Patent GB-585109-A (GB)
Title: Improvement in process for reacting ketene and hydrocyanic acid
Filed: 1945-01-17
Abstract: 1-Cyanovinyl acetate and dimolecular acetyl cyanide (1,1-dicyanoethyl acetate) are prepared by condensing ketene and anhydrous hydrocyanic acid, preferably in the proportions of from 2 to 3 mols. of the former per mol. of the latter, at a temperature within the range between about -50 DEG  C. and about 30 DEG  C. in the presence of a basic condensation catalyst which under the conditions of the condensation does not substantially react with ketene to form non-basic reaction products and which, desirably, is soluble in the reaction mixture; preferably, an anhydrous volatile organic solvent is present.  The use of the higher temperatures, for example 10 DEG to 30 DEG  C., favours formation of the acetyl cyanide dimer.  As basic catalysts there are specified tertiary aliphatic and aromatic amines; the quaternary ammonium bases; the alkali metal hydroxides, alkoxides, aryloxides, amides and cyanides; alkali metal alcoholates; and the alkali metal salts of organic and weak inorganic acids. Examples of such catalysts are triethylamine, triethanolamine, triisopropanolamine, pyridine, tetraethanolammonium hydroxide, trimethyl benzyl ammonium hydroxide, tetraethylammonium hydroxide, sodium and potassium hydroxides, sodium methylate, potassium ethylate, sodium alcoholates derived from hexanol, octanol and glycol mono-ethers, sodium phenate, sodium and potassium naphtholate, sodamide, potassium cyanide, sodium acetate, sodium carbonate, potassium borate, sodium silicate and N-substituted morpholines such as N-2-cyanoethyl morpholine. Suitable solvents are those inert to the reactants and catalyst, but solvents containing active groups may be used.  Such solvents are carboxylic acid anhydrides such as acetic anhydride, aliphatic ethers such as diethyl ether and dioxane, esters of carboxylic acids such as methyl acetate, ethyl acetate and 1-cyanovinyl acetate itself, ketones such as acetone, and mixtures of one or more of these with acetic anhydride; an excess of the hydrocyanic acid may also be used.  The condensation may be effected by slowly introducing a stream of ketene vapours into an agitated liquid body of the hydrocyanic acid and catalyst which are preferably in solution in a volatile anhydrous organic liquid; if desired, the ketene may be added in successive portions. Advantageously, the ketene and hydrocyanic acid may be introduced concurrently into a solution of the catalyst in the solvent.  The products are isolated by distillation under reduced pressure.  By neutralizing the reaction mixture with, for example, acetic or sulphuric acid prior to distillation thereof, an increased yield of dimolecular acetyl cyanide is obtained at the expense of the cyanovinyl acetate. 1-Cyanovinyl acetate may be used in copolymerization with other unsaturated organic compounds. Examples are given illustrating the above modifications, the following being typical: (1) ketene is slowly introduced into anhydrous hydrocyanic acid containing pyridine as catalyst at -20 DEG  C. and cyanovinyl acetate and dimolecular acetyl cyanide isolated by distillation under reduced pressure; (2) ketene is reacted with an anhydrous mixture of hydrocyanic acid, triethylamine and diethyl ether and the products recovered as in (1); (3) a reaction mixture obtained as in (2) above is neutralized with glacial acetic acid and distilled under reduced pressure yielding mainly acetyl cyanide dimer and some cyanovinyl acetate; (5) ketene and anhydrous hydrocyanic acid are added concurrently to acetic anhydride containing triethanolamine at 0 DEG  C. and the reaction mixture worked up yielding mainly cyanovinyl acetate with some acetyl cyanide dimer.