scholarly journals Reactivity/rate constant ratio for scavengers of charged particles in nonpolar liquids

1979 ◽  
Vol 83 (9) ◽  
pp. 1130-1133 ◽  
Author(s):  
James A. Crumb ◽  
James K. Baird
Keyword(s):  
Rate Constant ◽  
Charged Particles ◽  
Constant Ratio ◽  
Rate Constant Ratio ◽  
Nonpolar Liquids

1999 R.U. Lemieux Award Lecture Adventures with azo-, azoxy-, and hydrazoarenes: from the Wallach to the benzidine rearrangement. Molecular electronics

2000 ◽  
Vol 78 (10) ◽  
pp. 1251-1271 ◽  
Author(s):  
Erwin Buncel
Keyword(s):  
Molecular Electronics ◽  
Rate Constant ◽  
Reaction Pathway ◽  
Solvent Polarity ◽  
Molecular Switch ◽  
Reaction Pathways ◽  
Optical Data ◽  
Constant Ratio ◽  
Rate Constant Ratio ◽  
Acid Catalyzed

The author's studies with aromatic azo-, azoxy-, and hydrazo-dye molecules, comprising kinetic and equilibrium investigations, as well as synthesis of novel molecules having photogenic properties, are described under the following highlights: A. Wallach rearrangement and cognate studies with azoxyarenes — (1) Elucidation of the mechanism of the Wallach rearrangement of azoxybenzene through the kinetic observation of a two-proton process which, together with a pKa study, was interpreted on the basis of formation of a deoxygenated, dicationic, symmetrical species as a key, short-lived reaction intermediate. (2) The proposal of a general acid-catalyzed pathway in concentrated sulfuric acid (catalysis by H2SO4 and H3SO+4. (3) Elucidation of the consecutive sulfonations of reaction products of azoxybenzene in the 100% H2SO4 region, and the diprotonation equilibria for p-hydroxyazobenzene, thus shedding light on past reaction pathway and product studies. (4) The observation of a novel reaction pathway for 2,4,6,2',4',6'-hexamethy lazoxybenzene. (5) The observation of a dichotomy of reaction pathways for α- and β-2-phenylazoxynaphthalenes: reaction via the dicationic intermediate and via quinoid intermediate species; comprising two isomeric compounds reacting by different pathways to give the same product. (6) Identification and structure proof of α- and β-isomers observed for the first time in the peracid oxidation of phenylazopyridine. (7) Observation of a rate constant ratio of 22 000 in the rearrangement of these α- and β-isomers, and the proposal of differential barriers for transition states leading to a tricationic intermediate. B. Benzidine rearrangement and cognate studies — (8) Observation of the acid-catalyzed hydroxylation of phenylazopyridine to p-hydroxyphenylazopyridine and the proposal of an SNAr mechanism with formation of an intermediate hydrazo species in the reaction. (9) First study of benzidine type rearrangement-disproportionation of phenylhydrazopyridine in acid media. (10) Proposal of a A [Formula: see text] B [Formula: see text] C [Formula: see text] D type reaction profile for the consecutive hydroxylation[Formula: see text]disproportionation processes of phenylazopyridine in aq H2SO4. (11) Proposal of 10-π and 14π-electron electrocyclic processes in the benzidine type rearrangement-disproportionation of phenylhydrazopyridine. (12) Identification and structural elucidation of a dimer formed from phenylazopyridine as a minor product and proposal of a reaction mechanism. C. Facile acid-catalyzed demethylation via SNAr/A-SE2 mechanisms and studies of tautomerism — (13) Observation of an abnormally facile acid-catalyzed cleavage (demethylation) of 4-methoxyphenylazopyridine via an SNAr mechanism. (14) Observation of two reaction pathways, SNAr and A-SE2, for the consecutive demethylations of 3,4-dimethoxyphenylazopyridine, with rate constant ratio of 7 000:1 favoring the SNAr process. (15) Quantitation of the tautomeric and protonation equilibria of 4-hydroxyphenylazopyridine, produced in (13). D. A new solvent polarity scale, molecular switches, and molecular electronics — (16) Establishment of a π*azo solvent polarity scale based on solvatochromism of a series of azomerocyanine molecules ("Buncel's dye"). (17) Some glimpses are presented of current forays into molecular electronics, as emanating from the above studies: (a) spiropyran (SP) <—> merocyanine (MC) thermo- and photochromic "molecular switch" systems; (b) synthesis and characterization of azo-functionalized star-burst dendrimers with photoswitchable properties and potential applications in optical data storage systems, holographic gratings, and drug delivery systems as host molecules.Key words: Wallach rearrangement, benzidine disproportionation, azoarenes, azoxyarenes, dendrimers, hydrazoarenes, dendrimers, solvatochromism, photochromism, thermochromism, spiropyran-merocyanine molecular switch.

Determination of the Rate Constant Ratio in Competitive Consecutive Second-order Reactions

1957 ◽  
Vol 79 (18) ◽  
pp. 4838-4839 ◽  
Author(s):  
W. G. McMillan
Keyword(s):  
Rate Constant ◽  
Second Order ◽  
Constant Ratio ◽  
Rate Constant Ratio

Temperature Independent Factor in the Rate Constant Ratio for Isotopic Reactions: Four Center Systems

1959 ◽  
Vol 81 (7) ◽  
pp. 1532-1535 ◽  
Author(s):  
Peter E. Yankwich ◽  
Richard M. Ikeda
Keyword(s):  
Rate Constant ◽  
Independent Factor ◽  
Constant Ratio ◽  
Rate Constant Ratio

Photolysis of, and the reactions of H-atoms with, isopropanethiol

1988 ◽  
Vol 66 (8) ◽  
pp. 2025-2033 ◽  
Author(s):  
W. W. Lam ◽  
T. Yokota ◽  
I. Safarik ◽  
O. P. Strausz
Keyword(s):  
Rate Constant ◽  
Thermal Reaction ◽  
Inert Gas ◽  
Constant Ratio ◽  
Temperature Range ◽  
Rate Constant Ratio ◽  
Photolytic Decomposition

Detailed investigation of the photolysis of i-C3H7SH has been carried out in the absence and presence of the inert gas, n-C4H10. A mechanism consisting of three primary photochemical steps: [Formula: see text], [Formula: see text]; [Formula: see text], [Formula: see text]; [Formula: see text],[Formula: see text]; six hot reaction steps and seven thermal reaction steps adequately explains all the experimental observations. As in the case of hot H* atoms both the H-atom abstraction, [Formula: see text], and the SH-displacement, [Formula: see text], reactions occur with thermalized H-atoms, with the rate constant ratio k7/k8 = 19.2 ± 4.3 at 25 °C. The Arrhenius expressions have been determined over the temperature range 25–145 °C, to be: k7 = (4.0 ± 0.7) × 1012 exp [(−1066 ± 43)/RT] and k8 = (2.8 ± 0.6) × 1012 exp[(−2597 ± 114)/RT] cm3 mol−1 s−1. It was found that the overall mechanism for the photolytic decomposition of i-C3H7SH is analogous to that established for C2H5SH in previous investigations.

Rate constant ratio for the reactions of hydroxyl with methane-d and methane

1993 ◽  
Vol 97 (33) ◽  
pp. 8564-8566 ◽  
Author(s):  
W. B. DeMore
Keyword(s):  
Rate Constant ◽  
Constant Ratio ◽  
Rate Constant Ratio

Determination of the rate constant ratio for the reactions of the ethylperoxy radical with NO and NO2

1990 ◽  
Vol 168 (1) ◽  
pp. 14-19 ◽  
Author(s):  
G. Elfers ◽  
F. Zabel ◽  
K.H. Becker
Keyword(s):  
Rate Constant ◽  
Constant Ratio ◽  
Rate Constant Ratio
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