Hydrazine salts applications

This is by far the most important reaction of tetrazolium salts and accounts for the bulk of their many applications. A large variety of reagents can reduce tetrazolium salts, e.g., 53 to formazans, e.g., 51. Ascorbic acid, hydrazine, and hydroxylamine have been recommended for the preparation of formazans from tetrazolium salts.245 Stronger reducing agents such as ammonium sulfide, sodium amalgam, sodium dithionite, and catalytic hydrogenation can further reduce the formazans to the amidrazones, e.g.,... 

Since A,A -disubstituted hydrazines are readily available from a variety of sources (see Volume I, Chapter 14), their dehydrogenation constitutes a widely applicable route to both aliphatic and aromatic azo compounds. Such oxidative procedures are of particular value in the aliphatic series because so many of the procedures applicable to aromatic compounds, such as the coupling with diazonium salts, have no counterpart. The oxidation reactions permit the formation not only of azoalkanes, but also of a host of azo compounds containing other functional groups, e.g., a-carbonyl azo compounds [83], a-nitrile azo compounds [84], azo derivatives of phosphoric acid [85], phenyl-phosphoric acid derivatives [86],... 

This pyrazole synthesis, which undoubtedly profits from the thermodynamic stability of the end products, gives excellent yields (Table VI). Its range of application is limited, however, by the fact that the reaction of 3-substituted unsymmetrical dithiolium salts with substituted hydrazones leads to mixtures of isomers which can be separated only with difficulty. On the other hand, it does permit the preparation of a single 4,5-disubstituted pyrazole from a 3,4-disub-stituted salt and a substituted hydrazine. 

A few examples of the reduction of aliphatic diazo compounds to hydrazines exist," but this is not a generally applicable method for the synthesis of alkylhydrazines. On the other hand, arylhydrazines can be prepared by reduction of aromatic diazonium salts.The most commonly used reagents for this conversion are sulfur dioxide (or sodium sulfite) and tin(II) chloride, these being used to reduce arenediazo-nium chlorides in aqueous solution. Several other reagents, including sodium amalgam and triphenylphosphine, have been used for specific reductions of this type. Arenediazonium tetrafluoro-borates have been reduced to the correspwnding hydrazinium salts (3) by benzeneselenol in dichloro-... 

Hydrazine is commercially available as aqueous solutions and, in smaller quantities, in the form of salts. Hydrazine forms a high boiling point azeotrope with water, whose composition is close to a 1 1 molar ratio, corresponding to 64% hydrazine. This solution is known as hydrazine hydrate . The capacity statistics in table 1.4-1 relate to hydrazine hydrate . Anhydrous hydrazine is only produced in very small quantities for special applications in satellite technology. 

The statements made above concerning the replacement of a diazogroup by hydrogen are also applicable to this reaction. If it is desired to prepare an amido-compound from an amido-free compound, and if the direct reduction of the diazo-compound by sodium stannous oxide or alcohol (see page 210) has been shown to be impracticable, then, as above, the hydrochloric add salt of the corresponding hydrazine is prepared, the free hydrazine is liberated, and oxidised with caustic soda. The amido-free substance is not always easily volatile, as in the example dted. In a case of this kind, the oxidation may be effected in an open vessel the reaction product is obtained tither by filtering or by extracting with ether. It may be pointed out here that it is more convenient to separate the hydrazine from the hydrochloric add salt, and subject this to oxidation. If a hydrochloric add salt of a hydrazine is oxidised it may happen that the hydrazine radical will be replaced by chlorine ... 

Hydrazine derivatives also open the ring of pyrylium salts (18) to form open-chain products (19) which undergo recyclization. The applicability of this method of synthesis is strictly limited as only polyaryl pyrylium salts react smoothly. Of possible hydrazine derivatives, only alkyl or aryl hydrazines were used.33-41... 

The principle of Wohler s method provides a method of very wide and varied applicability for the preparation of urea derivatives. Alkali cyanates and isocyanic and isothiocyanic esters on the one hand and ammonia, amines, amides, hydrazines, etc., on the other, undergo the reaction. When an alkali cyanate is used it is usually possible to work in aqueous solution and add the amine as a salt alternatively, the free amine can be used in dilute acetic acid room temperature or moderate temperatures usually suffice. A series of examples for the preparation of monoarylureas by this method is to be found in Organic Syntheses.64... 

In a series of communications between 1959 and 1962, Ugi described the four-component condensation of an oxo-containing species, amine, isocyanide, and carboxylic acid to give a-acylamino carboxamide products. This discovery introduced the multicomponent reaction to the field of peptide chemistry and, thus, dramatically increased its applicability. Ugi showed that a broad range of nucleophilic components — including hydrogen sulfide, hydrogen selenide, hydrazoic acids, cyanates, thiocyanates, carbonic acid monoesters, salts of secondary amines, and water - were viable partaers in the reaction. In addition, procedures made use of either ketones or aldehydes as the oxo-containing component. Primary or secondary amines, hydroxylamines, ammonia, hydrazides and hydrazines were found to successfully participate as the amine component. 

Of all the hydrazine nitrate salts only nickel hydrazine nitrate has been suggested for practical applications. Although it was first reported more than 50 years ago it still has not found wider application [22]. Despite the earlier information that nickel hydrazine nitrate is not reliably initiated in blasting caps [6,16] it has been recently suggested as a primary explosive that is suitable as a replacement for lead azide as an intermediate charge in commercial detonators [15,22]. Other authors recommended NHN as a complete replacement for lead styphnate and a partial replacement of lead azide in detonators [18]. 

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