Chemical structure in the context of Chemical classification

Ozone (/ˈoʊzoʊn/ ), also called trioxygen, is an inorganic molecule with the chemical formula O
₃. It is a pale-blue gas with a distinctively pungent odour. It is an allotrope of oxygen that is much less stable than the diatomic allotrope O
₂, breaking down in the lower atmosphere to O
₂ (dioxygen). Ozone is formed from dioxygen by the action of ultraviolet (UV) light and electrical discharges within the Earth's atmosphere. It is present in very low concentrations throughout the atmosphere, with its highest concentration high in the ozone layer of the stratosphere, which absorbs most of the Sun's ultraviolet (UV) radiation.

Ozone's odour is reminiscent of chlorine, and detectable by many people at concentrations of as little as 0.1 ppm in air. Ozone's O₃ structure was determined in 1865. The molecule was later proven to have a bent structure and to be weakly diamagnetic. At standard temperature and pressure, ozone is a pale blue gas that condenses at cryogenic temperatures to a dark blue liquid and finally a violet-black solid. Ozone's instability with regard to more common dioxygen is such that both concentrated gas and liquid ozone may decompose explosively at elevated temperatures, physical shock, or fast warming to the boiling point. It is therefore used commercially only in low concentrations.

A chemical property is any of a material's properties that becomes evident during, or after, a chemical reaction; that is, any attribute that can be established only by changing a substance's chemical identity. Simply speaking, chemical properties cannot be determined just by viewing or touching the substance; the substance's internal structure must be affected greatly for its chemical properties to be investigated. When a substance goes under a chemical reaction, the properties will change drastically, resulting in chemical change. However, a catalytic property would also be a chemical property.

Chemical properties can be contrasted with physical properties, which can be discerned without changing the substance's structure. However, for many properties within the scope of physical chemistry, and other disciplines at the boundary between chemistry and physics, the distinction may be a matter of researcher's perspective. Material properties, both physical and chemical, can be viewed as supervenient; i.e., secondary to the underlying reality. Several layers of superveniency are possible.

A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a chemical name since it does not contain any words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulae can fully specify the structure of only the simplest of molecules and chemical substances, and are generally more limited in power than chemical names and structural formulae.

The simplest types of chemical formulae are called empirical formulae, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulae indicate the simple numbers of each type of atom in a molecule, with no information on structure. For example, the empirical formula for glucose is CH₂O (twice as many hydrogen atoms as carbon and oxygen), while its molecular formula is C₆H₁₂O₆ (12 hydrogen atoms, six carbon and oxygen atoms).

A drug class is a group of medications and other compounds that share similar chemical structures, act through the same mechanism of action (i.e., binding to the same biological target), have similar modes of action, and/or are used to treat similar diseases. The FDA has long worked to classify and license new medications. Its Drug Evaluation and Research Center categorizes these medications based on both their chemical and therapeutic classes.

In several major drug classification systems, these four types of classifications are organized into a hierarchy. For example, fibrates are a chemical class of drugs (amphipathic carboxylic acids) that share the same mechanism of action (PPAR agonist), the same mode of action (reducing blood triglyceride levels), and are used to prevent and treat the same disease (atherosclerosis). However, not all PPAR agonists are fibrates, not all triglyceride-lowering agents are PPAR agonists, and not all drugs used to treat atherosclerosis lower triglycerides.A drug class is typically defined by a prototype drug, the most important, and typically the first developed drug within the class, used as a reference for comparison.

In chemistry, azide (/ˈeɪzaɪd/, AY-zyd) is a linear, polyatomic anion with the formula N−3 and structure N=N=N. It is the conjugate base of hydrazoic acid HN₃. Organic azides are organic compounds with the formula RN₃, containing the azide functional group. The dominant application of azides is as a propellant in air bags.

In organic chemistry, an acetyl group is a functional group denoted by the chemical formula −COCH₃ and the structure −C(=O)−CH₃. It is sometimes represented by the symbol Ac (not to be confused with the element actinium). In IUPAC nomenclature, an acetyl group is called an ethanoyl group.

An acetyl group contains a methyl group (−CH₃) that is single-bonded to a carbonyl (C=O), making it an acyl group. The carbonyl center of an acyl radical has one non-bonded electron with which it forms a chemical bond to the remainder (denoted with the letter R) of the molecule.

Chalcedony (/kælˈsɛdəni/ kal-SED-ə-nee or /ˈkælsəˌdoʊni/ KAL-sə-doh-nee) is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical structure (based on the chemical composition of quartz) is SiO₂ (silicon dioxide).

Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from pale to nearly black. The color of chalcedony sold commercially is often enhanced by dyeing or heating.

Acaricides are pesticides that kill members of the arachnid subclass Acari, which includes ticks and mites.Acaricides are used both in medicine and agriculture, although the desired selective toxicity differs between the two fields.

Sodium cyanide is a compound with the formula NaCN and the structure Na C≡N. It is a white, water-soluble solid. Cyanide has a high affinity for metals, which leads to the high toxicity of this salt. Its main application, in gold mining, also exploits its high reactivity toward metals. It is a moderately strong base.

In theoretical chemistry, an energy profile is a theoretical representation of a chemical reaction or process as a single energetic pathway as the reactants are transformed into products. This pathway runs along the reaction coordinate, which is a parametric curve that follows the pathway of the reaction and indicates its progress; thus, energy profiles are also called reaction coordinate diagrams. They are derived from the corresponding potential energy surface (PES), which is used in computational chemistry to model chemical reactions by relating the energy of a molecule(s) to its structure (within the Born–Oppenheimer approximation).

Qualitatively, the reaction coordinate diagrams (one-dimensional energy surfaces) have numerous applications. Chemists use reaction coordinate diagrams as both an analytical and pedagogical aid for rationalizing and illustrating kinetic and thermodynamic events. The purpose of energy profiles and surfaces is to provide a qualitative representation of how potential energy varies with molecular motion for a given reaction or process.

Alexander Mikhaylovich Butlerov (Russian: Алекса́ндр Миха́йлович Бу́тлеров; 15 September 1828 – 17 August 1886) was a Russian chemist, one of the principal creators of the theory of chemical structure (1857–1861), the first to incorporate double bonds into structural formulas, the discoverer of hexamine (1859), the discoverer of formaldehyde (1859) and the discoverer of the formose reaction (1861). He first proposed the idea of possible tetrahedral arrangement of valence bonds in carbon compounds in 1862.

The crater Butlerov on the Moon is named after him. In 1956 the Academy of Sciences of the USSR established the A. M. Butlerov Prize.

Singlet oxygen, systematically named dioxygen(singlet) and dioxidene, is a gaseous inorganic chemical with two oxygen atoms in a quantum state where all electrons are spin-paired, known as a singlet state. It is the lowest excited state of the diatomic oxygen molecule, which in general has the chemical structure O=O and chemical formula O
₂. Singlet oxygen can be written more specifically as
[O
₂] or
O
₂. The more prevalent ground state of O
₂ is known as triplet oxygen. At room temperature, singlet oxygen will slowly decay into triplet oxygen, releasing the energy of excitation.

Singlet oxygen is a gas with physical properties differing only subtly from the ground state. In terms of its chemical reactivity, however, singlet oxygen is far more reactive toward organic compounds. It is responsible for the photodegradation of many materials but can be put to constructive use in preparative organic chemistry and photodynamic therapy. Trace amounts of singlet oxygen are found in the upper atmosphere and in polluted urban atmospheres where it contributes to the formation of lung-damaging nitrogen dioxide. It often appears and coexists confounded in environments that also generate ozone, such as pine forests with photodegradation of turpentine.

Musk is a class of aromatic substances commonly used as base notes in perfumery. They include glandular secretions from animals such as the musk deer, numerous plants emitting similar fragrances, and artificial substances with similar odors. Musk was a name originally given to a substance with a strong odor obtained from a gland of the musk deer. The substance has been used as a popular perfume fixative since ancient times and is one of the most expensive animal products in the world. The name originates from the Late Greek μόσχος 'moskhos', from Persian mushk and Sanskrit मुष्क muṣka (lit. 'testicle') derived from Proto-Indo-European noun múh₂s meaning "mouse". The deer gland was thought to resemble a scrotum. The term is applied to various plants and animals of similar smell (e.g., muskox) and has come to encompass a wide variety of aromatic substances with similar odors, despite their often differing chemical structures and molecular shapes.

Natural musk was used extensively in perfumery until the late 19th century when economic and ethical motives led to the adoption of synthetic musk, which is now used almost exclusively. The organic compound primarily responsible for the characteristic odor of musk is muscone. There are several ways of preparing the commercial musk, and the best method is to dry the pod by sunning and airing immediately after it is taken from the animal. Natural musk is usually packed in hermetically-sealed vessels and wooden boxes lined with tin foil because of its powerful diffusion of odor.

A structural analog, also known as a chemical analog or simply an analog, is a compound having a structure similar to that of another compound, but differing from it in respect to a certain component.

It can differ in one or more atoms, functional groups, or substructures, which are replaced with other atoms, groups, or substructures. A structural analog can be imagined to be formed, at least theoretically, from the other compound. Structural analogs are often isoelectronic.

In materials science and molecular biology, thermostability is the ability of a substance to resist irreversible change in its chemical or physical structure, often by resisting decomposition or polymerization, at a high relative temperature.

Thermostable materials may be used industrially as fire retardants. A thermostable plastic, an uncommon and unconventional term, is likely to refer to a thermosetting plastic that cannot be reshaped when heated, than to a thermoplastic that can be remelted and recast.

In pharmacology and pharmaceutics, a prototype drug is an individual drug that represents a drug class – group of medications having similar chemical structures, mechanism of action and mode of action. Prototypes are the most important, and typically the first developed drugs within the class, and are used as a reference to which all other drugs are compared.