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Ï€-bond
In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals has an electron density of zero at a shared nodal plane that passes through the two bonded nuclei. This plane also is a nodal plane for the molecular orbital of the pi bond. Pi bonds can form in double and triple bonds but do not form in single bonds in most cases. The Greek letter π in their name refers to p orbitals, since the orbital symmetry of the pi bond is the same as that of the p orbital when seen down the bond axis. One common form of this sort of bonding involves p orbitals themselves, though d orbitals also engage in pi bonding. This latter mode forms part of the basis for metal-metal multiple bonding. Properties Pi bonds are usually weaker than sigma bonds. The C–C double bond, composed of one sigma and one pi b ...
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Ethylene 3D
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon double bonds). Ethylene is widely used in the chemical industry, and its worldwide production (over 150 million tonnes in 2016) exceeds that of any other organic compound. Much of this production goes toward creating polyethylene, which is a widely used plastic containing polymer chains of ethylene units in various chain lengths. Production greenhouse gas emissions, emits greenhouse gases, including methane from feedstock production and carbon dioxide from any non-sustainable energy used. Ethylene is also an important natural plant hormone and is used in agriculture to induce ripening of fruits. The hydrate of ethylene is ethanol. Structure and properties This hydrocarbon has four hydrogen atoms bound to a pair of carbon atoms that are con ...
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Quintuple Bond
A quintuple bond in chemistry is an unusual type of chemical bond, first reported in 2005 for a chromium, dichromium compound. Single bonds, double bonds, and triple bonds are commonplace in chemistry. Quadruple bonds are rarer and are currently known only among the transition metals, especially for chromium, Cr, molybdenum, Mo, tungsten, W, and rhenium, Re, e.g. [Mo2Cl8]4− and [Re2Cl8]2−. In a quintuple bond, ten electrons participate in bonding between the two metal centers, allocated as σ2Ï€4δ4. In some cases of high-order bonds between metal atoms, the metal-metal bonding is facilitated by ligands that link the two metal centers and reduce the interatomic distance. By contrast, the chromium dimer with quintuple bonding is stabilized by a bulky terphenyl (2,6-[(2,6-diisopropyl)phenyl]phenyl) ligands. The species is stable up to 200 Â°C. The chromium–chromium quintuple bond has been analyzed with multireference ''ab initio'' and density functional theory, DFT method ...
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Covalent Bond
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full valence shell, corresponding to a stable electronic configuration. In organic chemistry, covalent bonding is much more common than ionic bonding. Covalent bonding also includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, three-center two-electron bonds and three-center four-electron bonds. The term "covalence" was introduced by Irving Langmuir in 1919, with Nevil Sidgwick using "co-valent link" in the 1920s. Merriam-Webster dates the specific phrase ''covalent bond'' to 1939, recognizing its first known ...
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Quadruple Bond
A quadruple bond is a type of chemical bond between two atoms involving eight electrons. This bond is an extension of the more familiar types of covalent bonds: double bonds and triple bonds. Stable quadruple bonds are most common among the transition metals in the middle of the , such as rhenium, tungsten, technetium, molybdenum and chromium. Typically the ligands that support quadruple bonds are π-donors, not π-acceptors. Quadruple bonds are rare as compared to double bonds and triple bonds, but hundreds of compounds with such bonds have been prepared. History Chromium(II) acetate, Cr2(''μ''-O2CCH3)4(H2O)2, was the first chemical compound containing a quadruple bond to be synthesized. It was described in 1844 by E. Peligot, although its distinctive bonding was not recognized for more than a century. The first crystallographic study of a compound with a quadruple bond was provided by Soviet chemists for salts of . The very short Re–Re distance was noted. This short dist ...
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Chemical Bond
A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons as in covalent bonds, or some combination of these effects. Chemical bonds are described as having different strengths: there are "strong bonds" or "primary bonds" such as covalent, ionic and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole–dipole interactions, the London dispersion force, and hydrogen bonding. Since opposite electric charges attract, the negatively charged electrons surrounding the nucleus and the positively charged protons within a nucleus attract each other. Electrons shared between two nuclei will be attracted to both of them. "Constructive quantum mechanical wavefunction interference" stabilizes the paired nuclei (see Theories of chemical bonding). Bonded nuclei maintain an optima ...
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Sigma Bond
In chemistry, sigma bonds (σ bonds) or sigma overlap are the strongest type of covalent chemical bond. They are formed by head-on overlapping between atomic orbitals along the internuclear axis. Sigma bonding is most simply defined for diatomic molecules using the language and tools of symmetry groups. In this formal approach, a σ-bond is symmetrical with respect to rotation about the bond axis. By this definition, common forms of sigma bonds are s+s, pz+pz, s+pz and dz2+dz2 (where z is defined as the axis of the bond or the internuclear axis). Quantum theory also indicates that molecular orbitals (MO) of identical symmetry actually mix or ''hybridize''. As a practical consequence of this mixing of diatomic molecules, the wavefunctions s+s and pz+pz molecular orbitals become blended. The extent of this mixing (or hybridization or blending) depends on the relative energies of the MOs of like symmetry. For homodiatomics ( homonuclear diatomic molecules), bonding σ orbit ...
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Delta Bond
In chemistry, a delta bond (δ bond) is a Covalent bond, covalent chemical bond, in which four lobes of an atomic orbital on one atom orbital overlap, overlap four lobes of an atomic orbital on another atom. This overlap leads to the formation of a bonding molecular orbital with two nodal planes which contain the internuclear axis and go through both atoms. The Greek letter δ in their name refers to d orbitals, since the orbital symmetry of the δ bond is the same as that of the usual (4-lobed) type of d orbital when seen down the bond axis. This type of bonding is observed in atoms that have occupied d orbitals with low enough energy to participate in covalent bonding, for example, in organometallic species of transition metals. Some rhenium, molybdenum, technetium, and chromium compounds contain a quadruple bond, consisting of one sigma bond, σ bond, two pi bond, π bonds and one δ bond. The orbital symmetry of the δ bonding orbital is different from that of a Pi bond, π ...
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Transition Metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. The lanthanide and actinide elements (the f-block) are called inner transition metals and are sometimes considered to be transition metals as well. They are lustrous metals with good electrical and thermal conductivity. Most (with the exception of group 11 and group 12) are hard and strong, and have high melting and boiling temperatures. They form compounds in any of two or more different oxidation states and bind to a variety of ligands to form coordination complexes that are often coloured. They form many useful alloys and are often employed as catalysts in elemental form or in compounds such as coordination complexes and oxides. Most are strongly paramagnetic because of their unpaired d electrons, as are many of their compounds. All of the elements that are ...
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Acetylene
Acetylene (Chemical nomenclature, systematic name: ethyne) is a chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure form and thus is usually handled as a solution. Pure acetylene is odorless, but commercial grades usually have a marked odor due to impurities such as divinyl sulfide and phosphine.Compressed Gas Association (1995Material Safety and Data Sheet – Acetylene As an alkyne, acetylene is Saturated and unsaturated compounds, unsaturated because its two carbon atoms are Chemical bond, bonded together in a triple bond. The carbon–carbon triple bond places all four atoms in the same straight line, with CCH bond angles of 180°. The triple bond in acetylene results in a high energy content that is released when acetylene is burned. Discovery Acetylene was discovered in 1836 by Edmund Davy, who identified it as a "new carburet ...
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Antibond
In theoretical chemistry, an antibonding orbital is a type of molecular orbital that weakens the chemical bond between two atoms and helps to raise the energy of the molecule relative to the separated atoms. Such an orbital has one or more nodes in the bonding region between the nuclei. The density of the electrons in the orbital is concentrated outside the bonding region and acts to pull one nucleus away from the other and tends to cause mutual repulsion between the two atoms. This is in contrast to a bonding molecular orbital, which has a lower energy than that of the separate atoms, and is responsible for chemical bonds. Diatomic molecules Antibonding molecular orbitals (MOs) are normally ''higher'' in energy than bonding molecular orbitals. Bonding and antibonding orbitals form when atoms combine into molecules. If two hydrogen atoms are initially far apart, they have identical atomic orbitals. However, as the spacing between the two atoms becomes smaller, the electron wave ...
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Diatomic Molecule
Diatomic molecules () are molecules composed of only two atoms, of the same or different chemical elements. If a diatomic molecule consists of two atoms of the same element, such as hydrogen () or oxygen (), then it is said to be homonuclear molecule, homonuclear. Otherwise, if a diatomic molecule consists of two different atoms, such as carbon monoxide () or nitric oxide (), the molecule is said to be heteronuclear molecule, heteronuclear. The bond in a homonuclear diatomic molecule is non-polar. The only chemical elements that form stable homonuclear diatomic molecules at standard temperature and pressure (STP) (or at typical laboratory conditions of 1 bar (pressure), bar and 25 Â°C) are the gases hydrogen (), nitrogen (), oxygen (), fluorine (), and chlorine (), and the liquid bromine (). The noble gases (helium, neon, argon, krypton, xenon, and radon) are also gases at STP, but they are monatomic. The homonuclear diatomic gases and noble gases together are called "ele ...
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