In chemistry, pi bonds (π bonds) are covalent chemical bonds where two lobes of one involved electron orbital overlap two lobes of the other involved electron orbital. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic An atomic orbital is a Mathematical function that describes the wave-like behavior of an electron in an atom Only one of the orbital's nodal planes passes through both of the involved nuclei. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom
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. In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other P orbitals usually engage in this sort of bonding. D orbitals are also assumed to engage in pi bonding but this is not necessarily the case in reality, although the concept of bonding d orbitals still accounts well for hypervalence.
Pi bonds are usually weaker than sigma bonds because their (negatively charged) electron density is farther from the positive charge of the atomic nucleus, which requires more energy. In Chemistry, sigma bonds ( σ bonds) are the strongest type of covalent Chemical bond. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom From the perspective of quantum mechanics, this bond's weakness is explained by significantly less overlap between the component p-orbitals due to their parallel orientation. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons
Although the pi bond by itself is weaker than a sigma bond, pi bonds are often components of multiple bonds, together with sigma bonds. The combination of pi and sigma bond is stronger than either bond by itself. The enhanced strength of a multiple bond vs. a single (sigma bond) is indicated in many ways, but most obviously by a contraction in bond lengths. For example in organic chemistry, carbon-carbon bond lengths are ethane (154 pm), ethylene (133 pm) and acetylene (120 pm). In Molecular geometry, bond length or bond distance is the average distance between nuclei of two bonded Atoms in a Molecule. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where A picometre ( American spelling: picometer, symbol pm) is a unit of Length in the Metric system, equal to one trillionth Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. Acetylene ( IUPAC name ethyne), C2H2 is a Hydrocarbon belonging to the group of Alkynes It is the simplest of all alkynes
In addition to one sigma bond, a pair of atoms connected via double bond and triple bonds have one or two pi bonds, respectively. Pi bonds result from overlap of atomic orbitals that with two areas of overlap. Pi-bonds are more diffuse bonds than the sigma bonds. Electrons in pi bonds are sometimes referred to as pi electrons. Molecular fragments joined by a pi bond cannot rotate about that bond without breaking the pi bond, because rotation involves destroying the parallel orientation of the constituent p orbitals.
Special cases
Pi bonds do not necessarily connect a pair of atoms that are also sigma-bonded.
In certain metal complexes, pi interactions between a metal atom and alkyne and alkene pi antibonding orbitals form pi-bonds. Alkynes are Hydrocarbons that have at least one Triple bond between two Carbon atoms with the formula CnH2n-2. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon
In some cases of multiple bonds between two atoms, there is no sigma bond at all, only pi bonds. Examples include diiron hexacarbonyl (Fe2(CO)6), dicarbon (C2) and the borane B2H2. In chemistry a borane is a chemical compound of Boron and Hydrogen. In these compounds the central bond consists only of pi bonding, and in order to achieve maximum orbital overlap the bond distances are much shorter than expected. [1]
See also
References
- ^ Bond length and bond multiplicity: σ-bond prevents short π-bonds Eluvathingal D. Stacking in Supramolecular chemistry refers to a stacked arrangement of Aromatic Molecules which interact through aromatic interactions A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic In Chemistry, delta bonds ( δ bonds) are Chemical bonds of the covalent type where four lobes of one involved electron Orbital Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. In Chemistry, sigma bonds ( σ bonds) are the strongest type of covalent Chemical bond. Jemmis, Biswarup Pathak, R. Bruce King, Henry F. Schaefer III Chemical Communications, 2006, 2164 - 2166 Abstract
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