Hydrazine, hydrate

In the absence of the hydrocarbon even a small amount of air in the hydrazine vapor is sufficient at elevated temperature to initiate a violent explosion. Source Olin 1956 

Glass flasks cannot be used in the preparation because of the high temperature required in the distillation. The amount of water given in the procedure was found to be the most satisfactory. If less water is used, the yield is lowered while more water dilutes the product without increasing the yield. 

The product is sometimes contaminated with silicic acid from the glass of the condenser. This may be removed by filtration. All of the corks should be covered with tin foil in order to avoid having them attacked by the hydrazine hydrate. 

Hydrazine hydrate may be titrated against standard acid using methyl orange as an indicator, or it may be titrated against iodine with 

Titration by iodine and by acid give the same results, showing that practically no ammonia is present in the hydrazine hydrate prepared by this method. 

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Dissolve 10 g. of chloro- 2,4-dinitrobenzenet in 50 ml. of dioxan in a 250 ml. conical flask. Dilute 8 ml. of hydrazine hydrate with an equal volume of water and add this slowly with shaking to the dioxan solution, keeping the temperature between zo " and 25°. Heat under reflux for 10 minutes to complete the reaction and then add 5 ml. of ethanol and heat again for 5 minutes. Cool and filter oflF the orange 2,4-dinitrophenylhydra-zine. Recrystallise the dry product from ethyl acetate m.p. 200° (decomp.). Yield, 7 g. 

The 40-45 per cent, hydrazine solution may be concentrated as follows. A mixture of 150 g. (144 ml.) of the solution and 230 ml. of xylene is distilled from a 500 ml. round-bottomed flask through a well-lagged Hempel (or other efficient fractionating) column fitted into a cork covered with tin foil. All the xylene passes over with about 85 ml. of water. Upon distillation of the residue, about 50 g. of 90-95 per cent, hydrazine hydrate (5) are obtained. 

Hydrazine hydrate may be titrated with standard acid using methyl orange as indicator or, alternatively, against standard iodine solution with starch as indicator. In the latter case about 0-1 g., accurately weighed, of the hydrazine hydrate solution is diluted with about 100 ml. of water, 2-3 drops of starch indicator added, and immediately before titration 6 g. of sodium bicarbonate are introduced. Rapid titration with iodine gives a satisfactory end point. 

Hydrazine hydrate of 60 per cent, and 100 per cent, are available commercially. The preparation from hydrazine sulphate is hardly worth while. 

Place 1 0 ml. of hydrazine hydrate (CAUTION corrosive chemical) in a test-tube fitted with a short refiux condenser. Add 10 g. of the methyl or ethyl ester dropwise (or portionwise) and heat the mixture gently under refiux for 15 minutes. Then add just enough absolute ethanol through the condenser to produce a clear solution, refiux for a further 2-3 hours, distil oflF the ethyl alcohol, and cool. Filter oflF the crystals of the acid hydrazide, and recrystallise from ethanol, dilute ethanol or from water. 

Place 36 -0 g. of redistilled acetophenone, b.p. 201° (Section IV,136), 300 ml. of diethylene glycol, 30 ml. of 90 per cent, hydrazine hydrate and 40 g. of potassium hydroxide pellets in a 500 ml. Claisen flask provided with a reflux condenser and a thermometer dipping into the liquid (compare Fig. Ill, 31, 1). Warm the mixture on a boiling water bath until most of the potassium hydroxide has dissolved and then reflux (free flame) for one hour. Arrange the apparatus for distillation and distil until the temperature in the liquid rises to 175° (1) keep the distillate (ca. 50 ml.). Replace the reflux condenser in the flask and continue the refluxing for 3 hours. 

The independent preparation of potassium phthabmide (from a solution of phthalimide in absolute ethanol and potassium hydroxide in 75 per cent, ethanol) may be avoided in many cases by boiling phthalimide with the halide in the presence of anhydrous potassium carbonate. The N-substituted phthalimide (I) is frequently cleav with difficulty this is often facilitated by reaction with hydrazine hydrate to give an intermediate product, which is easily decomposed by hydrochloric acid to 3deld the insoluble hydrazide of phthaUc acid (II) and the primary amine (III) ... 

The modified procedure involves refluxing the N-substituted phthaUmide in alcohol with an equivalent quantity of hydrazine hydrate, followed by removal of the alcohol and heating the residue with hydrochloric acid on a steam bath the phthalyl hydtazide produced is filtered off, leaving the amine hydrochloride in solution. The Gabriel synthesis has been employed in the preparation of a wide variety of amino compounds, including aliphatic amines and amino acids it provides an unequivocal synthesis of a pure primary amine. 

Benzylatnine. Warm an alcoholic suspension of 118-5 g. of finely-powdered benzyl phthalimide with 25 g. of 100 per cent, hydrazine hydrate (CAUTION corrosive liquid) a white, gelatinous precipitate is produced rapidly. Decompose the latter (when its formation appears complete) by heating with excess of hydrochloric acid on a steam bath. Collect the phthalyl hydrazide which separates by suction filtration, and wash it with a little water. Concentrate the filtrate by distillation to remove alcohol, cool, filter from the small amount of precipitated phthalyl hydrazide, render alkaline with excess of sodium hydroxide solution, and extract the liberated benzylamine with ether. Dry the ethereal solution with potassium hydroxide pellets, remove the solvent (compare Fig. //, 13, 4) on a water bath and finally distil the residue. Collect the benzylamine at 185-187° the 3ueld is 50 g. 

Method 2. Drop 10 g. of hydrazine hydrate (85 per cent, aqueous solution see Section 11,49,Id) into a hot solution of 35 g. of benzil (Section IV,126) in 70 ml. of alcohol with stirring. When about three-fourths of the hydrazine hydrate has been introduced, the product begins to separate. After all the reagent has been added, heat the solution under reflux for 5 minutes, cool to 0°, filter at the pump, and wash twice with 20 ml. portions of alcohol. The yield of benzil monohydrazone, m.p. 149-151° (decomp.), is almost quantitative. 

Girard s reagent T is carbohydrazidomethyltrimethylammonium chloride (I) and is prepared by the reaction of the quaternary ammonium salt formed from ethyl chloroacetate and trimethylamine with hydrazine hydrate in alco-hoUc solution ... 

Hydrazine hydrate of 95-100 per cent, concentration is a commercial product. The 40-60 per cent, solution may be concentrated to 80-85 per cent, strength by distillation with xylene in an all-glass apparatus. 

Girard s reagent P , C5H5NCH2C0NHNH2 C1. In a 1-htre threenecked flask, equipped as in the previous preparation, place 200 ml. of absolute ethyl alcohol, 63 g. (64 -5 ml.) of pure anhydrous pyridine and 98 - 5 g. (84 5 ml.) of ethyl chloroacetate. Heat the mixture under reflux for 2-3 hours until the formation of the quaternary salt is complete acidify a small test-portion with dilute sulphuric acid it should dissolve completely and no odour of ethyl chloroacetate should be apparent. Cool the mixture in ice and salt. Replace the thermometer by a dropping funnel, and add a solution of 40 g. of 100 per cent, hydrazine hydrate in 60 ml. of absolute ethanol all at once. A vigorous exothermic reaction soon develops and is accompanied by vigorous effervescence. The pro duct separates almost immediately. When cold, filter with suction, wash... 

With Stirring, hydrazine hydrate (4 ml in 30 ml of THh ) was added over 60 min. The reaction mixture was then cooled to room temperature and filtered through Celite. The filtrate was concentrated in vacuo and the residue purified by chromatography through silica gel using 10% ether in hexane for elution. The fractions containing product were combined and evaporated to give the product as a clear oil (2.94g, 50%). 

Acetyl-3-mercaptopropanol reacts with acetaldehyde in the presence of hydrazine hydrate to yield 2,4-dimethyl-5-(/3-hydroxyethyl)thiazole (10), R, = Rj = Me, R3 = CH2CH2OH (556). 

Thus esters were converted to hydrazides with an excess of hydrazine hydrate in alcohol with a yield of 84% (66). 

Heating diethyl 2-phenyl-4,5-thiazoledicarboxylate (16) in alcohol with an excess of hydrazine hydrate gave a mixture of cyclohydrazide (17) and the open-chain 2-phenyl-4,5-thiazoledicarboxylic dihydrazide (18) (Scheme 11) (5). The relative amounts of these two products depended on... 

Mercury(II) oxide Chlorine, hydrazine hydrate, hydrogen peroxide, hypophosphorous acid, magnesium, phosphorus, sulfur, butadiene, hydrocarbons, methanethiol... 

Tin(ll) chloride Boron trifluoride, ethylene oxide, hydrazine hydrate, nitrates, Na, K, hydrogen peroxide... 

The many advantageous properties of hydrazine ensure continued commercial utility. Hydrazine is available in anhydrous form as well as aqueous solutions, typically 35, 51.2, 54.4, and 64 wt % N2H4 (54.7, 80, 85, and 100% hydrazine hydrate). 

The freezing point diagram for the hydrazine—water system (Eig. 1) shows two low melting eutectics and a compound at 64 wt % hydrazine having a melting point of —51.6°C. The latter corresponds to hydrazine hydrate [7803-57-8] which has a 1 1 molar ratio of hydrazine to water. The anomalous behavior of certain physical properties such as viscosity and density at the hydrate composition indicates that the hydrate exists both in the Hquid as well as in the soHd phase. In the vapor phase, hydrazine hydrate partially dissociates. 

Table 1 summarizes some of the physical properties of anhydrous hydrazine, hydrazine hydrate, monomethyUiydrazine, and unsymmetrical dimethyUiydrazine (6—8). A comprehensive review of the physical and thermodynamic properties of the hydrazines is available (9). 

A process for heating alkyldithiocarbamate salts (31) in the presence of hydrazine hydrate to produce 4-alhylthiosernicarbazides (32) has been described... 

Whereas there is sometimes confusion in how concentrations of aqueous solutions of hydrazine ate expressed, concentrations of wt % N2H4 ate used herein. In many parts of the wodd, however, concentrations ate often expressed in terms of wt % hydrazine hydrate, N2H4 -H2 O. Hydrazine hydrate is 64 wt % N2H, 36% H2O. The correlation between the two systems is therefore ... 

Automobile safety air bags use sodium azide [26628-22-8] NaN, for gas generation. It can be made from hydrazine by refluxing ethyl or Abutyl nitrite with hydrazine hydrate and sodium hydroxide in alcohol (209,210) ... 

Treatment of a hydtoxyirninoirnine with one equivalent of hydrazine hydrate gave a nitrosopyrazole, which on addition of excess hydrazine hydrate yielded a 4-aminopytazole derivative (eq. 6) (37). 

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,... 

Hydroxyphthalazin-l(2//)-one is obtained in a smooth reaction between phthalic anhydride and hydrazine hydrate and this is again the starting compound for many 1-substituted and/or 1,4-disubstituted phthalazines. The transformations of 1,4-dichloro-phthalazine, which is prepared in the usual manner, follow a similar pattern as shown for pyridazines in Scheme 110. On the other hand, phthalonitrile is the preferential starting compound for amino- and hydrazino-phthalazines. The most satisfactory synthesis of phthalazine is the reaction between a,a,a, a -tetrachloro-o-xylene and hydrazine sulfate in sulfuric acid (67FRP1438827), alt iough catalytic dehalogenation of 1-chloro- or 1,4-dichloro-phthalazine or oxidation of 1-hydrazinophthalazine also provides the parent compound in moderate yield. 

The aminolysis of esters of pyrimidine occurs normally to yield amides. The reagent is commonly alcoholic ammonia or alcoholic amine, usually at room temperature for 20-24 hours, but occasionally under refiux aqueous amine or even undiluted amine are used sometimes. The process is exemplified in the conversion of methyl pyrimidine-5-carboxylate (193 R = Me) or its 4-isomer by methanolic ammonia at 25 °C into the amide (196) or pyrimidine-4-carboxamide, respectively (60MI21300), and in the butylaminolysis of butyl ttracil-6-carboxylate (butyl orotate) by ethanolic butylamine to give A-butyluracil-5-carboxamide (187) (60JOC1950). Hydrazides are made similarly from esters with ethanolic hydrazine hydrate. 

Indazoles can also be prepared by the [CCC + NN] method. For instance indazolones have been obtained rather simply by the action of hydrazine hydrate on 2-halobenzoic esters (78S633). 

Most of these compounds, for instance pyrazole itself, are today commercially available, so there is only a minor interest in detailing the experimental procedures used. The best way to prepare pyrazole is the Protopopova method (Section 4.04.3.3.2) and a modification using hydrazine hydrate instead of a hydrazine salt has recently been patented (80GEP2922591). 

Isothiazolium salts (59) react with phenylhydrazine to give pyrazoles (60) (72AHC(14)l) (see Section 4.02.1.6). When treated with hydrazine hydrate, 3-chloro-l,2-benzisothiazole gives di-(o-cyanophenyl) disulfide (73SST(2)556), but 2,1-benzisothiazole gives o-aminobenz-aldehyde azine (72AHC( 14)43). 2-Substituted saccharins give the expected o-sulfamoyl-benzohydrazides. 

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