Methamphetamine, also referred to as meth, is a psychostimulant that belongs to amphetamine and phenethylamine class of psychoactive drugs. It is a synthesized chemical, unlike cocaine which is derived from a plant.Structurally, meth is similar to amphetamine and methcathinone. Although it is relatively easy to synthesize meth, it involves the risk of handling corrosive and flammable chemicals, specifically solvents that are used for purification as well as extraction. Improper handling of solvents causes fires and explosions and that is how illegal production is generally discovered.The major ways in which meth is made is by starting with either one of the isomeric compounds ephedrine and pseudoephedrine or phenyl-2-propanone. One procedure involves the reductive amination of P2P with methylamine. Usually, P2P is obtained from acetic anhydride and phenylacetic acid though there are many other methods of obtaining it. Phenylacetic acid arises from benzychloride, benzaldehyde or benzylcyanide. Methylamine which is important for all these methods is made from nitromethane, fuel used in model airplanes, formaldehyde and ammonium chloride or methyl iodide and hexamine. For California's motorcycle gangs, this was the preferred production method. However, processing became difficult when DEA imposed restrictions on these chemicals. Pseudoephedrine, phenylacetone, ephedrine and phenylacetic acid figure in list I and acetic anhydride in list II of the chemicals subjected to control and regulation measures by DEA. The method that uses these compounds requires the use of mercuric chloride and leads to environmental pollution by leaving behind lead and mercury. The methamphetamine produced through this process is racemic as it will partly consist of undesired isomer levomethamphetamine. The Leuckart method also uses P2P to make a racemic product. The procedure uses methylformamide in formic acid to create an intermediate product N-formyl-methamphetamine. This intermediate product is then decarboxylated using hydrochloric acid. The nitropropene method is a less frequently used method. It involves condensation of benzaldehyde with nitroethane to make 1-phenyl-2-nitropropene. It is then reduced by hydrogenation of the double bond as well as nitro group reduction. The latter process is carried out by making use of hydrogen over lithium aluminum hydride or a palladium catalyst. In the oxime method, the reaction between P2P and hydroxylamine produces an intermediate which is hydrogenated by passing hydrogen over lithium aluminum hydride or a palladium catalyst. Illegal synthesis of methamphetamine is commonly done by reducing ephedrine or pseudoephedrine. This is because it makes the more active isomer d-methamphetamine. Whereas the maximum conversion rate that can be achieved for ephedrine and pseudoephedrine is around 92%, illegal laboratories producing methamphetamine achieve a conversion of 50% to 75%. Further, most illicit production methods consist of the hydroxyl group protonation on the pseudoephedrine or ephedrine molecule. The Nagi method dates back to times of discovery of the drug. However, the method became popular among illicit producers only by 1982. This method makes use of hydrogen iodide and red phosphorous. Hydrogen iodide reduces pseudoephedrine or ephedrine to methamphetamine. When heated iodoephedrine is formed due to rapid iodination of the precursor hydrogen iodide. In the second step, phosphorous provides assistance by reacting with iodine and forming phosphorous triiodide which in turn reacts with water to form phosphorous acid and regenerate hydrogen iodide. If phosphorous acid or hypophosphorous acid is used instead of red phosphorous, highly toxic phosphine gas is produced. The reaction also produces flammable and toxic white phosphorous waste. However, methamphetamine made in this method is generally 95% pure. The Emde route consists of reducing ephedrine to chloroephedrine with the help of thionyl chloride. Chloroephedrine is then subjected to hydrogenation with palladium or platinum as catalyst. Another method, the Rosenmund route, also makes of hydrogen gas and palladium poisoned with barium sulfate as catalyst. For the reduction reaction, perchloric acid is made use of in place of thionyl chloride. The Nazzi method or Birch reduction became popular during the 1990s and involves a chemical reaction between pseudoephedrine, liquid anhydrous ammonia and an alkali metal such as lithium or sodium. The reaction is continued till ammonia completely evaporates. Ammonia and the metal are highly reactive. Further, liquid ammonia's temperature makes it vulnerable to explosive boiling at the time of adding reactants. Ready availability of liquid ammonia in the farming areas was instrumental in making this method popular in the mid-western states of America. A simplified one-pot synthesis known as "Shake 'n Bake" has become very popular recently. This method can be conveniently used for making small batches so that pseudoephedrine restrictions may be less effective. In this method, crushed pseudoephedrine tablets are placed inside a non-pressurized container having water, ammonium nitrate and a hydrophobic solvent like Coleman fuel or automotive starting fuel. Lithium from lithium batteries and lye are added to the container. Hydrogen chloride gas is then used to recover the crystals which are then purified. Making methamphetamine using this method can be dangerous as it is important to relieve the pressure inside the container periodically, exposing lithium to air can cause fire and an abandoned reaction can become a fire hazard.