497-20-1Relevant articles and documents
Matrix-Controlled Photochemistry of Benzene and Pyridine
Johnstone, Duncan E.,Sodeau, John R.
, p. 165 - 169 (1991)
Dewar benzene has been shown to be a primary product from the photolysis of benzene in low temperature argon matrices at 253.7 nm.This is the first observation of Dewar benzene production at this wavelength and a mechanism is proposed that involves benzene S1-S2 state mixing induced by the matrix environment.Analogous experiments on the photolysis of pyridine show that the only primary products are isomeric species derived at least in part from a triplet state of pyridine, probably T1.This is the first observation of photochemistry from the T1 state and may be the process responsible for the small values of τp and ψp in pyridine.Analysis of the IR spectral bands points to the main product being Dewar pyridine although other isomers cannot be ruled out.In contrast to the gas phase, no decomposition of pyridine was found in matrices poducing compounds such as acrylonitrile, ethyne, and hydrogen cyanide.
Shock Tube Study of Thermal Rearrangement of 1,5-Hexadiyne over Wide Temperature and Pressure Regime
Tranter, Robert S.,Tang, Weiyong,Anderson, Ken B.,Brezinsky, Kenneth
, p. 3406 - 3415 (2007/10/03)
The pyrolysis of 1,5-hexadiyne has been studied in a high-pressure single pulse shock tube to investigate the mechanisms involved in the production of benzene from propargyl radicals. Analysis of the reaction products by gas chromatography and matrix isolation Fourier transform infrared spectroscopy has positively identified six linear C6H6 species and two cyclic C6H6 species. Of these species cis-1,3-hexadien-5- yne and trans-1,3-hexadiene-5-yne have been unambiguously identified for the first time and provide vital information concerning a low-temperature route to benzene that does not involve the formation of fulvene; however, the data also provide support for two high-temperature paths from propargyl radicals to benzene via fulvene. Thus experimental evidence has been gained that supports two different routes to benzene formation. The mechanisms and rate coefficients that have been obtained in this work are discussed.
Carbon-oxygen bond strength in diphenyl ether and phenyl vinyl ether: An experimental and computational study
Van Scheppingen, Wibo,Dorrestijn, Edwin,Arenas, Isabel,Mulder, Peter,Korth, Hans-Gert
, p. 5404 - 5411 (2007/10/03)
The thermal decomposition of gaseous diphenyl ether (DPE) and phenyl vinyl ether (PVE) has been studied, at atmospheric pressure in hydrogen and in a very low-pressure reactor, over a temperature range of 1050-1200 K. The high-pressure rate constant for homolytic bond cleavage C6H5O-C6H5 → C6H5O? + C6H5? (1) obeys k1 (s-1) = 1015.50 exp(-75.7/RT). Two pathways can be distinguished for C6H5OC2H3: C6H5? + C2H3O? (2) and C6H5O? + C2H3? (3). The overall rate constant follows k2+3 (s-1) = 1015.50 exp(-73.3/RT). The rate ratio, v2/v3, amounts to 1.8 and appears to be temperature independent These findings result in bond dissociation energies (BDE) at 298 K for C6H5O-C6H5, C6H5-OC2H3, and C6H5O-C2H3 of 78.8 ,75.9, and 76.0 kcal mol-1, respectively. The enthalpies for reactions 1-3 have been also determined at 298 and 1130 K by ab-initio calculations using the density functional theory formalism on the B3LYP/6-31G(d) and B3LYP/ 6-311++G(d,p) level. Comparison between experiments and theoretical calculations reveals distinct variances (ca 3-4 kcal mol-1) for the BDE(C-O) in aryl ethers and the BDE(O-H) in phenol and vinyl alcohol but a close agreement for the BDE(C-H) in the related hydrocarbons: toluene, benzene, and ethene.
