Denatonium
Template:Short description Template:Chembox Denatonium, usually available as denatonium benzoate (under trade names such as Denatrol, BITTERANT-b, BITTER+PLUS, Bitrex, Bitrix, and Aversion) and as denatonium saccharinate (BITTERANT-s), is the bitterest chemical compound known, with bitterness thresholds of 0.05 ppm for the benzoate and 0.01 ppm for the saccharinate.<ref name="auto">Template:Cite conference</ref> It was discovered in 1958 during research on local anesthetics by T. & H. Smith of Edinburgh, Scotland, and registered under the trademark Bitrex.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Dilutions of as little as 10 ppm are unbearably bitter to most people. Denatonium salts are usually colorless and odorless solids, but are often traded as solutions. They are used as aversive agents (bitterants) to prevent inappropriate ingestion. Denatonium is used in denatured alcohol,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> antifreeze, preventive nail biting preparations, respirator mask fit-testing, animal repellents, liquid soaps, shampoos, and Nintendo Switch game cards to prevent accidental swallowing or choking by children. It is not known to pose any long-term health risks.<ref name="auto"/>
The name denatonium reflects the substance's primary use as a denaturant and its chemical nature as a cation, hence -onium as a Neo-Latin suffix.
Structure, synthesis, and physical propertiesEdit
Denatonium is a quaternary ammonium cation. It is composed as a salt with any of several anions, such as benzoate or saccharinate. It can be obtained by the quaternization of lidocaine, a popular anesthetic, with benzyl chloride or a similar reagent.<ref name=":0">Template:Cite journal</ref> To obtain other salts, like the benzoate, the formed denatonium chloride is subjected to an anion exchange reaction with sodium benzoate, or first sodium hydroxide to make denatonium hydroxide followed by neutralization with benzoic acid.<ref name=":0" /> Other similar compounds are procaine and benzocaine.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
BiochemistryEdit
Denatonium in humans is recognized by eight distinct bitter taste receptors: TAS2R4, TAS2R8, TAS2R10, TAS2R39, TAS2R43, TAS2R16, TAS2R46, and TAS2R47, being by far Template:Clarify to the compound.<ref name="Meyerhof2010">Template:Cite journal</ref><ref name=bitterdb>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Denatonium can act as a bronchodilator by activating bitter taste receptors in the airway smooth muscle.<ref name="Desphande2010">Template:Cite journal</ref>
ApplicationsEdit
The bitterness of the compound guides most applications of denatonium. Denatonium benzoate is used to denature ethanol so that it is not treated as an alcoholic beverage with respect to taxation and sales restrictions. One designation in particular, SD-40B, indicates that ethanol has been denatured using denatonium benzoate.
Denatonium is commonly included in placebos used in clinical trials to mimic the bitter taste of certain medications.<ref name="auto" />
Denatonium benzoate is an ingredient in certain nail polishes and varnishes designed to discourage nail biting, as the bitter denatonium serves as an aversive.<ref name="pmid8881096">Template:Cite journal</ref>
Denatonium also discourages consumption of poisonous alcohols such as methanol and additives such as ethylene glycol. It is also added to many kinds of harmful liquids, including solvents (such as nail polish remover), paints, varnishes, toiletries and other personal care items, special nail polish for preventing nail biting, and various other household products. It is also added to less hazardous aerosol products (such as gas dusters) to discourage inhalant abuse of the volatile vapors.Template:Citation needed
In 1995, the U.S. state of Oregon required that denatonium benzoate be added to products containing sweet-tasting ethylene glycol and methanol such as antifreeze and windshield washer fluid to prevent poisonings of children and animals.<ref name="Mullins">Template:Cite journal</ref> In December 2012, U.S. manufacturers voluntarily agreed to add denatonium benzoate to antifreeze sold nationwide.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Animals are known to have different sensitivities to the effects of denatonium. It is used in some animal repellents (especially for such large mammals as deer). It has been used to safeguard rat poisons from human consumption,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> as humans are able to detect denatonium at much lower concentrations than rodents.<ref>Frank ME, Bouverat BP, MacKinnon BI, Hettinger TP. The distinctiveness of ionic and nonionic bitter stimuli. Physiol Behav. 2004 Jan;80(4):421-31. {{#invoke:doi|main}}</ref>
Nintendo Switch game cartridges are coated in denatonium benzoate to prevent young children from consuming them.<ref name="IGNcitesbadtaste">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Lithium button cells, which can cause severe internal injuries if swallowed, are sometimes coated with denatonium benzoate to discourage small children from swallowing them.
