Acetylene, ions from, reactions

Acetylene Ion. No evidence for the contribution of ion-molecule reactions originating with acetylene ion to product formation has been obtained to date. By analogy with the two preceding sections, we may assume that the third-order complex should dissociate at pressures below about 50 torr. Unfortunately, the nature of the dissociation products would make this process almost unrecognizable. The additional formation of hydrogen and hydrogen atoms would be hidden in the sizable excess of the production of these species in other primary acts while the methyl radical formation would probably be minor compared with that resulting from ethylene ion reactions. The fate of the acetylene ion remains an unanswered question in ethylene radiolysis. 

Other products commonly isolated from reactions of DMAD with heterocycles include dimethyl fumarate (17), the acetylene presumably acting as a dehydrogenating agent, and dimethyl methoxyfumarate (18).22 The latter could arise from the addition of methanol, present as an impurity, to the acetylene, or by nucleophilic attack on the carbonyl group of the acetylenic ester followed by expulsion of methoxide ion, which then undergoes a normal nucleophilic addition to the activated triple bond. It can be obtained, among other products, from the reaction of pyridine with DMAD in methanol.23... 

M2+02 (M = Mg, Ca, Sr) coordinatively unsaturated pairs are able to abstract a hydrogen ion from acetylenic hydrocarbons following the reaction path shown in Scheme 4 (—, surface plane R, alkyl group), with formation... 

The difference between the heats of formation of C8HeO+ from reactions (10) and (11) (46 kcal) probably exceeds the uncertainties and errors mentioned above, which suggests that the fragment ion does not have a ground-state benzofuran structure (2). The close similarity (within experimental error) of the heats of formation in reactions (10) and (12), is consistent with the acetylenic-phenol structure (4) for the ion (Occolowitz and White, 1968) but this does not form proof of identity. The... 

The formal addition of perfluorinated pyridine, pyrimidine, pyridazine or of pentafluorobenzo-nitrile to fluorinated acetylenes in the presence of cesium fluoride in sulfolane leads to fluorinated aryl-substituted alkenes. " In the first reaction step fluoride ion adds to the fluorinated acetylene to give a vinyl carbanion, which substitutes, in a second step, a fluoride ion from the perfluorinated aromatic compound. Some examples of this type of reaction are shown by the formation of... 

The effect of electrical fields on the radiolysis of ethane has been examined by Ausloos et and this study has shown that excited molecules contribute a great deal to the products. The experiments were conducted in the presence of nitric oxide, and free-radical reactions were therefore suppressed. The importance of reactions (12)-(14) was clearly demonstrated by the use of various isotopic mixtures. Propane is formed exclusively by the insertion of CH2 into C2H6 and the yield is nearly equal to the yield of molecular methane from reaction (14). Acetylene is formed from a neutral excited ethane, probably via a hot ethylidene radical. Butene and a fraction of the propene arise from ion precursors while n-butane appears to be formed both by ionic reactions and by the combination of ethyl radicals. The decomposition of excited ethane to give methyl radicals, reaction (15), has been shown by Yang and Gant °° to be relatively unimportant. The importance of molecular hydrogen elimination has been shown in several studies ° °. ... 

The AlCl3 mediated electrophilic substitution of alkynylsilanes with acid chlorides provides a convenient route to alkynyl ketones. Transfer of the acetylenic moiety from silicon to the acyl chloride proceeds via the acyl cation (acylium ion) formed by reaction of the acyl chloride with AlClg. " ... 

Decoking of catalyst pellets Ion exchange reactions Hydrogen storage in metal lattice Semiconductor doping Combustion of coal Reduction of ore Production of acetylene from CaC2 Semiconductor etching... 

Since sodium methyl acetylide is the salt of the extremely weak acid, methyl acetylene, the acetylide ion is a stronger base, thus this reaction involves substitution of acetylide ion for halide ion. From this it can readily be seen that the metal ion, sodium, bonds to the released halide ion and the acetylide ion bonds to the alkyl group yielding a higher alkyne, plus a metal halide as the byproduct. 

This chapter is divided into three sections. Section 1 covers the electron ionization (El) mass spectra of acetylenic compounds and discusses the types of singly and doubly charged cations formed on electron impact. Section 2 concerns the unimolecular chemistry of ions with C=C bonds. Finally, Section 3 is devoted to the ion-molecule reactions of acetylenic ions and acetylenes. The material mainly originates from articles that have been published within the last decade and is presented with considerable detail. This review does not claim to be exhaustive nevertheless, it provides examples from all areas of active mass spectrometry research in C=C bonded molecules, so that the reader can learn about the important and novel developments in this area. 

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