Reagents Gibbs

Benzoylate the amino groups by overspotting at [103] the start This makes detection with Gibbs reagent possible... 

Sulfur-containing samples show colored spots when sprayed with 2,6-dibromo-quinone-4-chlorimide Gibbs reagent). For preparation, 2 g of this compound is dissolved in 100 ml of acetic acid or ethanol. Heating to 110°C is necessary to give a reaction. This reagent also creates colored zones when samples contain phenols. For reactions with phenols, only the less-reactive 2,6-dichloroquinone-4-chlorimide can be used under the same conditions. 

Genistein-piperazine complexes 367 Gentianaceae 967 Gibbs energy 224 Gibbs reagent 990... 

Chemical tests with FeCh [47] or Gibbs reagent [27] and acetylation [27] or methylation [42] are used to show the phenolic nature of benzophenones. IR has been useful in showing that benzophenones contain hydroxyl groups, both conjugated and nonconjugatcd ketone groups, and aromatic C=C bonds. 

Phenols, amino compounds, aromatic hydrocarbons, and coumarins 1% 2,6-Dibromoquinone-4-chloroimide in methanol (Gibbs reagent) heat at 110°C for 2-5 min Different colored zones... 

React FeClj violet, Gibbs reagent blue, NaOCl red... 

Dichloro-4-(chloroimino)- 2,5-cyclohexadien-1-one Gibbs reagent CeH2Cl3NO 101-38-2 210.445 66 ... 

Ethyl tert-pentyl ether 4849 Flufenamic acid 10411 Gibbs reagent 3141... 

In these cases it is usually possible to explain why the color is formed. The reactions can be further classified, on the basis of the type of colored compound formed, into reactions leading to the formation of azo dyes, di- or triphenylmethane dyes, xanthene dyes, polymethine dyes, indophenols, etc. Azo dyes are formed, for example, in the reaction of diazonium salts and phenols (p. 192) or amines (p. 324), azomethines in the reaction of primary aromatic amines with aromatic aldehydes (p. 215), di- and triphenylmethane dyes in the reaction of aromatic aldehydes with aromatic hydrocarbons in concentrated sulfuric acid (p. 213), triphenylmethane dyes in the reaction of phenols with aromatic aldehydes or oxalic acid (p. 196), xanthene dyes in the reaction of anhydrides of dicarboxylic acids with resorcinol (p. 196), polymethine dyes are formed after the cleavage of the pyridine ring in the reaction of the glutaconaldehyde formed and barbituric acid (p. 378), indophenols on reaction of phenols with Gibbs reagent (p. 195), or 4-aminoantipyrine according to Emerson (p. 194), or on the Liebermann reaction (p. 195). 

Optimum conditions, both with respect to the concentration of the tested substance and to the amount of the reagent. The Gibbs reagent mentioned above is, for example, most suitable for the detection of small amounts (several micrograms) of phenols in aqueous solutions, but it is impossible to carry out the reaction by putting 1 g of phenol into a test tube and adding the reagent. 

Maltoryzine (9), C11H14O4, reacted negatively with ninhydrin. Schiff s, and Gibbs reagents, whereas positive reactions were obtained with ferric chloride, methyl red, and 2,4-dinitrophenylhydrazine. Its uv spectrum, (e), 220 (12,900), 280 (1290), and 320 nm (129), indicated that the compound contained the oxygenated benzoyl group. The ir spectrum of 9 indicated the presence of the hydroxy (3300 cm ) and carbonyl (1700 cm )... 

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