Radiolytic technique

The radiolytic technique has also been applied to the reaction of alkyl radicals R with Ni1 porphyrins anions.279 In analogy with the postulated reaction of NiIF43o to form CH3NiinF430, short lived R-Ni111 products have been detected. 

In the early 1980s, one of the authors of this chapter began to study argon matrix isolation of radical cations235 by applying the radiolytic techniques elaborated by Hamill and Shida. A central factor was the addition of an electron scavenger to the matrix which was expected to increase the yield of radical cations and the selectivity of the method. For practical reasons, X-rays replaced y-rays as a radiolytic source and argon was chosen as a matrix material because of its substantial cross section for interaction with keV photons (which presumably effect resonant core ionization of Ar). Due to the temporal separation of the process of matrix isolation of the neutral molecules and their ionization, it was possible to obtain difference spectra which show exclusively the bands of the radical cations. 

Since its first modem application in the late fifties, radiolysis has been extensively employed for generating transient ion-dipole complexes in the gas phase and to investigate their reactivity in the absence of the perturbing effects of solvation and ion pairing. The growing impact of the radiolytic technique in the gas-phase... 

Contrary to the case of anionic reactions, the formation of a strong proton-bound dimer for alcohols suggests that nucleophilic displacement may actually involve a frontside attack. Recent experiments carried out at atmospheric pressure by Speranza and Angelini (1980) using radiolytic techniques with isolation and glc analysis of neutral products reveal some interesting stereochemistry. For example, the reaction of protonated epoxy-rra/is-but-2-ene with H20 results in 98% inversion of configuration, while a similar reaction with cis-1 -chloro-4-methylcyclohexane results in approximately 80% of tro/is-4-methylcyclohexanol. With the high pressures utilized and with the possible participation of cluster ions a likelihood in this case, the data are consistent with a Walden inversion for these cases. 

Transition from non-metallic clusters consisting of only a few atoms to nanosized metallic particles consisting of thousands of atoms and the concomitant conversion from covalent bond to continuous band structures have been the subject of intense scrutiny in both the gas phase and the solid state during the last decade [503-505]. It is only recently that modern-day colloid chemists have launched investigations into the kinetics and mechanisms of duster formation and cluster aggregation in aqueous solutions. Steady-state and pulse-radiolytic techniques have been used primarily to examine the evolution of nanosized metallic particles in metal-ion solutions [506-508]. 

Spectroscopic evidence for the transient formation of the trans-stilbene radical cation could be obtained when colloidal TiOj suspended in an acetonitrile solution containing trans-stilbene (a species which should also be exothermically oxidized by a TiO valence band hole) was excited with a laser pulse The observed transient was identical in spectroscopic features and in lifetime with an authentic sample of the stilbene cation radical generated in the same medium via pulse radiolytic techniques. That the surface influences the subsequent chemistry of this species can be seen in the distribution of products observed under steady state illumination, Eq. (4) 2 . ... 

It seems then that one-electron oxidized guanine in the solid-state deprotonates at the amino group. There is however no good evidence that this occurs in aqueous solution. A study of guanine derivatives in aqueous solution using pulse radiolytic techniques concluded that one-electron oxidized guanine deprotonated at Nl [55], Early ab initio calculations on guanine concluded that G(N1-H) is the more stable than G(N2-H) [56], However more recent DFT and molecular dynamics calculations have come to the opposite conclusion [57], Calculations have also been performed on G C base pairs. Hutter and Clark have concluded that proton transfer... 

Pulse radiolytic techniques facilitated estimates of the rate constants for reactions between benzyl and diphenylmethyl carbenium ions and a series of alkenes and... 

Thallium(ii) has been generated in the pulse radiolysis of TF and in IM-HC104. The rates of the reaction of TF + OH and TF + H have been measured, and from data on the Fe TF reaction, the free energy of formation of TF has been shown to be 42 kcal mol. TF plays no part in the TF-TF exchange. Three chloride complexes of TF have also been characterized by radiolytic techniques. Absorption spectra for TICF, TICI2, and TlCls" have been reported. In the complex formation reaction... 

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