- Equilibrium of acyl transfer between pyridine N-oxides and their acylonium salts
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Transfer of acyl groups from N-acyloxypyridinium salts to pyridine N-oxides in acetonitrile was studied. The equilibrium constants of acyl exchange were determined. These quantities vary in the range covering eight orders of magnitude, depending on the st
- Rubachenko,Schroeder,Chotii,Kovalenko,Red'ko,Lenska
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p. 1241 - 1246
(2008/12/22)
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- Rate and equilibrium constants of benzoyl group transfer between pyridine N-oxides
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Kinetic characteristics of 19 transfer reactions of benzoyl group from N-benzoyloxypyridinium salts to pyridine N-oxides and 4-dimethylaminopyridine were studied in acetonitrile by the stopped-flow method. The rate of an identical reaction for 4-methoxypyridine was measured by dynamic NMR spectroscopy. For 5 other identical reactions the rates were estimated from Bronsted correlations. Equilibrium constants were estimated with the use of UV spectrophotometry (6), IR spectroscopy (2), from kinetic data (K ij = k ij /k ji ) (2), and in one case as logK i-j = logK i-x - logK j-x . The second order rate constants (k ij ) varied in the range 102-105 l mol -1 s-1, the equilibrium constants (K ij ) in the range 102-10-2; the activation parameters (ΔH ≠) were within 15-50 kJ mol-1, (-ΔS ≠) -20-110 J mol-1 K-1. The reactions under study occur in a single stage following the concerted SN2 mechanism through an early associative transition state. The benzoyl groups exchange rate and equilibrium are well described by simplified Marcus equation (omitting the quadratic term). 2005 Pleiades Publishing, Inc.
- Rybachenko,Schroeder,Chotii,Lenska,Red'Ko,Kovalenko
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p. 774 - 778
(2007/10/03)
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- Rate and Equilibrium Constants of Dimethylcarbamoyl Transfer between Pyridine N-Oxides
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Dimethylcarbamoyl transfer from N-acyloxypyridinium salts to pyridine N-oxides in acetonitrile occurs in one stage by the forced concerted SN2 mechanism. The rate and equilibrium of the reaction are fairly described by the Bronsted equation. The Marcus equation provides a much higher quality of reactivity predictions.
- Schroeder,Rybachenko,Chotii,Kovalenko,Grebenyuk,Lenska,Eitner
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p. 455 - 462
(2007/10/03)
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- The Rate and Equilibrium Constants for N-, O-Acyl Transfer
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Reactions with dimethylcarbamoyl group transfer from N-acylpyridinium salts to pyridine N-oxides and from N-acyloxypyridinium salts to pyridines in acetonirile solutions were studied. Their rate and equilibrium constants and activation parameters were determined. The reactions were shown to be one-step and to follow the SN2 mechanism. Equations relating the rate and equilibrium parameters of the N-O and O-N acyl transfer reactions to the basicity of the nucleophile and outgoing group were obtained.
- Rybachenko,Chotii,Kovalenko,Shreder
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p. 1695 - 1698
(2007/10/03)
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- Equilibrium of acetyl transfer between pyridine N-Oxides and their acetylonium salts
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The equilibrium constants of acetyl transfer between O-acetylonium salts of a series of pyridine N-oxides and 4-(4-dimethylaminostyryl)pyridine N-oxide in acetonitrile and methylene chloride were determined. The equilibrium constants correlate with the ac
- Rybachenko,Chotii,Kovalenko,Schroeder
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p. 786 - 788
(2007/10/03)
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- Acetyl exchange between pyridine N-oxides in acetonitrile solutions: An attempt to apply the Marcus equation to acetyl transfer
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Forty-three (including eight identical) reactions of acetyl transfer from N-acetyloxypyridinium salts to pyridine N-oxides in acetonitrile solutions were studied. The rate constants k2 vary in the range 107-10-1 1 mol-1 s-1; the equilibrium constants K, in the range 107-10-7; the activation enthalpy ΔH≠, in the range 17-30 kJ mol-1; the activation entropy -ΔS≠, in the range 60-85 J mol-1 K-1; and the heat of reaction -ΔH0, within ±50 kJ mol-1. All reactions occur in a single stage by the concerted SN2 mechanism with a low degree of bond cleavage in the transition state. The rate and equilibrium of the acetyl exchange are satisfactorily described by the Bronsted equation. The quality of predicting the reactivity is substantially improved by introducing into the correlation equation a second parameter, the rates of identical reactions.
- Rybachenko,Schroeder,Chotii,Titov,Kovalenko,Leska,Grebenyuk
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p. 1608 - 1615
(2007/10/03)
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- Intramolecular charge transfer processes in a series of styryl derivatives of pyridine and quinoline N-oxides
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Intramolecular charge transfer processes in a series of the trans-isomers of styryl derivatives of pyridines and quinolines, their hydrochlorides and molecular complexes with BF3 have been studied by electronic and IR spectroscopy. Electron don
- Andreev,Batotsyrenova,Ryzhakov,Rodina
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p. 941 - 949
(2007/10/03)
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