Hydronium perchlorate

Hydronium perchlorate is an inorganic chemical compound with the chemical formula [H₃O]ClO₄. It is an unusual salt due to it being a solid and stable hydronium salt. It consists of hydronium cations [H₃O]⁺ and perchlorate anions ClO−4.

Hydronium perchlorate

Hydronium cation, [H3O]+   Oxygen, O   Hydrogen, H Perchlorate anion, ClO−4   Chlorine, Cl   Oxygen, O
Names
Other names Oxonium perchlorate Perchloric acid monohydrate
Identifiers
CAS Number	13444-99-0 Y
3D model (JSmol)	Interactive image
ChemSpider	25936644
PubChem CID	85613441
InChI InChI=1S/ClHO4.H2O/c2-1(3,4)5;/h(H,2,3,4,5);1H2 Key: AIUIJBDEQKTMHT-UHFFFAOYSA-N
SMILES [OH3+].[O-][Cl](=O)(=O)=O
Properties
Chemical formula	[H3O]ClO4
Molar mass	118.47 g·mol−1
Appearance	Colorless solid
Density	1.96 g/cm3
Melting point	45 °C (113 °F; 318 K)
Structure[1]
Crystal structure	Orthorhombic
Space group	Pnma
Lattice constant	a = 9.2343 Å, b = 5.8178 Å, c = 7.4606 Å
Related compounds
Other anions	Hydronium chloride
Other cations	Perchloric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Production

Hydronium perchlorate is produced by the reaction of anhydrous perchloric acid and water in a 1:1 molar ratio:^[2]

HClO₄ + H₂O → [H₃O]⁺ClO−4

A more analytically reliable method was reported using the macrocyclic Schiff base of sodium 2,6-diformyl-4-methylphenolate and 2,6-diformyl-4-methylphenol as a chelating agent to sequester Cu(II): transmetallation of the macrocycle with copper(II) perchlorate yielded colorless crystals of hydronium perchlorate.^[1]

It can also be produced by the reaction of anhydrous nitric acid and perchloric acid.^{[3][clarification needed]}