Iodoform

Iodoform
IUPAC name Triiodomethane
Other names Iodoform, Methyl triiodide, Carbon triiodide, TIM
Identifiers
CAS number	75-47-8 Y
PubChem	6374
ChemSpider	6134 Y
UNII	KXI2J76489 Y
EC number	200-874-5
KEGG	D01910 Y
ChEBI	CHEBI:37758 Y
RTECS number	PB7000000
Jmol-3D images	Image 1
SMILES IC(I)I
InChI InChI=1S/CHI3/c2-1(3)4/h1H Y Key: OKJPEAGHQZHRQV-UHFFFAOYSA-N Y InChI=1/CHI3/c2-1(3)4/h1H
Properties
Molecular formula	CHI3
Molar mass	393.73 g/mol
Appearance	Yellow crystals
Density	4.008 g/cm3
Melting point	123 °C
Boiling point	217 °C (expl.)
Solubility in water	0.1 g/L at 20 °C (slightly soluble in glycerol and petroleum ether; moderately soluble in chloroform and acetic acid, highly soluble in benzene, ethanol (78 g/L at 25 °C), acetone (120 g/L at 25 °C) and ether (136 g/L at 25 °C))
log P	3.83
kH	0.34 mol.kg-1.bar-1
Structure
Crystal structure	Hexagonal
Molecular shape	Tetrahedral
Hazards
EU classification	Harmful (Xn), Dangerous for the environment (N)
R-phrases	R20/21/22, R36/37/38
S-phrases	S22, S26, S36/37/39
NFPA 704	0 2 1
Flash point	204 °C
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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 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, CH₃I₃).

Synthesis and reactions

Iodoform was first prepared by Georges Serrulas in 1822 and its molecular formula was identified by Jean-Baptiste Dumas in 1834. 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, 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

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

Applications

The compound finds small scale use as a disinfectant.^[1] 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.

References

1. ^ Phyllis A. Lyday "Iodine and Iodine Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.

• Merck Index, 12 Edition, 5054.

See also

• Iodoform reaction

External links

• NIOSH Pocket Guide to Chemical Hazards 0343
• MSDS at Oxford University
• MSDS at JT Baker
• A Method for the Specific Conversion of Iodoform to Carbon Dioxide
• Article at 1911 Encyclopaedia Britannica
• Preparation