Phenylhydrazine, reaction with decomposition

A systematic investigation of the phenylation of thiophene with phenyl radicals generated by different methods has been carried out (73IJS295). Phenyl radicals have been produced by the following methods (i) Gomberg reaction (ii) oxidation of phenylhydrazine (iii) thermal decomposition of AT-nitrosoacetanilide (iv) thermal decomposition of... 

Pyridazines were obtained also by photolysis of 1-phenyl-l-vinyl azide in the presence of iron pentacarbonyl (3,6-di-phenylpyridazine was obtained in 1.1% yield) (78HCA589) or by thermal decomposition of an allenic hydrazonate (81JA7011). Acetylenic hydrazides can be transformed into pyridazines [84BSF(2)129], and thermal cyclization of dialkali metal salts of cu-hydroxyketone tosylhydrazones afforded pyridazines in moderate yield (85TL655). Propionyl phenylhydrazine, after reaction with 4-bromobutyronitrile, converts into a pyridazine (87SC1253). 

The reactions in the decomposition of 13,6-trimethyl-2-oxo-l, 2-dihydropyrazine methiodide with alkali metal hydroxide to give 1,4,6-trimethyl-3-methylene-2-oxo-1,2,3,4-tetrahydropyrazine (1105) and its reaction with benzenediazonium chloride or phenylhydrazine to give l,4,6-trimethyl-2-oxo-3-phenylazomethylene-l,2,3,4-tetrahydropyrazine (1105,1132) have been described. 

Two reactions used in steroid chemistry were modified by Bennett for histochemical use. Frozen sections of either unfixed or formalin-fixed tissue were used, with no differences reported in their reactivity (see, however, Section V.2) the sections were 80 to 100 microns in thickness. In the first method, sections were treated with phenylhydrazine hydrochloride (1 %) in acetate buffer, pH 6 to 6.5, overnight. The formation of yellow phenylhydrazones indicated the presence of carbonyl groups. The pH of the solution was kept low enough to prevent extensive accumulation of the decomposition products of phenylhydrazine, which are yellow and soluble in lipid. In order to avoid reaction with ascorbic acid the sections were first oxidized briefly with iodine or indophenol. Since dehydro-ascorbic acid, which is formed by the oxidation of ascorbate, also forms phenylhydrazones, it is doubtful that this procedure had any value. However, since ascorbic acid and its oxidation product are soluble in most aqueous mixtures, they probably would not remain in sections as ordinarily treated. 

Arylgold(III) complexes have also been obtained from the reactions of tetrachloroaurate(III) salts with substituted phenylhydrazines (303, 304). Thus were prepared the compounds R4N[AuCl3Ar] (R = Et or -Bu Ar = C6H5, p-ClC6H4, / -BrC6H4, or p-NC CsH, which were characterized by their H-NMR and vibrational spectra. Arylgold(III) species have been postulated as intermediates (3OS) in the thermal decomposition of [AuCl3(azobenzene)]. 

A 1% solution of D-galactose diphenylformazan in alcohol is red when treated with hydrogen sulfide, it is rapidly decolorized and, after a few days, gives D-thiogalactonic acid phenylhydrazide, which crystallizes in colorless needles. Phenylhydrazine, a byproduct of the decomposition reaction, may be isolated from the mother liquor. 

An interesting intermediate, possibly deriving from Weygand s Scheme B, was isolated by Haas and Seeliger from the reaction of u-glucose with phenylhydrazine in acetic acid or hydrochloric acid. This product is 3-(D-fflrol)fno-tetrahydroxybutyl)cinoline (30), produced, not by the hydrolytic decomposition of the osazone, but by the cyclization of the intermediate glycosulose 2-(phenylhydrazone) (28) or the aldimine 2-(phen-ylhydrazone) (29). 

Carbohydrates that can exist in solution in an acychc form with a free aldehyde or ketone function react with three equivalents of phenylhydrazine to form bright yellow crystalline derivatives called phenylosazones, together with anihne and ammonia as the other products of the reaction. For example, a- and p-D-glucopyranoses 4 and 5 are in dynamic equilibrium in aqueous solution with the ring-opened form 3 (Sec. 23.2), which, because of its free aldehyde group, will react with phenylhydrazine to form the phenylosazone 17, as shown in Equation 23.6. Since phenylosazones are readily identified by either their melting points or temperatures of thermal decomposition, these derivatives may be used to characterize carbohydrates. 

The reaction of phenylhydrazine with the sugars was discovered by Fischer 202) and was extensively employed in the classical work which established the configuration of the sugars. The products obtained have been widely employed for characterization and identification although they are somewhat difficult to purify, and the melting points are often decomposition points 203). 

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