Phenylhydrazine preparation

Dissolve I g. of pinacol (preparation, p. 148) in 20 ml. of water, and add 20 ml. of the 5% aqueous sodium periodate solution. After 15 minutes, distil the clear solution, collecting the first 5 ml. of distillate. Treat this distillate with 2,4-dinitro-phenylhydrazine solution A (p. 263). Acetone 2,4-dinitrophenyl-hydrazone rapidly separates from the solution when filtered off, washed with a small quantity of ethanol, and dried, it has m.p. 126-127°, and after recrystallisation from ethanol it has m.p. 128°. 

Phenylhydrazine is usually dissolved in acetic acid for hydrazone formation if a salt of phenylhydrazine with an inorganic acid is used, it must be mixed with an excess of sodium acetate (see preparation of osazones, p. 137). 

Mix 6 2 ml. (6 4 g.) of pure ethyl acetoacetate and 5 ml. of pure phenylhydrazine in an evaporating-basin of about 75 ml. capacity, add 0 5 ml. of acetic acid and then heat the mixture on a briskly boiling water-bath (preferably in a fume-cupboard) for I hour, occasionally stirring the mixture with a short glass rod. Then allow the heavy yellow syrup to cool somewhat, add 30-40 ml. of ether, and stir the mixture vigorously the syrup may now dissolve and the solution shortly afterwards deposit the crystalline pyrazolone, or at lower temperatures the syrup may solidify directly. Note. If the laboratory has been inoculated by previous preparations, the syrup may solidify whilst still on the water-bath in this case the solid product when cold must be chipped out of the basin, and ground in a mortar with the ether.) Now filter the product at the pump, and wash the solid material thoroughly with ether. Recrystallise the product from a small quantity of a mixture of equal volumes of water and ethanol. The methyl-phenyl-pyrazolone is obtained... 

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... 

The leagent may also 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 becaiise 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. 

P Keto esters (t.g., ethyl ocetoacetate) are soluble in solutions of caustic alkalis but not in sodium carbonate solution. They give colours with freshly prepared ferric chloride solution a little alcohol should be added to bring the ester into solution. Sodium ethoxide solution reacts to yield sodio compounds, which usually crystallise out in the cold. Phenylhydrazine yields pyrazolones. They are hydrolysed by boiling sulphuric acid to the Corresponding ketones, which can be identified as usual (Section 111,74). 

Phenylhydrazine may be prepared by reducing phenyldiazonium chloride solution with excess of warm sodium sulphite solution, followed by acidification with hydrochloric acid, when the hydrochloride crystallises out on cooling. Treatment of the latter with excess of sodium hydroxide solution liberates the free base. The reaction is believed to proceed through the following stages —... 

The use of liquid phenylhydrazine in the preparation of phenylhydrazones is not recommended for beginners because of the liiglily poisonous character of the liquid (see Section IV,89). A phenylhydrazine reagent may, however, be used. 

An interesting application is the preparation of 1 2 3 4-tetrahydrocarb azole (VI), which is formed when phenylhydrazine is added to a boiling aolutiai of cyclohexanone in acetic acid the plienylhydrazone (V) Intermediately produced undergoes ring closure directly ... 

Prepare acetophenonephenylhydrazone by warming a mixture of 20 g. of acetophenone (Section IV, 136) and 18 g. of phenylhydrazine on a water bath for 1 hour. Dissolve the hot mixture in 40 ml. of rectihed spirit, and shake or stir to induce crystallisation. Cool the mixture in ice, filter and wash with 12 ml. of rectified spirit. Dry in a vacuum desiccator over anhydrous calcium chloride for at least half an hour. The yield of phenylhydrazone, m.p. 105-106 , is 28 g. 

The acetone test reagent consists of a 0 1 per cent, solution of 2 4-dinitro-phenylhydrazine and is prepared as follows Dissolve 0-25 g. of 2 4-dinitrophenyl-hydrazine in 60 ml. of water and 42 ml. of concentrated hydrochloric acid by warming on a water bath cool the clear yellow solution and dilute to 250 ml. with water. The acetone test is considered negative when 5 ml. of the reagent and 4-5 drops of the distillate give no cloudiness or precipitate of acetone 2 4-dinitro-phenylhydrazone within 30 seconds. After a negative test is obtained, it is stron y recommended that the mixture in the flask be refluxed for 5-10 minutes with complete condensation and then to collect a few drops of distillate for another test. If no acetone is now detected, the reduction is complete. 

Hydroxyaminopyridazine 1-oxides are usually formed by catalytic hydrogenation of the corresponding nitro derivatives over palladium-charcoal in methanol, provided that the reaction is stopped after absorption of two moles of hydrogen. 3-Hydroxyaminopyridazine 1-oxide and 6-amino-4-hydroxyamino-3-methoxypyridazine 1-oxide are prepared in this way, while 5-hydroxyamino-3-methylpyridazine 2-oxide and 5-hydroxyamino-6-methoxy-3-methylpyridazine 2-oxide are obtained by chemical reduction of the corresponding nitro compounds with phenylhydrazine. 

Phthalic anhydride and diethyl phthalate are easily converted with hydrazine into 4-hydroxyphthalazin-l(2/f)-one. Its substituted derivatives have been prepared using substituted hydrazines, substituted phthalic anhydrides, or diesters or disodium salts of substituted phthalic acids (Scheme 81). However, condensation of phenylhydrazine with phthalic anhydride gives only a small amount of the corresponding phthalazine, the main product being 2-anilinophthalimide. This can be rearranged in the presence of base into the phthalazine derivative. For the preparation of 2,3-disubstituted derivatives, 1,2-disub-stituted hydrazines are reacted with the appropriate phthalic anhydrides or phthaloyl chlorides. Derivatives of 4-amino- or 4-hydrazino-phthalazin-l(2iT)-one have been prepared either from the corresponding monothiophthalimide and 3-aminoisoindolin-3-one (1S4) or from ethyl 2-cyanobenzoate (155) and hydrazine hydrate (Scheme 82). Similarly,... 

Phenylhydrazides have been prepared from amino acid esters and phenylhydrazine in 70% yield they are cleaved by oxidation [Cu(OAc)2, 95°, 10 min, 67% yield FeCyi NHCl, 96°, 14 min, 85% yield ]. 

The Bucherer carbazole synthesis was pivotal in the preparation of the first hexahelicene 37a. Reaction of 2,7-dihydroxynaphthalene 35 with phenylhydrazine and sodium bisulfite afforded helicene 37a although in low yield. More recently, the synthesis was extended to the preparation of 37b using 2,5-dimethylphenylhydrazine 36b. ... 

They are best prepared by heating the aldehyde in alcoholic solution, on the water-bath, under a reflux condenser, with slightly more than the equimolecular quantity of phenylhydrazine hydrochloride, with acetate of sodium added. Thirty to sixty minutes is usually sufi cient for the reaction. 

One gram of Ceylon citronella oil or 0 5 grams of Java citronella oil is mixed with 10 c.c. of a freshly prepared 2 per cent, alcoholic solution of redistilled phenylhydrazine and allowed to stand for one to one and a half hours in a flask of about 50 c.c. capacity closed with a glass stopper. Twenty c.c. of decinormal hydrochloric acid is then added, thoroughly... 

Imine formation from such reagents as hydroxylamine and 2,4-dinitro-phenylhydrazine is sometimes useful because the products of these reactions— oximes and 2,4-dinitrophenylhydrazones (2,4-DNPs), respectively—are often crystalline and easy to handle. Such crystalline derivatives are occasionally prepared as a means of purifying and characterizing liquid ketones or aldehydes. 

Pyrazolo[4,3-e][l, 2,4][triazines 365 were prepared (80JHC209) by treatment of 4-bromo-3-phenylpyrazol-5-ylhydrazonyl chlorides 364, obtained from 363, with hydrazine or phenylhydrazine. It should be noted that the reaction of 3-phenylpyrazol-5-ylhydrazonyl chloride gave (77JHC227) pyrazolo[l,5-c][l,2,4]triazine (Scheme 79). 

Diphenylcarbazido is prepared by heating a mixture of phenylhydrazine and urea at 155° ... 

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