Solvents, effect on the kinetics

Brown-Hammett correlation of 1-aryl-1-cyclobutylethyl p-nitrobenzoate gave a p+ value of -3.94 which is more positive than that of a model compound, l-aryl-l,2-dimethylpropyl p-nitrobenzoate (p+ = -4.65), which indicates substantial neighboring group participation of the cyclobutyl ring even in tertiary carbocationic systems.12 Solvent effects on the kinetics of the solvolysis... 

A major source of error in any indirect method is inaccuracy of the basis rate constants. Errors can result from determinations of rate constants by a sequence of several indirect studies or by an unanticipated solvent effect on the kinetics of a basis reaction. An error can also result in calibration of a radical clock if the requisite assumption that the clock radical will react with a rate constant equal to that of a simple model radical is not correct. Nevertheless, indirect methods in general, and radical clock studies in particular, have been the workhorse of radical kinetic determinations. 

Chemical reactions at supercritical conditions are good examples of solvation effects on rate constants. While the most compelling reason to carry out reactions at (near) supercritical conditions is the abihty to tune the solvation conditions of the medium (chemical potentials) and attenuate transport limitations by adjustment of the system pressure and/or temperature, there has been considerable speculation on explanations for the unusual behavior (occasionally referred to as anomalies) in reaction kinetics at near and supercritical conditions. True near-critical anomalies in reaction equilibrium, if any, will only appear within an extremely small neighborhood of the system s critical point, which is unattainable for all practical purposes. This is because the near-critical anomaly in the equilibrium extent of the reaction has the same near-critical behavior as the internal energy. However, it is not as clear that the kinetics of reactions should be free of anomalies in the near-critical region. Therefore, a more accurate description of solvent effect on the kinetic rate constant of reactions conducted in or near supercritical media is desirable (Chialvo et al., 1998). 

Dynamical Solvent Effects on the Kinetics of Redox Reactions... 

The dynamical solvent effects on the kinetics of electron-transfer processes have been reviewed in detail in Refs [24a] and [32] and concisely in Section 3.6 of Ref. [8]. 

J. Troe I would like to comment on the role of the solvent in the photoisomerization of frans-stilbene, as discussed by Prof. Marcus. From our extensive studies in series of nonpolar and polar solvents in compressed gases and in the liquid phase, a very detailed picture arises we now can distinguish specifically different types of solvation first, there is strong interaction with polar solvents second, we can distinguish two kinds of interaction with nonpolar solvents, one site specific of only mildly polarizable small alkanes that possibly can squeeze in between the two phenyl groups in stilbene and one non-site specific of more polarizable large alkanes that can only solvate around the outer periphery of stilbene. These different types of solvation result in characteristically different solvent effects on the kinetics. 

Kinetic studies have been reported of the reactions of a series of 2-substituted-5-nitrothiophenes (substituent = Br, OMe, OPh, OC6H4-4-NO2) with secondary amines in room-temperature ionic liquids. The kinetic behaviour is similar to that of the corresponding reactions in methanol so that most reactions do not show base catalysis. The observation that reactivity is higher in the ionic liquids than in methanol (or benzene) is attributed to relatively poor solvation of the reagents by the ionic liquids. As in conventional solvents, 2-bromo-3-nitrothiophene shows higher reactivity than 2-bromo-5-nitrothiophene.42 Solvent effects on the kinetics of the alkaline hydrolysis of 2-phenylthio-3,5-dinitropyridine in aqueous organic solvents have been analysed.43... 

Solvent effects on the kinetics and mechanism of unimolecular heterolysis of commercial organohalogen compounds have been investigated.9-11 The reaction rate is satisfactorily correlated by parameters for polarity, electrophilicity, and cohesion of the solvent, whereas the solvent nucleophilicity and polarizability exert no effect. 

LePree, J.M. Connors, K.A. Solvent effects on chemical processes. 11. Solvent effects on the kinetics of decarboxyla-tive dechlorination of A-chloro amino acids in binary aqueous-organic solvents. J. Pharm. Sci. 1996, 85 (6), 560-566. 

Grampp and Jaenicke [36] have carried out detailed studies of solvent effects on the kinetics of electron transfer for a variety of organic redox couples. The kinetic data were obtained by electron spin resonance (ESR) line-broadening experiments for very fast reactions with rates close to the diffusion-limited value. Some of the reactions were clearly diabatic, and others adiabatic on the basis of the solvent effect. 

Among different coumarin derivatives used, 7-Amino-4-trifluoromethylcoumarin (ATFMC) revealed the most promising characteristics as an efficient fluorescent emitter. AFTMC is used in the synthesis of a substrate for fluorimetric assay of proteolytic enzymes and for use as a laser dye. We have recently investigated the chemiluminescence reactions of some peroxyoxalate esters, hydrogen peroxide and AFTMC. In this paper we report the solvent effects on the kinetics of the chemiluminescence process of the peroxyoxalate chemiluminescence in the presence of AFTMC. 

Reactions of 2-Thiophenesulfonyl Chloride with Anilines. Arcoria and coworkers (126) have studied solvent effects on the kinetics of the reactions of 2-thiophenesulfonyl chloride with a series of ring-substituted aniline derivatives. Using the data in the eight of their solvents which are aliphatic and whose solvatochromic parameters are known (18,50,102,103,104,105,111,112), we have found correlations with tt and a to be excellent. 

Buchner R, Hefter G (2009) Interactions and dynamics in electrolyte solutions by dielectric spectroscopy. Phys Chem Chem Phys 11 8984—8999 Cabani S, Gianni P, MoUica V, Lepori L (1981) Group contributions to the thermodynamic properties of non-ionic organic solutes in dilute aqueous solutions. 1 Solut Chem 10 563-595 Caldin EF, Bennetto HP (1971) Solvent effects on the kinetics of the nickel(ll) and cobalt(ll) ions with 2,2 -bipyridyl and 2,2, 2"-terpyridyl. J Chem Soc A 1971 2191-2198 Chang T-M, Dang LX (2008) Computational studies of liquid water and diluted water in carbon tetrachloride. J Phys Chem A 112 1694—1700... 

The advantages associated with the sol-gel process make it a suitable method for the preparation of engineering products [1, 2]. In most cases silica gels are prepared by hydrolysis of a mixture of silicic acid esters such as tetramethoxysilane (TMOS), alcohol (methanol), and water under acid or basic conditions. Different solvents are used to avoid the development of cracks during the drying step [3, 4]. Several investigations have focused on the solvent effects on the kinetics of the hydrolysis reaction and on the influence on pore size distribution and surface area [5,6]. 

Solvent effects on the kinetics of ring closure and ring opening have been studied for reaction (6),... 

Shimizu and Hirai (1987) studied the solvent effect on the kinetics of resin catalyzed esterification of octanoic acid with 1-butanol catalyzed by macroreticular sulfonic acid resin (Amberlyst 15) in the presence of various organic solvents and water. They concluded that the extent of the selectivity of the resin catalyst depend on the alkyl... 

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