Hydrazine

Names IUPAC nameSystematic IUPAC nameOther names Identifiers 878137 ChEBIChEMBLChemSpiderECHA InfoCard100.005.560EC Number190 KEGGMeSHHydrazineRTECS numberUNIIUN number2029 Properties N₂H₄Molar mass32.046 g·mol Appearance Colorless, fuming, oily liquid OdorAmmonia-like Density1.021 g/cm Melting point2 °C; 35 °F; 275 K Boiling point114 °C; 237 °F; 387 K Miscible log P0.67 Vapor pressure1 kPa (at 30.7 °C) Acidity (pK_a) 8.10 ([N₂H₅]) Basicity (pK_b) 5.90 Conjugate acidHydrazinium1.46044 (at 22 °C) Viscosity0.876 cP Structure Triangular pyramidal at N 1.85 D Thermochemistry 121.52 J/(K·mol) 50.63 kJ/mol Hazards GHS labelling: DangerH226, H301, H311, H314, H317, H331, H350, H410P201, P261, P273, P280, P301+P310, P305+P351+P338NFPA 704 (fire diamond) Flash point52 °C (126 °F; 325 K) 24 to 270 °C (75 to 518 °F; 297 to 543 K) Explosive limits1.8–100% Lethal dose or concentration (LD, LC): 59–60 mg/kg (oral in rats, mice) 260 ppm (rat, 4 h)
630 ppm (rat, 1 h)
570 ppm (rat, 4 h)
252 ppm (mouse, 4 h) NIOSH (US health exposure limits): TWA 1 ppm (1.3 mg/m) [skin] Ca C 0.03 ppm (0.04 mg/m) [2-hour] Ca [50 ppm] Safety data sheet (SDS) ICSC 0281Related compounds Tetrafluorohydrazine
Hydrogen peroxide
Diphosphane
Diphosphorus tetraiodideOrganic hydrazinesAmmonia
TriazaneDiazene
Triazene
Tetrazene
Diphosphene

Hydrazine is an inorganic compound with the chemical formulaN₂H₄. It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous 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 airbags. 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. As of 2000, approximately 120,000 tons of hydrazine hydrate (corresponding to a 64% solution of hydrazine in water by weight) were manufactured worldwide per year.

Hydrazines are a class of organic substances derived by replacing one or more hydrogen atoms in hydrazine by an organic group.

In 2019, the first examples of isomorphism between organic hydrazinosolvates and their corresponding hydrates were discovered, demonstrating that hydrazine molecules can undergo isomorphous substitution by water within crystalline frameworks such as 18-crown-6 complexes.