COMMUNICATIONS
Catalyzed Hydration of Nitriles to Amides A simple, convenient, and inexpensive general process for the hydration of nitriles to amides under the influence of a manganese dioxide catalyst i s described. The reaction can b e conducted in a simple fixed-bed continuous reactor a t moderate temperatures with reaction times of a few hours. An aqueous solution or suspension of the nitrile is employed. In most instances essentially quantitative yields of amide are obtained with complete freedom from coproducts or side reactions. The catalyst i s commercially available and has a long useful life.
T h e extensive development of ammoxidation processes, together with new applications of hydrogen cyanide technology, has made a large variety of nitriles actually or potentially available in recent years. The traditional methods for converting nitriles to amides, on the other hand, have not been as fully exploited because they are sensitive and as a result, relatively expensive to adapt to a commercial scale. Hydration by use of dilute acid or alkali, for example, requires careful control of reaction time, temperature, and concentration to minimize over hydrolysis. The use of sulfuric acid monohydrate affords high yields in many instances, but the ensuing amide sulfate must be neutralized carefully with ammonia or lime. Alkaline hydrogen peroxide, often a useful laboratory reagent, is prohibitively hazardous on a commercial scale because of the molar quantities of molecular oxygen evolved. A new and potentially useful synthesis for amides became available a few years ago when we obtained a patent (Haefele, 1968) on the manganese dioxide catalyzed hydration of nitriles. Shortly after our application was filed, another group (Cook et al., 1966) published the results of essentially identical findings in their laboratory. From the early stages of our investigation, the reaction had the potential for becoming a valuable commercial process. As exemplified by this M ork, it is a simple, generally applicable catalytic process which can be conducted under mild conditions with a minimum of hazards, affording high yields of amides free from coproducts or side reactions. Experimental
The manganese dioxide catalyst was obtained from the
E. J. Lavino Co. and was designated as Lavinore C. The nitriles were purchased from usual sources and generally were reagent grade or the equivalent. Apparatus and General Procedure. T h e apparatus consisted of a jacketed glass tube, 2 X 100 em, fed (upflow) b y a n FhII lab pump from a reservoir. T h e outlet of t h e reactor led by way of a siphon break t o a n appropriate receiver. T h e apparatus was charged with 500 grams of '/pin. extruded pellets of Larinore C catalyst. An aqueous solution of the nit rile, generally a t a coiicentration of lJ1, was passed through the catalyst bed maintained a t the appropriate temperature by circulating hot water or steam on the jacket of the reactor. For nitriles with limited solubility in water, a modification of the procedure was employed where 364
Ind. Eng. Chem. Prod. Res. Develop., Vol. 1 1 , No. 3, 1972
the nitrile-water mixture was emulsified with the aid of a n inert wetting agent such as Triton X-200. The effluent from tlie reactor mas collected, analyzed for unreacted nitrile and when possible for amide by a gas-chromatographic method, and then evaporated to dryness to obtain the product, typically as a white, crystalline material of good purity. If any unchanged nitrile was present, it usually codistilled with the water and could be recovered and recycled. Materials balance studies showed that the yields were essentially quantitative. The liquid flow rate could be adjusted to optimize the conversion. I n the absence of complicating factors, the reaction followed approximate zero-order kinetics so that a simple extrapolation could be used to estimate a contact time a t 100% conversion. The reaction parameters and results for a variety of nitriles are summarized in Table I. Results and Discussion
A new general process for the hydration of nitriles to amides under the influence of a manganese dioxide catalyst is described. Laboratory work indicates that the reaction can be conducted in a simple fixed-bed continuous reactor. The yields are essentially quantitative, the process being free from coproducts or side reactions. The commercial catalyst used in this work is readily available in quantity a t a reasonable cost. We have prepared numerous samples of catalyst in our laboratory, and the active materials all fall in the category of hydrated, activated manganese dioxide (Evans, 1959; bfeth-Cohn and Suschityky, 1969). Studies of catalyst life indicate t'hat in the absence of complicating factors, the catalyst maintains its activity indefinitely. The process is applicable over a broad range of nitrile concentrations. We have operated with nitrile concentration as high as 30% and below 3% \Tith no anomalous results. Ordinarily, the upper concentration limit would be est'ablished by t,he mater solubility of the substrate. However, the use of the variation described which employs a n aqueous suspension of the nitrile extends this limit somewhat'. I n some instances it might also be advantageous to use a solubilizing solvent, such as dioxane, t-butyl alcohol, or pyridine t,o maintain a homogeneous solution. Moderate temperatures may ordinarily be employed for the process. As anticipated the reaction rate increases with increasing temperature. For any but the most active nitriles,
Table 1. Reaction Parameters and Results for Manganese Dioxide Catalyzed Hydration of Nitriles to Amides Contact time, hr Nitrile
Concn
Temp, OC
Conversion,a
%
Obsd
Extrapolatedb
1Ilf 1.45 Acetonitrile 70 63 2.3 Propionitrile 2.25 1-Jf 73 70 3.1 0 5M n-Butyronitrile 83 70 3.00 3.6 n-Butyronitrile' 70 2.75 1*lf 4.1 67 71 Isobutyronitrile 75 2.75 0 5211 3.9 Succinonitrile 100 0 5v 0.50 100 0.5 59 -1diponitrile 0.75 1.3 0 5-lf 100 4.4 .Icrylonitriled 65 2.83 1Jf 70 Benzonitrile' 0.41 1Jf 85 20 2.1 lJi 0.51 3-C yanop yridinee 100 0.5 85 2.67 60 4.5 25 lcetone cyanohydriii 1Jf Yields for the compounds in this table are essentially quantitat,ive. Contact times are extrapolated to 1007, conversion. c Aqueous feed solution ivas emulsified with the aid of 0.045 Triton X-200. A polymerization inhibitor was added to the feed solution. e In a catalyst exhaustion study there was no significant loss in catalyst activity after more than 60 grams of productjgram of catalyst had been formed.
temperatures above n,bout 50°C are generally necessary for practical purposes. &ktat,mospheric pressure the boiling point of the nitrile-water inisture imposes the upper temperature limit. The reaction rnay be conducted under pressure to increase reaction temperature and therefore rate, but the additional difficulty does not seem to warrant such operation. The reactioii time (contact time) will vary somewhat depending upon the reactivity of the nitrile. 21s indicated in Table I, typical contact times fall in the range of less than one t o a few hours. In general, the order of reactivity is approsiniately cyanopyridines > aromatic nitriles > aliphatic nitriles > vinyl cyanides. Various electronic and steric factors, although they have not been thoroughly investigated, undoubtedly come irit,o play. Acknowledgment
The authors wish to thank E. T. Smith and H. E. Moser for technical assistance.
Literature Cited
Cook, J. J., Forbes, E. J., Khan, G. M., Chem. Commun., 121-2 (1966). Evans, 11. >I., Quart. Rev., 13, 61-70 (1959). Haefele, L. R. (to R. J. Reynolds Tobacco C O . ) , U.S. Patent 3,366,639 (January 30, 1968). 3Ieth-Cohn, O., Siischityky, H., Chem.Ind., 443-50 (1969). LOUIS R. H h E F E L E l HARVEY J. YOUNG
Research Department
R. J . Reynolds Industries, Inc. J6'inston-Salem, N C 271 02 Present address, 1732 Meadowbrook Drive, Winston-Salem, NC 27104. To whom correspondence should be addressed. RECEIVED for review November 12, 1971 ACCEPTEDMay 30, 1972
Preparation and Wetting Characteristics of Some Poly(F1uorinated Aromatic Glycidyl Ethers) Some fluorine-substituted aromatic glycidyl ethers were homopolymerized b y means of a triethylaluminumwater catalyst. Films of these polymers cast from m-xylenehexafluoride solution were clear and approached Teflon in their low critical surface tensions of wetting. The desirable wettability characteristics, however, were obtained with a modest amount of fluorine substitution.
T h e r e has been much interest in recent years in the polymerization of el)o.;ides by orgaiionietallic catalysts. Vandenberg (1969) has made a n extensive study of the syntheses, stereochemistry, structure, and polymerization mechanisms. Price and Brecker (1969). L-eshima et al. (1966), and Kuntz and Kroll (1970) have likewise contributed substantially to the area. catalyst systern of triethylaluminum and water (TEXHzO) has proved to be particularly potent for high-molecular-
weight polymerizations which often yield stereoregular polymers of the polyether type. Pittman et al. (1970) have recently prepared some fluoroepoxy polymers by use of Lewis acid catalysts and studied t h e wetting characteristics of films of these materials. I n addition, Pittman et al. (1968) and Elmer e t al. (1968) have described some fluorinated aliphatic glycidyl ethers in the patent literature. Ind. Eng. Chem. Prod. Res. Develop., Vol. 11, No. 3, 1972
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