Kinetic Studies of Bimolecular Nucleophilic Substitution. V. Rates of SN2 and E2 Reactions of 1,2-Dichloroethane with Various Nucleophiles in Aqueous Solutions

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Abstract
The rates of the reactions of 1, 2-dichloroethane with sodium hydroxide, sodium phenoxide, trimethylamine, pyridine, and sodium acetate have been measured in aqueous solutions at 110 and 120°C. On the assumption that the substitution reaction of 1, 2-dichloroethane produces two equivalents of the chloride ion because of the greater reactivity of the mono-substitution products (β-substituted ethyl chlorides) than that of the starting substrate, while the elimination product from 1, 2-dichloroethane, i. e., vinyl chloride, does not react with the bases under the reaction conditions employed, the kSN2 and kE2 have been calculated from the rate of the chloride-ion liberation and from the number of moles of the base required to react with one mole of the substrate. For a series of kSN2 values there is no linear relation between the rates and the pKa’s of the conjugate acids, whereas a parallelism exists between the kE2 and the pKa. The stronger the base, the more the elimination is promoted.