The thermal decomposition of bis(4-carboxybenzyl)hyponitrite (SOTS-1) in aerated water under physiological conditions has previously been shown to give the superoxide radical anion in a yield of 40 mol % (Ingold, K. U.; et al. J. Am. Chem. Soc. 1997, 119, 12364). The absolute kinetics of the elementary reactions involved in the cascade of events leading from the first-formed water-soluble benzyloxyl radical to superoxide have been determined by laser flash photolysis. On the basis of these kinetics it is concluded that SOTS-1 will be suitable for studies of superoxide-induced oxidative stress in most biological systems. A water-assisted 1,2-H shift converting benzyloxyl into the benzyl ketyl radical is an important step in the above reaction cascade. The kinetics of the 1,2-H shift assisted by H 2 O, D 2 O, and a number of nucleophilic alcohols have been measured for the first time. These data have led to a proposed new mechanism involving the initial formation of a ketyl radical anion and an oxonium cation which generally collapse to give the neutral ketyl radical as the first observable product on the time scale of our experiments (ca. 80 ns).

Introduction: Our meta-analysis indicated that aging influences the outcomes of acute pancreatitis (AP), however, a potential role for comorbidities was implicated, as well. Here, we aimed to determine how age and comorbidities modify the outcomes in AP in a cohort-analysis of Hungarian AP cases. Materials and Methods: Data of patients diagnosed with AP by the revised Atlanta criteria were extracted from the Hungarian Registry for Pancreatic Patients. Outcomes of interest were mortality, severity, length of hospitalization, local, and systemic complications of AP. Comorbidities were measured by means of Charlson Comorbidity Index (CCI) covering pre-existing chronic conditions. Non-parametric univariate and multivariate statistics were used in statistical analysis. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. Results: A total of 1203 patients from 18 centers were included. Median age at admission was 58 years (range: 18–95 years), median CCI was 2 (range: 0–10). Only severe comorbidities (CCI ≥ 3) predicted mortality (OR = 4.48; CI: 1.57–12.80). Although severe comorbidities predicted AP severity (OR = 2.10, CI: 1.08–4.09), middle (35–64 years) and old age (≥65 years) were strong predictors with borderline significance, as well (OR = 7.40, CI: 0.99–55.31 and OR = 6.92, CI: 0.91–52.70, respectively). Similarly, middle and old age predicted a length of hospitalization ≥9 days. Interestingly, the middle-aged patients (35–64 years) were three times more likely to develop pancreatic necrosis than young adults (OR = 3.21, CI: 1.26–8.19), whereas the old-aged (≥65 years) were almost nine times more likely to develop systemic complications than young adults (OR = 8.93, CI: 1.20–66.80), though having severe comorbidities (CCI ≥ 3) was a predisposing factor, as well. Conclusion: Our results proved that both aging and comorbidities modify the outcomes of AP. Comorbidities determine mortality whereas both comorbidities and aging predict severity of AP. Regarding complications, middle-aged patients are the most likely to develop local complications; in contrast, those having severe comorbidities are prone to develop systemic complications. Studies validating the implementation of CCI-based predictive scores are awaited.

One-and two-electron transfer reactions of 3,5-di-tert-butylcatechol and the corresponding quinone were studied by fast kinetic spectroscopy coupled with laser photolysis and pulse radiolysis, and by cyclic voltammetry in aqueous solutions. Photoionization of catechol yields the same semiquinone radical as the formate-radical-induced quinone reduction in the pulse radiolysis experiment. The neutral semiquinone radical deprotonates at pK, = 6.0 2 0. I, as deduced from the pH induced changes in the radical spectra. The twoelectron reduction potentials of quinone and catechol were measured by cyclic voltammetry in aqueous solutions containing 25% methanol in the pH range 3-14. The pH dependence has two linear parts with slopes of 0.056 and 0.03 VIpH, intersecting at pK, = 10.0. This is in excellent agreement with pKa = 10.05 ? 0.05 obtained spectrophotometrically. The reduction potential of 3,5-di-tert-butyl quinone, E7 = 0.01 ? 0.04 V, was obtained from the one-electron transfer equilibrium of the quinone with the oxygen/superoxide redox couple by pulse radiolysis. The rate constant of the reaction of quinone with the superoxide radical, k = 1.2 x lo9 M-I sK', is higher than those of the superoxide reduction by catechols and phenols (typically -lo5 MK1 s-I); thus, lignin o-quinones could be efficient scavengers of superoxide under the conditions relevant for the photo-induced yellowing of lignin-rich paper. The reaction with 0; effectively bleaches yellow quinone and generates metastable furanone, which hydrolyses to muconic acid, thus completely eliminating yellow quinone. 3,5-Ditert-butylquinone also undergoes rapid bleaching with ascorbate, k = 600 2 100 M-I S-I, in methanol. The reaction has a 1:l stoichiometry and leads to complete reduction of quinone to catechol with concomitant oxidation of ascorbate to dehydroascorbate. This unusual selectivity and the fact that the reaction of the milder oxidant 3,5-di-tert-butylquinone is an order of magnitude faster than that of stronger oxidantp-benzoquinone (k = 60 2 10 M-' s-') suggest that a nucleophilic attack of quinone at the ascorbate double bond initiates the reaction.Key words: superoxide, lignin, photochemistry, quinone.RCsumC : Faisant appel A voltampCromCtrie cyclique et h la spectroscopie cinktique rapide couplee A photolyse laser et A la radiolyse pulsCe, on a CtudiC les rkactions de transfert d'un et de deux Clectrons du 3,5-di-tertbutylcatCcho1 et la quinone correspondante, en solutions aqueses. La photoionisation du catCchol fournit le meme radical semiquinone que celui produit lors de la rCduction radicalaire de la quinone induite par le formiate dans 17expCrience de radiolyse pulsCe. Sur la base des changements induits de pH dans le spectre radicalaire, le radical semiquinone neutre se diprotone h un pK, = 6,O 2 0,l. On a utilisC la voltampCromCtrie cyclique pour mesurer les potentiels de rCduction h deux electrons quinonelcatCcho1 en solutions aqueuses contenant 25% de mtthanol, A des pH allant de 3 A 14. La relation avec le pH prCsente d...

Low intensity irradiation of 1,3-dichloro-1,3-diphenylpropane (1) in cyclohexane leads to the formation of 3-chloro-1,3-diphenylpropyl radical (2) through homolytic C−Cl bond cleavage. Radical 2 gives rise to final products typical of free radical reactions. Neither 1,2-diphenylcyclopropanes (6) nor 3-cyclohexyl-1,3-diphenylpropene (20) are obtained under these conditions. Nevertheless, high intensity laser irradiation of the initially formed monoradical 2 leads to the 1,3-diphenylpropenyl radical (3) detected with nanosecond techniques. This intermediate is completely trapped by the cyclohexyl radicals generated in the medium to yield 20. Photolysis of 1 with the laser-drop technique leads to the cyclopropanes 6 as major photoproducts.

A four-member ring hypervalent iodine radical has been detected in the laser flash photolysis of 1,3-diiodo-1,3-diphenylpropane. This species absorbs at 320 nm, has a lifetime of ∼9.5 μs in cyclohexane, and is not quenchable by oxygen. Excitation of this radical by means of laser-drop photolysis results the formation of trans-1,2-diphenylcyclopropane through concerted iodine extrusion.