157033-41-5Relevant articles and documents
ACID DEACTIVATION OF A NUCLEOPHILE IN THE PHASE-TRANSFER PHENOLYSIS OF CYCLOPHOSPHAZENES AND ITS MECHANISM UNDER HOMOGENEOUS CONDITIONS
Afon'kin, A. A.,Shumeiko, A. E.,Popov, A. F.
, p. 457 - 463 (2007/10/02)
The reactions of tetraalkylammonium salts of 2,4-dinitrophenol (ArO-Q+) with the cyclic trimer of phosphonitrile chloride were studied in a two-phase system of a buffer solution and benzene and in a homogeneous system modeling the conditions of the organic phase. In a two-phase system the aryloxide ion, while being incompletely ionized in the aqueous phase, is extracted into the organic phase together with the neutral form of the phenol, which results in the inhibition of the reaction of monoaryloxyphosphazene formation. The reason lies in the deactivation of the nucleophile as a result of the formation of less reactive complexes with an H bond between the anion and/or the ion pair ArO-Q+ and the proton donor (ROH) contained in the organic phase. On the basis of the kinetic relations and of the results of a study of the equilibrium processes it was found that in the case of strong proton donors (phenols) complexes of the anion and of the ion pair ArO-Q+ with a composition of 1:1 react with the substrate, but in case of weak donors (alcohols) an ion pair not bound into a complex and associations with the anion with compositions of 1:1 and 1:2 react. The reactivity of the complexes of composition 1:1 is thus proportional to the values of the constants of complex formation with ROH, and the inhibiting action of the latter is governed by a single correlation equation without regard to the type of the H-bond acceptor and to the nature of ROH. On the basis of the quantum-chemical calculations it was supposed that the ambiguous effect of ROH on the nucleophilicity of the anions and of the ArO-Q+ ion pairs is determined by the differences in specific solvation between the transition states of the reactions involving these forms of the reagent.
