Reactions of pyrazine radical anions in solution. I. Study of the kinetics of the dimerization of pyrazine radical anions

1971 ◽  
Vol 24 (11) ◽  
pp. 2287 ◽  
Author(s):  
RS Hay ◽  
PJ Pomery
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Rate Constants ◽  
Electronic Absorption Spectra ◽  
Radical Anions ◽  
Light Reaction ◽  
First Order ◽  
Kinetics Of Reaction ◽  
Kinetics Of ◽  
Metallic Potassium

The radical anions of pyrazine (pz-.) have been prepared at 294'K by reducing pyrazine (pz) with metallic potassium in 1,2-dimethoxyethane (dme). The resulting reactions of the radical anions are postulat'ed as being described by the equations: The e.s.r, and electronic absorption spectra of all pertinent species were recorded and examined. The kinetics of reaction (1) have been investigated in the dark as well as in light and values of the rate constants have been determined. I n light, reaction (1) did not conform strictly to second-order kinetics and this may be explained by an interaction of pyrazine with dme. The dimer dianion species (-pz-pz-, 2K7) was found to be stable in the dark but decayed slowly in light. This decay was found to exhibit first-order kmetics.

Photocolouration of 2,4,4,6-Tetraaryl-4H-pyrans and Their Heteroanalogues: Importance of Hypervalent Photoisomers

1995 ◽  
Vol 60 (10) ◽  
pp. 1621-1633 ◽  
Author(s):  
Stanislav Böhm ◽  
Mojmír Adamec ◽  
Stanislav Nešpůrek ◽  
Josef Kuthan
Keyword(s):  
Reaction Kinetics ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Theoretical Data ◽  
Order Reaction ◽  
Bleaching Process ◽  
First Order ◽  
Photodegradation Products ◽  
Hypervalent Molecules

Molecular geometries of 2,4,4,6-tetraphenyl-4H-pyran (Ia), 4,4-(biphenyl-2,2e-diyl)-2,6-diphenyl-4H-pyran (Ib) and their heterocyclic isomers II-V were optimized by the PM3 method and used for the calculation of electronic absorption spectra by the CNDO/S-CI procedure. Comparison of the theoretical data with experimental UV-VIS absorption spectra made possible to select hypervalent molecules IIIa, IIIb, IVa and IVb being responsible for the photocolouration of 4H-pyrans Ia, Ib, while compounds Va, Vb, VI and VII come into account as possible photodegradation products. The bleaching process of the UV illuminated compound Ia is analyzed in terms of dispersive first-order reaction kinetics.

Electronic absorption spectra of the radical anions and cations of fullerenes: C60 and C70

1991 ◽  
Vol 180 (5) ◽  
pp. 446-450 ◽  
Author(s):  
Tatsuhisa Kato ◽  
Takeshi Kodama ◽  
Tadamasa Shida ◽  
Takashi Nakagawa ◽  
Yoko Matsui ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Radical Anions ◽  
Fullerenes C60 And C70 ◽  
Anions And Cations

Submerged upflow biotower operation and computer simulation

1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson
Keyword(s):  
Computer Simulation ◽  
Benzoic Acid ◽  
Computer Model ◽  
Rate Constants ◽  
Batch Mode ◽  
Operational Conditions ◽  
First Order ◽  
Low Concentrations ◽  
Biological Transformation ◽  
Kinetics Of

A two step operation is proposed for the biodegradation of low concentrations (< 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.

Stereochemistry of [carbonato-bis((S)-prolinato)]cobaltate(III) anion

1984 ◽  
Vol 49 (3) ◽  
pp. 680-683 ◽  
Author(s):  
Bohumil Hájek ◽  
Dagmar Sýkorová ◽  
Jiří Chyba
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Cd Spectra

The λ-C1-cis(N), δ-C1-cis(N), λ-C2-cis(N) and δ-C2-cis(N) isomers of the complex K[Co((S)-Pro)2CO3] were chromatographically separated and characterized by their electronic absorption spectra and CD spectra.

Niobocene Dichloride and Niobocene Diiodide: Electronic Absorption Spectra and Electron Spin Resonance

1998 ◽  
Vol 63 (5) ◽  
pp. 628-635 ◽  
Author(s):  
Jana Holubová ◽  
Zdeněk Černošek ◽  
Ivan Pavlík
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Point Group ◽  
Esr Spectra ◽  
Ligand Field ◽  
Orbital Interaction ◽  
Symmetry Point Group ◽  
Spin Orbital ◽  
Halide Ligands

The effect of the halide ligand on the bonding of niobium in niobocene dichloride and niobocene diiodide was investigated. The electronic absorption spectra of the two compounds in the range of d-d transitions were resolved into four bands corresponding to transitions of the d1 electron between five frontier orbitals in a molecule of symmetry point group C2v. The energies of the frontier molecular orbitals were determined relatively to the energy of the orbitals in the spherically symmetric ligand field formed by the appropriate halide ligands. The effect of the halide ligands on the spin-orbital interaction of the HOMO orbital is discussed qualitatively on the basis the ESR spectra.

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