Haloalkane
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.
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.
[citation needed] Haloalkanes can also be classified according to the type of halogen on group 17 responding to a specific halogenoalkane.
Haloalkanes containing carbon bonded to fluorine, chlorine, bromine, and iodine results in organofluorine, organochlorine, organobromine and organoiodine compounds, respectively.
Several classes of widely used haloalkanes are classified in this way chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs).
[citation needed] Haloalkanes generally resemble the parent alkanes in being colorless, relatively odorless, and hydrophobic.
The melting and boiling points of chloro-, bromo-, and iodoalkanes are higher than the analogous alkanes, scaling with the atomic weight and number of halides.
Many fluoroalkanes, however, go against this trend and have lower melting and boiling points than their nonfluorinated analogues due to the decreased polarizability of fluorine.
[3] The formal naming of haloalkanes should follow IUPAC nomenclature, which put the halogen as a prefix to the alkane.
However, many of these compounds have already an established trivial name, which is endorsed by the IUPAC nomenclature, for example chloroform (trichloromethane) and methylene chloride (dichloromethane).
However, some exceptions are known: ionic liquids suppress the formation or promote the cleavage of ethers,[4] hydrochloric acid converts tertiary alcohols to choloroalkanes, and primary and secondary alcohols convert similarly in the presence of a Lewis acid activator, such as zinc chloride.
[citation needed] In the laboratory, more active deoxygenating and halogenating agents combine with base to effect the conversion.
The heavier halogens do not require preformed reagents: A catalytic amount of PBr3 may be used for the transformation using phosphorus and bromine; PBr3 is formed in situ.
[citation needed] Primary aromatic amines yield diazonium ions in a solution of sodium nitrite.
[citation needed] Hydrolysis, a reaction in which water breaks a bond, is a good example of the nucleophilic nature of haloalkanes.
This OH− is a nucleophile with a clearly negative charge, as it has excess electrons it donates them to the carbon, which results in a covalent bond between the two.
[citation needed] Haloalkanes react with ionic nucleophiles (e.g. cyanide, thiocyanate, azide); the halogen is replaced by the respective group.
For example, after undergoing substitution reactions, cyanoalkanes may be hydrolyzed to carboxylic acids, or reduced to primary amines using lithium aluminium hydride.
[citation needed] In dehydrohalogenation reactions, the halogen and an adjacent proton are removed from halocarbons, thus forming an alkene.
[citation needed] Haloalkanes undergo free-radical reactions with elemental magnesium to give alkyl-magnesium compound: Grignard reagent.
Alkali metals such as sodium and lithium are able to cause haloalkanes to couple in Wurtz reaction, giving symmetrical alkanes.
Important halogenated polymers include polyvinyl chloride (PVC), and polytetrafluoroethene (PTFE, or teflon).
Similarly, great interest has been shown in remediation of man made halocarbons such as those produced on large scale, such as dry cleaning fluids.
The more reactive members of this large class of compounds generally pose greater risk, e.g. carbon tetrachloride.
