Vanillin-HCl

Most pyrogallol derivatives did not precipitate either (Table III). A small precipitation occurred with pyrogallol (which may be considered as a hydroxyresorcinol) and it reacts with vanillin/HCl also (7). However, any additional substitution eliminates this reactivity, e.g., gallic acid (Table IV). Purpurogallin did precipitate with formaldehyde. It is not very soluble in the reaction mixture, and it is a tropolone. Structures of this type might interfere, but in tea and probably in wine the known tropolone derivatives are flavonoids (I, 25). 

Vanillin-HCl is prepared by making a 0.05% (w/v) solution in 50% ethanol. This is then mixed in a 2 5 ratio with concentrated HC1. The mix is applied to the specimen for 1 min. Alternatively, the sample is immersed in... 

Although several qualification and quantitation methods for tannins have been developed, only a few are specific towards hydrolyzable or condensed tannins. Among colorimetric methods, the Folin-Denis or Folin Ciocalteu reagents (for total phenolics), and vanillin-HCl and w-BuOH-HCl methods are widely used for quantification of condensed tannins [80]. 

Prisms from EtOH. M.p. 118-19°. Cherry-red col. with vanillin HCl. 

Gunzherg s reagent (detection of HCl in gastric juice) dissolve 4 g of phloroglucinol and 2 g of vanillin in 100 mL of absolute alcohol use only a freshly prepared solution. 

Purified by recrystn from aqueous MeOH. It is estimated colorimetrically with H3PO4 in EtOH followed by vanillin and HCl [Hayward and Seymour i4/w/ Chem 20 572 1948]. The 3,5-dinitrobenzoyl derivative has m 92-93°. [J Am Chem Soc 83 3114 7967.]... 

The catalytically active cationic complex is preformed by reaction of complex 12 with the strong acid HCIO4 the phenolic oxygen is protonated and the coordinative bond of the bidentate vanillin ligand to platinum is cleaved at this end. In contrast to the treatment of 12 with HCl, which gives an inactive chloro-platinum complex, the non-coordinating anion [0104] leaves a vacant coordination site on the central metal, thus rendering it catalytically active. 

Beam test. One of the easiest of these is the Duquenois test. Prepare an extract as above and evaporate it to dryness. Add four drops Duquenois reagent (0.4 g vanillin, five drops acetaldehyde in 20 ml 95% ethanol), then eight drops concentrated HCl, mix and let stand ten minutes. The violet color can be compared against standards of known THC content as above. If the color is too intense, use less sample or less extract and vice versa. 

The plate is sprayed with 5 ml of 1% etlianoHc vanillin solution, followed by 3 ml concentrated HCl, then evaluated in vis. Colours are intensified by heating for 5 min at 100 C. 

One-tenth gram powdered grass, 5ml petroleum ether grind in mortar and let soak fifteen minutes. Filter and add 1ml of the petroleum ether carefully to 2 ml 15% HCl in absolute ethanol. Red color at boundary of two layers indicates THC. After shaking, the upper layer is colorless and the lower orange-pink which turns colorless after addition of 1 ml of water. Alternatively, evaporate the petroleum ether, add 2 ml Duquenois reagent (12 drops acetaldehyde, 1 g vanillin, 50 ml ethanol), 2 ml HCl and stir. Let stand 10 minutes and add 2 ml chloroform shake and let separate. A purple chloroform layer indicates THC. 

Vanillin allowed to react with equimolar amount of aminoacetal in abs. ethanol, hydrogenated with PtOg, filtered, coned, in vacuo, taken up in 6 iV HCl, extracted with ether, allowed to stand overnight, and hydrogenated with 5%-palladium-on-carbon 6-hydroxy-7-methoxy-l,2,3,4-tetrahydroisoquinoline. Y 71%. — This new synthesis is simple and relatively trouble-free. F. e. s. J. M. Bobbitt, K. L. Khanna, and J. M. Kiely, Ghem. Ind. 1964, 1950 J. Org. Chem. 50,2247 (1965). 

The presence of proanthocyanidins in plant tissue may be readily detected by hydrolysis with hot alcoholic acid (108) to produce the anthocyanidin pigment (e.g. cyanidin) that may be positively identified by paper chromatography or cellulose TLC in Forestal solvent (H0Ac H20 HCl, 30 10 3 v/v/v), or by a colorimetric method using vanillin and concentrated hydrochloric acid (17). The latter is very sensitive. 

Problem 28.— Write the equation for the reaction between (a) vanillin, and NH2-NH2, b) hydrazobenzene and aqueous HCl. 

Li X, Deng S, Fu H, Mu G (2008a) Synergism between rare earth cerium(IV) ion and vanillin on the corrosion of cold rolled steel in 1.0 M HCl solution . Corrosion Science, 50, 3599-3609. 

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