 were recorded at Giessen in a spectral range (370-1270 cm-1) which covers both the R branch of the torsion-rotation band and the P branch of the nu6 band which appear at low and high wavenumbers, respectively. From the low wavenumber data, the partial pressure of H2O2 present in the cell during the recording of the spectra was determined by calibrating the observed absorptions in the torsion-rotation band with intensities computed using the permanent H2O2 dipole moment measured by Stark effect (A. Perrin, J.-M. Flaud, C. Camy-Peyret, R. Schermaul, M. Winnewisser, J.-Y. Mandin, V. Dana, M. Badaoui, and J. Koput, J. Mol. Spectrosc. 1996. 176, 287-296) and [E. A. Cohen and H. M. Pickett, J. Mol. Spectrosc. 1981. 87, 582-583). In the high frequency range, this value of the partial pressure of H2O2 was used to measure absolute line intensities in the nu6 band. Finally, the line intensities in the nu6 band were fitted using the theoretical methods described in detail in our previous works. Using these new results on line intensities together with the line position parameters that we obtained previously, a new synthetic spectra of the nu6 band was generated, leading to a total band intensity of 0.185 x 10(-16) cm-1/(molecule.cm-2) at 296 K. It has to be pointed out that the new line intensities agree to within the experimental uncertainties with the individual line intensity measurements performed previously by May and by Sams. Copyright 1999 Academic Press.