Ethyne, production

HOCH2CH2CH2CH2OH. B.p. 228"C. Prepared ethyne plus methanal, hydrogenated to butanediol. Used in production of y-buty-rolactone and 2-pyrrolidone. Widely used in polyurethane products, butylenes See butenes. 

As far as we are aware, the azo coupling of an ethyne derivative was only investigated over half a century ago Ainley and (Sir Robert) Robinson (1937) investigated the reaction of phenylethynes (phenylacetylenes) with diazonium ions (Scheme 12-59). Unsubstituted phenylethyne did not give identifiable products with the 4-nitrobenzenediazonium ion, but with the more nucleophilic 4-methoxyphenyl-ethyne an azo compound (12.119) was formed. On reaction with water it gives an arylhydrazone of an a-ketoaldehyde (12.120). 

Write a balanced chemical equation for (a) the hydrogenation of ethyne (acetylene, C2H2) to ethene (C2H4) by hydrogen (give the oxidation number of the carbon atoms in the reactant and product) (b) the shift reaction (sometimes called the water gas shift reaction, WGSR) (c) the reaction of barium hydride with water. 

The destruction of DDT by ball milling with CaO resulted in substantial loss of chloride and produced a graphitic product containing some residual chlorine. In addition, an exceptional rearrangement occnrred with the formation of bis(4-chlorophenyl)ethyne that was identified by H NMR (Hall et al. 1996) (Figure 1.28). 

The reaction of 95 with Me3SiC=CMe shows clearly that the B-CHEt bond is more reactive than the BCH2 bond, and the products (E)-96 and (E)-97 are formed in a 1 1 ratio (note that there are 2BCH2 bonds in 95). In the case of the tert-butyl derivative, steric factors control the process. Moreover, repulsion between the Et and SnMe3 substituents results in the preferential formation of (Z)-99 <2001JOM(620)51>. On the other hand, reaction with bis(triethyltin)ethyne gives only product (Z)-100 (Scheme 38) <2003JOM(687)108>. 

As mentioned above the 1,1-organoboration reaction is reversible, and exchange is slow on the NMR timescale. This statement is in agreement with the chemical behavior of equilibrated mixtures of products. Thus, treatment of silicon borahomoadamantane derivative 92 with bis(trimethylstannyl)ethyne leads to the tin-containing compound 93 and liberation of bis(trimethylsilyl)ethyne (Scheme 44). With pyridine, the equilibrium is moved toward 1-boraadamantane completely due to the complexation <2001JOM(620)51>. 

Microwave-induced, catalytic gas-phase reactions have primary been pursued by Wan [63, 64], Wan et al. [65] have used pulsed-microwave radiation (millisecond high-energy pulses) to study the reaction of methane in the absence of oxygen. The reaction was performed by use of a series of nickel catalysts. The structure of the products seemed to be function of both the catalyst and the power and frequency of microwave pulses. A Ni/Si02 catalyst has been reported to produce 93% ethyne, whereas under the same irradiation conditions a Ni powder catalyst produced 83% ethene and 8.5 % ethane, but no ethyne. 

Pyrolysis of methane under the action of pulsed microwave radiation in the presence of solid catalysts has been reported by Russian authors [71, 72], The application of pulse microwave power was shown to be a promising means of production of hydrogen syngas, ethyne, and filament carbon. 

Treatment of the ethyne derivative 71 with palladium chloride and mercuric chloride in the presence of carbon monoxide at a pressure of 1 atmosphere1131 gave methyl 2-(2,3,5-tri-0-benzyl-/3-D-ribofuran-osyl)maleate113c in high yield. This product may be considered to be a useful precursor to showdomycin. 

Vitamin B12 catalyzed also the dechlorination of tetrachloroethene (PCE) to tri-chloroethene (TCE) and 1,2-dichloroethene (DCE) in the presence of dithiothreitol or Ti(III) citrate [137-141], but zero-valent metals have also been used as bulk electron donors [142, 143]. With vitamin B12, carbon mass recoveries were 81-84% for PCE reduction and 89% for TCE reduction cis-l,2-DCE, ethene, and ethyne were the main products [138, 139]. Using Ni(II) humic acid complexes, TCE reduction was more rapid, leading to ethane and ethene as the primary products [144, 145]. Angst, Schwarzenbach and colleagues [140, 141] have shown that the corrinoid-catalyzed dechlorinations of the DCE isomers and vinyl chloride (VC) to ethene and ethyne were pH-dependent, and showed the reactivity order 1,1-DCE>VC> trans-DCE>cis-DCE. Similar results have been obtained by Lesage and colleagues [146]. Dror and Schlautmann [147, 148] have demonstrated the importance of specific core metals and their solubility for the reactivity of a porphyrin complex. 

The next step of the dissociative route is coordination of ethyne to the dissociation product 12 followed by ethyne-carbene insertion to form the metallatriene intermediate 13. This process is highly exothermic, the release of energy starting from 12c being of 175.7 kJ mol 1 [27],... 

The reaction of calcium carbide with water yields two products. One is ethyne gas (C2H2). From your observation in step 6, suggest what the other product is, and write a balanced chemical equation for the reaction. 

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