Polymerization and Decomposition of Acetylene Hydrocarbons

Abstract

Few fields in hydrocarbon chemistry offer the variety and the interest presented by the reactions of polymerization and decomposition of the acetylene hydrocarbons. The many products include gases, aliphatic and aromatic liquids, tars, and solids of unusual properties. There is variety too, in the means used to cause reaction, which include heat, chemical reagents, detonants, electric discharge, alpha particles, cathode rays, light, and electro-magnetic fields.The interest in these reactions lies in part in their variability under changing experimental conditions. A single method of excitation, depending upon the conditions under which it is employed, may give rise to a gas, a low-boiling liquid, or an infusible solid. The elucidation of the mechanisms by which products so varied come from a single substance is a study of compelling interest. Attention is drawn to these reactions, moreover, by their commercial significance. Acetylenes have been proposed-and to some extent used-as a source of carbon, aromatic hydrocarbons, drying oils, synthetic rubber, and porous adsorbents.Reactions of polymerization and decomposition are considered together for two reasons.As in the case of hydrocarbons of other series, changes of both types may be produced by the same agencies, and they often occur simultaneously.Almost exclusively the investigations recorded concern acetylene itself. Only a few of the higher members of the series have been studied. This is understandable, as acetylene is readily obtained and there is hope of obtaining useful substances from it, while its homologs, even in the laboratory, are rarities.I. Acetylene A. Introduction.The outstanding properties of acetylene are its unsaturation and its endothermic character. To its unsaturation, enabling it to add to itself, or to other substances, may be attributed its ability to form simple and complex polymers. Its endothermic character tenders it unstable, so that violent excitation, particularly at somewhat elevated pressure, will cause it to revert to its elements, sometimes with explosive violence.Acetylene may be converted into polymers of comparatively simple structure by combination of two, three or four molecules, under the action of chemical reagents or the silent discharge, but only if reaction is carried out * Presented before the

Reductive Dechlorination of Trichloroethene by Zero-valent Iron Nanoparticles: Reactivity Enhancement through Sulfidation Treatment

“…Acetylene is a reactive chemical and it readily undergoes polymerization reactions on metal surfaces to form longer chain hydrocarbons, 54 or in the presence of a hydrogen source, hydrogenates to more saturated products. Our separate experiments reacting acetylene with nZVI and S-nZVI confirm that both solids are able to rapidly transform acetylene into ethene, ethane, and higher order hydrocarbons (SI Figure S3).…”

The Kinetics of Elementary Reactions of the Simple Hydrocarbons.

“…Acetylene 1. The thermal decomposition and polymerization No attempt will be made to review the enormous literature on the effect of heat on acetylene, since comprehensive discussions from a pyrolytic point of view already exist (40,42). The products of the reactions are usually so complicated as to defy analysis; consequently very little is known which is of value from the standpoint of this review.…”

“…In this review an attempt has been made to include all data which seem to be pertinent to the kinetic analysis of the simple thermal and photochemical reactions of the lower paraffins, olefins, and acetylenic hydrocarbons. No attempt has been made to include references to purely pyrolytic investigations, or to catalytic processes, since a number of comprehensive reviews of this kind already exist (35,36,41,42,43,45,46,48,57,77, 181, and especially 40). In spite of their importance, the oxidation and halogenation reactions of the hydrocarbons have not been included, since these do not seem to have advanced as yet to the stage where we can disentangle the processes into their component parts with any degree of certainty.…”

The Friedel-Crafts Syntheses.

“…Besides the examples mentioned above there are many cases in which methyl (259,391,98,172), amino (274, 410), and methoxyl (410, 256, 256a, 134) activate the nucleus so that substitution occurs with increased ease. VI.…”