The gas-phase thermal and photochemical decomposition of heterocyclic compounds containing nitrogen, oxygen, or sulfur

1977 ◽  
Vol 77 (4) ◽  
pp. 473-511 ◽  
Author(s):  
Silvia. Braslavsky ◽  
Julian. Heicklen
Keyword(s):  
Gas Phase ◽  
Heterocyclic Compounds ◽  
Photochemical Decomposition

Mechanism of the Direct Photochemical Decomposition of Thietane and its Derivatives in the Vapor Phase, in Solution, and in Glassy Matrices

1975 ◽  
Vol 53 (12) ◽  
pp. 1744-1755 ◽  
Author(s):  
David R. Dice ◽  
Ronald P. Steer
Keyword(s):  
Low Temperature ◽  
Gas Phase ◽  
Vapor Phase ◽  
Low Temperatures ◽  
Condensed Media ◽  
Photochemical Decomposition ◽  
Glassy Matrices

The direct photolyses of thietane, 3-ethyl-2-propylthietane, and 3-methylthietane in the vapor phase, in solution, and in glassy matrices at low temperatures have been examined. The effects of varying the photolysis wavelength, the temperature, the pressure and the phase of the substrate, and of adding inert thermalizers on the nature and yields of the various products have been measured. The results are interpreted in terms of initial C—S cleavage to give a 1,4-biradical which may, in the gas phase, decompose or ring close before complete equilibration of the various rotamers is achieved, or which may be thermalized in condensed media and trapped in glassy matrices at low temperature.

The thermal and photochemical decomposition of maleic anhydride in the gas phase

1981 ◽  
Vol 59 (9) ◽  
pp. 1342-1346 ◽  
Author(s):  
R. A. Back ◽  
J. M. Parsons
Keyword(s):  
Maleic Anhydride ◽  
Gas Phase ◽  
Light Emission ◽  
Order Rate Constant ◽  
Static System ◽  
Collisional Quenching ◽  
Vibrationally Excited ◽  
Concerted Mechanism ◽  
Photochemical Decomposition ◽  
Weak Light

The thermal decomposition of maleic anhydride has been studied in the gas phase in a static system at temperatures from 645 to 760 K and pressures from 0.7 to 20 Torr. The first-order rate constant for the homogeneous unimolecular reaction,[Formula: see text]is described by the Arrhenius parameters log A (s−1) = 14.33 (±0.3), and E = 60.9 (± 1) kcal/mol. The reaction appears to proceed through a concerted mechanism rather than a biradical one.The photochemical decomposition, studied at wavelengths from 220 to 350 nm, yielded the same products. At 300 nm and below, the decomposition was unaffected by pressure, but at longer wavelengths collisional quenching was observed. Weak light emission was observed on excitation between 350 and 380 nm. The absorption spectrum was measured from 250 to 400 nm, and three overlapping transitions, π*←π, π*←n+, and π*←n−, can be distinguished. The mechanism of the photolysis is discussed and it is concluded that it probably proceeds through internal conversion to a vibrationally excited ground state.

The photochemical decomposition of methyl iodide in presence of nitric oxide - II. Reactions of nitrosomethane

1959 ◽  
Vol 249 (1257) ◽  
pp. 258-269 ◽  
Keyword(s):  
Nitric Oxide ◽  
Gas Phase ◽  
Methyl Iodide ◽  
Initial Rate ◽  
Wavelength Region ◽  
Order Reaction ◽  
Methyl Radicals ◽  
Second Order Reaction ◽  
Photochemical Decomposition ◽  
Rate Method

A product of the photolysis, in presence of a small quantity of nitric oxide, of methyl iodide reacts with excess nitric oxide to form a substance(s), Y , which absorbs light throughout the wavelength region 2300 to 5300 Å. The initial products of the photolysis, in presence of small quantities of nitric oxide, of both acetone and acetaldehyde react similarly. The species undergoing the reaction is believed to be monomeric nitrosomethane, formed by the association of methyl radicals with nitric oxide. The order of the reaction to form Y , as determined by the initial rate method, is one with respect to nitrosomethane and two with respect to nitric oxide. The extent of the reaction, which can be used as a measure of nitrosomethane concentration, depends on the concentration of nitric oxide. In absence of excess nitric oxide the monomer disappears slowly from the gas phase in a second-order reaction, which is thought to be the dimerization to nitrosomethane dimer.

Direct photoisomerization of CH2I2vs. CHBr3 in the gas phase: a joint 50 fs experimental and multireference resonance-theoretical study

2016 ◽  
Vol 18 (41) ◽  
pp. 28883-28892 ◽  
Author(s):  
Veniamin A. Borin ◽  
Sergey M. Matveev ◽  
Darya S. Budkina ◽  
Patrick Z. El-Khoury ◽  
Alexander N. Tarnovsky
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Photochemical Decomposition ◽  
Way Of Thinking

Photoisomerization: a new way of thinking about a longstanding problem concerning UV photochemical decomposition of alkyl di- and polyhalides in the gas phase.

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