Hydrogen iodide
Hydrogen iodide (HI) is a diatomic molecule and hydrogen halide. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different in that the former is a gas under standard conditions, whereas the other is an aqueous solution of the gas. They are interconvertible. HI is used in organic and inorganic synthesis as one of the primary sources of iodine and as a reducing agent.
| Names | |
|---|---|
| IUPAC name
Hydrogen iodide | |
| Systematic IUPAC name
Iodane | |
| Other names
Hydroiodic acid (aqueous solution) Iodine hydride | |
| Identifiers | |
3D model (JSmol) |
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.030.087 |
| EC Number |
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| KEGG | |
PubChem CID |
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| RTECS number |
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| UNII | |
| UN number | 1787 2197 |
CompTox Dashboard (EPA) |
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SMILES
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| Properties | |
| HI | |
| Molar mass | 127.912 g·mol−1 |
| Appearance | Colorless gas |
| Odor | acrid |
| Density | 2.85 g/mL (−47 °C) |
| Melting point | −50.80 °C (−59.44 °F; 222.35 K) |
| Boiling point | −35.36 °C (−31.65 °F; 237.79 K) |
| approximately 245 g/100 ml | |
| Acidity (pKa) | −10 (in water, estimate); −9.5 (±1.0) 2.8 (in acetonitrile) |
| Conjugate acid | Iodonium |
| Conjugate base | Iodide |
Refractive index (nD) |
1.466 (16 °C) |
| Structure | |
Molecular shape |
Terminus |
| 0.38 D | |
| Thermochemistry | |
Heat capacity (C) |
29.2 J·mol−1·K−1 |
Std molar entropy (S⦵298) |
206.6 J·mol−1·K−1 |
Std enthalpy of formation (ΔfH⦵298) |
26.5 kJ·mol−1 |
Gibbs free energy (ΔfG⦵) |
1.7 kJ·mol−1 |
Enthalpy of fusion (ΔfH⦵fus) |
2.87 kJ·mol−1 |
Enthalpy of vaporization (ΔfHvap) |
17.36 kJ·mol−1 |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
Toxic, corrosive, harmful and irritant |
| GHS labelling: | |
| Danger | |
| H302, H314 | |
| P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501 | |
| NFPA 704 (fire diamond) |
3
0
1 COR |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) |
345 mg/kg (rat, orally) |
| Safety data sheet (SDS) | hydrogen iodide |
| Related compounds | |
Other anions |
Hydrogen fluoride Hydrogen chloride Hydrogen bromide Hydrogen astatide |
| Supplementary data page | |
| Hydrogen iodide (data page) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references | |
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