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Penta-1,4-diyne
1,4-Pentadiyne (penta-1,4-diyne) is a chemical compound belonging to the alkynes. The compound is the structural isomer to 1,3-pentadiyne. Preparation Until the late 1960s, no successful synthesis of this seemingly simply preparable molecule was described. Although long-chain and more complex 1,4-diynes had been synthesized successfully before, synthesis approaches starting from sodium acetylide and propargyl bromide or from the acetylene Grignard reagent with propargyl bromide and copper(I) chloride failed and mostly 1,3-pentadiyne was obtained as rearrangement product. The successful isolation in small amounts succeeded by reacting propargyl bromide and to the respective Normant cuprate converted acetylene grignard (usage of copper(I) chloride) in THF and an, compared to previous attempts additional, flash distillation and GLC of the distillate. An improved synthesis method was published by Verkruijsse and Hasselaar in 1979. Copper chloride was substituted by copper(I) b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Debye
The debye (symbol: D) (; ) is a CGS unit (a non- SI metric unit) of electric dipole momentTwo equal and opposite charges separated by some distance constitute an electric dipole. This dipole possesses an electric dipole moment whose value is given as charge times length of separation, it is a vector whose direction is in the direction of the unit vector of the position vector of the positive charge w.r.t negative charge: :p = ''q''r. named in honour of the physicist Peter J. W. Debye. It is defined as statcoulomb-centimeters.The statcoulomb is also known as the franklin or electrostatic unit of charge. :1 statC = 1 Fr = 1 esu = 1 cm3/2⋅g1/2⋅s−1. Historically the debye was defined as the dipole moment resulting from two charges of opposite sign but an equal magnitude of 10−10 statcoulomb10−10 statcoulomb corresponds to approximately 0.2083 units of elementary charge. (generally called e.s.u. (electrostatic unit) in older scientific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extraction (chemistry)
Extraction in chemistry is a separation process consisting of the separation of a substance from a matrix. Common examples include '' liquid-liquid extraction'', and ''solid phase extraction''. The distribution of a solute between two phases is an equilibrium condition described by partition theory. This is based on exactly how the analyte moves from the initial solvent into the extracting solvent. The term ''washing'' may also be used to refer to an extraction in which impurities are extracted from the solvent containing the desired compound. Types of extraction * Liquid–liquid extraction * Solid-phase extraction * Acid-base extraction * Supercritical fluid extraction * Ultrasound-assisted extraction * Heat reflux extraction * Mechanochemical-assisted extraction * Maceration * Microwave-assisted extraction * Instant controlled pressure drop extraction (DIC, from the French, Détente instantanée contrôlée) * Perstraction Laboratory applications and examples Liquid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planet
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a young protostar orbited by a protoplanetary disk. Planets grow in this disk by the gradual accumulation of material driven by gravity, a process called accretion. The Solar System has at least eight planets: the terrestrial planets Mercury, Venus, Earth and Mars, and the giant planets Jupiter, Saturn, Uranus and Neptune. These planets each rotate around an axis tilted with respect to its orbital pole. All of them possess an atmosphere, although that of Mercury is tenuous, and some share such features as ice caps, seasons, volcanism, hurricanes, tectonics, and even hydrology. Apart from Venus and Mars, the Solar System planets generate magnetic fields, and all except Venus and Mercury have natural satellites. The giant planets bear plan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phys
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular succession of events." Physics is one of the most fundamental scientific disciplines, with its main goal being to understand how the universe behaves. "Physics is one of the most fundamental of the sciences. Scientists of all disciplines use the ideas of physics, including chemists who study the structure of molecules, paleontologists who try to reconstruct how dinosaurs walked, and climatologists who study how human activities affect the atmosphere and oceans. Physics is also the foundation of all engineering and technology. No engineer could design a flat-screen TV, an interplanetary spacecraft, or even a better mousetrap without first understanding the basic laws of physics. (. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrochemistry
Astrochemistry is the study of the abundance and reactions of molecules in the Universe, and their interaction with radiation. The discipline is an overlap of astronomy and chemistry. The word "astrochemistry" may be applied to both the Solar System and the interstellar medium. The study of the abundance of elements and isotope ratios in Solar System objects, such as meteorites, is also called cosmochemistry, while the study of interstellar atoms and molecules and their interaction with radiation is sometimes called molecular astrophysics. The formation, atomic and chemical composition, evolution and fate of molecular gas clouds is of special interest, because it is from these clouds that solar systems form. History As an offshoot of the disciplines of astronomy and chemistry, the history of astrochemistry is founded upon the shared history of the two fields. The development of advanced observational and experimental spectroscopy has allowed for the detection of an ever-increas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allene
In organic chemistry, allenes are organic compounds in which one carbon atom has double bonds with each of its two adjacent carbon centres (). Allenes are classified as diene#Classes, cumulated dienes. The parent compound of this class is propadiene, which is itself also called ''allene''. Compounds with an allene-type structure but with more than three carbon atoms are members of a larger class of compounds called cumulenes with bonding. History For many years, allenes were viewed as curiosities but thought to be synthetically useless and difficult to prepare and to work with.The Chemistry of the Allenes (vol. 1−3); Landor, S. R., Ed.; cademic Press: London, 1982. Reportedly, the first synthesis of an allene, glutinic acid, was performed in an attempt to prove the non-existence of this class of compounds. The situation began to change in the 1950s, and more than 300 papers on allenes have been published in 2012 alone. These compounds are not just interesting intermediates ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyrolyse 3-Ethynylcycloprop-1-en
The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''pyro'' "fire", "heat", "fever" and ''lysis'' "separating". Pyrolysis is most commonly used in the treatment of organic materials. It is one of the processes involved in charring wood.''Burning of wood'' , InnoFireWood's website. Accessed on 2010-02-06. In general, pyrolysis of organic substances produces volatile products and leaves , a carbon-rich solid residue. Extreme pyrolysis, which leaves mostly [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UV Radiation
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights. Although long-wavelength ultraviolet is not considered an ionizing radiation because its photons lack the energy to ionize atoms, it can cause chemical reactions and causes many substances to glow or fluoresce. Consequently, the chemical and biological effects of UV are greater than simple heating effects, and many practical applications of UV radiation derive from its interactions with organic molecules. Short-wave ultraviolet light damages DNA and sterilizes surfaces with which it comes into contact. For h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photochemistry
Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400–750 nm) or infrared radiation (750–2500 nm). In nature, photochemistry is of immense importance as it is the basis of photosynthesis, vision, and the formation of vitamin D with sunlight. Photochemical reactions proceed differently than temperature-driven reactions. Photochemical paths access high energy intermediates that cannot be generated thermally, thereby overcoming large activation barriers in a short period of time, and allowing reactions otherwise inaccessible by thermal processes. Photochemistry can also be destructive, as illustrated by the photodegradation of plastics. Concept Grotthuss–Draper law and Stark-Einstein law Photoexcitation is the first step in a photochemical process where the reactant is elevated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahedron Lett
''Tetrahedron Letters'' is a weekly international journal for rapid publication of full original research papers in the field of organic chemistry. According to the ''Journal Citation Reports'', the journal has a 2020 impact factor of 2.415. Indexing ''Tetrahedron Letters'' is indexed in: References See also *''Tetrahedron In geometry, a tetrahedron (plural: tetrahedra or tetrahedrons), also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the o ...'' *'' Tetrahedron: Asymmetry'' Chemistry journals Weekly journals Publications established in 1959 Elsevier academic journals {{chem-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
