Solvolysis rates in mixed organic solvents

M. A. Mousa; E. M. Diefallah; A. F. Shaaban; M. M. Azab

doi:10.1515/zpch-1989-270147

I I . Kinetics of dehydrochlorination of 1,1, 1-trichloro-2,2-dipbenylethane by base in methanol/isopropanol mixed solvents

De Gruyter Oldenbourg | 2017

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ISSN 0323-4479 • Z. phys. Chemie • Leipzig • 270 (1989) 6 • S. 1177-1184 Chemistry Department, Faculty of Science, Benha University, Benha (Egypt) Solvolysis rates in mixed organic solvents: II. Kinetics of dehydrochlorination of 1,1, l-trichloro-2,2-dipbenyIethane by base in methanol/isopropanol mixed solvents By M. A. Mousa1, E. M. Diefallah, A. F. Shaaban and M. M. Azab With 5 Figures and 2 Tables (Received ISth October 1986; in rev. version 8th September 1987) Abstract The kinetics of dehydrochlorination of l,],l-trichloro-2,2-diphenylethane by methoxide and iso-propoxide ions in methanol-isopropanol solutions have been studied over the temperature range 30 to 50°C. The rate of the reaction is first order with respect to both the l,l,l-trichloro-2,2-diphenylethane and the methoxide or isopropoxide ion concentrations. When the concentration of methanol in the solvent is increased the rate constant of the dehalogenation reaction first increases to a maximum at about 0.1 methanol mole fraction, then decreases. The influence of solvent variation on reaction rate has been examined in terms of changes in the activation parameters. The results do not support any simple correlation between the macroscopic dielectric constant of the medium and the reaction rate constant. Solvent effects on the thermodynamic parameters which characterize the activation process (Aare discussed in terms of the electrostatic theory and on the basis of the change in the solvent structure. Introduction The solvolysis of many organic compounds has been studied in aqueous-organic mixed solvents by several investigators [1-11]. However, a limited number of kinetic studies has been done in mixed solvents of non-aqueous solution. In this paper we present a detailed study of the rates and mechanism of the dehydrochlorination of 1,1,1-tri-chloro-2,2-diphenylethane (TDE) by methoxide and isopropoxide ions in a series of methanol-isopropanol solutions. Such a study would provide more information about the role played by the solvent molecules in a mixture of organic solvents. Experimental Methanol and isopropanol used in this work were of analar grade. However, the alcohols were made drier, just prior to use, according to recommended procedures [12]. Isopropyl alcohol was more dehydrated by refluxing it with quicklime overnight and then distilled. The obtained alcohol was refluxed with anhydrous calcium chloride and then fractionally distilled. The middle fraction (with b.p. 82.5°C) was used to make all the solutions. While, methanol (A.R.) was made drier by refluxing it with Mg-wire 1 M. A. MOUSA, Department of Chemistry, Centre of Science and Mathematics, P. O. Box 1070, Taif, Saudi Arabia.

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Solvolysis rates in mixed organic solvents

I I . Kinetics of dehydrochlorination of 1,1, 1-trichloro-2,2-dipbenylethane by base in methanol/isopropanol mixed solvents

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