EtherIn organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be classified into two varieties: if the alkyl or aryl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers.
Protecting groupA protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In many preparations of delicate organic compounds, some specific parts of their molecules cannot survive the required reagents or chemical environments. Then, these parts, or groups, must be protected. For example, lithium aluminium hydride is a highly reactive but useful reagent capable of reducing esters to alcohols.
CarbonateA carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word carbonate may also refer to a carbonate ester, an organic compound containing the carbonate group . The term is also used as a verb, to describe carbonation: the process of raising the concentrations of carbonate and bicarbonate ions in water to produce carbonated water and other carbonated beverages - either by the addition of carbon dioxide gas under pressure or by dissolving carbonate or bicarbonate salts into the water.
DemethylationDemethylation is the chemical process resulting in the removal of a methyl group (CH3) from a molecule. A common way of demethylation is the replacement of a methyl group by a hydrogen atom, resulting in a net loss of one carbon and two hydrogen atoms. The counterpart of demethylation is methylation. In biochemical systems, the process of demethylation is catalyzed by demethylases. These enzymes oxidize N-methyl groups, which occur in histones and some forms of DNA: R2N-CH3 + O → R2N-H + CH2O One such oxidative enzyme family is the cytochrome P450.
Synthetic fuelSynthetic fuel or synfuel is a liquid fuel, or sometimes gaseous fuel, obtained from syngas, a mixture of carbon monoxide and hydrogen, in which the syngas was derived from gasification of solid feedstocks such as coal or biomass or by reforming of natural gas. Common ways for refining synthetic fuels include the Fischer–Tropsch conversion, methanol to gasoline conversion, or direct coal liquefaction. The term 'synthetic fuel' or 'synfuel' has several different meanings and it may include different types of fuels.
Topic mapA topic map is a standard for the representation and interchange of knowledge, with an emphasis on the findability of information. Topic maps were originally developed in the late 1990s as a way to represent back-of-the-book index structures so that multiple indexes from different sources could be merged. However, the developers quickly realized that with a little additional generalization, they could create a meta-model with potentially far wider application. The ISO/IEC standard is formally known as ISO/IEC 13250:2003.
Compatibility (geochemistry)Compatibility is a term used by geochemists to describe how elements partition themselves in the solid and melt within Earth's mantle. In geochemistry, compatibility is a measure of how readily a particular trace element substitutes for a major element within a mineral. Compatibility of an ion is controlled by two things: its valence and its ionic radius. Both must approximate those of the major element for the trace element to be compatible in the mineral. For instance, olivine (an abundant mineral in the upper mantle) has the chemical formula (Mg,Fe)2SiO4.
Synthetic fiberSynthetic fibers or synthetic fibres (in British English; see spelling differences) are fibers made by humans through chemical synthesis, as opposed to natural fibers that are directly derived from living organisms, such as plants (like cotton) or fur from animals. They are the result of extensive research by scientists to replicate naturally occurring animal and plant fibers. In general, synthetic fibers are created by extruding fiber-forming materials through spinnerets, forming a fiber.
Synthetic cannabinoidsSynthetic cannabinoids are a class of designer drug molecules that bind to the same receptors to which cannabinoids (THC, CBD and many others) in cannabis plants attach. These novel psychoactive substances should not be confused with synthetic phytocannabinoids (THC or CBD obtained by chemical synthesis) or synthetic endocannabinoids from which they are in many aspects distinct. Typically, synthetic cannabinoids are sprayed onto plant matter and are usually smoked, although they have also been ingested as a concentrated liquid form in the US (United States) and UK (United Kingdom) since 2016.
Strangeness and quark–gluon plasmaIn high-energy nuclear physics, strangeness production in relativistic heavy-ion collisions is a signature and diagnostic tool of quark–gluon plasma (QGP) formation and properties. Unlike up and down quarks, from which everyday matter is made, heavier quark flavors such as strange and charm typically approach chemical equilibrium in a dynamic evolution process. QGP (also known as quark matter) is an interacting localized assembly of quarks and gluons at thermal (kinetic) and not necessarily chemical (abundance) equilibrium.
Topic-prominent languageA topic-prominent language is a language that organizes its syntax to emphasize the topic–comment structure of the sentence. The term is best known in American linguistics from Charles N. Li and Sandra Thompson, who distinguished topic-prominent languages, such as Korean and Japanese, from subject-prominent languages, such as English. In Li and Thompson's (1976) view, topic-prominent languages have morphology or syntax that highlights the distinction between the topic and the comment (what is said about the topic).
Galvanic corrosionGalvanic corrosion (also called bimetallic corrosion or dissimilar metal corrosion) is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte. A similar galvanic reaction is exploited in primary cells to generate a useful electrical voltage to power portable devices. This phenomenon is named after Italian physician Luigi Galvani (1737-1798).
CubismCubism is an early-20th-century avant-garde art movement that revolutionized European painting and sculpture, and inspired related artistic movements in music, literature, and architecture. In Cubist works of art, the subjects are analysed, broken up, and reassembled in an abstract form—instead of depicting objects from a single perspective, the artist depicts the subject from multiple perspectives to represent the subject in a greater context. Cubism has been considered the most influential art movement of the 20th century.
Flashback (psychology)A flashback, or involuntary recurrent memory, is a psychological phenomenon in which an individual has a sudden, usually powerful, re-experiencing of a past experience or elements of a past experience. These experiences can be frightful, happy, sad, exciting, or any number of other emotions. The term is used particularly when the memory is recalled involuntarily, especially when it is so intense that the person "relives" the experience, and is unable to fully recognize it as memory of a past experience and not something that is happening in "real time".
Synthetic-aperture sonarSynthetic-aperture sonar (SAS) is a form of sonar in which sophisticated post-processing of sonar data is used in ways closely analogous to synthetic-aperture radar. Synthetic-aperture sonars combine a number of acoustic pings to form an image with much higher along-track resolution than conventional sonars. The along-track resolution can approach half the length of one sonar element, though is downward limited by 1/4 wavelength. The principle of synthetic-aperture sonar is to move the sonar while illuminating the same spot on the sea floor with several pings.
