Patent GB-621198-A (GB)
Title: Process of preparing vanillic acid and vanillyl alcohol condensation products from vanillin
Filed: 1945-05-01
Abstract: Vanillin dissolved in excess aqueous caustic alkali and treated with silver in a form presenting a high ratio of surface to mass yields sodium vanillate and condensation products of vanillyl alcohol.  In examples: (1) and (2) an aqueous sodium hydroxide solution of vanillin is boiled with silver prepared as in (3), filtered and the filtrate in (1) acidified with sulphur dioxide and vanillin acid and vanillyl alcohol condensation products extracted therefrom with ether and separated with sodium bicarbonate solution, and in (2) acidified with carbon dioxide and the alcoholic condensation products extracted with ether, vanillic acid remaining in solution; procedure as in (1) is preferred when unreacted vanillin is present in the filtrate since this will remain in the aqueous layer during the ether extraction; in (3) moist silver oxide obtained by treating aqueous silver nitrate solution with sodium hydroxide is reduced with vanillin in aqueous caustic soda solution to yield silver which is filtered off, the filtrate yielding on acidification with carbon dioxide vanillic acid and 4-41 - dihydroxy - 3,31 - dimethoxy - diphenylmethane, a condensation product of vanillyl alcohol.  The Specification as open to inspection under Sect. 91 states that the process may be applied to any ortho or para hydroxy, amino or substituted amino benzaldehyde, syringaldehyde being instanced, and that alkaline earth, e.g. calcium, hydroxides may be employed in place of caustic alkalies.  A further example is given in which an aqueous caustic soda solution of vanillin is drawn through a bed of silver to yield vanillic acid and vanillyl alcohol.ALSO:Vanillin dissolved in excess aqueous caustic alkali and treated with silver in a form presenting a high ratio of surface to mass yields sodium vanillate and condensation products of vanillyl alcohol.  In examples: (1) and (2) an aqueous sodium hydroxide solution of vanillin is boiled with silver prepared as in (3), filtered and the filtrate in (1) acidified with sulphur dioxide and vanillic acid and vanillyl alcohol condensation products extracted therefrom with ether and separated with sodium bicarbonate solution, and in (2) acidified with carbon dioxide and the alcoholic condensation products extracted with ether vanillic acid remaining in solution; procedure as in (1) is preferred when unreacted vanillin is present in the filtrate since this will remain in the aqueous layer during the ether extraction; in (3) moist silver oxide, obtained by treating aqueous silver nitrate solution with sodium hydroxide, is reduced with vanillin in aqueous caustic soda solution to yield silver, which is filtered off, the filtrate yielding on acidification with carbon dioxide, vanillic acid and 4,41-dihydroxy-3,31-dimethoxy - diphenylmethane, a condensation product of vanillyl alcohol.  The Specification as open to inspection under Sect. 91 states that the process may be applied to any ortho- or para-hydroxy, amino or substituted amino benzaldehyde, syringaldehyde being instanced, and that alkaline earth, e.g. calcium, hydroxides may be employed in place of caustic alkalies.  A further example is given in which an aqueous caustic soda solution of vanillin is drawn through a bed of silver to yield vanillic acid and vanillyl alcohol.