Enantiomer in the context of "Racemic mixture"

Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. Lysine contains an α-amino group (which is in the protonated −NH+3 form when the lysine is dissolved in water at physiological pH), an α-carboxylic acid group (which is in the deprotonated −COO form when the lysine is dissolved in water at physiological pH), and a side chain (CH₂)₄NH₂ (which is partially protonated when the lysine is dissolved in water at physiological pH), and so it is classified as a basic, charged (in water at physiological pH), aliphatic amino acid. It is encoded by the codons AAA and AAG. Like almost all other amino acids, the α-carbon is chiral and lysine may refer to either enantiomer or a racemic mixture of both. For the purpose of this article, lysine will refer to the biologically active enantiomer L-lysine, where the α-carbon is in the S configuration.

The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are connected to one another. The chemical bonding within the molecule is also shown, either explicitly or implicitly. Unlike other chemical formula types, which have a limited number of symbols and are capable of only limited descriptive power, structural formulas provide a more complete geometric representation of the molecular structure. For example, many chemical compounds exist in different isomeric forms, which have different enantiomeric structures but the same molecular formula. There are multiple types of ways to draw these structural formulas such as: Lewis structures, condensed formulas, skeletal formulas, Newman projections, Cyclohexane conformations, Haworth projections, and Fischer projections.

Several systematic chemical naming formats, as in chemical databases, are used that are equivalent to, and as powerful as, geometric structures. These chemical nomenclature systems include SMILES, InChI and CML. These systematic chemical names can be converted to structural formulas and vice versa, but chemists nearly always describe a chemical reaction or synthesis using structural formulas rather than chemical names, because the structural formulas allow the chemist to visualize the molecules and the structural changes that occur in them during chemical reactions. ChemSketch and ChemDraw are popular downloads/websites that allow users to draw reactions and structural formulas, typically in the Lewis Structure style.

Ribose is a simple sugar and carbohydrate with molecular formula C₅H₁₀O₅ and the linear-form composition H−(C=O)−(CHOH)₄−H. The naturally occurring form, d-ribose, is a component of the ribonucleotides from which RNA is built, and so this compound is necessary for coding, decoding, regulation and expression of genes. It has a structural analog, deoxyribose, which is a similarly essential component of DNA. l-ribose is an unnatural sugar that was first prepared by Emil Fischer and Oscar Piloty in 1891. It was not until 1909 that Phoebus Levene and Walter Jacobs recognised that d-ribose was a natural product, the enantiomer of Fischer and Piloty's product, and an essential component of nucleic acids. Fischer chose the name "ribose" as it is a partial rearrangement of the name of another sugar, arabinose, of which ribose is an epimer at the 2' carbon; both names also relate to gum arabic, from which arabinose was first isolated and from which they prepared l-ribose.

A triose is a monosaccharide, or simple sugar, containing three carbon atoms. There are only three possible trioses: the two enantiomers of glyceraldehyde, which are aldoses; and dihydroxyacetone, a ketose which is symmetrical and therefore has no enantiomers.

Trioses are important in photosynthesis and cellular respiration. During glycolysis, fructose-1,6-bisphosphate is broken down into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Lactic acid and pyruvic acid are later derived from these molecules.

Thebaine (paramorphine), also known as codeine methyl enol ether, is an opiate alkaloid, its name coming from the Greek Θῆβαι, Thēbai (Thebes), an ancient city in Upper Egypt. A minor constituent of opium, thebaine is chemically similar to both morphine and codeine, but has stimulatory rather than depressant effects. At high doses, it causes convulsions similar to strychnine poisoning. The synthetic enantiomer (+)-thebaine does show analgesic effects apparently mediated through opioid receptors, unlike the inactive natural enantiomer (−)-thebaine. While thebaine is not used therapeutically, it is the main alkaloid extracted from Papaver bracteatum (Iranian opium / Persian poppy) and can be converted industrially into a variety of compounds, including hydrocodone, hydromorphone, oxycodone, oxymorphone, nalbuphine, naloxone, naltrexone, buprenorphine, butorphanol and etorphine.

Thebaine is controlled under international law, is listed as a Class A drug under the Misuse of Drugs Act 1971 in the United Kingdom, is controlled as an analog of a Schedule II drug per the Analog Act in the United States, and is controlled with its derivatives and salts, as a Schedule I substance of the Controlled Drugs and Substances Act in Canada. The 2013 US Drug Enforcement Administration (DEA) aggregate manufacturing quota for thebaine (ACSCN 9333) was unchanged from the previous year at 145 metric tons.

Amphetamine is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, and obesity; it is also used to treat binge eating disorder in the form of its inactive prodrug lisdexamfetamine. Amphetamine was discovered as a chemical in 1887 by Lazăr Edeleanu, and then as a drug in the late 1920s. It exists as two enantiomers: levoamphetamine and dextroamphetamine. Amphetamine properly refers to a specific chemical, the racemic free base, which is equal parts of the two enantiomers in their pure amine forms. The term is frequently used informally to refer to any combination of the enantiomers, or to either of them alone. Historically, it has been used to treat nasal congestion and depression. Amphetamine is also used as an athletic performance enhancer and cognitive enhancer, and recreationally as an aphrodisiac and euphoriant. It is a prescription drug in many countries, and unauthorized possession and distribution of amphetamine are often tightly controlled due to the significant health risks associated with recreational use.

The first amphetamine pharmaceutical was Benzedrine, a brand which was used to treat a variety of conditions. Pharmaceutical amphetamine is prescribed as racemic amphetamine, Adderall, dextroamphetamine, or the inactive prodrug lisdexamfetamine. Amphetamine increases monoamine and excitatory neurotransmission in the brain, with its most pronounced effects targeting the norepinephrine and dopamine neurotransmitter systems.

Methamphetamine is a central nervous system (CNS) stimulant that is primarily used as a recreational or performance-enhancing drug and less commonly as a second-line treatment for attention deficit hyperactivity disorder (ADHD). It has also been researched as a potential treatment for traumatic brain injury. Methamphetamine was discovered in 1893 and exists as two enantiomers: levo-methamphetamine and dextro-methamphetamine. Methamphetamine properly refers to a specific chemical substance, the racemic free base, which is an equal mixture of levomethamphetamine and dextromethamphetamine in their pure amine forms, but the hydrochloride salt, commonly called crystal meth, is widely used. Methamphetamine is rarely prescribed over concerns involving its potential for misuse as an aphrodisiac and euphoriant, among other concerns, as well as the availability of other drugs with comparable effects and treatment efficacy such as dextroamphetamine and lisdexamfetamine. While pharmaceutical formulations of methamphetamine in the United States are labeled as methamphetamine hydrochloride, they contain dextromethamphetamine as the active ingredient. Dextromethamphetamine is a stronger CNS stimulant than levomethamphetamine.

Both racemic methamphetamine and dextromethamphetamine are illicitly trafficked and sold owing to their potential for recreational use and ease of manufacture. The highest prevalence of illegal methamphetamine use occurs in parts of Asia and Oceania, and in the United States, where racemic methamphetamine and dextromethamphetamine are classified as Schedule II controlled substances. Levomethamphetamine is available as an over-the-counter (OTC) drug for use as an inhaled nasal decongestant in the United States and is seldom abused. Internationally, the production, distribution, sale, and possession of methamphetamine is restricted or banned in many countries, owing to its placement in schedule II of the United Nations Convention on Psychotropic Substances treaty. While dextromethamphetamine is a more potent drug, racemic methamphetamine is illicitly produced more often, owing to the relative ease of synthesis and regulatory limits of chemical precursor availability.

l-Glucose is an organic compound with formula C₆H₁₂O₆ or O=CH[CH(OH)]₅H, specifically one of the aldohexose monosaccharides. As the l-isomer of glucose, it is the enantiomer of the more common d-glucose.

l-Glucose does not occur naturally in living organisms, but can be synthesized in the laboratory. l-Glucose is indistinguishable in taste from d-glucose, but cannot be used by living organisms as a source of energy because it cannot be phosphorylated by hexokinase, the first enzyme in the glycolysis pathway. One of the known exceptions is in Trinickia caryophylli, a plant pathogenic bacterium, which contains the enzyme d-threo-aldose 1-dehydrogenase which is capable of oxidizing l-glucose.

In chemistry, a molecule or ion is called chiral (/ˈkaɪrəl/) if it cannot be superposed on its mirror image by any combination of rotations, translations, and some conformational changes. This geometric property is called chirality (/kaɪˈrælɪti/). The terms are derived from Ancient Greek χείρ (cheir) 'hand'; which is the canonical example of an object with this property.

A chiral molecule or ion exists in two stereoisomers that are mirror images of each other, called enantiomers; they are often distinguished as either "right-handed" or "left-handed" by their absolute configuration or some other criterion. The two enantiomers have the same chemical properties, except when reacting with other chiral compounds. They also have the same physical properties, except that they often have opposite optical activities. A homogeneous mixture of the two enantiomers in equal parts, a racemic mixture, differs chemically and physically from the pure enantiomers.