Hydrazinium chloride

Hydrazinium chloride can be synthesized by the reaction of hydrazine and hydrogen chloride.^[6]

H₂N−NH₂ + HCl → [H₂N−NH₃]⁺Cl⁻

Hydrazinium chloride has an orthorhombic crystal structure (a = 1249 pm, b = 2185 pm, c = 441 pm) with the space group Fdd2. The crystal of hydrazinium chloride obtained from an alcoholic solution are very fine needles parallel to the c axis.^[4][7]

Hydrazinium chloride passes through several phase transitions at elevated pressures. The structure of phase I at room temperature and 1.8 GPa is confirmed to be space group C2/c. A structural transition from phase I to phase II is observed at 7.3 GPa. Pressure-induced position variation of hydrogen atoms in −NH+3 units during the phase transition is attributed to the formation of N―H···Cl hydrogen bonds. Finally, a further transition from phase II to phase III accompanied with a slight distortion in the hydrazinium ions occurs above 19.8 GPa. Phase III exists up to at least 39.5 GPa.^[8]

Hydrazinium chloride is commonly used as a reagent in the synthesis of pyrazoles. It is used as a catalyst in the synthesis of titanium oxide polymers via catalytic sol-gel process, and in preparation of amorphous titanium dioxide thin films with high refractive indices and high transparency.^[9]

Hydrazinium chloride is often used as a reducing agent in various chemical reactions and has uses in the preparation of other hydrazine derivatives. It is also used in the preparation of certain pharmaceuticals and as a reagent in analytical chemistry.^[10]

Hydrazinium chloride can be used to synthesize energetic materials containing hydrazinium cation.^[11][12]