Patent GB-738888-A (GB)
Title: Improvements in the production of oximes
Filed: 1953-06-21
Abstract: Oximes are produced by a process which consists in introducing aqueous solutions of about equivalent amounts of secondary aliphatic or cycloaliphatic aci-nitro compounds or their salts p  and of thiosulphates simultaneously into excess aqueous acid. Suitable nitro compounds are e.g. 2-nitropropane, nitrocyclohexane, nitrocyclopentane, methylated nitrocyclohexanes, the secondary nitrobutanes and -hexanes and they are preferably used in the forms of their alkali metal-, alkaline earth metal or ammonium salts or in the free aci-forms. The solutions of the salts may be stirred, either after previous mixing or simultaneously but separately into dilute acids, e.g. sulphuric, phosphoric, hydrochloric or paratoluene sulphonic acid and inert organic solvents may be used.  A reaction mixture obtained from compounds which yield thiosulphates in known manner may be used instead of pure thiosulphates, e.g. mixtures of water-soluble sulphites and sulphur, sulphides and sulphur dioxide, sulphides and polythionates or of polythionates and alkalies.  The formation of the thiosulphate may take place before mixing with the aci-nitro-compounds and their salts or in the presence of the aci-nitro compound salts.  Thiosulphates may be regenerated after removal of the oximes from the reacted mixture by known methods for converting polythionic acids or their salts to thiosulphates, e.g. the mother liquor may be reduced with alkali metal sulphides or amalgams, e.g. as obtained by the electrolysis of alkali metal chlorides, or the mother liquors may be boiled with alkali carbonates or alkaline earth hydroxides or merely heated to obtain sulphur dioxide and sulphur which may be employed in the preparation of thiosulphate by the usual methods. In examples cyclohexanone oxime is obtained in processes in which nitrocyclohexane is dissolved in caustic soda solution and the solution allowed to flow with aqueous sodium thiosulphate into dilute sulphur acid (1); sodium sulphite, sulphur powder and water are mixed with nitrocyclohexane dissolved in caustic soda solution and when the sulphur has dissolved the mixture is allowed to flow into dilute sulphuric acid (2); the sodium thiosulphate in a process similar to (1) is prepared by mixing sodium sulphide solution with potassium tetrathionate suspension (3); the thiosulphate is obtained by boiling potassium tetrathionate with sodium carbonate (4); aqueous sodium thiosulphate is added to a solution of nitrocyclohexane in caustic soda solution and the mixture added to dilute sulphuric acid, the mixture is neutralized with alkali carbonate, the oxime is filtered off and the filtrate is treated with sodium sulphide to regenerate the thiosulphate which is employed in treating further nitrocyclohexane in caustic soda solution (5); in a similar process the thiosulphate is regenerated by boiling the filtrate with calcium hydroxide or calcium hydroxide (6) in a similar process the cyclohexanone oxime is filtered off, the filtrate is distilled with lime to obtain cyclohexanone and the thiosulphate is regenerated by boiling the residue with sodium sulphide and sulphur (7); a mixture of nitrocyclohexane dissolved in caustic soda solution, aqueous sodium thiosulphate and dilute sulphuric acid is passed through a cooled stainless steel coil and the reaction product is neutralized (8); acetone oxime is obtained by mixing aqueous sodium thiosulphate solution with 2-nitropropane dissolved in caustic soda solution adding dilute sulphuric acid to the mixture, neutralizing the mixture with sodium carbonate and extracting the oxime with ether (9); in a similar process 2-nitropropane dissolved in calcium hydroxide aqueous solution is mixed with aqueous calcium thiosulphate and added to dilute hydrochloric acid (10); diethyl ketone oxime is obtained by adding a mixture of 3-nitropropane dissolved in caustic soda solution with aqueous sodium thiosulphate to dilute sulphuric acid (11); cyclopentanone oxime is obtained by adding a solution of nitrocyclopentane in aqueous ammonia mixed with aqueous ammonium thiosulphate to a mixture of ice and sulphuric acid (12); and 1-methylcyclohexanone-(3) oxime is obtained by mixing a solution of 1-methyl-3-nitrocyclohexane in aqueous caustic soda solution with aqueous sodium thiosulphate and adding the mixture to dilute sulphuric acid (13).  Specification 716,099 is referred to.