Patent GB-646954-A (GB)
Title: Improvements in or relating to alkyl esters of alpha-cyano acrylic acid, and the preparation thereof
Filed: 1948-01-02
Abstract: Monomeric esters of alpha cyano acrylic acid obtained by reacting an alkyl cyano acetate with an alkali metal alcoholate and treating the product with a compound of the formula R-O-CH2- halogen, where R is an organic radical, are polymerized by warming to slightly above room temperature. Autopolymerization of the monomer is prevented by gaseous inhibitants of which the preferred compound is nitric oxide. In the preparation of the monomer, nitric oxide is present to inhibit polymerization in the vapour phase and sufficient dissolves to prevent polymerization at room temperature.  When polymerization is desired it is sufficient to heat the nitric oxide-containing monomer to 50 DEG  C. to obtain a smooth polymerization.  The polymer, which is a hard clear glass-like resin, may be purified by crystallization from a solvent, for example polymeric isobutyl alpha - cyano acrylate, m.p. 130-135 DEG  C., may be purified by precipitating the polymer from an ether solution with hexane.  Ethyl alpha cyano acrylate, m.p. 150-160 DEG  C., is soluble in acetone but insoluble in alcohol and ether.  The methyl compound, m.p. 200-205 DEG  C., soluble in acetone and nitroethane, insoluble in alcohol and ether.ALSO:Alkyl esters of a -cyano acrylic acid are prepared by reacting an alkyl cyano-acetate with an alkali metal alcoholate and reacting the resultant metallic derivative with a compound of the formula ROCH2X, wherein R is an organic radical having its connecting valence on a carbon atom and having all its hydrogen atoms connected to carbon atoms and X is a halogen atom, e.g. a chloromethyl ester of a monocarboxylic acid or a chloromethyl ether, and separating the resulting alkyl a -cyano acrylate from the reaction mixture. Suitable reactants of the formula ROCH2X are chloromethyl acetate, propionate benzoate and chloroacetate and the methyl-, ethyl-, propyl-and triphenylmethyl-, chloromethyl ethers.  The reaction of the alkali metal alcoholate with the alkyl cyano-acetate is preferably carried out at a temperature of 75-95 DEG  C.  The reaction between the alkali metal derivative of the alkyl cyanoacetate and the compound ROCH2X is carried out at a temperature of not more than 50 DEG  C. preferably at 35 DEG  C. or lower.  The resultant addition product decomposes readily aided by the addition of water giving the alkyl a -cyano-acrylate and a compound ROH which may, for instance, be an alcohol or a carboxylic acid according to the nature of R.  The alkyl esters of a -cyano acrylic acid are isolated by vacuum distillation.  Polymerization of the product is prevented by performing the distillation in the presence of a gaseous inhibitor, e.g. nitric oxide, and the addition of an inhibitor such as picric acid to the receiver.  In examples: (1) ethyl cyanoacetate is reacted with sodium ethoxide, the reaction mixture is added to chloromethyl acetate and the product is dilutes with water, forming ethyl-a -cyano acrylate; (2) methyl cyanoacetate and sodium methoxide are used in the process of (1) giving methyl-a -cyano acrylate; (3) isobutyl cyanoacetate and sodium isobutoxide are used in the process of (1) giving isobutyl-a -cyano acrylate; and (4) chloromethyl methyl ether is used in place of chloromethyl acetate in the process of (1), giving ethyl-a -cyano acrylate.  1 - Cyano - 1 - carbomethoxy - cyclohexene - 3 is formed by the Diels Alder reaction between methyl-a -cyano acrylate and butadiene.