multifunctional methacrylates to yield tough photopolymers is a widely researched topic, whereby addition–fragmentation chaintransfer (AFCT) agents represent one viable class of additives. Vinyl ethers have been described as potent AFCT agents in radical polymerization but are unexamined in network formation via photopolymerization. In this article, we present a sterically hindered vinyl ether as AFCT
Kinetic Study of the Phthalimide <i>N</i>-Oxyl Radical in Acetic Acid. Hydrogen Abstraction from Substituted Toluenes, Benzaldehydes, and Benzyl Alcohols
作者:Nobuyoshi Koshino、Basudeb Saha、James H. Espenson
DOI:10.1021/jo0348017
日期:2003.11.1
N-oxyl (PINO) radical was generated by the oxidation of N-hydroxyphthalimide (NHPI) with Pb(OAc)4 in acetic acid. The molar absorptivity of PINO* is 1.36 x 10(3) L mol(-1) cm(-1) at lambda(max) 382 nm. The PINO radical decomposes slowly with a second-order rate constant of 0.6 +/- 0.1 L mol(-1) s(-1) at 25 degrees C. The reactions of PINO(*) with substituted toluenes, benzaldehydes, and benzyl alcohols
邻苯二甲酰亚胺N-氧基(PINO)自由基是通过在乙酸中用Pb(OAc)4氧化N-羟基邻苯二甲酰亚胺(NHPI)生成的。PINO *在λ(最大)382 nm处的摩尔吸收率为1.36 x 10(3)L mol(-1)cm(-1)。PINO自由基在25摄氏度下以0.6 +/- 0.1 L mol(-1)s(-1)的二级速率常数缓慢分解。PINO(*)与取代的甲苯,苯甲醛和苄醇的反应在氩气气氛下进行了研究。通过Hammett分析将二阶速率常数关联起来。与甲苯和苄醇的反应与sigma +的相关性更好(rho = -1.3和-0.41),与苯甲醛的反应与sigma +的相关性更好(rho = -0.91)。还研究了动力学同位素效应,并获得了相当大的k(H)/ k(D)值:25.0(对二甲苯),27。在25摄氏度下为1(甲苯),27.5(苯甲醛)和16.9(苄醇)。从与对二甲苯和对二甲苯-d(10)
Modulation of Lifetimes and Diastereomeric Discrimination in Triplet-Excited Substituted Butane-1,4-diones through Intramolecular Charge-Transfer Quenching
作者:J. N. Moorthy、S. L. Monahan、R. B. Sunoj、J. Chandrasekhar、C. Bohne
DOI:10.1021/ja9818708
日期:1999.4.1
lifetimes have been determined for the diastereomers of a broad set of butane-1,4-dione derivatives (1−3). A remarkable dependence of lifetimes on conformationalpreferences is revealed in that the lifetimes are shorter for the meso diastereomers of 1−3 than those for the racemic ones. The intramolecular β-phenyl quenching is promoted in the case of meso diastereomers by virtue of the gauche relationship
production of freeradicals by the sunscreen agent, butyl-methoxydibenzoylmethane (BMDBM). Spin-trapping/electron paramagnetic resonance spectroscopy was used to evaluate the formation of radicals and the extent of BMDBM photodegradation was measured by high-performance liquid chromatography. The stable 2,2,6,6-tetramethylpiperidine-1-oxyl, nitroxide radical (TEMPO) was used as spin-trap. Any free radicals
The additionrateconstants of five differently substituted benzoyl radicals to butyl acrylate were determined by continuous-wave time-resolved EPR (TR-EPR at X-band (9 GHz) and at W-band (95 GHz)) spectroscopy. Remarkably, the reactivity of the benzoyl radicals, is divided into two domains: One is established at low (<1.25 M) concentrations of butyl acrylate with rateconstants in the range of 106