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Diphosphenes
Diphosphene is a type of organophosphorus compound that has a phosphorus–phosphorus double bond, denoted by R-P=P-R'. These compounds are not common but are of theoretical interest. Normally, compounds with the empirical formula RP exist as rings. However, like other multiple bonds between heavy main-group elements, P=P double bonds can be stabilized by a large steric hindrance from the substitutions. The first isolated diphosphene bis(2,4,6-tri-tert-butylphenyl)diphosphene was exemplified by Masaaki Yoshifuji and his coworkers in 1981, in which diphosphene is stabilized by two bulky phenyl group. Synthesis Synthesis of aryl-substituted diphosphene In 1877, Köhler and Michaelis claimed that they synthesized the first isolated diphosphene (PhP=PPh). However, the molecular weight determination and X-ray crystallographic analysis later proved that this "diphosphene" only had a P-P single bond. Then the research to diphosphenes kept silent over almost 20 years until Masaaki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Double Bond Rule
In chemistry, the double bond rule states that elements with a principal quantum number greater than 2 for their valence electrons (period 3 elements and higher) tend not to form multiple bonds (e.g. double bonds and triple bonds). The double bonds, when they exist, are often weak due to poor orbital overlap. Although such compounds are not intrinsically unstable, they instead tend to polymerize. An example is the rapid polymerization that occurs upon condensation of disulfur, the heavy analogue of . Numerous violations to the rule exist. Other meanings Another unrelated double bond rule exists that relates to the enhanced reactivity of sigma bonds attached to an atom adjacent to a double bond. In bromoalkenes, the C–Br bond is very stable, but in an allyl bromide, this bond is very reactive. Likewise, bromobenzenes are generally inert, whereas benzylic bromides are reactive. The first to observe the phenomenon was Conrad Laar Conrad Peter Laar (22 March 1853 – 11 Fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organophosphorus Compound
Organophosphorus compounds are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective insecticides, although some are extremely toxic to humans, including sarin and VX nerve agents. Organophosphorus chemistry is the corresponding science of the properties and reactivity of organophosphorus compounds. Phosphorus, like nitrogen, is in group 15 of the periodic table, and thus phosphorus compounds and nitrogen compounds have many similar properties. The definition of organophosphorus compounds is variable, which can lead to confusion. In industrial and environmental chemistry, an organophosphorus compound need contain only an organic substituent, but need not have a direct phosphorus-carbon (P-C) bond. Thus a large proportion of pesticides (e.g., malathion), are often included in this class of compounds. Phosphorus can adopt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Double Bond
In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist between two different elements: for example, in a carbonyl group between a carbon atom and an oxygen atom. Other common double bonds are found in azo compounds (N=N), imines (C=N), and sulfoxides (S=O). In a skeletal formula, a double bond is drawn as two parallel lines (=) between the two connected atoms; typographically, the equals sign is used for this. Double bonds were first introduced in chemical notation by Russian chemist Alexander Butlerov. Double bonds involving carbon are stronger and shorter than single bonds. The bond order is two. Double bonds are also electron-rich, which makes them potentially more reactive in the presence of a strong electron acceptor (as in addition reactions of the halogens). File:Ethene structural.svg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theoretical Chemistry
Theoretical chemistry is the branch of chemistry which develops theoretical generalizations that are part of the theoretical arsenal of modern chemistry: for example, the concepts of chemical bonding, chemical reaction, valence, the surface of potential energy, molecular orbitals, orbital interactions, and molecule activation. Overview Theoretical chemistry unites principles and concepts common to all branches of chemistry. Within the framework of theoretical chemistry, there is a systematization of chemical laws, principles and rules, their refinement and detailing, the construction of a hierarchy. The central place in theoretical chemistry is occupied by the doctrine of the interconnection of the structure and properties of molecular systems. It uses mathematical and physical methods to explain the structures and dynamics of chemical systems and to correlate, understand, and predict their thermodynamic and kinetic properties. In the most general sense, it is explanation of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steric Effects
Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivity of ions and molecules. Steric effects complement electronic effects, which dictate the shape and reactivity of molecules. Steric repulsive forces between overlapping electron clouds result in structured groupings of molecules stabilized by the way that opposites attract and like charges repel. Steric hindrance Steric hindrance is a consequence of steric effects. Steric hindrance is the slowing of chemical reactions due to steric bulk. It is usually manifested in ''intermolecular reactions'', whereas discussion of steric effects often focus on ''intramolecular interactions''. Steric hindrance is often exploited to control selectivity, such as slowing unwanted side-reactions. Steric hindrance between adjacent groups can also affect torsional ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Masaaki Yoshifuji
Masaaki (written: , , , , , , , , , , , , , , , , , , , , , , , , , or ) is a masculine Japanese given name. Notable people with the name include: *, Japanese politician *, Japanese poet *, Japanese baseball player *, Japanese singer-songwriter *, Japanese baseball player *, Japanese politician *, Japanese judoka *, Japanese footballer *, Japanese footballer *, Japanese ninjutsu practitioner *, Japanese footballer *, Japanese food historian *, Japanese drummer *, Japanese footballer *, Japanese aviator *, Japanese baseball player *, Japanese business theorist *, Japanese ''daimyō'' *, Japanese politician *, Japanese Go player *, Japanese politician *, Japanese sport wrestler *, Japanese footballer and manager *, Japanese footballer *, Japanese academic *, Japanese guitarist *, Japanese baseball player *, Japanese footballer *, Japanese baseball player *, Japanese baseball player *, Japanese cross-country skier *, Japanese video game producer *, Japanese professional wrestler *, Ja ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
