Phenylhydrazine hydrochloride, preparation

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. 

About 15 c.c. of the distillate are treated with 1 c.c. of aqueous 4 % phenylhydrazine hydrochloride solution, 3-4 drops of freshly prepared 0-5% sodium nitroprusside solution and sufficient concentrated caustic soda solution to render the liquid alkaline an intense blue coloration gradually, and especially on heating, changing to red, indicates formaldehyde. 

In a 1-1. three-necked flask fitted with a stirrer, a thermometer, and a dropping funnel are placed 300 cc. of water and 55.S cc. of concentrated hydrochloric acid. The flask is surrounded by an ice-salt bath, the stirrer is started, and 33.5 g. (0.31 mole) of phenylhydrazine (Note 1) is added dropwise (five to ten minutes is required). Phenylhydrazine hydrochloride separates as fine white plates. Stirring is continued and, after the temperature has fallen to 0°, 100 cc. of ether is added, after which a previously prepared solution of 25 g. of technical sodium nitrite in 30 cc. of water is added from the dropping funnel at such a rate that the temperature never rises above 5°. This requires twenty-five to thirty minutes. 

Phenyl azide has been prepared by the action of nitrous acid upon phenylhydrazine hydrochloride 1 of ammonia upon diazo-... 

Indolomorphinans can be prepared from their 6-ketomorphinan precursors via Fischer indole synthesis with phenylhydrazine hydrochloride in glacial acetic acid [43, 49, 50], while benzofuromorphinans can be synthesized from the corresponding 6-ketomorphinans using 0-phenyI hydroxylamine hydrochloride and methanesulfonic acid in MeOH (Scheme 8) [43]. 

When the starting materials in the foregoing preparation are brought together in ether and the phenylhydrazine hydrochloride filtered off, the addition of water to the dry mass gives a white powder. This may be crystallised from chloroform, and is the dihydrazide, CeH5.P(NH.NH.C6H5)2. 

To 10 ml of a 1 per cent phenylhydrazine hydrochloride solution (prepared by suspending 1 g of phenylhydrazine in about 5 ml of water, adding 2 ml of concentrated hydrochloric acid and 80 ml of water, filtering and diluting to 100 ml), add sufficient solution under test to contain between 0 05 and 0 25 mg of formaldehyde and dilute to 50 ml. To 10 ml of this solution add 1 0 ml of freshly prepared 5 per cent potassium ferricyanide solution and 4 0 ml of concentrated hydrochloric acid, dilute to 20 ml and allow to stand for ten minutes. Prepare simultaneously a series of standard comparison solutions using 2 ml of the phenylhydrazine solution, 7 ml of water, measured amounts of a solution of formaldehyde containing 1 mg of formaldehyde per litre (say, 1, 2, 5 ml), 10 ml of the ferricyanide solution and 4 0 ml of concentrated hydrochloric acid dilute to 20 ml with water and allow to stand for ten minutes. Compare the colour of the test solution against those of the standard comparison solutions. 

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. 

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 —... 

Small Quantities. Wear eye protection, laboratory coat, and butyl rubber gloves. Work in the fume hood. Prepare a dilute aqueous (5%) solution of phenylhydrazine (phenylhydrazine-HCl add 3 mL of 10% NaOH for each 1 g of the hydrochloride) by adding slowly to the appropriate volume of water. For each 1 g of phenylhydrazine or phenylhydrazine-HCl, place 18 mL (about 25% excess) of commercial laundry bleach (containing about 5.25% sodium hypochlorite) into a three-necked, round-bottom flask equipped with a stirrer, thermometer, and dropping funnel. Add the aqueous phenylhydrazine to the stirred hypochlorite solution, monitoring the rate of addition by rise in temperature. The temperature is maintained at 45-50°C, and addition takes about 1 hour. Stirring is continued for 2 hours until the temperature gradually falls to room temperature. The cooled reaction mixture can be flushed down the drain with at least 50 times its volume of water.6... 

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). 

---