Phenylhydrazine acetate reagent

P-Phenylethyl alcohol, 812,816 Phenylethylene, 1015,1024 a-Phenylethylamine, 560, 566 P-Phenylethy,amine, 560, 567,569 Phenylethylbarbituric acid, 1003,1005 P-Phenylethyl bromide, 283 P-Phenylethyl iodide, 288 Phenylglycine-o-carboxylic acid, 980 Phenylglyoxal, 866 Phenylhydrazine, 635, 636 hydrochloride, 636, 637 Phenylhydrazine acetate reagent, 343, 721 ... 

The reaction of these aldehydes, derived from periodate oxidation, with carbonyl reagents has also been investigated. Studies 147 148 were made on oxidized laminarin, a (1 —> 3)-linked polysaccharide, in which only the terminal residues had been oxidized. The addition of phenylhydrazine acetate detached the remainder of the terminal residue as glyoxal phenyl-osazone. When the aldehydic compounds derived from the periodate oxidation of raffinose and trehalose818a were reacted with p-nitrophenylhydrazine, the authors were surprised to find that one molecule of oxidized raffinose, containing six aldehydic functions, reacts with only three molecules of the reagent, and that the four aldehydic functions of the oxidized trehalose molecule react with only two. The reactions of periodate-oxidized carbo-... 

Prepare a solution of phenylhydrazine by dissolving 1 0 g. of phenyl-hydrazine hydrochloride and 1 5 g. of crystallised sodium acetate in 10 ml. of water if the resulting solution is turbid, filter. Add a solution of 0 5 ml. of cycZohexanone in 8 ml. of water to the reagent... 

Method D. Dissolve 25 g. of colourless phenylhydrazine hydrochloride (recrystal-lise, if necessary) in 250 ml. of water warming may be required. Add 45 g. of crystallised sodium acetate to the cold solution and shake until dissolved. Add 0-6 g. of decolourising carbon, shake, and filter into a dark bottle. The reagent should not be kept for longer than 1 month. 

Isatin (190) is a compound with interesting chemistry. It can be iV-acetylated with acetic anhydride, iV-methylated via its sodium or potassium salt and O-methylated via its silver salt. Oxidation of isatins with hydrogen peroxide in methanolic sodium methoxide yields methyl anthranilates (81AG(E)882>. In moist air, O-methylisatin (191) forms methylisatoid (192). Isatin forms normal carbonyl derivatives (193) with ketonic reagents such as hydroxylamine and phenylhydrazine and the reactive 3-carbonyl group also undergoes aldol condensation with active methylene compounds. Isatin forms a complex derivative, isamic acid (194), with ammonia (76JCS(P1)2004). 

Isolation of Citronellal and Citral. At the close of each experiment (7 to 10 days), the nests were frozen intact. Groups of 200 workers were placed in a micro-Soxhlet apparatus and extracted for 8 hours with methylene chloride. A few milligrams of carrier citronellal and citral were added and the mixture was applied to a thin-layer chromatoplate (silica gel G) which was developed with hexane-ethyl acetate (92 to 8) to separate citronellal and citral (3). The aldehydes were detected by spraying with a solution of 2, 4-dini-trophenylhydrazine in tetrahydrofuran (20) and the citronellal and citral peaks were scraped off and allowed to react with excess dinitro-phenylhydrazine reagent for a further 12 hours. 

The reagent may alao be prepared by dissolving 1 ml. of phenylhydrazine in a solution of 1 ml. of glacial acetic acid and 10 ml. of water. This procedure is not so convenient as that from the solid hydrochloride because of the poisonous character of phenylhydrazine (both liquid and vapour). If the liquid is accidentally spilled on the skin, wash it at once with dilute acetic acid, followed by soap and water. 

The reagent consists of a solution of 1 part of phenylhydrazine dissolved in 2 parts of glacial acetic acid. 

Phenylhydrazine reagent. Dissolve 1 g phenylhydrazine, C6H5.NH.NH2, in 2 ml glacial acetic acid. 

H) Preparation of Phenylhydrazones. Place 0.5 ml of benzaldehyde in a tube, and add 5 ml of phenylhydrazine reagent. Stopper the tube securely, shake the contents vigorously for 1-2 minutes, and allow to stand for 10 minutes, with occasional shaking. Filter the crystals with suction, and wash first with one per cent acetic acid and then with water. The yield is about 1 g. If it is desired to determine the melting point, the product is recrystallized from methanol or ethanol. 

In order to reduce an orange dye which is formed when the diazonium salt is added to the bisulfite solution, a small amount of zinc and acetic acid is added. To prepare the base, the hydrochloride is treated with excess 30 per cent sodium hydroxide solution, and the oily base is extracted with ether. The ethereal extract is dried and, after removal of ether, is distilled under reduced pressure. Substituted phenylhydrazines, such as p-nitrophcnylhydrazine and p-bromophenylhydrazine, are prepared in the same manner. Arylhydrazines are strong bases forming characteristic salts, which are important reagents in the identification of aldehydes, ketones, and sugars (see preparation of phenylhydrazones and osazones). 

It should be mentioned that the pyranoid structure in the compound is extraordinarily stable. Oxidation by hypoiodite gave an almost theoretical value but was unusually slow. The compound reacted slowly with hot Fehling solution, and gave no products with phenylhydrazine or similar reagents. The 6,7-monoisopropylidene acetal, obtained by hydrolysis of (40), was also obtained crystalline. 

Initially, sulfuric acid was used to initate the Borsche—Drechsel cyclization. However, Perkin found that acetic acid provided cleaner products. Recently, other reagents—such as cerium ammonium nitrate (CAN) and the more environmentally friendly acidic ionic liquids —have been used to catalyze the ring formation. It should be noted that people have found it difficult to promote the cyclization when there are substituents at the ortho-position of the phenylhydrazine. This difficulty becomes more pronounced when both the hydrazine and the cyclohexanone have a-substitution This difficulty usually leads to low yields compared with other methods of forming the carbazole. 

Reagent Mixture of phenylhydrazine and glacial acetic acid (1 2)... 

Reagents phenylhydrazine (freshly distilled), 50% acetic acid, ethanol. 

---