Vanillin-potassium hydroxide

Aromatic aldehydes react in basic as well acidic medium. Thus vanillin and primary amines yield Schiff s bases (cf. vanillin-potassium hydroxide reagent in Volume 1 a). Colored phenolates are formed at the same time. As would be expected secondary amines, indole derivatives and lysergic acid derivatives do not react. 

Vanillin-potassium hydroxide Dehydroascorbic acid (0.1% in 95% n-butanol)... 

Vanillin-potassium hydroxide A 2% solution of vanillin in n-propanol is sprayed on the plate, which is heated (100°C, 10 min) and sprayed again with 1% ethanolic potassium hydroxide. Reheating yields a variety of colors observed under daylight. 

Vanillin-Phosphoric Acid and Vanillin-Potassium Hydroxide... 

In 1874, Tiemann and Ha arm ann examined the stmcture of vanillin and reported it to be 3-methoxy-4-hydroxybenzaldehyde. This was not a difficult task because, on treatment with potassium hydroxide, vanillin (1) gave protocatechaic acid [99-50-3] (2), which, in turn, was decarboxylated to catechol [120-80-9] (3) by dry distillation (eq. 1). As both compounds were known at that time, the position of the substituent groups in vanillin was estabHshed. Finally, Reimer synthesized vanillin from guaiacol [90-05-1] and thus proved the identity of its stmcture. In 1894 RhcJ)ne-Poulenc began producing vanillin on an industrial scale. Since then, many other producers have entered into vanillin production, often only to leave it behind. 

Fusion with Alkali Alone. Alkali lignin was first fused with potassium hydroxide at 180°-190°C. under standard conditions used previously for converting vanillin to vanillic acid (10) and syringaldehyde to syringic acid (14). Under these conditions, protocatechuic and vanillic acids were the chief oxidation products, but over 70% of the lignin was recovered as a lignin-like polymeric product. Longer fusion times helped... 

A product of sufficient pinity for most synthetic purposes may be prepared rapidly and conveniently by the method of Barger and Silberschmidt, J. Chem. Soc. 133,2924 (1928). In a i-l. three-necked, round-bottomed flask (or a wide-mouthed bottle) fitted with a mechanical stirrer, a reflux condenser, and two separatory fuimels, 152 g. (i mole) of vanillin is melted by warming on a steam bath. With vigorous stirring, a solution of 92 g. (1.5 moles) of 90 per cent potassium hydroxide in 150 cc. of svater is run in at the rate of two or three drops a second twenty seconds after this is started, the addition of 160 g. (120 cc., 1.25 moles) of dimethyl sulfate is begun at about the same rate. Just before use, the dimethyl sulfate is washed with an equal volume of ice water, followed by one-third its volume of cold, saturated... 

The conversion of eugenole into iso-eugenole and of safrole into iso-safrole is accomplished by boiling with alcoholic potassium hydroxide. The oxidation products of these ethers are other important essential oil constituents. Eugenole yields the corresponing aldehyde which is known as vanillin, the chief constituent of vanilla beans from which vanilla extract is made. Safrole by oxidation yields a compound known as piperonal also as heliotropine. It has the odor of heliotrope flowers and is used as artificial heliotrope essence. These latter compounds and also constituents of other essential oils will be considered in detail later in their proper chemical relationship (p. 66i, etc.). 

In a stainless-steel beaker of approximately 3-1. volume (180 mm. by ISO mm.) (Note 1), equipped with an efficient mechanical stainless-steel stirrer and heated by an electric hot plate, are placed 84 g. (2 moles) of 97% sodium hydroxide pellets, 332 g. (5 moles) of 85% potassium hydroxide pellets (Note 2), and SO ml. of water. The mixture is stirred and heated. When the temperature of the fluid mixture reaches 160°, 152 g. (1 mole) of vanillin is added in portions over a period of 2.5-3 minutes at a rate sufficient to maintain the reaction (Note 3). The temperature at this point is 190-195°. Stirring is continued and heat is applied until the temperature reaches 240- 245° (Note 4). The temperature is maintained at 240-245° for 5 minutes. The hot plate is removed, and the mixture is allowed to cool with stirring. When the mixture has cooled to about 150-160°, 1 1. of water is added, and the mixture is stirred until all the fusion mixture is dissolved. The solution is transferred to a 4-1. beaker, another 500 ml. of water is added, and sulfur dioxide gas is introduced for 2 minutes (Note 5) the mixture is Ihen completely acidified... 

The two major tests up until very recently have been the Beam and Duquenois tests. In the Beam test, cannabis is mixed with alcohol and potassium hydroxide. If a purple color develops, cannabis is presumed present. The Beam test, however, is more sensitive to some cannabinoids (e.g., cannabidiol and cannabigerol) than others, and the mixture will not turn purple if these cannabinoids are missing. The Duquenois test involves mixing the unknown substance with vanillin, acetaldehyde, alcohol, and hydrochloric acid. If a violet color develops, the test substance is presumed to be cannabis. Although the Duquenois test is more sensitive than the Beam test, it is not as specific - a violet color will also develop in the presence of other substances, e.g., coffee. 

When eugenol. is boiled with an alcoholic solution of potassium hydroxide, it is converted into isoeugenol both compounds yield vanillin on oxidation with potassium permanganate —... 

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