Denatonium, usually available as denatonium benzoate (under trade names such as Denatrol, BITTERANT-b, BITTER+PLUS, Bitrex, and Aversion) and as denatonium saccharide (BITTERANT-s), is the most bitter chemical compound known, with bitterness thresholds of 0.05 ppm for the benzoate and 0.01 ppm for the saccharide. It was discovered in 1958 during research on local anesthetics by MacFarlan Smith of Edinburgh, Scotland, and registered under the trademark Bitrex.
|Preferred IUPAC name
3D model (JSmol)
CompTox Dashboard (EPA)
|Melting point||163 to 170 °C (325 to 338 °F; 436 to 443 K)|
|H302, H315, H318, H332, H412|
|P261, P264, P270, P271, P273, P280, P301+P312, P302+P352, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P330, P332+P313, P362, P501|
|NFPA 704 (fire diamond)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
(what is ?)
Dilutions of as little as 10 ppm are unbearably bitter to most humans. 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, 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.
Denatonium is a quaternary ammonium cation. It is a compound of a salt with an inert anion like benzoate or saccharide. It can be obtained by the quaternization of lidocaine, a popular anesthetic, with benzyl halides. It was synthesized for the first time in 1963 by reacting benzyl chloride with lidocaine. This reaction required heating the substrates to 110 ° C for 35 hours, nowadays reaction time can be reduced to two hours at 82 ° C by using acetonitrile as solvent and potassium iodide as catalyst. In order to obtain other salts, like the benzoate, the formed denatonium chloride is subjected to an anion exchange reaction with sodium benzoate in ethanol or to sodium hydroxide, and the resulting denatonium hydroxide is neutralized with benzoic acid. Other similar compounds are procaine and benzocaine.
One of the chemical names for the compound is lidocaine benzylbenzoate, although denatonium only denotes the quaternary ammonium cation species itself, and does not necessitate the benzoate counterion.
Denatonium in humans is recognized by eight distinct bitter taste receptors: TAS2R4, TAS2R8, TAS2R10, TAS2R39, TAS2R43, TAS2R16, TAS2R46, TAS2R47, with TAS2R47 being by far the most sensitive to the compound.
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 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.
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. In December 2012, U.S. manufacturers voluntarily agreed to add denatonium benzoate to antifreeze sold nationwide.
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, as humans are able to detect denatonium at much lower concentrations than rodents.