Patent GB-567914-A (GB)
Title: Manufacture of esters from acetylene
IPC: C07C69/145
Filed: 1943-05-14
Abstract: Vinyl and ethylidene esters of aliphatic carboxylic acids are produced by a process which comprises reacting acetylene with the aliphatic carboxylic acid in the presence of a mercury catalyst and a quaternary onium compound as hereinafter defined. Preferably, methane trisulphonic acid is also present in the reaction mixture.  Only small quantities of the quaternary onium compound are required, the useful range of concentration being between about 0.001 and 0.02 mol. per litre, and preferably between about 0.002 and 0.01 mol. per litre of reaction mixture. The quaternary onion compounds are defined as those compounds of nitrogen, phosphorus, arsenic and antimony, wherein four valencies are satified by carbon and the fifth valency by an anion. Specific compounds falling within this definition are the tetra-alkyl ammonium salts such as tetraethyl ammonium acetate, tetrapropyl ammonium sulphate, triamyl ethyl ammonium acetate, triamyl methyl ammonium sulphate, trimethyl cyclohexyl ammonium acetate, and triethyl cyclohexyl ammonium sulphate; the trialkyl monoaryl ammonium salts such as trimethyl phenyl ammonium acetate and triethyl phenyl ammonium sulphate; the trialkyl monoaralkyl ammonium salts, such as trimethyl benzyl-ammonium acetate, triethyl benzyl-ammonium acetate, and triamyl benzyl ammonium acetate; the alkyl pyridinium salts such as ethyl pyridinium acetate; the alkoxy alkyl trialkyl ammonium salts; the alkoxyalkyl dialkyl monoaryl ammonium salts; the betaines; the quaternary morpholinium and piperidinium compounds; the quaternary phosphonium compounds such as tetramethyl phosphonium acetate, tetra ethyl phosphonium acetate; and the quaternary arsonium compounds such as tetraethyl arsonium acetate.  The quaternary onium compounds may be in the form of a salt such as the acetate, propionate, butyrate, sulphate, methane trisulphonate, &c., or may be added to the reaction in the form of the hydroxide. Instead of the pure compound, the crude product or solution containing the desired compound may be used.  It is desirable to use quaternary onium compounds containing one aromatic group, since the presence of an aromatic group decreases the toxicity of the compound to the mercury catalyst.  As a rule, the quaternary ammonium compounds are most toxic, the quaternary phosphonium compounds less toxic, and the quaternary arsonium compounds still less toxic.  Preferably, compounds are used containing 5 to 18 carbon atoms and particularly salts or hydroxides containing as cations trimethyl phenyl ammonium-, dimethyl ethyl phenyl, ammonium-, methyl diethyl phenyl ammonium-and triethyl phenyl ammonium-.  The alkyl or aryl group may be substituted, the substituent atom or group being hydroxyl, halogen, carboxyl or p  nitrile.  Examples describe the preparation of vinyl and ethylidene acetates by the reaction of acetylene and acetic acid using as the quaternary onium compounds: trimethyl phenyl ammonium sulphate and ethyl pyridinium acetate. Reference is made to Specification 567,879, which describes and claims the use of the above quaternary compounds as stabilizers against polymerization of vinyl esters.