I. Studies in the Chemistry of Sodium Dithionite. Il. A Preliminary Study of the Catalyzed Addition of Hydrogen Chloride to Vinyl Chloride in a Stirred Reactor

Citation

Rinker, Robert Gene (1959) I. Studies in the Chemistry of Sodium Dithionite. Il. A Preliminary Study of the Catalyzed Addition of Hydrogen Chloride to Vinyl Chloride in a Stirred Reactor. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/VS2K-BE10. https://resolver.caltech.edu/CaltechETD:etd-02172006-104009

Abstract

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Part I: Rate studies of the air oxidation and thermal decomposition of aqueous sodium dithionite, Na2S2O4, were conducted. These experiments were supplemented by studies of the electron-paramagnetic-resonance properties and the electrolytic formation of dithionite.

In the air-oxidation experiments, the overall rate was observed to have half-order dependence on the dithionite concentration and a first-order dependence on molecular oxygen concentration. This could be explained mechanistically on the basis of an instantaneous equilibrium reaction between dithionite and the [...] radical ion.

The results of the EPR studies confirmed the presence of [...] and established the existence of equilibrium between the free radical and dithionite.

The electrolytic production of dithionite from a bisulfite solution gave current efficiencies of 75% but did not show conclusively that the reduction was either a one- or two-electron transfer process.

In the thermal decomposition studies, the overall rate showed a 3/2-order dependence on dithionite concentration and a half-order dependence on hydrogen ion concentration. A mechanism involving [...] or a protonated form of the radical in a reaction with the dimer appeared to fit the observed facts.

Part II: A preliminary rate study of the catalyzed addition-reaction between HCl and vinyl chloride was conducted in a continuous-flow stirred reactor. Gas-phase chromatography was used in the analysis of the chemical constituents.

The rate data for the primary reaction appeared to fit, at least empirically, a second-order rate law with respect to the forward reaction.

In addition to the primary reaction, fouling of the catalyst, ZnCl2, was also observed, but the decreasing conversion as a function of catalyst-exposure time reached an asymptotic value greater than zero. This indicated that the catalyst fouling was an irreversible dual-site mechanism.

The fact that 1,1 dichloroethane was formed exclusively in the primary reaction eliminated the possibility of a free-radical reaction. Because of the relatively low rate of reaction, even in the presence of a catalyst, the addition probably occurred by a four-center-type mechanism.

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