Hydroiodic acid

Hydroiodic acid
Space-filling model of hydrogen iodide	Space-filling model of water
The iodide anion	Space-filling model of the hydronium cation
Names
	Other names Aqueous hydrogen iodide; Hydriodic acid; Hydrogen iodide, hydrous; Hydronium iodide;
Identifiers
CAS Number	10034-85-2 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:43451 ;
ChemSpider	23224 ;
EC Number	233-109-9;
PubChem CID	24841;
RTECS number	MW3760000;
UNII	694C0EFT9Q ;
	InChI InChI=1S/BrH/h1H Key: CPELXLSAUQHCOX-UHFFFAOYSA-N ; InChI=1/BrH/h1H Key: CPELXLSAUQHCOX-UHFFFAOYAZ;
	SMILES [OH3+].[I-];
Properties
Chemical formula	HI(aq)
Molar mass	127.912 g·mol−1 (HI)
Appearance	colorless liquid
Odor	acrid
Density	1.70 g/mL, azeotrope; (57% HI by weight)
Boiling point	127 °C (261 °F; 400 K) 1.03 bar, azeotrope
Solubility in water	Aqueous solution
Acidity (pKa)	−9.3 (HI)
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314
Precautionary statements	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 0 ACID
Flash point	Non-flammable
Related compounds
Other anions	Hydrofluoric acid; Hydrochloric acid; Hydrobromic acid;
Related compounds	Hydrogen iodide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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]

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

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

^ 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.
^ 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 978-3527306732.
^ 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.
^ Jones, J. H. (2000). "The Cativa Process for the Manufacture of Acetic Acid" (PDF). Platinum Metals Rev. 44 (3): 94–105.
^ 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.
^ 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.

External links

[P82db-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.

[Ullmann-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 978-3527306732.

[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.

[Cativa-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.

[2]