32796-95-5Relevant academic research and scientific papers
Determination of the photochemical efficiency of o-quinodimethane ring closure in room-temperature solutions by using time-delayed, two-color photolysis technique
Ouchi, Akihiko,Sakuragi, Masako,Kitahara, Haruo,Zandomeneghi, Maurizio
, p. 2350 - 2357 (2000)
Photochemical efficiency of o-quinodimethane (3) ring closure at room temperature was determined by using a time-delayed, two-color photolysis technique. o-Quinodimethane (3) was generated by the photolysis of 1,2- bis[(phenylseleno)methyl]benzene (1) by a KrF (248 nm) laser pulse and thus- generated 3 was photolyzed by a subsequent XeCl (308 nm)/XeF (351 nm) laser pulse with varying delay time of 0 to 3 s. The time profile of 3 was monitored by the chemical analyses of benzocyclobutene (5) (a photochemical product of 3), which was formed by a one-photon process, and the spiro dimer of 3 (4) (a thermal product of 3) in the two-color photolysis experiments. The time profile of 3 followed a second-order decay kinetics. The photochemical efficiency was obtained by the analysis of the delay-time dependence of the product yields; those of the consumption of 3 and the conversion 3 → 5 by a single pulse of the excimer laser were 81% and 5.7% for the XeCl laser, and 73% and 2.3% for the XeF laser. This difference was attributed to the different excited states involved in the photolysis. In contrast to the photolysis of 3 in argon or rigid organic matrixes, it was revealed that photochemical conversion 3 → 5 was not the main path in the solutions, and intermolecular reactions predominated.
Photoelectron Spectrum and Energetics of the meta-Xylylene Diradical
Steglich, Mathias,Custodis, Victoria B. F.,Trevitt, Adam J.,Dasilva, Gabriel,Bodi, Andras,Hemberger, Patrick
, p. 14348 - 14351 (2017)
The meta-xylylene diradical m-C8H8 is a prototypical organic triplet that represents a building block for organic molecule-based magnets and also serves as a model compound for test and refinement of quantum chemical calculations. Flash vacuum pyrolysis of 1,3-bis-iodomethyl-benzene (m-C8H8I2) produces m-C8H8 in gas phase; we used photoelectron spectroscopy to probe the first two electronic states of the radical cation, and resolve the vibrational fine structure of the ground state band. The determined adiabatic ionization energy of m-C8H8 is (7.27 ± 0.01) eV. Heat of formation of the diradical was established measuring C-I bond dissociation thresholds in the precursor cation and utilizing a thermochemical cycle to yield ΔHf,298K = (325 ± 8) kJ mol-1, ca. 10 kJ mol-1 below the previous value.
A two-color laser photolysis method for determining reaction rates of short-lived intermediates by product analysis: Application to the o-Quinodimethane problem
Ouchi, Akihiko,Li, Zhong,Sakuragi, Masako,Majima, Tetsuro
, p. 1104 - 1108 (2003)
A time-delayed, two-color pulse laser photolysis technique was used for a kinetic study of short-lived transient species through product analysis, the determination of the rate constant of the cycloaddition of o-quinodimethane (1) and maleic anhydride (2) in room-temperature solutions, o-Quinodimethane (1) was generated from 1,2-bis[(phenylseleno)methyl]benzene (3) by the irradiation of a pulse of a KrF excimer laser (248 nm) in the presence of excess 2, and a successive pulse of a XeCl excimer laser (308 nm) was irradiated to the reaction mixture after varied delay times from 0 to 0.1 s for the decomposition of the remaining 1 to quench the cycloaddition reaction. The rate constant of the cycloaddition of 1 and 2 was 2.1 × 105 M-1 s-1, which was obtained by the analysis of the delay-time dependence of the product yields.
Mechanistic studies on the photogeneration of o-and p-xylylenes from aαα′-dichloroxylenes
Miranda, Miguel A.,Perez-Prieto, Julia,Font-Sanchis, Enrique,Scaiano
, p. 1541 - 1542 (1998)
Two-colour two-laser techniques have unambiguously proved that photolysis of the o-/p-(chloromethyl)benzyl radical leads to the sequential two-photon generation of o-/p-xylylene from α,α′-dichloro-o-/p-xylene.
Spectroscopic studies on photochemical formation of o-xylylene in solution
Fujiwara,Mishima,Tamai,Tanimoto,Mizuno,Ishii
, p. 4912 - 4915 (1997)
The photochemical formation of o-xylylene is studied by two-pulse fluorescence and transient absorption spectroscopy. o-Xylylene is produced by photolysis of α,α′-dichloro-o-xylene, α,α′-dibromo-o-xylene, α,α′-bis(trimethylstannyl)-o-xylene, and 2-indanon
A New Mode for the Generation of o-Xylylene by peri-Selenium Participation from 8,13-Dihydrobenzonaphthodiselenonin under Irradiation
Fujihara, Hisashi,Yabe, Masayoshi,Furukawa, Naomichi
, p. 5291 - 5292 (1993)
A new cyclic bis-selenide containing both benzylic methylene groups and a naphthalene ring, 8,13-dihydrobenzonaphthodiselenonin (1), was stable in the dark; however, the C-Se bond of 1 was readily cleaved to form o-xylylene (2) and naphtho-1,2-diselenole (3) under the scattered light in the laboratory.The o-xylylene generated from 1 under the scattered light or UV irradiation (254 nm) was trapped by several dienophiles.
Sequential Hydrogen Tunneling in o-Tolylmethylene
Lohmiller, Thomas,Sarkar, Sujan K.,Tatchen, J?rg,Henkel, Stefan,Schleif, Tim,Savitsky, Anton,Sanchez-Garcia, Elsa,Sander, Wolfram
, p. 17873 - 17879 (2021/09/14)
o-Tolylmethylene 1 is a metastable triplet carbene that rearranges to o-xylylene 2 even at temperatures as low as 2.7 K via [1,4] H atom tunneling. Electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopical techniq
Thermochemistry and photochemistry of spiroketals derived from indan-2-one: Stepwise processes versus coarctate fragmentations
Bucher, Goetz,Heitmann, Gernot,Herges, Rainer
, p. 1668 - 1676 (2013/10/22)
Coarctate reactions are defined as reactions that include atoms at which two bonds are made and two bonds are broken simultaneously. In the pursuit of the discovery of new coarctate reactions we investigate the fragmentation reactions of cyclic ketals. Three ketals with different ring sizes derived from indan-2-one were decomposed by photolysis and pyrolysis. Particularly clean is the photolysis of the indan-2-one ketal 1, which gives o-quinodimethane, carbon dioxide and ethylene. The mechanism formally corresponds to a photochemically allowed coarctate fragmentation. Pyrolysis of the five-ring ketal yields a number of products. This is in agreement with the fact that coarctate fragmentation observed upon irradiation would be thermochemically forbidden, although this exclusion principle does not hold for chelotropic reactions. In contrast, fragmentation of the seven-ring ketal 3 is thermochemically allowed and photochemically forbidden. Upon pyrolysis of 3 several products were isolated that could be explained by a coarctate fragmentation. However, the reaction is less clean and stepwise mechanisms may compete.
Quest for diatomic selenium
Rys, Andrzej Z.,Schultz, Erwin K. V.,Harpp, David N.
scheme or table, p. 351 - 371 (2011/01/12)
Metallocene pentaselenides and elemental selenium were employed in an effort to generate diatomic selenium (Se2) under thermal conditions. Trapping experiments were carried out with six dienes. A successful formation of a diselenium adduct was observed in the case of 5,6-dimethylene-cyclohexa-1,3- diene (1a). The other dienes produced the corresponding dihydroselenophenes. The in-depth study of the limitations of our method to generate Se2 is described; a plausible mechanism rationalizing the observed results is proposed.
Electro-organic reactions. Part 54: Quinodimethane chemistry; Part 2 - Electrogeneration and reactivity of o-quinodimethanes
Utley, James H.P.,Ramesh, Shalini,Salvatella, Xavier,Szunerits, Sabine,Motevalli, Majid,Nielsen, Merete F.
, p. 153 - 163 (2007/10/03)
The electrochemical generation and characterisation of a variety of o-quinodimethanes (o-QDMs) are described together with the outcome of preparative experiments in which they are key intermediates. The quinodimethanes are conveniently formed, in DMF, by both direct and redox-catalysed electroreduction of 1,2-bis(halomethyl)arenes. Their predominant reaction is polymerisation to poly(o-xylylene) (o-PX) polymers. In the presence of dienophiles the electrogenerated o-QDMs may undergo efficient cycloaddition reaction and distinctions between the possible mechanisms have been attempted on the basis of voltammetric, preparative and stereochemical experiments. Contrary to the precedent of the corresponding methyl ester, diphenyl maleate radical-anion isomerises only slowly to the fumarate radical-anion, yet co-electrolysis of 2,3-bis(bromomethyl)-1,4-dimethoxybenzene and diphenyl maleate or diphenyl fumarate gives exclusively the corresponding trans-adduct. Co-electrolysis of dimethyl maleate with either 1,2-bis(bromomethyl)benzene (more easily reduced) or 2,3-bis(bromomethyl)-1,4-dimethoxybenzene (less easily reduced) gave only o-PX polymer. The results are rationalised in terms of a double nucleophilic substitution mechanism where electron transfer between dienophile radical-anion and dihalide is relatively slow. Where electron transfer from maleate or fumarate radical-anions is likely to be fast o-quinodimethanes are formed by redox-catalysis and they polymerise rather than undergo Diels-Alder reaction. Dimerisation of the dienophile radical-anions, with k2 = 104 to 105 M-1 s-1, does not apparently compete with nucleophilic substitution or, where relevant, electron transfer.
