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A study is presented to demonstrate that two tautomers of one-electron-oxidized guanine are produced by the protonation of an 8-haloguanine electron adduct. The reaction of hydrated electrons [e.sub.aq.sup.-] with 8-haloguanosine or 8-halo-2'-deoxyguanosine produces the first observable transient species that decay unimolecularly to give the one-electron oxidized guanosine or 2'deoxyguanosine.

Ostwald ripening in which the size of nanoparticles increases at the expense of the smaller ones dues to atomization and diffusion between particles could be caused by the process of refluxing the nanoparticles during the Suzuki reaction. The nanoparticles increase in size during the beginning of the reaction and level off toward the end of the first cycle.

The potential cycloaddition reactions between cyclopentadiene and cycloheptariene are explored theoretically. B3LYP/6-31G* was used to locate the transition states, intermediates, and products for concerted pathways and stepwise pathways passing through diradical intermediates.

The experimental and computational study presented demonstrates that hydrogen bond donors can significantly change the spectroscopic and thermochemical properties of phenoxyl radicals. A strong H-bond donor such as hexafluoropropanol produces large variations of the hyperfine splitting constants indicative of a large redistribution of electron spin density which can be accounted for by the increased importance of the mesomeric structures (E-H) with electric charge separation.

The chemistry of model C5' DNA radicals are studied to determine the structural and reactivity effects in the formation of 5',8-cyclonucleoside. For this purpose, pulse radiolysis, product studies and density functional theory calculations are used.

Research is presented concerning the properties of the 2'-deoxyuridin-1'-yl radical and the thyminylmethyl radical. The use of bulk photolysis and laser flash photolysis to produce the two radicals is discussed.

Research was conducted to examine the impact of diffuse functions on geometry and isotropic hyperfine splitting (hfs) constants of radical anions at the UQCISD/6-311G(d,p) level. Unreliable geometry and hfs constants for radical anions that are kinetically unstable in the gas phase are provided by the utilization of standard diffuse functions. A proposed method for computing reliable hfs constants in radical cations is presented.

Research was conducted to examine the conformation and the electronic structure of various alpha-heterosubstituted acetone oximes using a multidisciplinary approach based on ultraviolet photoelectron, electron transmission and dissociative electron attachment spectroscopies and fully optimized ab initio 6-31G** and MP2/6-31G calculations. Results indicate that the characteristics of the acetone oximes are mainly governed by the mixing between the orbitals localized at the X and C = N fragments and by electrostatic interactions between the electronegative atoms and hydrogen.

The 2- and 3-furyl and the 2- and 3-thienyl forms of arylhydroxymethane undergo conformational analysis by electron paramagnetic resonance spectroscopy of their photoinduced radicals. The study shows that the radicals experience restricted rotation about the Ar-C(sub alpha) bond, leading to rotamers with unequal stabilities. In the 2-substituted forms, the E-isomer of the furyl derivatives and the Z-isomer of the thienyl derivatives prove to be the more stable rotamers. An intramolecular hydrogen bond in the furyls accounts for the higher rotation barrier in the Z conformer.

Ab initio molecular orbital calculations and electron configuration analysis revealed that beta-substituted ethyl radicals bearing second- and third-row elements have structural parameters resembling those of classical radicals with nonplanar radical centers. The presence of second-row elements on the ethyl substituents formed a nearly free C(alpha)-C(beta) bond rotation which facilitated the formation of a gauche structure. In addition, third-row elements produced a sizable rotation barrier which limited bond motion resulting in an eclipsed conformation.

Research has been conducted on the [3,3]-sigmatropic rearrangement. The radical-anion mechanism for this rearrangement has been developed and discussed.

The one-electron oxidation and one-electron reduction reactions of 8-oxo-7,8-dihydroguanine (8-oxo-G) and 8-aminoguanine (8-N[H.sub.2]-G) derivatives are examined. The one-electron reduction of 8-azidoguanine (8-[N.sub.3]-G) has produced the same transient of one-electron oxidation of 8-N[H.sub.2]-G, which has represented another example of generation of one-electron oxidized guanine derivatives under reducing conditions.

A detailed chemical radiation study of 8-bromo-2-aminoadenosine (8-Br-2AA) with reducing species and 2-aminoadenosine (2AA) with oxidizing species, in aqueous solution at various pH values is presented.

The effect of water on the O-H bond dissociation enthalpy (BDE) of para-substituted phenols using DFT calculations is examined. The experimental BDE values are fairly well reproduced by simple calculations carried out on the phenol/phenoxyl-water complexes, taking into account only hydrogen-bonding (HB) interactions of water molecules with molecular sites (HB model).

An attempt is made to intercept and identify free radicals from 5H-Pyridophenoxazin-5-one (PPH) generated under bioreductive conditions. It is proposed that the monoelectronic reduction of PPH in the proximity of DNA may eventually lead to radicals that could cause considerable damage to DNA and that PPH is able to suppress a large number of lymphoblastoid and solid tumor-derived cells at submicromolar concentrations.

The resonance energies for electron attachment to the chloromethanes are evaluated by means of bound and continuum multiple scattering Xα calculations. The results closely reproduce the experimental electron transmission spectroscopy data and confirm their previous assignment. Electron transmission and dissociative attachment spectra of monochloroalkanes are also reported, in order to obtain information on the effects of branching at the substituted carbon atom and of alkyl chain length on the resonance and chlorine anion production energies. [ABSTRACT FROM AUTHOR]

Examines the electron transmission and dissociative electron attachment spectra of 14 methyl chlorides and tetrachlorides. Comparison of the experimental resonance energies with the total electron scattering cross sections; Discussion of the sizes of tin and silicon derivatives; Implications of size measurement of fragment anions on compounds.

The electron transmission spectra of the fluoro-, bromo-, and iodomethanes (except CH2F2 ) and of some monohaloalkanes are reported. The resonance energies for electron attachment to the halomethanes have also been evaluated by means of bound and continuum multiple scattering Xα calculations, which closely reproduce the low-energy experimental data. A large electron affinity increase is observed on going from the fluorine to the heavier halogen derivatives, while within each series of halides the electron affinity increases with increasing number of halogen atoms. The ground anion state is found to be stable in CHBr3, CBr4, and in all the iodomethanes except CH3I. The fragment anion production, as a function of the electron impact energy, has been measured for some of the compounds under investigation, in order to obtain experimental information on anion states very close to zero energy or slightly stable, which are not accessible in electron transmission. [ABSTRACT FROM AUTHOR]

Relative kinetic data were determined for the 5-endo-trig cyclization of radical compared to hydrogen abstraction. The 5-endo-trig cyclization to form the five membered rings was strongly favored over exo cyclization to form the four-membered ring on thermodynamic grounds as well as kinetically.