34515-61-2Relevant academic research and scientific papers
An NMR, ESR, ENDOR and TRIPLE Resonance Investigation of a Cation Radical Formed From 1,2,4,5-Tetramethoxybenzene
Fairhurst, S.A.,Smith, I.M.,Sutcliffe, L.H.,Taylor, S.M.
, p. 231 - 235 (1982)
Several methods have been established for preparing cation radicals from 1,2,4,5-tetramethoxybenzene that allow highly resolved ESR spectra to be recorded.Precise values of hyperfine coupling constants for the aromatic and methoxy protons have been obtain
Laser photolysis investigation of induced quenching in photoreduction of benzophenone by alkylbenzenes and anisoles
Oekada, Kafsuji,Yamaji, Minora,Smzuka, Haruo
, p. 861 - 866 (2007/10/03)
The quenching processes of triplet benzophenone (JBP) by alkylbenzenes (AB) and anisole derivatives (AD) in benzene (Bz) and a mixture of acetonitriie (ACT-,) and water (4 :1 v/V; have been studied on the basis of rate constants and efficiencies determined by nanosecond laser flash photolysis a; 355 n m at 295 K. It was found that (1) the deactivation of 3BPby ADs in ACN H2O (4 :1 v/v) was governed by electron transfer (ET) to produce the benzophenone anion (BP'~) and corresponding cation (AD' + ) radicals wiih efficiencies, atj 1 whereas no chemical species were formed in Bz; and 2) photoreduction of 3BPby ABs resulted in benzophenone ketyl radical (BPK) formation by benzylic hydrogen abstraction (HA) with efficiencies XHA 1 in 3z and ACN-H2O (4 :1 v/v). The residual efficiency (a: 1 -ET or ! -aH/1) was attributed to a birnolecular process with no photochemical product, which was named 'induced-quenching (IQf. The quenching rate constants (Jcq) of ;'BPby ADs and ABs were less than the diffusion limits of both Bz and AC1~H2O (4 :1 v/v). The net bimolecular rate constants for the ET, HA and IQ processes were estimated from the k values and efficiencies. The rate constants (%T and k,Q) of ET and IQ with AD versus the oxidation potential (￡) of AD followed Rchm-Weller behaviour while logarithmic rate constants {/CHA and ki(j) of HA and IQ by ABs increased linearly with a decrease in the Em of AB. It was suggested, for the deactivation mechanism of 3BPby ABs and ADs (RH), that ;1) the IQ process was intersystem crossing (ISC) enhanced by the partial charge transfer (CT) character of the triplet excipiexes, 3(BP"~- A-RHa + )a,e; (2) radical ion formation by ET might be accomplished in a polar solvent by further CT interaction in the excipiex; (3) the process of BPK formation was inferred to be H-atom transfer in the exciplex, where the more protic H-atom was readily mobile, rather than ET followed by proton transfer and (4) the loss of efficiencies of photochemicalproduct formation was derived not from back ET but from the IQ process, inherent to photoreactions, via triplet excipiexes. The deactivation processes of 3BPby RH are illustrated in Scheme 1. I ET BP'- + RH'(3BP' + RHJcoj -3(BPO- RHg,.-BPK 4 R' BP + RH Scheme 1.
Pulse Radiolytic Investigations of Aqueous Solutions of Methoxybenzene Cation Radicals: The Effect of Colloidal RuO2
Brandys, Marek,Sasson, Richard E.,Rabani, Joseph
, p. 953 - 962 (2007/10/02)
The formation and decay of the radical cations of 1,4-dimethoxybenzene (DMB) and 1,2,4,5-tetramethoxybenzene (TMB) were investigated by the pulse radiolysis technique in the absence and the presence of colloidal RuO2 particles.DMB2. was obtained only by T12+ oxidation of DMB while TMB+.+ was produced by oxidation of TMB using both T12+ and Br2-.In the absence of RuO2 both DMB.+ and TMB.+ decay predominantly via a second-order process, although there is a contribution of a pseudo-first-order reaction.The rate constants for these reactions are reported.RuO2 colloidal particles catalyze the decay of both TMB.+ and DMB.+.The reactions of TMB.+ with RuO2 were found to depend on pH, pulse intensity, and colloidal concentration.At pH 3-4, adsorbtion of TMB.+ to the colloid is observed, followed by the decay of the remaining TMB.+ in the bulk.At higher pHs, loading of the RuO2 colloid by positive holes takes place until equilibrium is archieved between loaded holes and TMB.+ and again the remaining TMB.+ decays at a later stage.The fraction of TMB.+ that loads the colloidal particles increases with both pH and .It is also suggested that DMB.+ loads the RuO2 at the pH where experiments were performed. (TMB)2 and (DMB)2 dimers (or higher oligomers) are suggested to be the final products both in absence and presence of RuO2.No O2 is formed with the RuO2 colloid despite a favorable redox potential for water oxidation.
