scholarly journals On the mechanism of photocatalytic reactions with eosin Y

2014 ◽  
Vol 10 ◽  
pp. 981-989 ◽  
Author(s):  
Michal Majek ◽  
Fabiana Filace ◽  
Axel Jacobi von Wangelin
Keyword(s):  
Solvent Polarity ◽  
Quantum Yields ◽  
Eosin Y ◽  
Acid Base ◽  
Absorption Properties ◽  
Direct Photolysis ◽  
Radical Chain ◽  
Chain Reactions ◽  
Photocatalytic Reactions

A combined spectroscopic, synthetic, and apparative study has allowed a more detailed mechanistic rationalization of several recently reported eosin Y-catalyzed aromatic substitutions at arenediazonium salts. The operation of rapid acid–base equilibria, direct photolysis pathways, and radical chain reactions has been discussed on the basis of pH, solvent polarity, lamp type, absorption properties, and quantum yields. Determination of the latter proved to be an especially valuable tool for the distinction between radical chain and photocatalytic reactions.

scholarly journals Photochemical Chain Reactions in Amorphous Solids

1988 ◽  
Vol 9 (1-3) ◽  
pp. 155-170 ◽  
Author(s):  
Arthur J. Sedlacek ◽  
Charles A. Wight
Keyword(s):  
Solid State ◽  
Spray Deposition ◽  
Product Yield ◽  
Amorphous Solids ◽  
Quantum Yields ◽  
Intermediate Step ◽  
Radical Chain ◽  
Chain Reactions ◽  
Recombination Processes ◽  
The Subject

In this article, we review recent work in the authors' laboratory on the subject of free radical chain reactions of chlorine with small hydrocarbons in amorphous solids. The solids are formed as thin films by spray deposition of the gaseous reagents onto a cryogenic window. Reactions are initiated by excimer laser photolysis at 308 nm, which dissociates a small fraction of the chlorine molecules to atoms. Product yields and branching ratios are determined by infrared absorption spectroscopy. Reactions of chlorine with cyclopropane or cyclobutane proceed by true chain reactions, as evidenced by high product quantum yields (number of product molecules formed per laser photon absorbed by the sample). Measurements of the dependence of the product yield on the relative concentrations of chlorine and hydrocarbon provide clues to the reaction mechanism in the solid state. The cyclobutane reaction appears to involve H atom transfer from cyclobutane to cyclobutyl radical as an intermediate step in the overall reaction. Reaction of chlorine with propane, n-butane, or isobutane does not appear to involve chain propagation and is dominated by radical recombination processes which result in low quantum yields. All of these results are discussed in terms of reactions which occur in a solid state environment where molecular motion is severely restricted.

Photocatalytic Reactions Involving Radical Chain Reactions Using Microelectrodes†

1997 ◽  
Vol 101 (14) ◽  
pp. 2617-2620 ◽  
Author(s):  
Katsuyoshi Ikeda ◽  
Hideki Sakai ◽  
Ryo Baba ◽  
Kazuhito Hashimoto ◽  
Akira Fujishima
Keyword(s):  
Radical Chain ◽  
Chain Reactions ◽  
Photocatalytic Reactions

Spectrophotometric study of the acid-base and optical properties of the 5-bromo and 5-chloro derivatives of 2-(2-pyridylazo)-5-(diethylamino)phenol (BrPADAP, ClPADAP) and their complexation equilibria with zinc(II) ions

1982 ◽  
Vol 47 (10) ◽  
pp. 2676-2691 ◽  
Author(s):  
Miroslav Macka ◽  
Vlastimil Kubáň
Keyword(s):  
Equilibrium Constants ◽  
Spectrophotometric Study ◽  
Graphical Analysis ◽  
Alkaline Media ◽  
Acid Base ◽  
Ethanol Medium ◽  
Triton X ◽  
Mixed Water ◽  
Derivatives Of

The optical and acid-base characteristics of BrPADAP and ClPADAP were studied in mixed water-ethanol and water-DMF media and in 10% ethanol medium in the presence of cationic, anionic and nonionic tensides. The composition, optical characteristics, molar absorption coefficients and equilibrium constants of the ML and ML2 complexes with zinc(II) ions were found by graphical analysis and numerical interpretation of the absorbance curves by the modified SQUAD-G program. Optimal conditions were found for the spectrophotometric determination of Zn(II) in the presence of 0.1% Triton X-100 or 1% Brij 35 in alkaline media with pH = 6.5-10. BrPADAP and ClPADAP are the most sensitive reagents (ε = 1.3-1.6 . 105 mmol-1 cm2 at 557 and 560 nm, respectively) for the determination of zinc with high colour contrast of the reaction (Δλ = 104 nm) and selectivity similar to that for the other N-heterocyclic azodyes (PAN, PAR, etc.).

Bicarbonate and CO2 transport across the skin of the leopard frog, Rana pipiens: effect of PGF2alpha

1997 ◽  
Vol 272 (2) ◽  
pp. R640-R647 ◽  
Author(s):  
O. A. Candia ◽  
T. Yorio
Keyword(s):  
Methodological Approach ◽  
Transport Processes ◽  
Leopard Frog ◽  
Bicarbonate Transport ◽  
Amphibian Skin ◽  
Acid Base ◽  
Reliable Determination ◽  
Net Flux ◽  
Unidirectional Fluxes

The amphibian skin represents an important organ for osmoregulation and, like the mammalian kidney, maintains acid-base balance by secreting protons or base. However, the lack of a reliable and accurate method to measure the contribution of unidirectional fluxes of HCO3- ions to this mechanism has been an obstacle for the determination of the role of bicarbonate in epithelial acid-base homeostasis. Recently, one of us developed a method that allows for the reliable determination of transepithelial fluxes of bicarbonate, and this method was applied to determine unidirectional fluxes of (14)CO2 and H(14)CO3 under a variety of conditions. We report that the combined CO2 and HCO3- mucosal-to-serosal flux under 5% CO2 was 40% larger than the opposing flux, giving a net flux in the mucosal-to-serosal direction. This net flux was inhibited by acetazolamide. In CO2-free conditions, there was no detectable net flux; however, acetazolamide and PGF(2alpha) attenuated the mucosal-to-serosal flux and established an apparent secretion of HCO3-. A model is presented that depicts twelve vectors or components to the CO2 plus HCO3- fluxes in the frog skin. This model can accurately reproduce the experimental values measured from unidirectional fluxes of CO2 and HCO3- under a variety of conditions and can explain the effects of PGF(2alpha) on unidirectional 14C-labeled fluxes as a consequence of inhibition of H+ secretion to the apical bath, similar to what was previously suggested by our laboratory using a different methodological approach. The present method, utilizing radiolabeled HCO3-, may be useful as a means to evaluate the mechanism of action of hormones and drugs that may regulate acid-base homeostasis by altering proton and bicarbonate transport processes.

ChemInform Abstract: Concise Syntheses of L-Selenomethionine and of L-Selenocystine Using Radical Chain Reactions.

ChemInform ◽  
1987 ◽  
Vol 18 (4) ◽  
Author(s):  
D. H. R. BARTON ◽  
D. BRIDON ◽  
Y. HERVE ◽  
P. POTIER ◽  
J. THIERRY ◽  
...  
Keyword(s):  
Radical Chain ◽  
Chain Reactions
Sign in / Sign up

Export Citation Format

Share Document