Pyramidal alkene - Citizendia

Pyramidal alkenes are alkenes in which the two carbon atoms making up the double bond are not coplanar with their four substituents ^[1]. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny In Geometry, a set of points in space is coplanar if the points all lie in the same geometric plane. In Organic chemistry, a substituent is an atom or group of atoms substituted in place of a Hydrogen atom on the Parent chain of a Hydrocarbon This deformation from a trigonal planar geometry to a tetrahedral molecular geometry is the result of angle strain induced in the molecule due to geometric constraints. In Chemistry, trigonal planar is a Molecular geometry with one atom at the center and three atoms at the corners of a triangle all in one plane In a Tetrahedral molecular geometry a central Atom is located at the center with four Substituents that are located at the corners of a Tetrahedron. The presence of angle strain in a Molecule indicates that in a specific Chemical conformation there exist Bond angles that deviate from the ideal bond angles Pyramidal alkenes only exist in the laboratory but are of interest because much can be learned from them about the nature of chemical bonding ^[1]. 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 cycloheptene (1. Cycloheptene is a 7-membered Cycloalkene. It is a raw material in Organic chemistry and a Monomer in polymer synthesis 1) the cis isomer is an ordinary unstrained molecule but the heptane ring is too small to accommodate a trans configured alkene group resulting in strain and twisting of the double bond. Trans-2-butenesvg|right|thumb|Trans-2-butene]] In Chemistry, cis-trans isomerism or geometric isomerism or configuration isomerism is a form of The p-orbital misalignment is minimized by a degree of pyramidalization. In Chemistry, trigonal planar is a Molecular geometry with one atom at the center and three atoms at the corners of a triangle all in one plane In the related anti-bredt molecules it is not pyrimidalization but twisting that dominates. Bredt's rule is an empirical observation in Organic chemistry that states that a Double bond cannot be placed at the bridgehead of a bridged ring system unless the

Pyramidalized cage alkenes also exist where symmetrical bending of the substituents predominates without p-orbital misalignment.

The pyramidalization angle $\phi\$ (b) is defined as the angle between the plane defined by one of the doubly bonded carbons and its two substituents and the extension of the double bond and is calculated as:

$\ cos\phi\ = -cos(R-C-C)/[cos(1/2(R-C-R))]$

the butterfly bending angle or folding angle $\psi\$ (c) is defined as the angle between two planes and can be obtained by averaging the two torsional angles R1C:::CR3 and R2C:::CR4. Alkane stereochemistry concerns the Stereochemistry of linear Alkanes and the linear alkane Conformers The existence of more than one conformation is due

In alkenes 1. 2 and 1. 3 these angles are determined with x-ray crystallography as respectively 32. X-ray crystallography is a method of determining the arrangement of Atoms within a Crystal, in which a beam of X-rays strikes a crystal and scatters 4°/22. 7° and 27. 3°/35. 6°. Although stable, these alkenes are very reactive compared to ordinary alkenes. They are liable to dimerization to cyclobutadiene compounds or react with oxygen to epoxides. Cyclobutadiene is the smallest - Annulene (-annulene an extremely unstable Hydrocarbon having a lifetime shorter than five seconds in the free state An epoxide is a cyclic Ether with only three ring atoms This ring approximately is an Equilateral triangle, i

The compound tetradehydrodianthracene also with a 35° pyramidalization angle is synthesized in a photochemical cycloaddition of bromoanthracene followed by elimination of hydrogen bromide

This compound is very reactive in Diels-Alder reactions due to through-space interactions between the two alken groups. Photochemistry, a sub-discipline of Chemistry, is the study of the interactions between Atoms, small Molecules, and light (or Electromagnetic radiation A cycloaddition is a Pericyclic Chemical reaction, in which two π bonds are lost and two σ bonds are gained the resulting reaction is a Anthracene is a solid Polycyclic aromatic hydrocarbon consisting of three fused Benzene rings derived from Coal-tar. An elimination reaction is a type of Organic reaction in which two Substituents are removed from a molecule in either a one or two-step mechanism. Hydrogen bromide is the diatomic molecule H[[Bromine Br]] Under standard conditions HBr is a gas but it can be liquified The Diels-Alder reaction is an Organic chemical reaction (specifically a Cycloaddition) between a conjugated Diene and a substituted Alkene, This enhanced reactivity enabled in turn the synthesis of the first-ever Möbius aromat. Organic chemistry, Möbius aromaticity is a special type of Aromaticity believed to exist in a number of Organic molecules In terms of MO theory

In one study ^[2] the strained alkene 3. 4 was synthesized with the highest pyramidalizion angles yet, 33. 5° and 34. 3°. This compound is the double Diels-Alder adduct of the diiodide-cyclophane 3. The Diels-Alder reaction is an Organic chemical reaction (specifically a Cycloaddition) between a conjugated Diene and a substituted Alkene, cyclophane is a Hydrocarbon consisting of an Aromatic unit (typically a Benzene ring and an Aliphatic chain that forms a Bridge 1 and anthracene 3. Anthracene is a solid Polycyclic aromatic hydrocarbon consisting of three fused Benzene rings derived from Coal-tar. 3 by reaction in presence of potassium tert-butoxide in refluxing dibutyl ether through a di-aryne intermediate 3. An alkoxide is the Conjugate base of an Alcohol and therefore consists of an organic group bonded to a negatively charged Oxygen atom This article is about using reflux in chemical engineering and chemistry In Chemistry, an aryne is an uncharged Reactive intermediate derived from an aromatic system by removal of two ortho Substituents 2. This is a stable compound but will slowly react with oxygen to an epoxide when left standing as a chloroform solution. An epoxide is a cyclic Ether with only three ring atoms This ring approximately is an Equilateral triangle, i Chloroform, also known as trichloromethane and methyl trichloride, is a Chemical compound with formula C[[Hydrogen H]] Cl

In one study ^[3] , isolation of a pyramidal alkene is not even possible in by matrix isolation at extremely low temperatures unless stabilized by metal coordination:

Fig. 4 (Ph3P)2Pt Complex of 3,7-Dimethyltricyclo[3.3.0.03,7]oct-1(5)-ene

A reaction of the di-iodide 4. Matrix isolation is an experimental technique used in Chemistry and Physics which generally involves a material being trapped within an unreactive matrix The term complex in Chemistry is usually used to describe molecules or ensembles formed by the combination of Ligands and metal Ions. An iodide Ion is an iodine atom with a &minus1 charge. Compounds with iodine in formal Oxidation state &minus1 are called iodides 1 in fig. 4 with sodium amalgam in the presence of ethylenebis(triphenylphosphine)platinum(0) does not give the intermediate alkene 4. Sodium amalgam, commonly denoted Na(Hg is an Amalgam, or Alloy of mercury, with Sodium Metal. Zeise's salt is the Chemical compound with the formula K]Cl3(C2H4] In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon 2 but the platinum stabilized 4. 3. The sigma bond in this compound is destroyed in reaction with ethanol.

References

^ Chemistry of pyramidalized alkenes Santiago Vázquez, and Pelayo Camps Tetrahedron Volume 61, Issue 22, 30 May 2005, Pages 5147-5208 doi:10.1016/j.tet.2005.03.055
^ A Highly Pyramidalized Cage Alkene Formed via the Double Diels-Alder Cycloaddition of syn-4,5,13,14-Bis(dehydro)octafluoroparacyclophane to Anthracene Dolbier, W. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. R. , Jr. ; Zhai, Y. -A. ; Battiste, M. A. ; Abboud, K. A. ; Ghiviriga, I. ; J. Org. Chem.; (Article); 2005; 70(25); 10336-10341. The Journal of Organic Chemistry (abbreviated as J Org Chem or JOC) is a Scientific journal for original contributions of fundamental DOI: 10. 1021/jo051488v Abstract
^ Evidence for the Formation of the (Ph3P)2Pt Complex of 3,7-Dimethyltricyclo[3. 3. 0. 03,7]oct-1(5)-ene, the Most Highly Pyramidalized Alkene in a Homologous Series. Isolation and X-ray Structure of the Product of the Ethanol Addition to the Complex Fanitsa A. Theophanous, Anastasios J. Tasiopoulos, Athanassios Nicolaides, Xin Zhou, William T. G. Johnson, and Weston Thatcher Borden Org. Lett.; 2006; 8(14) pp 3001 - 3004; (Letter) doi:10.1021/ol060994j

Organic Letters (usually abbreviated as Org Lett) is a peer-reviewed Scientific journal, published since 1999 by the A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.

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