Iodoform

for use of the term "iodoform" in cryptography, see Group key
Iodoform
Names
Other names
Triiodomethane
Identifiers
ATC code D09AA13
1697010
75-47-8 Yes
ChEBI CHEBI:37758 Yes
ChEMBL ChEMBL1451116 
ChemSpider 6134 Yes
EC number 200-874-5
Jmol-3D images Image
KEGG D01910 Yes
MeSH iodoform
PubChem 6374
RTECS number PB7000000
UNII KXI2J76489 Yes
Properties
Molecular formula
 CHI3
Molar mass 393.73 g·mol−1
Appearance Pale, light yellow, opaque crystals
Odor Saffron-like[1]
Density 4.008 g mL−1[1]
Melting point 119 °C (246 °F; 392 K) [1]
Boiling point 218 °C (424 °F; 491 K) [1]
100 mg L−1[1]
Solubility in diethyl ether 136 g L−1
Solubility in acetone 120 g L−1
Solubility in ethanol 78 g L−1
log P 3.118
3.4 μmol Pa−1 kg−1
Structure
Crystal structure Hexagonal
Tetragonal
Molecular shape Tetrahedron
Thermochemistry
Specific
heat capacity (C)
 157.5 J K−1 mol−1
Std enthalpy of
formation (ΔfHo298)
 180.1–182.1 kJ mol−1
Std enthalpy of
combustion (ΔcHo298)
 −716.9–−718.1 kJ mol−1
Hazards
GHS pictograms
GHS signal word WARNING
H315, H319, H335
P261, P280, P305+351+338
EU classification Xn
R-phrases R20/21/22, R36/37/38
S-phrases S26, S36/37
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
0
2
1
Flash point 204 °C (399 °F; 477 K)
  • 355 mg kg−1 (oral, rat)[1]
  • 1180 mg kg−1 (dermal, rat)[1]
  • 1.6 mmol kg−1(s.c., mouse)[2]
US health exposure limits (NIOSH):
none[3]
0.6 ppm (10 mg/m3)[3]
N.D.[3]
Related compounds
Related haloalkanes
Related compounds
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Iodoform is the organoiodine compound with the formula CHI3. A pale yellow, crystalline, volatile substance, it has a penetrating odor (in older chemistry texts, the smell is sometimes referred to as the smell of hospitals) and, analogous to chloroform, sweetish taste. It is occasionally used as a disinfectant. It is also known as tri-iodomethane, carbon triiodide, and methyl triiodide.

Synthesis and reactions

The synthesis of Iodoform was first described by Georges Serrulas in 1822, by reactions of iodine vapour with steam over red hot coals, and also by reaction of potassium with ethanolic iodine in the presence of water;[4] and at much the same time independently by John Thomas Cooper.[5] It is synthesized in the haloform reaction by the reaction of iodine and sodium hydroxide with any one of these four kinds of organic compounds: (i) a methyl ketone: CH3COR, acetaldehyde (CH3CHO), ethanol (CH3CH2OH), and certain secondary alcohols (CH3CHROH, where R is an alkyl or aryl group).

The reaction of iodine and base with methyl ketones is so reliable that the "iodoform test" (the appearance of a yellow precipitate) is used to probe the presence of a methyl ketone. This is also the case when testing for secondary alcohols (methyl alcohols).

Some reagents (e.g. hydrogen iodide) convert iodoform to diiodomethane. Also conversion to carbon dioxide is possible: Iodoform reacts with aqueous silver nitrate to produce carbon monoxide. When treated with powdered elemental silver the iodoform is reduced, producing acetylene. Upon heating iodoform decomposes to produce diatomic iodine, hydrogen iodide gas, and carbon.

Natural occurrence

Angel's bonnets contain iodoform and show its characteristic odor.

Applications

The compound finds small scale use as a disinfectant.[2][6] Around the beginning of the 20th century it was used in medicine as a healing and antiseptic dressing for wounds and sores, although this use is now superseded by superior antiseptics. Adolf Hitler's mother, Klara Hitler, died of iodoform poisoning brought on by her treatment for breast cancer. It is the active ingredient in many ear powders for dogs and cats, along with zinc oxide and propanoic acid, which are used to prevent infection and facilitate removal of ear hair.

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Record in the GESTIS Substance Database of the IFA
  2. ↑ 2.0 2.1 Merck Index, 12 Edition, 5054
  3. ↑ 3.0 3.1 3.2 "NIOSH Pocket Guide to Chemical Hazards #0343". National Institute for Occupational Safety and Health (NIOSH).
  4. ↑ Surellas, Georges-Simon (1822), Notes sur l'Hydriodate de potasse et l'Acide hydriodique. -- Hydriodure de carbone; moyen d'obtenir, à l'instant, ce composé triple [Notes on the hydroiodide of potassium and on hydroiodic acid -- hydroiodide of carbon; means of obtaining instantly this compound of three elements] (in franch), Metz, France: Antoine, pp. 17–20, 28–29
  5. ↑ James, Frank A. J. L. "Cooper, John Thomas (1790–1854), chemist". Oxford Dictionary of National Biography. Oxford University Press. Retrieved 26 January 2012.
  6. ↑ Lyday, Phyllis A. (2005), "Iodine and Iodine Compounds", Ullmann's Encyclopedia of Industrial Chemistry (Wiley-VCH, Weinheim)

External links