Гидразин: свойства, применение и опасность

Colorless flammable liquid with an ammonia like odor

the class of antidepressants

Hydrazine is an inorganic compound with the chemical formula |N2H4|auto=yes. It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine hydrate (|N2H4*xH2O). Hydrazine is mainly used as a foaming agent in preparing polymer foams, but applications also include its uses as a precursor to pharmaceuticals and agrochemicals, as well as a long term storable propellant for in space spacecraft propulsion. Additionally, hydrazine is used in various rocket fuels and to prepare the gas precursors used in air bags. Hydrazine is used within both nuclear and conventional electrical power plant steam cycles as an oxygen scavenger to control concentrations of dissolved oxygen in an effort to reduce corrosion. , approximately 120,000 tons of hydrazine hydrate (corresponding to a 64% solution of hydrazine in water by weight) were manufactured worldwide per year. Space Shuttle, and U 2 spy plane use hydrazine to fuel their Emergency Start System in the event of an engine stall.

Hydrazine is a precursor to several pharmaceuticals and pesticides. Often these applications involve conversion of hydrazine to heterocyclic rings such as pyrazoles and pyridazines. Examples of commercialized bioactive hydrazine derivatives include cefazolin, rizatriptan, anastrozole, fluconazole, metazachlor, metamitron, metribuzin, paclobutrazol, diclobutrazole, propiconazole, hydrazine sulfate,

The Italian catalyst manufacturer Acta (chemical company) has proposed using hydrazine as an alternative to hydrogen in fuel cells. The chief benefit of using hydrazine is that it can produce over 200 mW/cm2 more than a similar hydrogen cell without requiring (expensive) platinum catalysts. Because the fuel is liquid at room temperature, it can be handled and stored more easily than hydrogen. By storing the hydrazine in a tank full of a double bonded carbon oxygen carbonyl, the fuel reacts and forms a safe solid called hydrazone. By then flushing the tank with warm water, the liquid hydrazine hydrate is released. Hydrazine has a higher electromotive force of 1.56 V compared to 1.23 V for hydrogen. Hydrazine breaks down in the cell to form nitrogen and hydrogen which bonds with oxygen, releasing water. From January–June 1991, the U. S. Army Research Laboratory conducted a review of early bulk loaded liquid propellant gun programs for possible relevance to the electrothermal chemical propulsion program.

Potential routes of hydrazine exposure include dermal, ocular, inhalation and ingestion. Hydrazine exposure can cause skin irritation/contact dermatitis and burning, irritation to the eyes/nose/throat, nausea/vomiting, shortness of breath, pulmonary edema, headache, dizziness, central nervous system depression, lethargy, temporary blindness, seizures and coma. Exposure can also cause organ damage to the liver, kidneys and central nervous system. Hydrazine is documented as a strong skin sensitizer with potential for cross sensitization to hydrazine derivatives following initial exposure. In addition to occupational uses reviewed above, exposure to hydrazine is also possible in small amounts from tobacco smoke. The International Agency for Research on Cancer (IARC) rates hydrazine as "2A—probably carcinogenic to humans" with a positive association observed between hydrazine exposure and lung cancer. Based on cohort and cross sectional studies of occupational hydrazine exposure, a committee from the National Academies of Sciences, Engineering and Medicine concluded that there is suggestive evidence of an association between hydrazine exposure and lung cancer, with insufficient evidence of association with cancer at other sites. The European Commission’s Scientific Committee on Occupational Exposure Limits (SCOEL) places hydrazine in carcinogen "group B—a genotoxic carcinogen". The genotoxic mechanism the committee cited references hydrazine's reaction with endogenous formaldehyde and formation of a DNA methylating agent. In the event of a hydrazine exposure related emergency, NIOSH recommends removing contaminated clothing immediately, washing skin with soap and water, and for eye exposure removing contact lenses and flushing eyes with water for at least 15 minutes. NIOSH also recommends anyone with potential hydrazine exposure to seek medical attention as soon as possible. For aerospace personnel, the United States Air Force uses an emergency exposure guideline, developed by the National Academy of Sciences Committee on Toxicology, which is utilized for non routine exposures of the general public and is called the Short Term Public Emergency Exposure Guideline (SPEGL). The SPEGL, which does not apply to occupational exposures, is defined as the acceptable peak concentration for unpredicted, single, short term emergency exposures of the general public and represents rare exposures in a worker's lifetime. For hydrazine the 1 hour SPEGL is 2 ppm, with a 24 hour SPEGL of 0.08 ppm.

A complete surveillance programme for hydrazine should include systematic analysis of biologic monitoring, medical screening and morbidity/mortality information. The CDC recommends surveillance summaries and education be provided for supervisors and workers. Pre placement and periodic medical screening should be conducted with specific focus on potential effects of hydrazine upon functioning of the eyes, skin, liver, kidneys, hematopoietic, nervous and respiratory systems. The molecule adopts a gauche conformation with a torsion angle of 91(2)° (dihedral angle between the planes containing the N N bond and the bisectors of the H N H angles). The rotational barrier is twice that of ethane. These structural properties resemble those of gaseous hydrogen peroxide, which adopts a "skewed" anticlinal conformation, and also experiences a strong rotational barrier. The structure of solid hydrazine was determined by X ray diffraction. In this phase the N N bond has a length of 1.46 Å and the nearest non bonded distances are 3.19, 3.25 and 3.30 Å.

Diverse synthetic pathways for hydrazine production have been developed. The key step is the creation of the N–N single bond. The many routes can be divided into those that use chlorine oxidants (and generate salt) and those that do not.

Hydrazine can be protonated to form various solid salts of the hydrazinium cation |[N2H5]+, by treatment with mineral acids. A common salt is hydrazinium hydrogensulfate, |[N2H5]+[HSO4] Hydrazinium hydrogensulfate was investigated as a treatment of cancer induced cachexia, but proved ineffective. Double protonation gives the hydrazinium dication or hydrazinediium, |[N2H6](2+), of which various salts are known.

Hydrazines are part of many organic syntheses, often those of practical significance in pharmaceuticals (see applications section), as well as in textile dyes and in photography. In the Einhorn Brunner reaction hydrazines react with imides to give triazoles. Being a good nucleophile, |N2H4 can attack sulfonyl halides and acyl halides. The tosylhydrazine also forms hydrazones upon treatment with carbonyls. Hydrazine is used to cleave N alkylated phthalimide derivatives. This scission reaction allows phthalimide anion to be used as amine precursor in the Gabriel synthesis.

Hydrazine is the intermediate in the anaerobic oxidation of ammonia (anammox) process. It is produced by some yeasts and the open ocean bacterium anammox (Brocadia anammoxidans). The false morel produces the poison gyromitrin which is an organic derivative of hydrazine that is converted to monomethylhydrazine by metabolic processes. Even the most popular edible "button" mushroom Agaricus bisporus produces organic hydrazine derivatives, including agaritine, a hydrazine derivative of an amino acid, and gyromitrin.

The name "hydrazine" was coined by Emil Fischer in 1875; he was trying to produce organic compounds that consisted of mono substituted hydrazine. By 1887, Theodor Curtius had produced hydrazine sulfate by treating organic diazides with dilute sulfuric acid; however, he was unable to obtain pure hydrazine, despite repeated efforts. Pure anhydrous hydrazine was first prepared by the Dutch chemist Lobry de Bruyn in 1895.