2690-18-8Relevant academic research and scientific papers
On the Mechanism of the Benzophenone-Sensitized Photolysis of 2,3-Diazabicyclohept-2-ene in the Laser Jet: Evidence for Intermolecular Triplet Diradical Reactions
Adam, Waldemar,Finzel, Ralf,Walther, Barbara
, p. 2137 - 2142 (2007/10/02)
The benzophenone-sensitized laser jet photolysis of 2,3-diazabicyclohept-2-ene (1) affords, besides the previously reported cyclopentene and housane (2), also cyclopentane, cyclopentadiene, and the dimers bicyclopent-2-en-1-yl (7), 3-cyclopentylcyclopent-1-ene (8), and 1,1'-bicyclopentyl (9).As a model reaction, the pyrolysis of dimer 8 at 600 deg C/ 20 Torr leads to the other dimers 7 and 9 together with cyclopentadiene, cyclopentene, and traces of cyclopentane.Control experiments showed that H abstraction by the cyclopentane-1,3-diyl diradical (3) from cyclohexene (as model substrate for cyclopentene) and addition to housane (2) with formation of diradical 6 are unlikely pathways.Instead, the product data available can be best explained in terms of an intermolecular disproportionation of two diradicals 3 to give the cyclopent-2-en-1-yl (4) and cyclopentyl (5) radical pair, which is subsequently converted to the observed products by in-cage and out-of-cage coupling and H transfer reactions.Such intermolecular diradical chemistry becomes feasible due to the high steady-state concentrations (ca. micromolar) generated in the laser jet.Two-photon processes take place, but are of subordinate importance. - Key Words: Laser jet/ Azoalkane/ Diradical/ Radical coupling
Deuterium-Hydrogen Exchange and Scrambling Reactions in the Pyrolysis of Labeled Cyclopentene. A Radical Mechanism
Kosnik, Kenneth G.,Benson, Sidney W.
, p. 2790 - 2795 (2007/10/02)
Inter- and intraradical mechanism that promote deuterium-hydrogen scrambling in labeled cyclopentene-d1 are investigated at 800 K and 1200 K.Rate constants are estimated for each step and for possible competing side reactions.The fast radical bimolecular exchange at 800 K and unimolecaular scrambling at 1200 K of labeled cyclopentene are shown to be faster than the Woodward-Hoffman allowed 1,4 concerted molecular elimination of hydrogen.The low-energy estimate of 8.0 kcal/mol by Lewis of the difference between the allowed 1,4 and disallowed 1,2 channels can thus be explained.No conclusions can be drawn concerning the 1,2 channel.The estimated rates of radical reactions are in agreement with experiments on the addition of D2 to cyclopentadiene at 300 deg C which shows only cis, 3-5 addition and with pyrolysis experiments at 500 +/- 20 deg C which show about 5percent contribution of a higher than first-order radical reaction.The mechanism of this radical decomposition is given and its steps are explicitly evaluated.
