Nickel degassed

Reppe s work also resulted in the high pressure route which was estabUshed by BASF at Ludwigshafen in 1956. In this process, acetylene, carbon monoxide, water, and a nickel catalyst react at about 200°C and 13.9 MPa (2016 psi) to give acryUc acid. Safety problems caused by handling of acetylene are alleviated by the use of tetrahydrofuran as an inert solvent. In this process, the catalyst is a mixture of nickel bromide with a cupric bromide promotor. The hquid reactor effluent is degassed and extracted. The acryUc acid is obtained by distillation of the extract and subsequendy esterified to the desked acryhc ester. The BASF process gives acryhc acid, whereas the Rohm and Haas process provides the esters dkecdy. 

Dimethoxybiphenyl can also be prepared by simply refluxing bis(4-methoxyphenyl)tellurium dichloride with degassed commercial Raney nickel. The yields are, however, lower and less reproducible, and the product may contain some bis(4-methoxyphenyl) telluride. 

The coupling reaction proceeds better when a rigorously degassed Raney nickel catalyst is used, but a nickel catalyst prepared by a much simplifled procedure (Note 9) is also effective. The coupling may also be promoted by other elements, including copper and palladium. 

In addition to the Raney nickel catalysts, Raney catalysts derived from iron, cobalt, and copper have been examined for their action on pyridine. At the boiling point of pyridine, degassed Raney iron gave only a very small yield of 2,2 -bipyridine but the activity of iron in this reaction is doubtful as the catalyst was subsequently found to contain 1.44% of nickel. Traces of 2,2 -bipyridine (detected spectroscopically) were formed from pyridine and a degassed, Raney cobalt catalyst but several Raney copper catalysts failed to produce detectable quantities of 2,2 -bipyridine following heating with pyridine. 

The Preparation of Substituted 2,2 -Bipyridines from Substituted Pyridines and Degassed Raney Nickel -i ... 

Several substituted pyridines have been examined using the degassed Raney nickel, and the results are summarized in Table I. As all the biaryls obtained formed colored chelates with either ferrous or cuprous ions, they must be derivatives of 2,2 -bipyridine. Structural ambiguities cannot arise with 2,2 -bipyridines derived from 2- and 4-substituted pyridines but 3-substituted pyridines could conceivably give three isomeric 2,2 -bipyridines (e.g., 3, 4, 5). In fact, however, each 3-substituted pyridine so far examined has given only one 2,2 -bipyridine. 

Reaction of -picoline over degassed Raney nickel was found to give 5,5 -dimethyl-2,2 -bipyridine (5), the structure of which was established by its synthesis from 2-bromo-5-methylpyridine. Oxidation of this dimethyl-2,2 -bipyridine, and similar oxidation of the diethyl-2,2 -bipyridine derived from 3-ethylpyridinc, gave the corresponding dicarboxylic acid and the same acid was produced by the action of degassed Raney nickel on sodium nicotinate (in water) or on ethyl nicotinate. These transformations established the 5,5 -substitution pattern for three 2,2 -bipyridines derived from 3-substituted pyridines but such evidence is not available for the biaryls... 

Inspection of Table I shows that the yields of 2,2 -bipyridines obtainable from a substituted pyridine in the reaction with degassed Raney nickel depend on the nature of the substituents and their positions in the ring. 

Starting material Nickel-alumina Palladium- on-carbon Degassed Raney nickeN ... 

Table II shows that, at least for the reactions with quinoline and with 4-methylquinoline (lepidine), nickel-alumina and degassed Raney nickel catalysts are of similar efficiency but better yields have been obtained with degassed Raney nickel, and only this catalyst produces the biaryl from 7-methyIquinoIine.

Most of the reactions with quinolines and degassed Raney nickels have been carried out at the atmospheric boiling point (above 230 C), a condition which is known to favor the formation of by-products. With quinoline and 4-methylquinoline (lepidine), however, the yields of the 2,2 -biquinolines were increased three to four times by heating in vacuo at 150° C, and it seems probable that other quinolines will behave similarly. Table II also shows that the yields of 2,2 -biquino-lines obtained under comparable conditions vary with the position of the methyl group in a fashion reminiscent of the trends observed with the pyridines (Table I). This similarity extends to the behavior of the two 2-methyl substituted quinolines studied, which undergo loss of the 2-methyl group to some extent and form traces of 2,2 -biquinolines. 

Sufficient data are not yet available to allow evaluation of the relative merits of palladium-on-carbon and degassed Raney nickel catalysts. Comparable yields of 2,2 -biquinolines have been obtained by both methods under suitable conditions but the percentage conversions with degassed Raney nickel have been found to be much lower, reflecting the extent of side reactions with this catalyst. However, work in this laboratory has shown that the reaction of quinoline with palladium-on-carbon is not free from complications for example, at least three products in addition to 2,2 -biquinoline have been detected by paper chromatography. 

Isoquinoline failed to react when refluxed over palladium-on-carbon, but with degassed Raney nickel it underw cnt extensive de-... 

As most of the work on this reaction has been carried out with degassed Raney nickel, it will be appropriate to summarize briefly current views concerning the nature of this catalyst. 

Several products other than 2,2 -biaryls have been isolated following reaction of pyridines with metal catalysts. From the reaction of a-picoline with nickel-alumina, Willink and Wibaut isolated three dimethylbipyridines in addition to the 6,6 -dimethyl-2,2 -bipyridine but their structures have not been elucidated. From the reaction of quinaldine with palladium-on-carbon, Rapoport and his co-workers " obtained a by-product which they regarded as l,2-di(2-quinolyl)-ethane. From the reactions of pyridines and quinolines with degassed Raney nickel several different types of by-product have been identified. The structures and modes of formation of these compounds are of interest as they lead to a better insight into the processes occurring when pyridines interact with metal catalysts. 

A. By-products from the Reaction of Pyridines with Degassed Raney Nickel... 

The crude 2,2 -bipyridine obtained from the reaction of pyridine and degassed Raney nickel was found to contain 1.5% of 2 6, 2"-terpyridine, but no 2,2 2, 2" 6 ",2 "-quaterpyridine could be detected. Moreover, experiments with 2,2 -bipyridine and Raney nickel have failed to yield quaterpyridine, and the amount of terpyridine formed in experiments with mixtures of pyridine and 2,2 -bipyridine was found to be no higher than in the reaction with pyridine itself. " ... 

The most important by-product formed in the reaction of pyridine with degassed Raney nickel is an organonickel complex which has been shown to be a complex of one molecule of 2,2 -bipyridine, two molecules of 2,2 -pyrrolylpyridine (17), and one nickel II ion. It is significant that, although the formation of 2,2 -bipyridine ceases after 50 hr refluxing, the formation of this complex continues for at least another 140 hr. 

Dimethyl-I,l -biphenyl has been prepared by a wide variety of procedures, but few of these are of any practical synthetic utility Classical radical biarjl syntheses such as the Gomberg reaction or the thermal decomposition of diaroyl peroxides give complex mixtures of products m which 4,4 dimethyl-l.l -biphenyl is a minor constituent A radical process maj also be involved in the formation of 4,4 dimethyl-1, l -biphenyl (13%) by treatment of 4-bromotoluene with hydrazine hydrate 5 4,4 -Dimethyl-l,l -biphenyl has been obtained in moderate to good yield (68-89%) by treatment of either dichlorobis(4-methyl phenyl)tellurium or l,l -tellurobis(4-methylbenzene) with degassed Raney nickel in 2 methoxyethyl ether 6... 

In the study of effects of ultrasound on the aqueous reactions of nickel, we found some interesting results, for example, the colloidal formation of Ni-DMG complex and degassing of NH3 during different experiments. When 25 ml of 0.001 M NiSC>4 solution was complexed with 5 ml of 1% dimethyl glyoxime (DMG) in faintly alkaline ammonia medium and sonicated for 30 minutes and compared with another set of 25 ml of complexed solution which was stirred mechanically, a colloidal solution of Ni-DMG complex was formed in sonicated condition. Particles of Ni-DMG complex did not settle even after keeping 3 1 h because of their smaller size, in sonicated solution, whereas in the unsonicated condition large particles of Ni-DMG complex settled down immediately. 

Ultrasound accelerated the degassing phenomenon and removed NH3 from the solution, therefore nickel remained in its hydrolysed form only. 

Into a Schlenk tube was placed Auf 1,5-cyclooctadiene)-nickeI(0) (2.6 mmol), 2,2 -bipyridyl (2.6mmol), 1,5-cyclooctadiene (0.2ml), DMF (4ml), and toluene (8 ml). The reaction mixture was heated to 80°C for 0.5 h under argon. The dibromide comonomers 623 and 634 dissolved in degassed toluene (8 ml molar ratio of dibromides to nickel complex 0.65) were added under argon to the DMF-toluene solution and the polymerization maintained at 80°C for 3 days in the dark. 2-Bromofluorene (molar ratio of dibromides to monobromide 0.1) dissolved in degassed toluene (1ml) was added and the reaction continued for 12 h. The polymers were precipitated by addition of the hot solution dropwise to an equivolume mixture of concentrated HC1, methanol, and acetone. The isolated polymers were then dissolved in toluene or dichlor-omethane and reprecipitated with methanol/acetone (1 1). The copolymers were dried at 80°C in vacuo. The isolated yields of copolymers 240a-c were 79-85%. 

Fig. 9. Sorption isotherms on reduced nickel catalyst plotted from the data of Maxted and Hassid. (Catalyst was degassed at 250°C. before making measurements.) Hj adsorption at 10 3 ram. when catalyst was contacted with Hj at — 190°C. and then evacuated prior to raising the temperature.

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