Cyclopentene and cyclopentadiene formation in isoprene pyrolysis.

Photoion mass-selected threshold photoelectron spectroscopy (ms-TPES) was used to identify the isoprene pyrolysis products in a SiC microreactor at 1400 °C with the help of literature and Franck-Condon simulated reference spectra for molecular species at the detected / ratios. The key observation is the presence of equimolar amounts of isoprene and cyclopentene at the pyrolysis temperature based on the / 68 ms-TPES, indicating kinetically allowed isoprene isomerization concurrently with fragmentation reactions. This isomerization was computationally explored and was found to take place a short-lived vinylcyclopropane intermediate, which was previously proposed to isomerize into isoprene and cyclopentene, with the latter product being dominant.

What a difference a chlorine makes: The remarkable unimolecular ion chemistry of phenyl formate and phenyl chloroformate.

Imaging photoelectron photoion coincidence (iPEPICO) spectroscopy and tandem mass spectrometry were employed to explore the ionisation and dissociative ionisation of phenyl formate (PF) and phenyl chloroformate (PCF). The threshold photoelectron spectra of both compounds are featureless and lack a definitive origin transition, owing to the internal rotation of the formate functional group relative to the benzene ring, active upon ionisation. CBS-QB3 calculations yield ionisation energies of 8.

The Unimolecular Chemistry of Methyl Chloroformate Ions and Neutrals: A Story of Near-Threshold Decomposition.

The near-threshold dissociation of ionized and neutral methyl chloroformate (CHCOOCl, MCF) was explored with imaging photoelectron photoion coincidence spectroscopy. The threshold photoelectron spectrum (TPES) for MCF was acquired for the first time; the large geometry changes upon ionization of MCF result in a broad, poorly defined TPES. Franck-Condon simulations are consistent with an adiabatic ionization energy (IE) of 10.

Probing the pyrolysis of ethyl formate in the dilute gas phase by synchrotron radiation and theory.

The thermal decomposition of the atmospheric constituent ethyl formate was studied by coupling flash pyrolysis with imaging photoelectron photoion coincidence (iPEPICO) spectroscopy using synchrotron vacuum ultraviolet (VUV) radiation at the Swiss Light Source (SLS). iPEPICO allows photoion mass-selected threshold photoelectron spectra (ms-TPES) to be obtained for pyrolysis products. By threshold photoionization and ion imaging, parent ions of neutral pyrolysis products and dissociative photoionization products could be distinguished, and multiple spectral carriers could be identified in several ms-TPES.

Characterization of Binding Properties of Cr(Phen) and Ru(Phen) Complexes with Human Lactoferrin.

This work presents research about [Cr(phen) ] and [Ru(phen) ] interaction with human lactoferrin (HLf), a key carrier protein of ferric cations. The photochemical and photophysical properties of [Cr(phen) ] and [Ru(phen) ] have been widely studied in the last decades due to their potential use as photosensitizers in photodynamic therapy (PDT). The behavior between the complexes and the protein was studied employing UV-visible absorption, fluorescence emission and circular dichroism spectroscopic techniques.

Probing the pyrolysis of methyl formate in the dilute gas phase by synchrotron radiation and theory.

The thermal dissociation of the atmospheric constituent methyl formate was probed by coupling pyrolysis with imaging photoelectron photoion coincidence spectroscopy (iPEPICO) using synchrotron VUV radiation at the Swiss Light Source (SLS). iPEPICO allows threshold photoelectron spectra to be obtained for pyrolysis products, distinguishing isomers and separating ionic and neutral dissociation pathways. In this work, the pyrolysis products of dilute methyl formate, CH OC(O)H, were elucidated to be CH OH + CO, 2 CH O and CH  + CO as in part distinct from the dissociation of the radical cation (CH OH  + CO and CH OH + HCO).

Infrared Emission from Photodissociation of Methyl Formate [HC(O)OCH] at 248 and 193 nm: Absence of Roaming Signature.

Following photodissociation at 248 nm of gaseous methyl formate (HC(O)OCH, 0.73 Torr) and Ar (0.14 Torr), temporally resolved vibration-rotational emission spectra of highly internally excited CO (ν ≤ 11, ≤ 27) in the 1850-2250 cm region were recorded with a step-scan Fourier-transform spectrometer.

Trifluoroacetic Acid and Trifluoroacetic Anhydride Radical Cations Dissociate near the Ionization Limit.

The threshold photoelectron spectra (TPES) and ion dissociation breakdown curves for trifluoroacetic acid (TFA) and trifluoroacetic anhydride (TFAN) were measured by imaging photoelectron photoion coincidence spectroscopy employing both effusive room-temperature samples and samples introduced in a seeded molecular beam. The fine structure in the breakdown diagram of TFA mirroring the vibrational progression in the TPES suggests that direct ionization to the state leads to parent ions with a lower "effective temperature" than nonresonant ionization in between the vibrational progression. Composite W1U, CBS-QB3, CBS-APNO, G3, and G4 calculations yielded an average ionization energy (IE) of 11.

Gas-Phase Reaction between CFO and CFC(O)OH: Characterization of CFC(O)OC(O)F.

The thermal decomposition of trifluoroacetic acid and carbonyl fluoride (CFO) has been extensively studied because of their importance in the oxidation of hydrochlorofluorocarbons in the atmosphere. We hitherto present the study of the thermal reaction between these two molecules. The reaction mechanism was studied using Fourier transform infrared spectroscopy in the temperature range of 513-573 K.

Reaction of Methyl Fluoroformyl Peroxycarbonate (FC(O)OOC(O)OCH) with Cl Atoms: Formation of Hydro-ChloroFluoro-Peroxides.

The products following Cl atom initiated reactions of FC(O)OOC(O)OCH in 50-760 Torr of N at 296 K were investigated using FTIR. Reaction of Cl atoms with methyl fluoroformyl peroxycarbonate proceeds mainly via attack at the methyl group, forming FC(O)OOC(O)OCH radicals. Further reaction of this kind of radical with Cl forms three new compounds: FC(O)OOC(O)OCHCl, FC(O)OOC(O)OCHCl, and FC(O)OOC(O)OCCl, whose existence was characterized experimentally by FTIR spectroscopy assisted by ab initio calculations at the B3LYP/6-31++G(d,p) level.

Properties and thermal decomposition of the hydro-fluoro-peroxide CH₃OC(O)OOC(O)F.

The thermal decomposition of methyl fluoroformyl peroxycarbonate CH3OC(O)OOC(O)F was studied in the range of 30- 96 °C using FTIR spectroscopy to follow the course of the reaction in the presence of either N2, O2, or CO as bath gases. The rate constants of the homogeneous first-order process fit the Arrhenius equation k(exp) = (5.4 ± 0.

Mechanism of photo-oxidation of heptafluorobutyric anhydride in the presence of NO2. Synthesis and characterization of heptafluoropropyl peroxynitrate, CF3CF2CF2OONO2.

The photolysis of heptafluorobutyric anhydride at 254 nm in the presence of NO(2) and O(2) has been studied. It leads to the formation of CF(3)CF(2)CF(2)OONO(2), CF(3)CF(2)OONO(2), and CF(2)O as the only fluorine-containing carbonaceous products. The formation of the new heptafluoropropyl peroxynitrate (HFPN, CF(3)CF(2)CF(2)OONO(2)), as one of the main products, is a consequence of the formation of CF(3)CF(2)CF(2)OO(•) radicals followed by the reaction with NO(2).

2-Chloroethylisocyanate. Thermal decomposition and spectroscopic properties.

2-Chloroethylisocyanate has been studied in a thorough way. NMR, Raman, FTIR, and Ar-matrix vibrational spectra of the molecule are presented and discussed with the complement of ab initio and DFT methods. The spectroscopic results reveal the existence of anti and gauche conformers that are equally populated in the gas phase.