Iodoform

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Iodoform
Stereo, skeletal formula of iodoform with the explicit hydrogen added
Ball and stick model of iodoform Spacefill model of iodoform
Sample of crystalline iodoform in a watchglass
Identifiers
CAS number 75-47-8 YesY
PubChem 6374
ChemSpider 6134 YesY
UNII KXI2J76489 YesY
EC number 200-874-5
KEGG D01910 YesY
MeSH iodoform
ChEBI CHEBI:37758 YesY
ChEMBL CHEMBL1451116 N
RTECS number PB7000000
ATC code D09AA13
Beilstein Reference 1697010
Jmol-3D images Image 1
Properties
Molecular formula CHI3
Molar mass 393.73 g mol−1
Appearance Pale, light yellow, opaque crystals
Density 4.008 g mL−1
Melting point 121.10 °C; 249.98 °F; 394.25 K
Solubility in water 100 mg L−1 (at 20 °C)
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
kH 3.4 μmol Pa−1 kg−1
Structure
Crystal structure Hexagonal
Coordination
geometry
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 The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word WARNING
GHS hazard statements H315, H319, H335
GHS precautionary statements P261, P280, P305+351+338
EU classification Harmful 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
Flash point 204 °C (399 °F; 477 K)
LD50
  • 355 mg kg−1 (oral, rat)
  • 1.184 g kg−1 (dermal, rat)
Related compounds
Related alkanes
Related compounds
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
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, and sometimes also referred to as carbon triiodide (which is not strictly correct, as this compound also contains hydrogen) or methyl triiodide (which is somewhat ambiguous as that name could also refer to the methylated triiodide ion, CHI3).

Synthesis and reactions[edit]

Iodoform was first prepared by Georges Serrulas in 1822;[1] and at much the same time independently by John Thomas Cooper.[2] 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).

Iodoform synthesis.svg

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, which is oxidized by mixture of sulfuric acid and iodine pentaoxide. 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[edit]

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

Applications[edit]

The compound finds small scale use as a disinfectant.[3] 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, to prevent infection and facilitate removal of ear hair, along with zinc oxide and propanoic acid.

See also[edit]

References[edit]

  • Merck Index, 12 Edition, 5054.
  1. ^ Georges-Simon Surellas, 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] (Metz, France: Antoine, 1822). On pages 17-20, Surellas produced iodoform by passing a mixture of iodine vapor and steam over red-hot coals. However, later, on pages 28-29, he produced iodoform by adding potassium metal to a solution of iodine in ethanol (which also contained some water).
  2. ^ James, Frank A. J. L. "Cooper, John Thomas (1790–1854), chemist". Oxford Dictionary of National Biography. Oxford University Press. Retrieved 26 January 2012. 
  3. ^ Phyllis A. Lyday "Iodine and Iodine Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.

External links[edit]