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Dithiete
Dithiete is an unsaturated heterocyclic compound that contains two adjacent sulfur atoms and two sp2-hybridized carbon centers. Derivatives are known collectively as dithietes or 1,2-dithietes. With 6 π electrons, 1,2-dithietes are examples of aromatic organosulfur compounds. A few 1,2-dithietes have been isolated. Unsubstituted 1,2-dithiete has been generated in thermolytic reactions and was characterized by microwave spectroscopy, ultraviolet photoelectron spectroscopy and infrared spectroscopy in a low temperature matrix. The open ring isomer, dithioglyoxal, HC(S)C(S)H, is less stable than the 1,2-dithiete. The dithione can be prepared (as ''trans''-dithioglyoxal) by low temperature photolysis of 1,3-dithiol-2-one. Quantum chemical calculations reproduce the observed greater stability of 1,2-dithiete only if large basis-sets with polarization functions are used. : See also * Dithietane - the corresponding saturated ring * Thiete Thiete is a heterocyclic compound contai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiete
Thiete is a heterocyclic compound containing an unsaturated four-membered ring with three carbon atoms and one sulfur atom. It is more commonly encountered not on its own, but in anellated derivatives, several of which have been synthesized. Thietes are generally not very stable. Structure Thiete is a valence isomer of the compound thioacrolein (CH2=CHCH=S) and undergoes ring opening to it at temperatures below 400°C. Thiete has been shown to be planar, with a C-S-C angle of 76.8 degrees. Derivatives Benzothietes are thietes annulated to benzo group. Such species are prepared by flash vacuum pyrolysis of 2-mercaptobenzyl alcohols. They are precursors to other S-heterocycles. Thiete 1,1-dioxides are sulfones, the parent being C3H4SO2. They are more stable than the parent thietes.Thomas C. Sedergran and Donald C. Dittmer "Thiete 1,1-dioxide and Chlorothiete 1,1-dioxide" Org. Synth. 1984, vol. 62, 210. Substituted thiete-1,1-dioxides can also be prepared by +2cycloaddition o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterocyclic Compound
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and applications of these heterocycles. Examples of heterocyclic compounds include all of the nucleic acids, the majority of drugs, most biomass (cellulose and related materials), and many natural and synthetic dyes. More than half of known compounds are heterocycles. 59% of US FDA-approved drugs contain nitrogen heterocycles. Classification The study of heterocyclic chemistry focuses especially on unsaturated derivatives, and the preponderance of work and applications involves unstrained 5- and 6-membered rings. Included are pyridine, thiophene, pyrrole, and furan. Another large class of heterocycles refers to those fused to benzene rings. For example, the fused benzene derivatives of pyridine, thiophene, pyrrole, and furan are quinol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared Spectroscopy
Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms. It can be used to characterize new materials or identify and verify known and unknown samples. The method or technique of infrared spectroscopy is conducted with an instrument called an infrared spectrometer (or spectrophotometer) which produces an infrared spectrum. An IR spectrum can be visualized in a graph of infrared light absorbance (or transmittance) on the vertical axis vs. frequency, wavenumber or wavelength on the horizontal axis. Typical units of wavenumber used in IR spectra are reciprocal centimeters, with the symbol cm−1. Units of IR wavelength are commonly given in micrometers (formerly called "microns"), symbol μm, which are related to the wavenumber in a reciprocal way. A com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Disulfides
Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product of decay, or is composed of organic compounds * Organic compound, a compound that contains carbon ** Organic chemistry, chemistry involving organic compounds Farming, certification and products * Organic farming, agriculture conducted according to certain standards, especially the use of stated methods of fertilization and pest control * Organic certification, accreditation process for producers of organically-farmed products * Organic horticulture, the science and art of growing fruits, vegetables, flowers, or ornamental plants by following the essential principles of organic agriculture * Organic products, "organics": ** Organic food, food produced from organic farming methods and often certified organic according to organic farming stan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organosulfur Compounds
Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature abounds with organosulfur compounds—sulfur is vital for life. Of the 20 common amino acids, two (cysteine and methionine) are organosulfur compounds, and the antibiotics penicillin and sulfa drugs both contain sulfur. While sulfur-containing antibiotics save many lives, sulfur mustard is a deadly chemical warfare agent. Fossil fuels, coal, petroleum, and natural gas, which are derived from ancient organisms, necessarily contain organosulfur compounds, Desulfurization, the removal of which is a Claus process, major focus of oil refineries. Sulfur shares the chalcogen group with oxygen, selenium, and tellurium, and it is expected that organosulfur compounds have similarities with carbon–oxygen, carbon–selenium, and carbon–tellurium compounds. A classical chemical test for the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dithietane
Dithietanes are saturated heterocyclic compounds that contain two divalent sulfur atoms and two sp3-hybridized carbon centers. Two isomers are possible for this class of organosulfur compounds: 1,2-Dithietanes 1,2-dithietanes, 4-membered rings where the two sulfur atoms are adjacent, are very rare. The first stable 1,2-dithietane to be reported was the so-called dithiatopazine formed by intramolecular photodimerization of a dithiocarbonyl compound. 1,2-Dithietanes are to be distinguished from 1,2-dithietes, containing two adjacent sulfur atoms and two sp2-hybridized carbon centers. A stable 1,2-dithietane ''derivative'' is ''trans''-3,4-diethyl-1,2-dithietane 1,1-dioxide, formed by the spontaneous dimerization of the lachrymatory agent syn-propanethial-S-oxide, found in onion. 1,3-Dithietanes In 1,3-dithietanes, the sulfur atoms are non-adjacent. 1,3-Dithietane itself, a colorless, easily sublimed, crystalline, unpleasant-smelling solid with melting point 105-10 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarization Function
In theoretical chemistry, theoretical and computational chemistry, a basis set is a set of Function (mathematics), functions (called basis functions) that is used to represent the Wave function, electronic wave function in the Hartree–Fock method or Density functional theory, density-functional theory in order to turn the partial differential equations of the model into algebraic equations suitable for efficient implementation on a computer. The use of basis sets is equivalent to the use of an approximate resolution of the identity: the Atomic orbital, orbitals , \psi_i\rangle are expanded within the basis set as a linear combination of the basis functions , \psi_i\rangle \approx \sum_\mu c_ , \mu\rangle, where the expansion coefficients c_ are given by c_ = \sum_\nu \langle \mu, \nu \rangle^ \langle \nu , \psi_i \rangle. The basis set can either be composed of atomic orbitals (yielding the linear combination of atomic orbitals approach), which is the usual choice within the qua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photolysis
Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by photons. It is defined as the interaction of one or more photons with one target molecule. Photodissociation is not limited to visible light. Any photon with sufficient energy can affect the chemical bonds of a chemical compound. Since a photon energy, photon's energy is inversely proportional to its wavelength, electromagnetic radiations with the energy of visible light or higher, such as ultraviolet light, x-rays, and gamma rays can induce such reactions. Photolysis in photosynthesis Photolysis is part of the light-dependent reactions, light-dependent reaction or light phase or photochemical phase or Hill reaction of photosynthesis. The general reaction of photosynthetic photolysis can be given in terms of photons as: :\ce + 2 \text \longrightarrow \ce The chemical nature of "A" depends on the type of organism. Purple su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultraviolet Photoelectron Spectroscopy
Ultraviolet photoelectron spectroscopy (UPS) refers to the measurement of kinetic energy spectra of photoelectrons emitted by molecules which have absorbed ultraviolet photons, in order to determine molecular orbital energies in the valence region. Basic theory If Albert Einstein's photoelectric law is applied to a free molecule, the kinetic energy ( E_K) of an emitted photoelectron is given by : E_K = h\nu - I\,, where ''h'' is Planck's constant, ν is the frequency of the ionizing light, and I is an ionization energy for the formation of a singly charged ion in either the ground state or an excited state. According to Koopmans' theorem, each such ionization energy may be identified with the energy of an occupied molecular orbital. The ground-state ion is formed by removal of an electron from the highest occupied molecular orbital, while excited ions are formed by removal of an electron from a lower occupied orbital. History Prior to 1960, virtually all measurements of photoel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thiirene
Thiirene is an organosulfur compound with the formula C2H2S. It can be viewed as a derivative of cyclopropene, but with the methylene group replaced by sulfur. It is antiaromatic and very labile. Thiirenes and derivatives No thiirene has been isolated at room temperature, but they have been observed spectroscopically at low temperatures. Thiirene-''S''-oxides and ''S''-alkylthiirinium salts have been characterized by X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles .... References {{chemistry-stub Sulfur heterocycles Three-membered rings ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microwave Spectroscopy
Microwave spectroscopy is the spectroscopy method that employs microwaves, i.e. electromagnetic radiation at GHz frequencies, for the study of matter. History The ammonia molecule NH3 is shaped like a pyramid 0.38 Å in height, with an equilateral triangle of hydrogens forming the base.The nitrogen situated on the axis has two equivalent equilibrium positions above and below the triangle of hydrogens, and this raises the possibility of the nitrogen tunneling up and down, through the plane of the H-atoms. In 1932 Dennison et al. ... analyzed the vibrational energy of this molecule and concluded that the vibrational energy would be split into pairs by the presence of these two equilibrium positions. The next year Wright and Randall observed ... a splitting of 0.67 cm–1 in far infrared lines, corresponding to ν = 20 GHz, the value predicted by theory.In 1934 Cleeton and Williams ... constructed a grating echelette spectrometer in order to measure this splitting directly, thereb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
