Acetylenes studies

The reaction of acetylenes with the iron carbonyls gives a wide variety of stable complexes, the composition of which depends on the alkyne, the carbonyl, the reaction temperature, and the solvent used in the preparation (Table III) 116, 117, 118, 120, 182, 187). Iron dodecacarbonyl yields as many as seven different kinds of complexes, depending on the acetylene studied. The complexes are generally yellow, red, or black, soluble in organic solvents, and are invariably diamagnetic they show infrared absorption... 

Unsaturated hydrocarbons that contain one or more triple bonds between carbon atoms in a chain are called alkynes. Triple bonds involve the sharing of three pairs of electrons. The simplest and most commonly used alkyne is ethyne (C2H2), which is widely known by its common name acetylene. Study the models of ethyne in the following diagram. 

Weinelt M, Huber W, Zebisch P, Steinruck H-P, Ulbricht P, Birkenheuer U, Boettger J C and Rdsch N 1995 The adsorption of acetylene on Ni(110) an experimental and theoretical study J. Chem. Phys. 102 9709... 

The mechanism of the reaction la not known with certainty. It is known from studies utilising as tracer that no change in the carbon skeleton occurs during the reaction, and also that unsaturated hydrocarbons can undergo reactions very similar to those of ketones thus both styiene and phenyl-acetylene can react with sulphur and morpholine to produce phenylaceto-thiomorphoUde, hydrolysis of which yields phenylacetic acid ... 

We have already discussed one important chemical property of alkynes the acidity of acetylene and terminal alkynes In the remaining sections of this chapter several other reactions of alkynes will be explored Most of them will be similar to reactions of alkenes Like alkenes alkynes undergo addition reactions We 11 begin with a reaction familiar to us from our study of alkenes namely catalytic hydrogenation... 

Gyclooctatetraene (GOT). Tetramerization of acetylene to cyclooctatetraene [629-20-9], CgHg, although interesting, does not seem to have been used commercially. Nickel salts serve as catalysts. Other catalysts give ben2ene. The mechanism of this cyclotetramerhation has been studied (4). 

Poly(l,3,4-oxadia2ole-2,5-diyl-vinylene) and poly(l,3,4-oxadia2ole-2,5-diyl-ethynylene) were synthesi2ed by polycondensation of fumaramide or acetylene-dicarboxamide with hydra2ine sulfate in PPA to study the effect of the two repeating units on polymer electronic and thermal properties (55). 

Dia ene deductions. Olefins, acetylenes, and azo-compounds are reduced by hydrazine in the presence of an oxidizing agent. Stereochemical studies of alkene and alkyne reductions suggest that hydrazine is partially oxidized to the transient diazene [3618-05-1] (diimide, diimine) (9) and that the cis-isomer of diazene is the actual hydrogenating agent, acting by a concerted attack on the unsaturated bond ... 

Several studies of spherical and cylindrical detonation in acetylene—oxygen and acetylene—air mixtures have been reported (82,83). The combustion and oxidation of acetylene are reviewed extensively in Reference 84. A study of the characteristics and destmctive effects of detonations in mixtures of acetylene (and other hydrocarbons) with air and oxygen-enriched air in earthen tuimels and large steel pipe is reported in Reference 81. 

The preferred quantitative deterrnination of traces of acetylene is gas chromatography, which permits an accurate analysis of quantities much less than 1 ppm. This procedure has been highly developed for air poUution studies (88) (see Airpollution control methods). Other physical methods, such as infrared and mass spectroscopy, have been widely used to determine acetylene in various mixtures. 

To extend the study of the apparent decomposition recombination reaction, and specifically to determine if the carbon atoms exchange with other atoms in other acetylene molecules, tests using carbon isotopes were conducted. A mixture of 50% regular acetylene, C2H2, and 50% heavy acetylene. 

Even with improvement in properties of polyacetylenes prepared from acetylene, the materials remained intractable. To avoid this problem, soluble precursor polymer methods for the production of polyacetylene have been developed. The most highly studied system utilizing this method, the Durham technique, is shown in equation 2. 

Copolymerizations of benzvalene with norhornene have been used to prepare block copolymers that are more stable and more soluble than the polybenzvalene (32). Upon conversion to (CH), some phase separation of nonconverted polynorhornene occurs. Other copolymerizations of acetylene with a variety of monomers and carrier polymers have been employed in the preparation of soluble polyacetylenes. Direct copolymeriza tion of acetylene with other monomers (33—39), and various techniques for grafting polyacetylene side chains onto solubilized carrier polymers (40—43), have been studied. In most cases, the resulting copolymers exhibit poorer electrical properties as solubiUty increases. 

Abstract—Carbon nanotubules were produced in a large amount by catalytic decomposition of acetylene in the presence of various supported transition metal catalysts. The influence of different parameters such as the nature of the support, the size of active metal particles and the reaction conditions on the formation of nanotubules was studied. The process was optimized towards the production of nanotubules having the same diameters as the fullerene tubules obtained from the arc-discharge method. The separation of tubules from the substrate, their purification and opening were also investigated. 

A very significant recent development in the field of catalytic hydrogenation has been the discovery that certain transition metal coordination complexes catalyze the hydrogenation of olefinic and acetylenic bonds in homogeneous solution.Of these catalysts tris-(triphenylphosphine)-chloror-hodium (131) has been studied most extensively.The mechanism of the deuteration of olefins with this catalyst is indicated by the following scheme (131 -> 135) ... 

The influence of hemispherical wire mesh screens (obstacles) on the behavior of hemispherical flames was studied by Dorge et al. (1976) on a laboratory scale. The dimensions of the wire mesh screens were varied. Maximum flame speeds for methane, propane, and acetylene are given in Table 4.1b. 

Although the emphasis in this chapter has been on tbe synthesis and mechanism of formation of simple enamines, brief mention will be made of the addition of amines to activated acetylenes to indicate the interest and activity in this area of substituted enamines. Since such additions tend to be stereospecific, inclusion in this section seems apropos. The addition of amines to acetylenes has been much studied 130), but the assigning of the stereochemistry about the newly formed double bond could not be done unequivocally until the techniques of NMR spectroscopy were well developed. In the research efforts described below, NMR spectroscopy was used to determine isomer content and to follow the progress of some of the reactions. 

Although the addition of hydrazine and its derivatives to acetylenic ketones has been studied in considerable detail, their interaction with hydrazones and mono-alkylhydrazones is less well known. Yandovskii and Klindukhova (74ZOR730) have studied the reaction between hydrazones and alkylhydrazones of aliphatic ketones with dipropynylketones and showed that hydrazones of acetone, methyl-ethylketone, and cyclohexane easily add to one of the triple bonds of dipropynylketone to form 4-methyl-1,1,3-trialkyl-2,3-diaza-l,4-nonadien-7-yn-6-ones (yields... 

A detailed study of the transformations of methylpyrazolylketones into acetylenes under the action of PCI5 and then a base indicates the sensitivity of these reactions to experimental conditions, the structure of the starting ketones, and the nature of the base (69TZV927 69KGS1055 76TZV2288). 

Similarly, the limitations and peculiarities of the cross-coupling of pyrazolyl-halides with terminal acetylenes have been fully and systematically studied by Russian chemists (86TH1 97TH1). 

For this reason, the heterocyclization of acetylenic derivatives of pyrazolecar-boxylic acids with different arrangements in the ring of the interacting groups was studied (Table XXVI). The reaction is carried out in boiling pyridine in the presence of catalytic amounts of PhC=CCu (81IZV1342). 4-Acetylenyl-l-methylpyrazole-5-carboxylic acids (Scheme 121) are fully isomerized into the pyranopyrazoles in 20 min in 62-84% yields. 

The data obtained allow us to make some generalizations for the heterocy-clization of the functionally substituted acetylenic derivatives of the benzene and pyrazole series. Studies of the heterocyclization of the functionally substituted acetylenic derivatives of substituted benzenes and pyrazoles reveal noticeable differences in their reactivities. 

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