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Information of Veratraldehyde! by yang W
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Information of Veratraldehyde! |
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1. Procedure In a 3-l. three-necked flask a mixture of 182 g. (1.2 moles) of vanillin (Note 1) and 450 cc. of boiling water is heated on a steam bath. A solution of sodium hydroxide is prepared by dissolving 150 g. of u.s.p. sodium hydroxide in 200–300 cc. of water and diluting to 750 cc. A 360-cc. portion of this solution is heated to about 100° and added in one lot to the hot mixture of vanillin and water (Note 2). The flask is now fitted with a reflux condenser, mechanical stirrer, and 250-cc. separatory funnel. Heating is continued on a steam bath, and 189 g. (142 cc.) of methyl sulfate (Note 3) is added through the separatory funnel just rapidly enough to maintain the gentle ebullition which starts after the addition of the first 10–15 cc. (Note 4). After the addition of all the methyl sulfate, which requires about one hour, the reaction mixture is heated for forty-five minutes longer and an additional portion of 39 g. (30 cc.) of methyl sulfate is added at the same rate as the first portion. At the end of this addition the reaction mixture should show an acid reaction to litmus (Note 5). After ten minutes' heating the reaction mixture is rendered slightly alkaline by the addition of about 60 cc. of the sodium hydroxide solution (prepared above), and another 39-g. portion of methyl sulfate is added. The alternate addition of sodium hydroxide solution and of methyl sulfate (39-g. portions) is repeated twice more, so that a total of 345 g. (2.7 moles) of methyl sulfate is added. The reaction mixture is then made strongly alkaline by the addition of 150 cc. of the sodium hydroxide solution and is heated for twenty minutes after the last addition of methyl sulfate. The reaction mixture is cooled rapidly to 25° (Note 6) with continued stirring, and the veratraldehyde is extracted with three 300-cc. portions of ether. 2. Notes 1. A good grade of vanillin (m.p. 81–82°) should be used. 2. The reactants are mixed while hot in order to avoid precipitation of the sodium salt of vanillin. 3. A practical grade of methyl sulfate gives satisfactory results. Methyl sulfate is very toxic; the vapor must not be inhaled or the liquid spilled. Ammonia is a specific antidote. The preparation is preferably carried out under a good hood. 4. The yield is usually lowered if this ebullition does not occur. 5. In order to obtain a good yield the reaction mixture must be allowed to become acid at several times. For this reason the last 156 g. of methyl sulfate is added in four small portions, and the reaction mixture is allowed to become acid after each portion is added. It is convenient to test the reaction of the solution by lowering through the condenser tube a glass tube with a piece of litmus paper attached at the end. 6. If the reaction mixture is cooled too slowly or below 25°, the veratraldehyde may solidify at this stage. If this occurs it is advisable to remelt the product before extracting with ether. 3. Discussion Veratraldehyde has been prepared by treatment of veratrole with hydrogen cyanide in the presence of aluminum chloride;1 by condensing veratrole with formylpiperidine and hydrolyzing the product;2 and by methylating vanillin with methyl iodide,3 methyl sulfate,4 methyl p-toluenesulfonate,5 or trimethylphenylammonium hydroxide. By: yang W
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