Alkenes ethene

Alkenes Ethene Auto, microb., vegetation OH,Og 1-1000 ppbv... 

For all but the two smallest alkenes, ethene and propene, the rate constants are at their high-pressure limits at 1 atm, and even for these two compounds, the effective rate constant is within 10% of k... 

The mechanisms of these reactions have much in common and have been studied extensively from this point of view. They also have very considerable synthetic utility. The addition of water to alkenes (hydration) is particularly important for the preparation of a number of commercially important alcohols. Thus ethanol and 2-propanol (isopropyl alcohol) are made on a very large scale by the hydration of the corresponding alkenes (ethene and propene) using sulfuric or phosphoric acids as catalysts. The nature of this type of reaction will be described later. 

Hydrocarbons with double bonds are called alkenes. Ethene, CH2=CH2, is the simplest example of an alkene. It used to be (and still widely is) called ethylene it is used in the manufacture of polyethylene. Benzene is a hydrocarbon with double bonds that has such distinct properties that it is regarded as the parent hydrocarbon of a whole new class of compounds called—for historical reasons—aromatic compounds. The benzene ring is exceptionally stable and can be found in many important compounds. 

Superacid-catalyzed alkylation of adamantane with lower alkenes (ethene, propene, isomeric butenes) has been investigated by Olah et al.151 in triflic acid and triflic acid-B(0S02CF3)3. Only trace amounts of 1 -ferf-butyladamantane (37) were detected in alkylation with 1- and 2-butenes, whereas isobutylene gave consistently relatively good yield of 37. Since isomerization of isomeric 1-butyladamantane under identical conditions did not give even traces of 37, its formation can be accounted for by (r-alkylation, that is, through the insertion of the ferf-butyl cation into the C—H bond (Scheme 5.22). This reaction is similar to that between ferf-butyl cation and isobutane to form 2,2,3,3-tetramethylbutane discussed above (Scheme 5.21). In either case, the pentacoordinate carbocation intermedate, which may also lead to hydride transfer, does not attain a linear geometry, despite the unfavorable steric interactions. 

In this case a /3-hydrogen (a hydrogen on the /3-carbon) could be lost from either the ethyl or the propyl group. In accord with Hofmann s rule the less highly substituted alkene, ethene, is found to be the major product. 

The great advantage of this method is that it can be used to build up structures of much larger molecules quickly and without having to imagine that the molecule is made up from isolated atoms. So it is easy to work out the structure of ethene (ethylene) the simplest alkene. Ethene is a planar molecule with bond angles dose to 120°. Our approach will be to hybridize all the orbitals needed for the C-H framework and see what is left over. In this case we need three bonds from each carbon atom (one to make a C-C bond and two to make C-H bonds). 

The gas-phase reactivity of Ln2+ with alkanes (methane, ethane, propane, n-butane) and alkenes (ethene, propene, 1-butene) was studied by Fourier transform ICR mass spectrometry. The reaction products consisted of different combinations of doubly charged organometallic ions-adducts or... 

The N—H jr is the main interaction in aniline/alkene (ethene, propene, butene) complex cations187,188.118 and 119 illustrate the calculated structures of aniline/ethene cluster cation. The aniline cation is bonded to the n electrons of alkene by one (118) or two (119) hydrogen bonds. Spectroscopic data emphasize that these interactions are different from that observed for the same neutral clusters44. 

The structure of the smallest alkene (ethene) was described in Section 1.8. Other alkenes have similar stmctures. Each double-bonded carbon of an alkene has three sp orbitals that lie in a plane with angles of 120°. Each of these sp orbitals overlaps an orbital of another atom to form a cr bond. Thus, one of the carbon-carbon bonds in a double bond is a cr bond, formed by the overlap of an sp orbital of one carbon with an sp orbital of the other carbon. The second carbon-carbon bond in the double bond (the TT bond) is formed from side-to-side overlap of the remaining p orbitals of the sp carbons. Because three points determine a plane, each sp carbon and the two atoms singly bonded to it lie in a plane. In order to achieve maximum orbital-orbital overlap, the two p orbitals must be parallel to each other. Therefore, all six atoms of the doublebond system are in the same plane. 

The second class of simple hydrocarbons, the alkenes, consists of molecules that contain at least one double-bonded carbon pair. Alkenes follow the same naming convention used for alkanes. A prefix (to describe the number of carbon atoms) is combined with the ending "ene" to denote an alkene. Ethene, for example is the two-carbon molecule that contains one double bond. The chemical formula for the simple alkenes follows the expression Because one of the carbon pairs is double... 

It is very common in both laboratory and industrial processes for such preparations to involve a sequence of reactions. For example, the commercial production of vinyl plastic (PVC) begins with the alkene ethene ... 

Plastics are polymers. Poly means many, thus a polymer molecule is a large molecule made by joining many small molecules together. The small molecules that go into a polymer are called monomers . A plastic may have more than one monomer, for example, two monomers may alternate to create the polymer molecule, such as in nylon. This section looks at different polymers based on the simplest alkene, ethene (C2H4). 

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