Carbon tetraiodide

Carbon tetraiodide is a tetrahalomethane with the molecular formula CI4. Being bright red, it is a relatively rare example of a highly colored methane derivative. It is only 2% by weight carbon, although other methane derivatives are known with still less carbon.

Carbon tetraiodide
Stereo, skeletal formula of carbon tetraiodide
Carbon tetraiodide crystals and solution
Ball and stick model of carbon tetraiodide
Spacefill model of carbon tetraiodide
Names
IUPAC name
Tetraiodomethane[1]
Identifiers
3D model (JSmol)
1733108
ChemSpider
ECHA InfoCard 100.007.335
EC Number
  • 208-068-5
RTECS number
  • FG4960000
Properties
CI4
Molar mass 519.629 g·mol−1
Appearance Dark violet crystals
Density 4.32 g mL−1
-136·10−6 cm3/mol
Structure
Tetragonal
Tetrahedral
0 D
Thermochemistry
0.500 J K−1 g−1
384.0–400.4 kJ mol−1
−794.4–−778.4 kJ mol−1
Hazards
GHS pictograms GHS07: Harmful
GHS signal word WARNING
H315, H319, H335
P261, P305+351+338
Related compounds
Related alkanes
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Structure

The tetrahedral molecule features C-I distances of 2.12 ± 0.02 Å.[2] The molecule is slightly crowded with short contacts between iodine atoms of 3.459 ± 0.03 Å, and possibly for this reason, it is thermally and photochemically unstable.

Carbon tetraiodide crystallizes in tetragonal crystal structure (a 6.409, c 9.558 (.10−1 nm)).[3]

It has zero dipole moment due to its symmetrically substituted tetrahedral molecule.

Properties, synthesis, uses

Carbon tetraiodide is slightly reactive towards water, giving iodoform and I2. It is soluble in nonpolar organic solvents. It decomposes thermally and photochemically to tetraiodoethylene, C2I4. Its synthesis entails AlCl3-catalyzed halide exchange, which is conducted at room temperature:[4]

The product crystallizes from the reaction solution.

Carbon tetraiodide is used as an iodination reagent, often upon reaction with bases.[5] Ketones are converted to 1,1-diiodoalkenes upon treatment with triphenylphosphine (PPh3) and carbon tetraiodide. Alcohols are converted in and to iodide, by a mechanism similar to the Appel reaction. In an Appel reaction, carbon tetrachloride is used to generate alkyl chlorides from alcohols.

Safety considerations

Manufacturers recommend that carbon tetraiodide be stored near 0 °C (32 °F). As a ready source of iodine, it is an irritant. Its LD50 is 178 mg.kg−1. In general, perhalogenated organic compounds should be considered toxic, with the narrow exception of small perfluoroalkanes (essentially inert due to the strength of the C-F bond).

References

  1. ^ "Tetraiodomethane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 27 March 2005. Identification and Related Records. Retrieved 29 February 2012.
  2. ^ Finbak, Chr.; Hassel, O. (1937). "Kristallstruktur und Molekülbau von CI4 und CBr4". Zeitschrift für Physikalische Chemie. B36: 301–308. doi:10.1515/zpch-1937-3621.
  3. ^ Pohl, S. (1982). "Die Kristallstruktur von CI4". Zeitschrift für Kristallographie. 159: 211–216. doi:10.1524/zkri.1982.159.14.211.
  4. ^ McArthur, R. E.; Simons, J. H. (1950). "Carbon Tetraiodide". Inorganic Syntheses. III: 37–39. doi:10.1002/9780470132340.ch8.
  5. ^ P. R. Schreiner, A. A. Fokin (2005). "Carbon Tetraiodide". In L. Paquette (ed.). Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons, Ltd.

Further reading

Appel reaction

The Appel reaction is an organic reaction that converts an alcohol into an alkyl chloride using triphenylphosphine and carbon tetrachloride. The use of carbon tetrabromide or bromine as a halide source will yield alkyl bromides, whereas using carbon tetraiodide, methyl iodide or iodine gives alkyl iodides. The reaction is credited to and named after Rolf Appel, it had however been described earlier. The use of this reaction is becoming less common, due to carbon tetrachloride being restricted under the Montreal protocol.

Drawbacks to the reaction are the use of toxic halogenating agents and the coproduction of organophosphorus product that must be separated from the organic product. The phosphorus reagent can be used in catalytic quantities. The corresponding alkyl bromide can also be synthesised by addition of lithium bromide as a source of bromide ions.

Compounds of carbon

Compounds of carbon are defined as chemical substances containing carbon. More compounds of carbon exist than any other chemical element except for hydrogen. Organic carbon compounds are far more numerous than inorganic carbon compounds. In general bonds of carbon with other elements are covalent bonds. Carbon is tetravalent but carbon free radicals and carbenes occur as short-lived intermediates. Ions of carbon are carbocations and carbanions are also short-lived. An important carbon property is catenation as the ability to form long carbon chains and rings.

Diiodomethane

Diiodomethane or methylene iodide, commonly abbreviated “MI”, is an organoiodine compound. Diiodomethane is a colorless liquid; however, it decomposes upon exposure to light liberating iodine, which colours samples brownish. It is slightly soluble in water, but soluble in organic solvents. It has a relatively high refractive index of 1.741, and a surface tension of 0.0508 N·m−1.

Ethane

Ethane ( or ) is an organic chemical compound with chemical formula C2H6. At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petrochemical by-product of petroleum refining. Its chief use is as feedstock for ethylene production.

Related compounds may be formed by replacing a hydrogen atom with another functional group; the ethane moiety is called an ethyl group. For example, an ethyl group linked to a hydroxyl group yields ethanol, the alcohol in beverages.

Ethyl iodide

Ethyl iodide (also iodoethane) is a colorless flammable chemical compound. It has the chemical formula C2H5I and is prepared by heating ethanol with iodine and phosphorus. On contact with air, especially on the effect of light, it decomposes and turns yellow or reddish from dissolved iodine.

It may also be prepared by reaction between hydroiodic acid and ethanol distilling off the ethyl iodide. Ethyl iodide should be stored in the presence of copper powder to avoid rapid decomposition, though even with this method samples do not last more than 1 year.

Because iodide is a good leaving group, ethyl iodide is an excellent ethylating agent. It is also used as the hydrogen radical promoter.

Haloalkane

The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of chemical compounds derived from alkanes containing one or more halogens. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially and, consequently, are known under many chemical and commercial names. They are used as flame retardants, fire extinguishants, refrigerants, propellants, solvents, and pharmaceuticals. Subsequent to the widespread use in commerce, many halocarbons have also been shown to be serious pollutants and toxins. For example, the chlorofluorocarbons have been shown to lead to ozone depletion. Methyl bromide is a controversial fumigant. Only haloalkanes which contain chlorine, bromine, and iodine are a threat to the ozone layer, but fluorinated volatile haloalkanes in theory may have activity as greenhouse gases. Methyl iodide, a naturally occurring substance, however, does not have ozone-depleting properties and the United States Environmental Protection Agency has designated the compound a non-ozone layer depleter. For more information, see Halomethane. Haloalkane or alkyl halides are the compounds which have the general formula "RX" where R is an alkyl or substituted alkyl group and X is a halogen (F, Cl, Br, I).

Haloalkanes have been known for centuries. Chloroethane was produced synthetically in the 15th century. The systematic synthesis of such compounds developed in the 19th century in step with the development of organic chemistry and the understanding of the structure of alkanes. Methods were developed for the selective formation of C-halogen bonds. Especially versatile methods included the addition of halogens to alkenes, hydrohalogenation of alkenes, and the conversion of alcohols to alkyl halides. These methods are so reliable and so easily implemented that haloalkanes became cheaply available for use in industrial chemistry because the halide could be further replaced by other functional groups.

While most haloalkanes are human-produced, non-artificial-source haloalkanes do occur on Earth, mostly through enzyme-mediated synthesis by bacteria, fungi, and especially sea macroalgae (seaweeds). More than 1600 halogenated organics have been identified, with bromoalkanes being the most common haloalkanes. Brominated organics in biology range from biologically produced methyl bromide to non-alkane aromatics and unsaturates (indoles, terpenes, acetogenins, and phenols). Halogenated alkanes in land plants are more rare, but do occur, as for example the fluoroacetate produced as a toxin by at least 40 species of known plants. Specific dehalogenase enzymes in bacteria which remove halogens from haloalkanes, are also known.

Halomethane

Halomethane compounds are derivatives of methane (CH4) with one or more of the hydrogen atoms replaced with halogen atoms (F, Cl, Br, or I). Halomethanes are both naturally occurring, especially in marine environments, and man-made, most notably as refrigerants, solvents, propellants, and fumigants. Many, including the chlorofluorocarbons, have attracted wide attention because they become active when exposed to ultraviolet light found at high altitudes and destroy the Earth's protective ozone layer.

Iodine

Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a lustrous, purple-black non-metallic solid at standard conditions that melts to form a deep violet liquid at 114 degrees Celsius, and boils to a violet gas at 184 degrees Celsius. The element was discovered by the French chemist Bernard Courtois in 1811. It was named two years later by Joseph Louis Gay-Lussac from this property, after the Greek ἰώδης "violet-coloured".

Iodine occurs in many oxidation states, including iodide (I−), iodate (IO−3), and the various periodate anions. It is the least abundant of the stable halogens, being the sixty-first most abundant element. It is the heaviest essential mineral nutrient. Iodine is essential in the synthesis of thyroid hormones. Iodine deficiency affects about two billion people and is the leading preventable cause of intellectual disabilities.

The dominant producers of iodine today are Chile and Japan. Iodine and its compounds are primarily used in nutrition. Due to its high atomic number and ease of attachment to organic compounds, it has also found favour as a non-toxic radiocontrast material. Because of the specificity of its uptake by the human body, radioactive isotopes of iodine can also be used to treat thyroid cancer. Iodine is also used as a catalyst in the industrial production of acetic acid and some polymers.

Iodoform

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

List of inorganic compounds

Although most compounds are referred to by their IUPAC systematic names (following IUPAC nomenclature), "traditional" names have also been kept where they are in wide use or of significant historical interests.

Methyl iodide

Methyl iodide, also called iodomethane, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one hydrogen atom by an atom of iodine. It is naturally emitted by rice plantations in small amounts. It is also produced in vast quantities estimated to be greater than 214,000 tons annually by algae and kelp in the world's temperate oceans, and in lesser amounts on land by terrestrial fungi and bacteria. It is used in organic synthesis as a source of methyl groups.

Tetrahalomethane

Tetrahalomethanes are fully halogenated methane derivatives of general formula CBrkCllFmInAtp, where:Tetrahalomethanes are on the border of inorganic and organic chemistry, thus they can be assigned both inorganic and organic names by IUPAC: tetrafluoromethane - carbon tetrafluoride, tetraiodomethane - carbon tetraiodide, dichlorodifluoromethane - carbon dichloride difluoride.

Each halogen (F, Cl, Br, I, At) forms a corresponding halomethane, but their stability decreases in order CF4 > CH4 > CCl4 > CBr4 > CI4 from exceptionally stable gaseous tetrafluoromethane with bond energy 515 kJ.mol−1 to solid tetraiodomethane, depending on bond energy.

Many mixed halomethanes are also known, such as CBrClF2.

Tetraiodide

tetraiodide may refer to:

Carbon tetraiodide, CI4

Diphosphorus tetraiodide, P2I4, an orange crystalline solid and a versatile reducing agent

Silicon tetraiodide, SiI4

Tellurium tetraiodide, TeI4

Titanium tetraiodide, TiI4

Unsubstituted
Monosubstituted
Disubstituted
Trisubstituted
Tetrasubstituted
Compounds
Carbon ions
Oxides and related

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