Compensation effect in the conjugate chlorination of 3-substituted propenes and 3,3-di(chloromethyl)oxetane

Abstract

UDC 541.311 The principles of the existence of a compensation effect have been discussed widely in recent times [i, 2]. Such an approach makes it possible to present a model of a real physicochemical effect and also to investigate a series of interesting relationships and, in particular, the dependence of the isokinetic temperature on the limiting stage of a reaction and the strength of the breaking and forming bonds. During investigation of the kinetic relationships governing the conjugate chlorination of 3,3-di(chloromethyl)oxetane with 3-substituted propenes we established a relation between the logarithms of the effective rate constants of the conjugate reaction and the reciprocal of the temperature (Fig. 1). For a series of substituted propenes (R = Cl, Br, OCOCHs) the rate constants increase with increase in temperature in the range of 0-20~ which corresponds to a positive temperature coefficient, and decrease with further increase in temperature in the range of 35-45~ For another group of substituents (R = OCH3, OCaUs, OC,HT) the positive temperature coefficient of the reaction in the range of 35-45~ is increased in comparison with the range of 0-20~ Conjugate chlorination was realized under nonradical conditions, i.e., in the dark with low concentrations of the olefin. Saturation of the solution with oxygen, degasslng of the solvent, the addition of radicalforming additives (acetyl peroxide, benzoyl peroxide), and the addition of "radical traps" (a-naphthol, 2-methyl-2-nitrosopropane) do not lead to a change in the initial reaction rate and indicate the absence of an appreciable contribution from the radical reaction path under the investigated conditions. This agrees with the results obtained for other conjugate ~ reactions [3-5]. The partial reaction orders in chlorine were second for all the substituents, and the partial order in propene was first, i.e., the consumption rate of chlorine in an excess of the oxetane is given by the equation.