Editing Halogen (section)

== Applications ==

=== Disinfectants ===
Both chlorine and bromine are used as [[disinfectants]] for drinking water, swimming pools, fresh wounds, spas, dishes, and surfaces. They kill [[bacteria]] and other potentially harmful [[microorganism]]s through a process known as [[Sterilization (microbiology)|sterilization]]. Their reactivity is also put to use in [[Bleaching agent|bleaching]]. [[Sodium hypochlorite]], which is produced from chlorine, is the active ingredient of most [[Cloth|fabric]] bleaches, and chlorine-derived bleaches are used in the production of some [[paper]] products.

=== Lighting ===
[[Halogen lamp]]s are a type of [[incandescent lamp]] using a [[tungsten]] filament in bulbs that have small amounts of a halogen, such as iodine or bromine added. This enables the production of lamps that are much smaller than non-halogen [[incandescent lightbulb]]s at the same [[watt]]age. The gas reduces the thinning of the filament and blackening of the inside of the bulb resulting in a bulb that has a much greater life. Halogen lamps glow at a higher temperature (2800 to 3400 [[kelvin]]) with a whiter colour than other incandescent bulbs. However, this requires bulbs to be manufactured from [[fused quartz]] rather than silica glass to reduce breakage.<ref name="Edison">{{cite web|title=The Halogen Lamp|url=http://www.edisontechcenter.org/halogen.html|website=Edison Tech Center|access-date=2014-09-05 }}</ref>

=== Drug components ===
In [[drug discovery]], the incorporation of halogen atoms into a lead drug candidate results in analogues that are usually more [[lipophilic]] and less water-soluble.<ref>{{cite book| first = G. | last= Thomas | title =Medicinal Chemistry an Introduction | publisher = John Wiley & Sons, West Sussex, UK| year=  2000 | isbn= 978-0-470-02597-0}}</ref> As a consequence, halogen atoms are used to improve penetration through [[lipid membrane]]s and tissues. It follows that there is a tendency for some halogenated drugs to accumulate in [[adipose tissue]].

The chemical reactivity of halogen atoms depends on both their point of attachment to the lead and the nature of the halogen. [[Aromatic]] halogen groups are far less reactive than [[aliphatic]] halogen groups, which can exhibit considerable chemical reactivity. For aliphatic carbon-halogen bonds, the C-F bond is the strongest and usually less chemically reactive than aliphatic C-H bonds. The other aliphatic-halogen bonds are weaker, their reactivity increasing down the periodic table. They are usually more chemically reactive than aliphatic C-H bonds. As a consequence, the most common halogen substitutions are the less reactive aromatic fluorine and chlorine groups.