Liquid-phase reactions, rate

In order to properly account for the effect of pressure on liquid phase reaction rates one should eliminate the pressure dependence of the concentration terms by expressing the latter in terms of mole ratios. It is then customary to express the general dependence of the rate... 

ET Denisov. Liquid-Phase Reaction Rate Constants. New York IFI/Plenum, 1974. 

AV Oberemko, AA Perchenko, ET Denisov, AL Aleksandrov. Neftekhimiya 11 229-235, 1971. ET Denisov. Liquid-Phase Reaction Rate Constants. New York IFI/Plenum, 1974. 

Enzymes are proteins that catalyze reactions. Thousands of enzymes have been classified and there is no clear limit as to the number that exists in nature or that can be created artificially. Enzymes have one or more catalytic sites that are similar in principle to the active sites on a solid catalyst that are discussed in Chapter 10, but there are major differences in the nature of the sites and in the nature of the reactions they catalyze. Mass transport to the active site of an enzyme is usually done in the liquid phase. Reaction rates in moles per volume per time are several orders of magnitude lower than rates typical of solid-catalyzed gas reactions. Optimal temperatures for enzymatic reactions span the range typical of living organisms, from about 4°C for cold-water fish, to about 40°C for birds and mammals, to over 100°C for thermophilic bacteria. Enzymatic reactions require very specific molecular orientations before they can proceed. As compensation for the lower reaction rates, enzymatic reactions are highly selective. They often require specific stereoisomers as the reactant (termed the substrate in the jargon of biochemistry) and can generate stereospecific products. Enzymes are subject to inhibition and deactivation like other forms of catalysis. 

A solid-liquid mass transfer coefficient of 0.015 cm/s was found by comparing the predictions of [S(IV)] to experimental results obtained under conditions in which the liquid phase kinetics were fast. The model was then applied to slurry oxidation under more general conditions by using liquid phase reaction rate kinetics obtained in clear solutions. The results of the model agree with experimental findings for the total rate of oxidation. 

E.T. Denisov, Liquid Phase Reaction Rate Constants, English translation by R.K. Johnson, IFI/Plenum, New York, 1974, pp. 249—279. 

The liquid side volumetric physical mass transfer coefficient was determined from the desorption rate of oxygen. Detailed description of the experimental set up, procedure and analysis of data is given by Tosyali [30]. Methods of estimating the interfacial CO2 concentration, diffusivities of CO2 and OH in the liquid phase, reaction rate constant, which are all required in data analysis, can be found elsewhere [31, 32]. ... 

Thus, for the reaction to have a significant effect on mass transfer rate, tiie rate constant must be in excess of 0.025 s L This is in fact the range of many liquid-phase reaction rates. The requirements become less stringent with an increase in film thickness. For 5 = 1 mm, for example, rafe consfants can be lowered by a factor of 100 to achieve the same result. 

The absolute and relative rate constants of the displacement reactions of carbon-centered radicals with molecules, which are listed in this chapter have been collected from the literature up to 1982. Considering the large number of relevant publications it has been very helpful to find several data compilations already in print. In particular, we would l e to acknowledge the collection of Rate Constants of Aliphatic Carbon-Centered Rascals in Aqueous Solutions by A.B. Ross and P. Neta (Radiation Chemistry Data Center, Radiation Laboratory, University of Notre Dame, NSRDS-NBS) and Liquid Phase Reaction Rate Constants by E.T. Denisov (IFl/PLENUM, New York, 1974, transl. from Russian, Nauka Press, Moscow, 1971). We would also like to acknowledge the help of Dr. Ch.-H. Fischer in many questions concerning the nomenclature of compounds. 

Denisov, E.T., 1974, Liquid - Phase Reactions Rate Constants, IFl/Plenum, New York. 

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