Preparation of Anhydrous Hydrazine

Hydrazine is generally obtained by reaction in the aqueous phase. It is subsequently concentrated by successive evaporations and rectifications and then, in order to eliminate the water to the maximum extent, one of the methods most recently employed consists in using the dehydrating power of alkaline or alkaline-earth substances, such as caustic soda, potash, or alkaline-earth oxides (quicklime of barium oxide). It is then separated from the dehydrating agent by distillation. 

The object of the present invention is, especially, to obtain anhydrous hydrazine at a concentration of 98—99% at least, with the same safety conditions as when for example aliphatic hydrocarbons are used. 

In the specification of (Olin 1956)— which is concerned with an improved process for concentrating aqueous hydrazine by distilling said hydrazine in contact with a dehydrating agent and a satmated hydrocarbon—it is pointed out that low-cost commercially available saturated hydrocarbons can be used, even if they contain minor amounts of unsaturated aromatics, as such amounts are permissible, but that unsaturated aromatic hydrocarbons in general are not suitable for the pimpose, due to their tendency to react with the hydrazine. 

In contradistinction to this and to what has hitherto been thought, the Inventors have ascertained that when used according to the process of the present invention hydrazine does not act upon the said unsaturated liquid aromatic hydrocarbons. On the contrary, it has been found that, by their use according to the process of the invention, anhydrous hydrazine can be obtained at a much greater degree of dryness... 

It has been observed that if there is introduced into the mixture a third mineral substance without vapour pressure, nothing is changed. There can then be added to the mixture dehydrating agents such as quicklime, barium oxides, caustic soda or caustic potash, it being possible to have the last two dehydrating agents, if necessary, in the form of an approximately saturated aqueous solution. 

---

There is given below, purely by way of illustration, an example of the preparation of anhydrous hydrazine in the presence of benzene. 

An important feature of this invention consists in the preparation of anhydrous hydrazine by dissociating the anhydrous hydrazine salt of phthalyl hydrazide itself. This salt can be prepared in anhydrous condition by the addition of ethyl alcohol to an aqueous solution of phthalylhydrazide in excess hydrazine hydrate and drying the resultant precipitate. Heat treatment of the anhydrous salt up to 180°C. under a pressure of 0.05 mm. of mercury in a vacuum distillation apparatus connected to a receiver cooled to about -40°C. gives a 92% 3deld of anhydrous hydrazine. 

Barber, H.J., Wragg, W.R. A Convenient Laboratory Preparation of Anhydrous Hydrazine Journal of the Chemical Society (1948) 1458... 

Several procedures are available for the preparation of anhydrous hydrazine. Of these, the dehydration of NgH H3O andthe cleavage of hydrazine salts with NH3 are of special Interest. The first method yields anhydrous N3H4, if an efficient column with about 15 theoretical plates is used. The distillation is carried out in a stream of N3, using a mixture of 100 g. of 78.5% hydrazine hydrate and 140 g. of NaOH. The N3H4 obtained is at least 99.5% pure. 

Hydrazinium salts, N2H5 X, are acids in anhydrous hydrazine, metallic hydrazides, N2H, are bases. Neutralization in this solvent system involves the hydrazinium and hydrazide ions and is the reverse of equation 7. Metal hydrazides, formally analogous to the metal amides, are prepared from anhydrous hydrazine and the metals as well as from metal amides, alkyls, or hydrides. (The term hydrazide is also used for organic compounds where the carboxyUc acid OH is substituted with a N2H2.) Sodium hydrazide [13598-47-5] is made from sodium or, more safely, from sodium amide (14) ... 

Hydrazine is an endothermic compound and the vapour is exceptionally hazardous in that once it is ignited, it will continue to bum by exothermic decomposition in complete absence of air or other oxidant [1]. Distillation of anhydrous hydrazine (prepared by dehydrating hydrazine hydrate with solid sodium... 

By conventional procedures, 106 gm of benzaldehyde reacts in 600 ml of ether with 66 gm of anhydrous hydrazine to give benzalhydrazone which is directly oxidized in anhydrous ether with 300 gm of mercuric oxide to phenyl-diazomethane.) (See Volume I, Chapter 15, p. 398, for oxidation of hydrazones, p. 390 for an alternative preparation of phenyldiazomethane.)... 

The azines represent another class of organic compounds which, in principle, should be reducible to azo compounds. The method is attractive since, with the availability of anhydrous hydrazine, azines are readily prepared from a wide variety of ketones and aldehydes. Evidently, introduction of 1 gram-molecule of hydrogen into an azine molecule has only recently been accomplished (see Section 6, Procedure 8) [73], Two preparations involving the 1,4-addition of chlorine to an azine system have been carried out and are illustrated here. 

The peptide resin prepared above was treated with a 20-fold excess of anhydrous hydrazine in DMF (20 ml) at laboratory temperature for 24 hours, and the mixture was filtered and evaporated to dryness. This procedure also removed the BrZ protecting group from the Tyr moeity. The residue was purified by gel filtration on a column (LH 20 Sephadex) using a 20 1 v/v mixture of water and acetic acid as eluant. There was thus obtained Pyr-His-Trp-Ser-Tyr-D-Ser(But)-Leu-Arg(H+)-Pro-NH-NH2. The structure of which was confirmed by amino acid analysis and mass spectroscopy. 

The hydrazone (49) was prepared by reacting naloxone with an excess of anhydrous hydrazine [85]. Naloxazone (49) was treated with naloxone to yield the azine (50). 

Procedure Prepare a solution by dissolving 31 grams of nitroform into 2000 mi IN liters of diethyl ether. Then prepare a suspension of hydrazi ne i n ether by adding 6.4 grams of anhydrous hydrazine into 200 mi IN liters of diethyl ether. Then place this hydrazi ne ether suspension into an ice bath. Afterwards, slowly add, drop-wise, the nitroform solution to the hydrazi ne ether suspension while rapidly stirring the hydrazine ether suspension and maintaining its temperature around 0 Celsius. After 332... 

Hydrazinium azide is prepared by the reaction of hydrazine with hydrazoic acid. To avoid the handling of the hazardous HN3, which is generally synthesized by the reaction of sodium azide with an acid, several procedures have been developed for this reaction. Hydrazoic acid has been generated by the reaction of ion-exchange resins, mineral acids, or stearic acid. It was then either passed through a solution of hydrazine in an inert gas stream or a solution of hydrazoic acid was added to a solution of hydrazine. Especially pure hydrazinium azide can be obtained by the reaction of anhydrous solutions of HN3 in diethyl ether with a suspension of anhydrous hydrazine in... 

Preparation of hydrazones. It usually is not possible to obtain a hydrazone in good yield by reaction of an aldehyde or ketone with hydrazine because of extensive formation of the azine. This difficulty is circumvented by conversion to the N,N-dimethylhydrazone, followed by exchange with hydrazine. The latter reaction is conducted by refluxing the N,N-dimethylhydrazone with a 2-3 fold excess of anhydrous hydrazine. 

The submitters found this method for the preparation 1 of anhydrous hydrazine to be superior to that given elsewhere.2... 

Fig. 179. Preparation of large quantities of anhydrous hydrazine. a) Tap /i) high-efficiency condensation trap /a) condensation trap m ) flow meter r) reaction tube s j) air cooling coll ...

Fig. 180. Simplified apparatus for the preparation of small amounts of anhydrous hydrazine Tj is connected to an aspirator Tg is connected to an ammonia cylinder ...

Hydrazine nitrate itself is a powerful high explosive. It is usually prepared through the low-temperature salinification of either anhydrous hydrazine or hydrazine hydrate with nitric acid 65 % in the presence of methanol as the medium. This approach, however, suffers from the high cost of anhydrous hydrazine and the... 

When PAZ is prepared from anhydrous hydrazine and trimeric glyoxal dihydrate a reddish-brown DMF soluble fraction of PAZ is obtained [6]. This fiuction has an absorption maximum at 420 ran with a tail extending to above 600 nm. This was interpreted as arising from n-% transitions from regions of the polymer (or, given the solubility, oligomer) with extended conjugation and away from the saturated defects. This is in accord with similar conclusions made about PAZ from the IR and NMR spectra. 

Reactions with Hydrazine. TIPSCl reacts with an excess of anhydrous hydrazine to form triisopropy Isilylhydrazine which can be used to prepare TIPS hydrazones (eq 20). TIPS hydrazones are unusually stable in air but readily form asymmetric azines upon treatment with TBAF and a slight excess of ketone or aldehyde (eq 20).31... 

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) ... 

MMHa.nd UDMH. MonomethyUiydrazine and yyz -dimethylhydrazine are manufactured by Olin Corp. using the same Raschig process and equipment employed for anhydrous hydrazine. Chloramine, prepared as described above, reacts with methylamine or dimethylamine instead of with... 

Hunsdiecker reaction, modified for preparation of 1-bromo-3-chlorocyclobutan9, 51, 106 Hydrazine, anhydrous, 50, 3, 4, 6... 

---