Hydrogenation acetylene derivatives

Semi-synthetic enzymes are produced by the reconstitution of apo-proteins with artificial active sites that yield novel catalytic functions [237]. For example, reconstitution of apo-myoglobin with Co(II)-protoporphyrin IX results in a novel biocatalyst that is capable of hydrogenating acetylene derivatives or evolving hydrogen [209, 238]. By the modification of the reconstitution of apo-proteins with artificial redox-active cofactors and the covalent attachment of photosensitizer units, photo-... 

Preferential dechlorination of polyhalides with replacement of chlorine by hydrogen Acetylene derivatives... 

Much more important is the hydrogenation product of butynediol, 1,4-butanediol [110-63-4]. The intermediate 2-butene-l,4-diol is also commercially available but has found few uses. 1,4-Butanediol, however, is used widely in polyurethanes and is of increasing interest for the preparation of thermoplastic polyesters, especially the terephthalate. Butanediol is also used as the starting material for a further series of chemicals including tetrahydrofuran, y-butyrolactone, 2-pyrrohdinone, A/-methylpyrrohdinone, and A/-vinylpyrrohdinone (see Acetylene-DERIVED chemicals). The 1,4-butanediol market essentially represents the only growing demand for acetylene as a feedstock. This demand is reported (34) as growing from 54,000 metric tons of acetylene in 1989 to a projected level of 88,000 metric tons in 1994. 

Diol Components. Ethylene glycol (ethane 1,2-diol) is made from ethylene by direct air oxidation to ethylene oxide and ring opening with water to give 1,2-diol (40) (see Glycols). Butane-1,4-diol is stiU made by the Reppe process acetylene reacts with formaldehyde in the presence of catalyst to give 2-butyne-l,4-diol which is hydrogenated to butanediol (see Acetylene-DERIVED chemicals). The ethynylation step depends on a special cuprous... 

Acetjiene has found use as a feedstock for production of chlorinated solvents by reaction with hydrogen chloride or chlorine (6). However, because of safety concerns and the lower price of other feedstock hydrocarbons, very Htfle acetylene is used to produce chlorinated hydrocarbons in the United States (see Acetylene-derived chemicals). 

Hydrogen cyanide adds to an olefinic double bond most readily when an adjacent activating group is present in the molecule, eg, carbonyl or cyano groups. In these cases, a Michael addition proceeds readily under basic catalysis, as with acrylonitrile (qv) to yield succinonitnle [110-61-2], C4H4N2, iu high yield (13). Formation of acrylonitrile by addition across the acetylenic bond can be accompHshed under catalytic conditions (see Acetylene-DERIVED chemicals). 

This observation may well explain the considerable difference between metal-olefin and metal-acetylene chemistry observed for the trinuclear metal carbonyl compounds of this group. As with iron, ruthenium and osmium have an extensive and rich chemistry, with acetylenic complexes involving in many instances polymerization reactions, and, as noted above for both ruthenium and osmium trinuclear carbonyl derivatives, olefin addition normally occurs with interaction at one olefin center. The main metal-ligand framework is often the same for both acetylene and olefin adducts, and differs in that, for the olefin complexes, two metal-hydrogen bonds are formed by transfer of hydrogen from the olefin. The steric requirements of these two edgebridging hydrogen atoms appear to be considerable and may reduce the tendency for the addition of the second olefin molecule to the metal cluster unit and hence restrict the equivalent chemistry to that observed for the acetylene derivatives. 

A further piece of evidence to elucidate the catalytic pathway of silylformylation was provided by a pair of deuterium-labeled reactions. The results revealed that the scrambling of hydrogen atoms between a hydrosilane and a terminal acetylene is minimal during the reaction and that the hydrogen atom of the formyl group and the vinylic hydrogen are derived from the hydrosilane and the acetylenic proton, respectively (Eq. 8) [15 bj. 

All the above-mentioned initiators are very sensitive towards substances with active hydrogen. Care must therefore be taken to exclude acids, water, thiols, amines, and acetylene derivatives. Oxygen, carbon dioxide, carbon monoxide, carbonyl compounds, and alkyl halides which can react with the initiator, also interfere with the reaction. Careful purification and drying of the starting materials and apparatus is, therefore, absolutely essential, especially when dealing with living polymers (see Example 3-19). 

The system A -bromoacetamide-hydrogen fluoride adds bromine monofluoride to acetylene derivatives.32 Hex-1-yne. hex-3-yne, 1.4-dichlorobut-2-yne, and phenylacetylene give the corresponding bromofiuoroalkenes, in no case is the addition of a second molecule of bromine monofluoride observed. Hex-1 -yne (3) produces 95% of the (E)- and 5% of the (Z)-isomcr 4. 

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. 

The greater stability of the digonal vinyl cation 161 than of the bridged cation 162 would imply that, at least in the gas phase, race-mization is involved as stereochemical course of any reaction with nucleophiles since both lobes of the empty p-orbital of 161 are available for a nucleophilic attack. Efforts to rationalize (Bumelle, 1964) early reports of stereospecific trans addition to acetylene derivatives have recently been complemented by a theoretical calculation of the energy profile for addition of hydrogen fluoride to acetylene in the gas phase (Hopkinson et at., 1971). The results of these calculations suggest that the bridged cation is possibly a transition state and not an intermediate. 

Linnett o gives a discussion of the use of valence force fieid with the addition ol selected cross terms. One method of reducing the number of constants to Tdc determined from the frequencies is to carry over from molecule to molecule certain force constants for squared terms and even for cross terms. Linnett mentions in this connection the work of Crawford and Brinkley who studied acetylene, ethane, methylacetylene, dimethylacetylene, hydrogen cyanide, methyl cyanide and the methyl halides in this way, and were able, for all the molecules, to account for 84 frequencies with 31 constants. Linnetttreated some of these compounds using a different force field. He was able to account satisfactorily for 25 frequencies using 11 force constants. From our point of view the trouble with these results is that Linnett obtained a value for the C - C force constant in these acetylene derivatives which was different from that obtained by Crawford and Brinkley. For C - C in methyl cyanide for example, Linnett obtained... 

Figure 42. The preparation of a photoenzyme by the reconstitution of a heme protein with Co(II)-protoporphyrin IX and the chemical modification of the protein backbone with a tethered chro-mophore. Hydrogen evolution and hydrogenation of acetylene derivatives photobiocatalyzed by the assembly.

Treatment of 75 with lithium acetylide ethylenediamine complex afforded the acetylene derivative 78 (85%), which was transformed into the vinyl alcohol 79 by partial hydrogenation using Lindlar catalyst. Employing the Mitsunobu reaction, compound 79 was transformed into the phthalimide 80, which was converted into the benzamide 82 (64%) via the primary amine 81 by sequential deacylation and benzoylation. When the... 

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