Лако-красочные материалы — производство

Nitrous acid or alkyl nitrites react with a number of nitrogen com­pounds to yield tetrazoles. For example, hydrazidines (87), which can be prepared in situ from the corresponding iminoesters, react with nitrous acid or its derivatives to give 1-substituted tetrazoles (88).150152 This reaction (Eq. 17), is one of the most extensively used methods for the […]

Extensive reviews of synthetic methods and properties of tetrazoles have been published.103,651 — 653 7.З.2.1. From Hydrazoic Acid The addition of hydrazoic acid to carbon-nitrogen unsaturated bonds as in hydrogen cyanide, nitriles, and isonitriles leads to unsubstituted, 5-, or (58) X Yield(%) Ref R Yield(%) Ref H 80 105 C6H5 16 124 z-C3H7 87 104 […]

Diaryl carbazides and thiocarbazides, e. g., 43, can be oxidized at alkaline pH to yield C-hydroxy or C-mercapto formazans (44) (Eq. 8).68,129 The replacement of C-halo formazans is considered to be a better method60 for the preparation of 44. A class of cyclic formazans (45) can be obtained by air oxidation of amidrazones (46) (Eq. […]

Formazans can undergo a variety of reactions leading to different formazans. These transformations include the reaction of substituents on the aromatic ring such as the hydrolysis of esters and nitriles,57 the reduction of nitro groups to amines,58 as well as esterification of carboxylic acids through their silver salts.57 Replacement of C-nitro formazans38 and C-halo formazans42,4 […]

Ethyl formate34,52 or orthoformate5 3,54 reacts with two equivalents of phenylhydrazine to yield 1,5-diphenylformazan (11); the reaction takes place under acidic conditions and involves an oxidation. Under basic conditions, ethyl nitrate reacts at the methylene position to yield 3-methyl-1,5-diphenyl — formazan (37) which can also be obtained from the reaction of phenyl — azoethane (38) […]

In general, tetrazolium salts are prepared by (a) oxidation of formazans and (b) alkylation of tetrazoles. Therefore, synthetic methods for formazans and tetrazoles are discussed first, followed by some direct and miscellaneous methods. 7.3.1. From Formazans Synthetic methods for formazans have been reviewed.1,2 73.1.1. From Diazonium Salts Electron-rich compounds such as hydrazones react with diazonium […]

Tetrazolium salts are derivatives of the 1H-tetrazole (1) or 2H-tetrazole (2). The CA numbering systems for tetrazoliums and formazans are shown in 3 and 4. It should be noted that the carbon atoms in 3 and 4 are DANIEL S. DANIEL • Clinical Chemistry Research and Development, Johnson & Johnson Clinical Diagnostics, Rochester, New York […]

DANIEL S. DANIEL 7.1. INTRODUCTION Tetrazolium salts are an important class of leuco dyes that have found a wide range of applications. They are unique among the synthetic leuco dyes in that the colored form of the dye is the reduced form rather than the oxidized form. There are at least three extensive reviews on […]

Leuco dye and coreactant are individually milled in an aqueous solution of binder such as poly(vinyl alcohol) or hydroxyethylcellulose by means of an attrition or sand mill until the particle size of the solid materials is about 1 qm or less in diameter. Smaller particles provide superior performance. These dispersions thus obtained are mixed together, […]