Neutral, crystalline ice samples were pulse irradiated in order to study phase and temperature effects on the properties of transient intermediates produced in radiolyzed water. These studies demonstrate that optical absorption bands with peaks near 670, at 280 ± 5, and at 230 ± 8 nm are detectable. The transient visible absorption is attributed to a solvated electron es−. Its spectrum, though unaffected by phase change, is influenced by temperature, dEmax / dT being −1.2 × 10−3 eV/deg. Ges− also depends on temperature, decreasing markedly from −5° to −40°C, but only slowly thereafter. The decay of es−, which is second order at −14°C (k = 1.5 × 1011 M−1·sec−1) and partly first order from −40° to −100°C [k(−60°C) = 1.1 × 104sec−1; ΔEact = 9 ± 2 kcal/mole], becomes slower with decreasing temperature. Over-all spectral, yield and kinetic considerations indicate that es− is structurally similar to eaq−, forms via pre-existing traps, and though immobile as a unit, decays both by reaction with H3O+ and by means of an equilibrial, mobile partner em−. These findings are viewed in terms of the polaron theory and other models for the solvated electron. The transient 280-nm absorption is assigned to a hydrogen-bonded hydroxyl radical OHt·. ESR data showing chemical and kinetic characteristics similar to the optical results confirm this assignment. Its molar extinction coefficient at −196°C is estimated as ε280 = 560 ± 50 M−1·cm−1 [using GOHt· (stable) = 0.8]. The over-all OHt· decay is complex. After prolonged irradiation, pseudo-first-order kinetics representing reaction with H2 and/or H2O2 is primarily observed. For low doses and at temperatures below −100°C, separate fast and slow decaying portions can be distinguished, the former attributable to H· reacting with OHt·, the latter to reaction involving only OHt·. Based on an empirical 32-order kinetic treatment [k(−59°C) ≤ 1 × 104 M−1 / 2·sec−1], ΔEact for the slow decay is determined to be 5.7 ± 0.7 kcal/mole. Qualitatively, this decay and the reaction with products are reconcilable with a mechanism involving OHt· in equilibrium with a mobile species OHm·. Second-order kinetic behavior observed at −14°C (k appears to be ∼108 M−1·sec−1) may also be consistent with this scheme. The full transient yield at −131°C is estimated to be 1.2. These findings imply that OH· is structurally different in both phases, but chemically similar. The relatively stable absorption at 230 nm is ascribed to HO2·. Spectral, chemical, and possibly, ESR evidence support this identification. Its yield is low, and it decays only very slowly at −14°C.

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Der Vierring im Benzocyclobuten (1) wird bei folgenden Umsetzungen unsymmetrisch (zwischen C-1 und C-7 bzw. C-2 und C-8) geoffnet: 1) bei der Nitrierung [Bildung von 2-und 4-Nitro-P-phenathylnitrat (3) und (4)] ; 2) bei der Acetylierung nach Friedel-Crafts (-+6); 3) bei der Kernjodierung mit Jz/HJO3 (1.9); 4) bei der Einwirkung von Chlorsulfonsaure auf 4-Jod-benzocyclobuten (410). Beim Studium der elektrophilen Substitution am Benzocyclobuten3~4) hatten wir gehofft, neue, abwandlungsfahige Benzocyclobuten-Derivate zu erhalten und Aussagen iiber den EinfluB des gespannten Vierringes auf die Reaktivitat des Benzolkerns machen zu konnen. Wir haben gezeigt3.4), daB sich im Gegensatz zu den hoheren Homologen des Benzocyclobutens (z. B. Indan oder Tetralin) der Vierring bei der Substitution offnet.Lloyd und Ongleys) haben unsere Ergebnisse bestatigt, ausgeweitet, in wenigen Fallen berichtigt und die mechanistischen Vorstellungen iiber die Ringoffnung verfeinert.der Offnung des Vierrings mit.In der vorliegenden Untersuchung teilen wir weitere Beobachtungen zum Problem

Esr spectroscopy has been used to examine basic aqueous solutions of nitroalkanes during radiolysis with highenergy electrons. Irradiation was carried out directly in the esr cavity; the sample container was a flat cell of high-purity silica. Although an intense esr line arose from the cell, this line was narrow and blanked out only a relatively small portion of the spectrum. The radicals detected in basic solutions (pH 10-12) of 5 X 10-3 M nitromethane were CH3Ñ02-and H0CH2Ñ02-. Use of the additives Ñ20 and methanol led to the conclusions that the CH3Ñ02~is formed by a reaction of the hydrated electron, that OH adds to the basic form of nitromethane (CH2=N02-) to give H0CH2Ñ02-, and that the alcohol radical formed by the OH attack on methanol also adds to this basic form but in competition with an electron exchange leading to CH3Ñ02-. The radical with the shortest lifetime, H0CH2Ñ02-, was found to have a half-life of about 1 msec. Several other nitroalkanes were studied with similar results.

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The g factors and proton hyperfine constants of 15 multiply carboxylated cyclohexadienyl radicals and all 19 of the carboxylated hydroxycyclohexadienyl radicals have been determined by the in situ radiolysis method. The g factors were measured with sufficient accuracy (±0.00002) to establish that they increase monotonically with total spin density on the positions substituted. The proton hyperfine data are interpreted to indicate that there is a 13% loss in spin density on the ring in the pentacarboxylate radical. Pronounced effects of asymmetric substitution are noted even when this substitution is at a position of low spin density. For the more highly charged hydroxycyclohexadienyl radicals the ESR spectra are sufficiently intense that the 13C containing radicals can be observed at the natural abundance level. Complete sets of 13C hyperfine data are reported for the 1,3,5-tricarboxylate, the three tetracarboxylate and the pentacarboxylate radicals. Definitive assignment of 13C hyperfine constants to the carboxyl groups attached to the conjugated system is possible. Values of 4.8, 1.3, and 6.8 G are attributed to positions 1, 2, and 3, respectively, in the pentacarboxylate radical. These hyperfine constants parallel almost exactly the proton values in the unsubstituted radical so that one can conclude that they can be used as a good indicator of the spin density on the adjacent ring carbon via a relation of the form aC(CO2−) = QC(CO2−) ρα. Correlation of the 13C and proton hyperfine data give a value of 15.8 G for QC(CO2−). Ring 13C hyperfine constants of ∼ 18, 12(2), 11(2), and 8.5 G are observed for each radical with the largest and smallest values being assigned, respectively, to the carbon atoms at positions 3 and 6. Comparisons among the different sets of values indicate variations from predictions based on the Karplus–Fraenkel treatment of the order of 10% so that specific assignment of the remaining four values is difficult. The hyperfine constants of the methylene protons in the substituted cyclohexadienyl radicals reflect very closely the loss in spin density to the carboxyl groups. Substitution in the hydroxycyclohexadienyl radicals, however, produces a far more pronounced and complicated effect that indicates a strong interaction between the OH group and the carboxyl groups substituted on the adjacent positions.

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ConclusionsMethylation analyses of polysaccharidea from wood [35,361, fungi [30,31,37-401, lichens [411, and bacteria 13*.34,421 have recently been performed in the authors' laboratory using the Hakomori procedure for methylation and GLC-mass spectrometry for the qualitative and quantitative analysis of the methylated sugars. This technique has the following advantages:1. It is more accurate and sensitive than previous procedures. It is thus possible to identify and determine the relative proportions of minor components, which may be structurally significant. The electrons solvated in metal-ammonia solutions are relatively stable; by contrast, hydrated electrons are very unstable and have been discovered only recently during radiolysis of water. They can be regarded as the simplest radicals, Radiation chemical production of solvated electrons has proved to be a particularly elegant method for the qualitative and quantitative investigation of the reactions between these electrons and numerous compounds, whose rates are partly controlled by diffusion. It has been possible in some cases to identgy optically and ESR-spectroscopically the resulting short-lived products (radical-anions). The similarity between the physical and chemical properties of electrons solvated in solutions and those of electrons stabilized in the solid phasesuggests that the two species are identical. . tionsC31, known for the past hundred years o r so. Several indirect proofs for the existence of hydrated electrons were published in the following yearsC4-71. The first direct proof was obtained in 1962 when a n intense blue color was observed after the irradiation of glasses formed by NaOH solutions[8,91, and whenshortly [4] E. Hayon and J .