Ultraviolet photoisomerizations and FT-IR investigations of matrix isolated oxalyl halide conformers

Schroeder, W. H.; Monnier, M.; Davidovics, G.; Allouche, A.; Verlaque, P.; Pourcin, J.; Bodot, Hubert

doi:10.1016/0022-2860(89)85165-8

Cited by 19 publications

(16 citation statements)

References 25 publications

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“…UV-induced photoprocesses in argon and xenon matrices were studied using FTIR. 9 UV photodissociation of oxalyl chloride to give CO and phosgene was reported in those studies but not considered in detail. Here we present an investigation of oxalyl chloride dissociation at 193 nm using photofragment translational spectroscopy.…”

Section: Introductionmentioning

confidence: 94%

Photodissociation of Oxalyl Chloride at 193 nm Probed via Synchrotron Radiation

Hemmi

Suits

1997

J. Phys. Chem. A

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The photodissociation dynamics of oxalyl chloride, (ClCO) 2 , have been studied at 193 nm using photofragment translational spectroscopy with intense tunable vacuum-UV probe light provided by undulator radiation at the Advanced Light Source. Time-of-flight spectra for m/e 28 (CO + ), 35 (Cl + ), and 63 (ClCO + ) are presented, along with translational energy distributions (P(E)) derived from forward convolution fitting. While the P(E) of (ClCO + ) has a single sharp peak, those of (CO + ) and (Cl + ) show quite similar bimodal distributions. These observations suggest that the first step is an impulsive three-body dissociation yielding fast components of CO and Cl and that the remaining ClCO subsequently decomposes to give the slow components. This picture confirms a previous study of the photodissociation of oxalyl chloride at 230 nm using the photofragment imaging technique and provides more insight into the overall dynamics of the process. In addition, the tunable vacuum-UV photoionization has allowed for the measurement of the photoionization efficiency curve for the chloroformyl radical for the first time.

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Section: Introductionmentioning

confidence: 94%

Photodissociation of Oxalyl Chloride at 193 nm Probed via Synchrotron Radiation

Hemmi

Suits

1997

J. Phys. Chem. A

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“…Both the cis and trans conformers have been observed in cryogenic rare gas matrices. 19 However, the observed bands in a supersonic jet obviously originate from the trans oxalyl chloride (C 2h ), which is concluded from the vibrational analysis given below. In oxalyl chloride, a pair of CdO bonds conjugate in the same manner as the glyoxal molecule.…”

Section: Resultsmentioning

confidence: 91%

“…We then consider Fermi resonance between the symmetric CdO stretching level and another vibrational level, which has been found for the S 0 state of oxalyl chloride in cryogenic rare gas matrices. 19 A number of vibronic bands can be seen in this CdO stretching band region. It also suggests that the density of vibrational levels is sufficiently high and Fermi resonance is probable.…”

Section: Resultsmentioning

confidence: 96%

“…The transition wavenumbers and assignments of the observed prominent bands are summarized in Table . Both the cis and trans conformers have been observed in cryogenic rare gas matrices . However, the observed bands in a supersonic jet obviously originate from the trans oxalyl chloride ( C 2 h ), which is concluded from the vibrational analysis given below.

1 Phosphorescence excitation spectrum of jet-cooled oxalyl chloride for the T 1 ← S 0 transition.

2 Rotational envelope of the T 1 band of jet-cooled oxalyl chloride. …”

Section: Resultsmentioning

confidence: 96%

“…These values are in good agreement with those determined in cryogenic rare gas matrices. 19,22 In the same manner, two peaks on the high-energy side of the 0 0 0 band are assigned to the 2 1 1 C-C stretching bands. The shift is also 7 cm -1 , and the peak separation is 0.6 cm -1 .…”

Section: Resultsmentioning

confidence: 99%

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Radiative and Nonradiative Processes in the Excited States of Jet-Cooled Oxalyl Chloride

et al. 1996

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Phosphorescence and fluorescence excitation spectra of oxalyl chloride (COCl) 2 have been observed in a supersonic jet. Strong phosphorescence was observed for excitation of the 0 0 0 band of the T 1 3 A u (nπ*) r S 0 transition. From a vibrational analysis, it is shown that the molecule has C 2h symmetry in the T 1 excited state as well as in the S 0 ground state. Small splittings due to 35 Cl and 37 Cl isotopes were found in several vibronic bands. For the excitation of the S 1 0 0 0 band, phosphorescence with a short lifetime was observed, indicating fast intersystem crossing in the origin level. In the higher energy region, we could not observe phosphorescence but only weak fluorescence. It suggests existence of active nonradiative processes such as internal conversion and predissociation in the vibrationally excited levels of the S 1 state. A single-vibronic-level (SVL) dispersed phosphorescence spectrum has also been observed for the excitation of the T 1 CdO stretching band. The spectrum was dominated by bands at the same wavelengths as those for the 0 0 0 excitation. This clearly shows that intramolecular vibrational redistribution (IVR) takes place within the long triplet lifetime. Although oxalyl chloride is assumed to be a "small molecule", the radiationless transitions have been found to be efficient in both the T 1 and S 1 states.

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UV photolysis of oxalyl chloride: ClCO radical decomposition and direct Cl2${\rm Cl}_2 {\rm }$ formation pathways

Stuhr,

Hesse,

Faßheber

et al. 2024

Int J of Chemical Kinetics

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Oxalyl chloride, , is widely used as a photolytic source of Cl atoms in reaction kinetics studies. photolysis is typically assumed to produce Cl atoms with an overall yield of 2 via three‐body dissociation, , followed by fast subsequent ClCO unimolecular decomposition of either the energetically excited fragment, , or the thermalized ClCO radical, . However, a study by Huang et al. (J. Phys. Chem. A 121 (2017) 2888–2895) found that UV photolysis of at directly yields with a photolysis quantum yield of . This new product pathway may complicate the use of as a clean source of Cl atoms and challenges the previously accepted photodissociation scheme. The purpose of the present work was 2‐fold. Firstly, the unimolecular decomposition of and ClCO radicals has been investigated in / gas mixtures after UV photolysis at and . Cl atoms were captured by added in excess such that concentration‐time profiles of HCl measured by means of mid‐infrared frequency modulation spectroscopy reflect the temporally separated Cl formation pathways. The low‐pressure thermal ClCO decomposition rate constant was determined to be at , which is in very good agreement with previously reported literature values. Secondly, the photolysis quantum yield of direct formation from photofragmentation was studied with time‐of‐flight mass spectrometry using a photoelectron photoion coincidence setup. Calibrated concentration‐time profiles were recorded and analyzed using kinetic simulations accounting for both direct and secondary formation of from photolysis and reactions involving Cl, ClCO, and , respectively. Direct formation could be confirmed, where wavelength‐dependent quantum yields of , , and at , , and were determined. Complementary quantum‐chemical calculations of the potential energy diagram for ground‐state photodissociation reveal a low‐lying energy barrier for the formation of phosgene, . We suggest that subsequent and Cl formation from energetically excited may actually play a role for the overall photodissociation of .

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Ultraviolet photoisomerizations and FT-IR investigations of matrix isolated oxalyl halide conformers

Cited by 19 publications

References 25 publications

Photodissociation of Oxalyl Chloride at 193 nm Probed via Synchrotron Radiation

Photodissociation of Oxalyl Chloride at 193 nm Probed via Synchrotron Radiation

Radiative and Nonradiative Processes in the Excited States of Jet-Cooled Oxalyl Chloride

UV photolysis of oxalyl chloride: ClCO radical decomposition and direct Cl2${\rm Cl}_2 {\rm }$ formation pathways

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