With Acetylenes

When phenylacetylenes (3 mol), tellurium dioxide (1 mol), and a lithium halide (14-18 mol) were refluxed in acetic acid, 3-halobenzotellurophenes were obtained in yields ranging from 21 to 92%. A tellurium (IV) acetate halide, formed from tellurium dioxide, Uthium halide, and acetic acid, probably adds to the carbon-carbon triple bond of the phenylacetylene. The intermediary 2-phenyl-2-haloethenyl tellurium acetate halide cyclizes probably by loss of acetic acid. The 3-halobenzotellurophene Te.Te-acetate halide is then reduced to 3-halobenzotellurophene by an excess of the phenylacetylene. Diphenylacety-lene and diphenyldiacetylene did not react under these conditions. 

To facilitate the isolation of the benzotellurophenes, many of which are oils, they were converted to the benzotellurophene Te, re-dichlorides. After the crystalline dichlorides had been purified by recrystallization, they were reduced to the benzotellurophenes with aqueous sodium disulfite  

3-BromobenzoteIlurophene 1,1-DichIoride A mixture of 2.0 g (19.6 mmoi) of phenylacetylene, 1.0 g (6.3 mmol) of tellurium dioxide, 2.0 g (23 mmol) of lithium bromide, and 50 ml of acetic acid is heated under reflux for 20 h, cooled to 20°, and poured into 150w/ of diethyl ether. 5% aqueous sodium hydrogen carbonate solution is added until all the acid has been neutralized. The organic phase is separated, dried with anhydrous calcium chloride, filtered, and evaporated. The brown, oily residue is dissolved in a mixture of 30 m/ of carbon tetrachloride and 10 m/ of petroleum ether (b.p. 30-40°). Chlorine is carefully bubbled through this solution until precipitation of the product ceases. The yellow precipitate is filtered and recrystallized from acetonitrile yield 2.2 g (92%) m.p. 263-265°. 

3-BromobenzotelIuropheneh 3-Bromobenzotellurophene dichloride is suspended in diethyl ether and an excess of 5% aqueous sodium disulfite solution is added. The mixture is shaken thoroughly until all of the organic material has dissolved. The organic layer is separated, dried with anhydrous calcium chloride, filtered, and the filtrate is evaporated. The oily residue is pure 3-bromobenzotellurophene yield 100%. See Table 20 for similary prepared benzotellurophene dichlorides and benzotellurophenes. 

Starting Materials Reflux time [h] Product. .. -benzotellurophene 1,1-dichloride) 1,1-Dichloride Benzotellurophene  

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Bromine. Slip the glass cover of a jar momentarily aside, add 2-3 ml. of bromine water, replace the cover and shake the contents of the jar vigorously. Note that the bromine is absorbed only very slowly, in marked contrast to the rapid absorption by ethylene. This slow reaction with bromine water is also in marked contrast to the action of chlorine water, which unites with acetylene with explosive violence. (Therefore do not attempt this test with chlorine or chlorine water.)... 

The rate of the reaction decreases with increasing number of substituents in the acetylenic halide, and it is higher with acetylenic bromides than with the corresponding chlorides. Methyl magnesium iodide gives equal amounts of 1,1- and 1,3--substitution products, whereas tert.-butylmagnesium bromide does not react. However, for some tert.-butyl substituted allenes there exists an attractive com-... 

Palladium also catalyses coupling of haloindolcs with acetylenes. The reaction is carried out in the presence of Cu(I) and presumably involves a copper acetylide as an intermediate[14]. 

The main problem in this technique is getting the atoms into the vapour phase, bearing in mind the typically low volatility of many materials to be analysed. The method used is to spray, in a very fine mist, a liquid molecular sample containing the atom concerned into a high-temperature flame. Air mixed with coal gas, propane or acetylene, or nitrous oxide mixed with acetylene, produce flames in the temperature range 2100 K to 3200 K, the higher temperature being necessary for such refractory elements as Al, Si, V, Ti and Be. 

Heating butanediol with acetylene in the presence of an acidic mercuric salt gives the cycHc acetal expected from butanediol and acetaldehyde (128). A commercially important reaction is with diisocyanates to form polyurethanes (129) (see Urethane POLYMERS). 

Acetylene-Based Routes. Walter Reppe, the father of modem acetylene chemistry, discovered the reaction of nickel carbonyl with acetylene and water or alcohols to give acryUc acid or esters (75,76). This discovery led to several processes which have been in commercial use. The original Reppe reaction requires a stoichiometric ratio of nickel carbonyl to acetylene. The Rohm and Haas modified or semicatalytic process provides 60—80% of the carbon monoxide from a separate carbon monoxide feed and the remainder from nickel carbonyl (77—78). The reactions for the synthesis of ethyl acrylate are... 

Vlayl fluoride [75-02-5] (VF) (fluoroethene) is a colorless gas at ambient conditions. It was first prepared by reaction of l,l-difluoro-2-bromoethane [359-07-9] with ziac (1). Most approaches to vinyl fluoride synthesis have employed reactions of acetylene [74-86-2] with hydrogen fluoride (HF) either directly (2—5) or utilizing catalysts (3,6—10). Other routes have iavolved ethylene [74-85-1] and HF (11), pyrolysis of 1,1-difluoroethane [624-72-6] (12,13) and fluorochloroethanes (14—18), reaction of 1,1-difluoroethane with acetylene (19,20), and halogen exchange of vinyl chloride [75-01-4] with HF (21—23). Physical properties of vinyl fluoride are given ia Table 1. 

It is difficult to indicate a representative price for acetylene because it is generally produced either for captive use or on contract. The price seems to be dictated mainly by the price movement of ethylene, often a coproduct as well as an alternative feedstock competing with acetylene. That is, in 1981 when ethylene was 0.55 per kg, acetylene was 1.12 per kg and when in 1987 the price of ethylene dropped to 0.31 per kg, acetylene dropped to 0.68 per kg. 

Transition-Metal Catalyzed Cyclizations. o-Halogenated anilines and anilides can serve as indole precursors in a group of reactions which are typically cataly2ed by transition metals. Several catalysts have been developed which convert o-haloanilines or anilides to indoles by reaction with acetylenes. An early procedure involved coupling to a copper acetyUde with o-iodoaniline. A more versatile procedure involves palladium catalysis of the reaction of an o-bromo- or o-trifluoromethylsulfonyloxyanihde with a triaLkylstaimylalkyne. The reaction is conducted in two stages, first with a Pd(0) and then a Pd(II) catalyst (29). 

Carbide lime is a waste lime hydrate by-product from the generation of acetylene from calcium carbide and may occur as a wet sludge or dry powder of widely varying purity and particle size. It is gray and has the pungent odor associated with acetylene (see Hydrocarbons, acetylene). 

Other Complexes. Several other classes of organonickel complexes are known. AHyl bromide and nickel carbonyl react to give a member of the TT-aHyl system [12012-90-7], [7T-C3H3NiBr]2 (100). Tris(r -ethene)nickel [50696-82-7] reacts with acetylene and l,2-bis(diisopropylphosphino)ethane to... 

Vinyl-2-PyrroHdinone. l-Vinyl-2-pyrroHdinone (VP) (l-ethenyl-2-pyrroHdinone, A/-vinyl-2-pyrroHdone, and V-Pyrol) is manufactured by ISP in the United States and by BASF in Germany by vinylation of 2-pyrroHdinone with acetylene. It forms the basis for a significant specialty polymer and copolymer industry and consumes the primary portion of aH 2-pyrroHdinone manufactured (see Vinyl polymers, n-vinyl monomers and polymers). 

There is Htde evidence of the direct formation of sodium carbide from the elements (29,30), but sodium and graphite form lamellar intercalation compounds (16,31—33). At 500—700°C, sodium and sodium carbonate produce the carbide, Na2C2 above 700°C, free carbon is also formed (34). Sodium reacts with carbon monoxide to give sodium carbide (34), and with acetylene to give sodium acetyHde, NaHC2, and sodium carbide (disodium acetyHde), Na2C2 (see Carbides) (8). 

Copper, aluminum, and their alloys should not be used in handling vinyhdene chloride. Copper can react with acetylenic impurities to form copper acetyhdes, whereas aluminum can react with the vinyhdene chloride to form aluminum chloralkyls. Both compounds are extremely reactive and potentially ha2ardous. 

Nonicosahedral carboranes can be prepared from the icosahedral species by similar degradation procedures or by reactions between boranes such as B H q and B H with acetylenes. The degradative reactions for intermediate C2B H 2 species (n = 6-9) have been described in detail (119). The small closo-Qr Yi 2 species (n = 3-5 are obtained by the direct thermal reaction (500—600°C) of B H using acetylene in a continuous-flow system. The combined yields approach 70% and the product distribution is around 5 5 1 of 2,4-C2B3H2 [20693-69-0] to l,6-C2B Hg [20693-67-8] to 1,5-C2B3H3 [20693-66-7] (120). A similar reaction (eq. 60) employing base catalysts, such as 2 6-dimethylpyridine at ambient temperature gives nido-2 >-(Z, ... 

CH3) 2CBrCHBrCH3 + H2O (CH3) 2CHCOCH3 + 2 HBr In the presence of base, bromine reacts with acetylenes to displace a hydrogen (28). 

The largest use for calcium carbide is in the production of acetylene for oxyacetylene welding and cutting. Companies producing compressed acetylene gas are located neat user plants to minimize freight costs on the gas cylinders. Some acetylene from carbide continues to compete with acetylene from petrochemical sources on a small scale. In Canada and other countries the production of calcium cyanamide from calcium carbide continues. More recentiy calcium carbide has found increased use as a desulfurizing reagent of blast-furnace metal for the production of steel and low sulfur nodular cast iron. 

The photolysis of chlorodiazirine was investigated in several cases. From chloromethyl-diazirine (232) vinyl chloride was formed as the stable primary product of stabilization of chloromethylcarbene, with acetylene and hydrogen chloride as secondary products. Some 1,1-dichloroethane was assumed to have been formed through a linear diazo compound by reaction with HCl. Added HBr yielded 1-bromo-l-chloroethane (76MI5Q800). 

Endo 3a,4,S,6,7,7a-Hexahydro-4,7-methano-2-lndene-l-one (2). A solution ol octacaibonyidcobalt (1.0 g, 3 mmol) and bicycio [2 2.1) hepi-2-ene 1 (3.0 g, 32 mmol) in Isooctane (100 mL) was stirred first with acetylene and then under a mixture of 1.1 of acetylene and carbon monoxyde at 60-70°C until gas absorption ceased (total 1550 mL). The mixture was concentrated and the residue chromatographed on neutral alumina. Petroleum ether PhH (1 1) eluted acetylene hexacaibonyl dicobalt 70 mg, PhH CHCla (1.1) eluted a yellow oil which after distillation afforded 3 54 g of 2 (74%), bp 101-102°C (15 mm) Colorless crystals from pentane, mp32°C. 

The apparatus must be flushed with acetylene in order to remove all traces of oxygen. Acetylene dissolved in acetone is most appropriate. Acetylene obtained from tanks which contain solvents such as dimethylformamide (or other solvents) gave lower yields of carbocupration. 

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