Unsaturated hydrocarbons Ethenes

Ethanol can be synthesized from the unsaturated hydrocarbon ethene, with phosphoric acid as a catalyst. 

The simplest unsaturated hydrocarbon is ethene, C2H4 or H2C=CH2, com- suggesting that isomers are built... 

The reactions of hydrocarbons with [LnO]+ and [ AcO]+ (where Ln = Ce and Nd and Ac = Th and U) have been compared (101) and indicate that the [AcO]+ ions are more reactive than the [LnO]+ ions. In the ions [LnO]+, the metals are in their stable oxidation state but are coordinately unsaturated. None of the [MO]+ ions react with H2, saturated hydrocarbons, ethene, propene, or benzene but they all react with 1,4-cyclohexadiene. The [AcO]+ ions gave benzene addition product ions AcOC6H6]+ as the sole product, whereas the [LnO]+ ions gave the cyclohexadiene and benzene addition product ions, [LnOC6H8]+ and [LnOC6H6]+. 

Alkenes (olefins) are unsaturated hydrocarbons that contain carbon-carbon double bonds. A double bond consists of a cr bond and a tt bond. A tt bond is weaker than a a bond, and this makes tt bonds more reactive than cr bonds. Thus, it bond is considered to be a functional group. Alkenes form a homologous series with general molecular formula C H2 . The simplest members of the series are ethene (C2H4), propene (CsHg), butene (C4Hg) and pentene (CsHjo)-... 

Ito et al. (173) have observed weak spectra from ethene adsorbed on evaporated Ni films, including vCH soft-modes at 2700 cm-1 and what could be an absorption band from a n complex at ca. 1000 cm"1. Partial Raman spectra have been observed from ethene adsorbed on Ni/Si02 at 180 K and at room-temperature (26, 211). Krasser et al. (26) appear to have interpreted the spectrum taken at 180 K predominantly in terms of a di-unsaturated hydrocarbon groupings. Krasser et al. interpret the ca. 990 cm "1 band as from the vCC mode of the di-cr species, but the EELS data on Ni( 111) suggest that the vCC mode should be near 1100 cm-, possibly that shown in the Raman spectrum at ca. 1070 cm"1. Indeed, the set of Raman bands... 

In 1968 Peterson published his results about the reaction of a-silylated carbanions with carbonyl compounds to achieve /3-hydroxyalkyl-silanes. He found that instantaneous elimination affords unsaturated hydrocarbons ( Peterson olefmation )180 Thus, the lithiated trimethyl-benzyl-silane (274) plus benzophenone (135) give via lithium l,l,2,-triphenyl-2-TMS-ethanolate (275) 1,1,2-triphenyl-ethene (276)180 ... 

O aikene an unsaturated hydrocarbon that contains at least one double bond between two of the carbon atoms in the chain the simplest aikene is ethene, CjH4 O homologous series a family of organic compounds with similar chemical properties as they contain the same functional group alkenes, alcohols, for instance O isomers molecules with the same molecular formula but different stnictural formulae O substitution reaction a reaction in which one or more hydrogen atoms in a hydrocarbon are replaced by atoms of another element... 

Recently, the response theory formalism was applied for the calculation of singlet-triplet spectra in polyenes and aromatic hydrocarbons [83,133,134,132]. In this section we shall discuss mainly the vertical Tn <— So transitions probability in polyenes. The minimum level of accuracy includes CAS calculations of the ground state correlating all x electrons followed by linear and quadratic multi-configuration response calculations. Because the ethene molecule is the simplest representative of unsaturated hydrocarbons, different types of active spaces and AO basis sets were tested more thoroughly for this molecule in order to study the convergence of the S-T transition probability with respect to the level of accuracy. 

The ability of a p-carbene to react with an unsaturated hydrocarbon and form an enlarged dimetallocycle encourages speculation over their role in such processes as alkene metathesis and Fischer-Tropsch synthesis. In Scheme 6 a possible mechanism for metathesis initiated by a p-carbene is presented, owing much to other workers (T7,22). Reactions of p-carbenes with alkenes are under investigation in our laboratory. Recently Pettit has observed that the p-methylene complex [Fe2(C0)8(p-CH2)] generates propene when subjected to a pressure of ethene and has also suggested the intermediacy of a three-carbon dimetallocycle (23). 

Symmetrical Di-chlor Ethane.— The isomeric di-chlor ethane is obtained when the unsaturated hydrocarbon ethylene, or ethene takes up two chlorine atoms, forming an addition product. 

Ethylene and Ethylidene Compounds.—The fact that the symmetrical di-chlor ethane is readily prepared from ethylene, has given to it the name of ethylene chloride. To distinguish the two isomers by name the other, the unsymmetrical di-chlor ethane, has been called ethylidene chloride. In connection with our discussion of the constitution of the ethene series of unsaturated hydrocarbons (p. 154), we have used the constitution of ethylene chloride as proving the constitution of ethylene or ethene, as H2C = CH2. Isomerism of the character shown in these two di-chlor ethanes, as above explained, is found in all classes of di-substitution products of ethane, so that we may express the compounds by general formulas as follows ... 

The unsaturated dibasic acids bear the same relation to the saturated dibasic acids, just considered, as the unsaturated mono-basic acids, acrylic acid, crotonic acid, etc. (p. 172), do to the saturated monobasic acids, acetic acid, etc. They are also the oxidation products of the unsaturated hydrocarbons, alcohols, and aldehydes just as oxalic and succinic acids are of the corresponding saturated compounds. As the simplest dibasic acid containing an ethylene unsaturated group will contain two carboxyl groups and also two doubly linked carbon atoms there must be at least four carbons in the compound. This compound will therefore correspond to succinic acid of the saturated series. Now succinic acid may be derived from either butane by oxidation or from ethane by substitution. Similarly the corresponding unsaturated acid may be derived from butene by oxidation or from ethene by substitution. All of these general relationships may be represented as follows ... 

The rules for naming an unsaturated hydrocarbon with fewer than four carbon atoms are similar to those for naming alkanes. A two-carbon alkene is named ethene, with the suffix -ene indicating that the molecule is an alkene. A three-carbon alkyne is named propyne, with the suffix -yne indicating that the molecule is an alkyne. 

Although the dehydrogenation proceeds further and ethene cannot be prepared by this reaction, it illustrates the generic relations. Ethene contains less hydrogen atoms than the saturated hydrocarbon ethane and therefore is considered as unsaturated. Further, ethene is the first member of alkenes or olefins, a class of unsaturated hydrocarbons represented by the general formula CnHjn. 

Unsaturated hydrocarbons that contain one or more double covalent bonds between carbon atoms in a chain are called alkenes. Because an alkene must have a double bond between carbon atoms, there is no 1-carbon alkene. The simplest alkene has two carbon atoms double-bonded to each other. The remaining four electrons— two from each carbon atom—are shared with four hydrogen atoms to give the molecule ethene (C2H4). 

Ethene or ethylene, C2H4 or H2C=CH2, is the simplest unsaturated hydrocarbon. 

Ethene, the simplest unsaturated hydrocarbon, has two carbon atoms joined by a double bond. Propene is an unsaturated hydrocarbon with three carbons. 

Some unsaturated hydrocarbons have more than one double bond. Butadiene (byew tub DI een) has four carbon atoms and two double bonds. The structures of ethene, propene, and butadiene are shown in Figure 5. 

The main primary product of the thermolysis with ethene was cyclopropane, provided that the alkenes were present in large excess. The observed isomerization to propene was shown to be a consecutive reaction. Cvetanovic et al. (1967) also found products that indicate the formation of allyl radical intermediates leading, in multi-step reactions, to hexa-l,3-diene, pent-l-ene, and butane. The authors assumed that these compounds resulted from recombination of allyl and ethyl radicals. It is well known from combustion chemistry that the addition of methylene precursors to unsaturated hydrocarbons leads to higher hydrocarbons as precursors of soot (see e.g., Homann and Wellmann, 1983). 

Alkenes are unsaturated hydrocarbons that contain a carbondouble bond, i.e., two adjacent carbon atoms are joined by two bonds. Alkenes have the general formula C H2 , where n is an integer greater than 1. The simplest member of the alkene family is C2H4 (lUPAC name ethene common name ethylene)... 

The importance of relativistic phenomena both in coordination complexes and in chemisorption has been reviewed. For complexes containing coordinated ethene or other unsaturated hydrocarbons, comparable quantitative information on all the Group 10 metals is extremely hard to come by, but calculations on various ethene and ethyne complexes (Table 4.13) performed by the non-local quasi-relativistic DF method are instructive. For each complex the bond energy is in the sequence Ni > Pt > Pd marked differences in the stabilities and reactivities of complexes of the type M"P2(CH3) (M = Pd, Pt P = PPhs) were also noted. In this context, it is never remarked that nearly all reactions homogeneously catalysed by metal salts or complexes, and metal-mediated reactions, involve elements from the first and second rows, and very rarely a third row element. Ruthenium, rhodium and palladium feature often osmium, iridium and platinum hardly at all. This is because very generally the complexes of the third row elements are too stable to be reactive. 

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