Replacement, of acetylenic hydrogen

Replacement, of acetylenic hydrogen atom by bromine, 46, 86 of acyl chlorine atom by fluoride atom using hydrogen fluoride, 46, 3... 

Replacement, of acetylenic hydrogen atom by bromine, 45, 86 of acyl chlorine atom by fluorine atom using hydrogen fluoride, 46, 3 of amino hydrogen atoms by thio-carbonyl group, 46, 19 of aromatic bromine atom by potassium /-butoxide, 46, 89 of a-chloro atom in ester using azide ion, 46, 47... 

Metal Acetylides. The replacement of a hydrogen atom on acetylene by a metal atom under basic conditions results in the formation of metal acetyhdes which react with water in a highly exothermic manner to yield acetylene and the corresponding metal hydroxide. Certain metal acetyUdes can be... 

Yasunobi T, Yasumoii I (1971) Pressure jump and isotope replacement studies of acetylene hydrogenation on palladium surface. J Phys Chem 75 880... 

It would appear, therefore, that all of the products identified in the vapor-phase radiolyses could be formed from excited molecules. Some products, however, are so much more abundant in vapor-phase radiolysis than in photolysis or liquid-phase radiolysis as to suggest the likelihood of additional precursors. In particular, the formation of acetylene, the isomerization of the xylenes, and the replacement of aromatic hydrogen by methyl groups are difficult to explain solely in terms of reactions of excited molecules. 

Propiolic Acid, HC=C.COOH, is a liquid with a pungent odor resembling that of acetic acid. After freezing it melts at 9°. It can be distilled without decomposition only under diminished pressure. It is interesting on account of the fact that its reactions show clearly its relation to acetylene. It forms as an acid, well characterized salts, and as a triple bonded compound, metallic derivatives, which result from the replacement of the hydrogen atom joined to carbon by silver or copper. When the acid is treated with an ammoniacal solution of silver nitrate a colorless, crystalline salt is formed, which soon turns yellow and explodes when struck. Propiolic acid may be prepared by the action of carbon dioxide on the sodium derivative of acetylene —... 

Just as imine resembles ethylene, hydrogen cyanide is similar to acetylene, with the same number of valence electrons. A lone pair on the N atom of HCN replaces one C—H bond of acetylene. 

Replacement of the Acetyleneic Hydrogen Atom of Terminal Alkynes... 

The addition reaction of alkyl and/or phenyl substituted silicon hydrides to acetylenes has limitations mainly due to the hydrogen donation step (cf. Scheme 5.1). Reaction (5.17) shows that the replacement of Ph by MesSi group in silanes made the reaction easier, the effect being cumulative. Indeed, the reaction time decreased from 88 h for PhsSiH to 3h for (TMS)3SiH [39], together with the amelioration of yields, and a slightly better cis stereoselectivity. 

Replacing the hydrogen in 68 with a phenyl group leads to the secondary acetylenic monomer 70. It was believed that this disubstituted acetylene would suppress the reaction of acetylene with itself and insure that there was an acetylene functionality available for reaction with the o-quinodimethane at 200 °G The DSC of 68 showed the presence of a single exothermic peak at 263 °C which the authors felt was adequate evidence for the occurrence of a Diels-Alder reaction between the acetylene and benzocyclobutene. Unfortunately they did not report on any control experiments such as that between diphenylacetylene and simple benzocyclobutene hydrocarbon or a monofunctional benzocyclobutene in order to isolate the low molecular weight cycloaddition product for subsequent characterization. The resulting homopolymer of 68 had a Tg of 274 °C and also had the best thermooxidative stability of all of the acetylenic benzocyclobutenes studied (84% weight retention after 200 h at 343 °C in air). 

Aeetylldes (Acetylene Derivatives, Inorganic) (Acetylenide or Carbide, in Ger). Acetylides are compds obtained by replacement of one or two hydrogen atoms of acetylene or its homologs or derivatives by a metal. Their structure may be as follows HC i CM1, ... 

Another major chlorinated hydrocarbon is vinyl chloride. For many years acetylene was the sole raw material for the production of vinyl chloride by a catalytic fixed bed vapor-phase process. This process is characterized by high yields and modest capital investment. Nevertheless, the high relative cost of acetylene provided an incentive to replace it in whole or in part by ethylene. The first step in this direction was the concurrent use of both raw materials. Ethylene was chlorinated to di-chloroethane, and the hydrogen chloride derived from the subsequent dehydrochlorination reacted with acetylene to form additional vinyl chloride. 

In the first example, nitration of the benzoate (140) with nitric acid affords the nitro derivative. Hydrogenation converts this to the anthranilate (141). In one of the standard conditions for forming quinazolones, that intermediate is then treated with ammonium formate to yield the heterocycle (142). Reaction of 142 with phosphorus oxychloride leads to the corresponding enol chloride (143). Condensation of 143 with m-iodoaniline (144) leads to displacement of chlorine and consequent formation of the aminoquinazoline (145). Reaction with the trimethylsilyl derivative of acetylene in the presence of tetrakis-triphenylphosphine palladium leads to replacement of iodine by the acetylide. Tributylammonium fluoride then removes the silyl protecting group to afford the kinase inhibitor erlotinib (146). ... 

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