Hydroiodic acid

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Hydroiodic acid
Space-filling model of hydrogen iodide Hydrogen-iodide-3D-vdW.svg
Space-filling model of hydrogen iodide
Space-filling model of water Water molecule 3D.svg
Space-filling model of water
The iodide anion Iodide ion.svg
The iodide anion
Space-filling model of the hydronium cation Hydronium-3D-vdW.svg
Space-filling model of the hydronium cation
An oxidized solution of hydroiodic acid Oxidized Hydriodic Acid.jpg
An oxidized solution of hydroiodic acid
Names
Other names
  • Aqueous hydrogen iodide
  • Hydriodic acid
  • Hydrogen iodide, hydrous
  • Hydronium iodide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
EC Number
  • 233-109-9
PubChem CID
RTECS number
  • MW3760000
UNII
  • InChI=1S/BrH/h1H Yes check.svgY
    Key: CPELXLSAUQHCOX-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/BrH/h1H
    Key: CPELXLSAUQHCOX-UHFFFAOYAZ
  • [OH3+].[I-]
Properties
HI(aq)
Molar mass 127.912 g·mol−1(HI)
Appearancecolorless liquid when pure, darkens on exposure to oxygen
Odor acrid
Density 1.70 g/mL, azeotrope
(57% HI by weight)
Boiling point 127 °C (261 °F; 400 K) 1.03 bar, azeotrope
Aqueous solution
Acidity (pKa)−9.3 (HI) [1]
Hazards
GHS labelling:
GHS-pictogram-acid.svg
Danger
H314
P260, P264, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazard ACID: Acid
3
0
0
ACID
Flash point Non-flammable
Related compounds
Other anions
Related compounds
 Hydrogen iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Hydroiodic acid (or hydriodic acid) is a colorless liquid. It is an aqueous solution of hydrogen iodide with the chemical formula H I(aq). It is a strong acid, in which hydrogen iodide is ionized completely in an aqueous solution. Concentrated aqueous solutions of hydrogen iodide are usually 48% to 57% HI by mass. [2]

Contents

Preparation

Reactions

Hydroiodic acid reacts with oxygen in air to give iodine:

4 HI(aq) + O2 → 2 H2O + 2 I2

Like hydrogen halides, hydroiodic acid adds to alkenes to give alkyl iodides. It can also be used as a reducing agent, for example in the reduction of aromatic nitro compounds to anilines. [3]

Cativa process

The Cativa process is a major end use of hydroiodic acid, which serves as a co-catalyst for the production of acetic acid by the carbonylation of methanol. [4] [5]

The catalytic cycle of the Cativa process Cativa-process-catalytic-cycle.png
The catalytic cycle of the Cativa process

Illicit uses

Hydroiodic acid is listed as a U.S. Federal DEA List I Chemical, owing to its use as a reducing agent related to the production of methamphetamine from ephedrine or pseudoephedrine (recovered from nasal decongestant pills). [6]

References

  1. ↑ Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 32. ISBN   0-08-029214-3. LCCN   82-16524.
  2. ↑ Lyday, Phyllis A. (2005). "Iodine and Iodine Compounds". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. pp. 382–390. doi:10.1002/14356007.a14_381. ISBN   978-3-527-30673-2.
  3. ↑ Kumar, J. S. Dileep; Ho, ManKit M.; Toyokuni, Tatsushi (2001). "Simple and chemoselective reduction of aromatic nitro compounds to aromatic amines: reduction with hydriodic acid revisited". Tetrahedron Letters. 42 (33): 5601–5603. doi:10.1016/s0040-4039(01)01083-8.
  4. ↑ Jones, J. H. (2000). "The Cativa Process for the Manufacture of Acetic Acid" (PDF). Platinum Metals Rev. 44 (3): 94–105.
  5. ↑ Sunley, G. J.; Watson, D. J. (2000). "High productivity methanol carbonylation catalysis using iridium - The Cativa process for the manufacture of acetic acid". Catalysis Today. 58 (4): 293–307. doi:10.1016/S0920-5861(00)00263-7.
  6. ↑ Skinner, Harry F. (1990). "Methamphetamine synthesis via hydriodic acid/Red phosphorus reduction of ephedrine". Forensic Science International. 48 (2): 123–134. doi:10.1016/0379-0738(90)90104-7.
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