Hydrocarbons alkene series

Compounds consisting of only carbon and hydrogen have the simplest compositions of all organic compounds. These compounds are called hydrocarbons. It is possible to classify the hydrocarbons into four series, based on the characteristic structures of the molecules in each series. These series are known as (1) the alkane series, (2) the alkene series, (3) the alkyne series, and (4) the aromatic series. There are many subdivisions of each series, and it is also possible to have molecules that could be classified as belonging to more than one series. 

The alkene series of hydrocarbons is characterized by having one double bond in the carbon chain. The characteristic formula for members of the series is C H2 . Since there must be at least two carbon atoms present to have a carbon-to-carbon double bond, the first member of this series is ethene, C2H4, also known as ethylene. Propene (propylene), C,Hh, and butene (butylene), C4HK, are the next two members of the series. Note that the systematic names of these compounds denote the number of carbon atoms in the chain with the name derived from that of the alkane having the same number of carbon atoms (Table 21-2). Note also that the characteristic ending -ene is part of the name of each of these compounds. 

The unsaturated open-chain hydrocarbons include the alkene or olefin series, the diene series, and the alkyne series. The alkene series is made up of chain hydrocarbons in which a double bond exists between two carbon atoms. The general formula for the series is CnH2n, where n is the number of carbon atoms. As in the paraffin series, the lower members are gases, intermediate compounds are liquids, and the higher members of the series are solids. The alkene series compounds are more active chemically than the saturated compounds. They react easily with substances such as halogens by adding atoms at the double bonds. 

Structure effects on the rate of selective or total oxidation of saturated and unsaturated hydrocarbons and their correlations have been used successfully in the exploration of the reaction mechanisms. Adams 150) has shown that the oxidation of alkenes to aldehydes or alkadienes on a BijOj-MoOj catalyst exhibits the same influence of alkene structure on rate as the attack by methyl radicals an excellent Type B correlation has been gained between the rate of these two processes for various alkenes (series 135, five reactants, positive slope). It was concluded on this basis that the rate-determining step of the oxidation is the abstraction of the allylic hydrogen. Similarly, Uchi-jima, Ishida, Uemitsu, and Yoneda 151) correlated the rate of the total oxidation of alkenes on NiO with the quantum-chemical index of delo-calizability of allylic hydrogens (series 136, five reactants). 

The cycloalkanes also are known as naphthenes, cycloparaffins, or alicyclic hydrocarbons. In the petroleum industry, this class of hydrocarbons is known as naphthenes. Naphthenes have saturated rings. The general formula for the ring without substituents is CnH2n. This is the same as the general formula for the alkene series however, the structural configurations differ completely and, thus, the physical and chemical properties are not at all similar. 

While rate coefficients for reactions with OH radicals with the lower members of the alkane and alkene series are well known from laboratory measurements, there exist only a few sporadic data for the higher homologues. It is possible, however, to estimate rate coefficients by an extrapolation of existing data where needed, and this allows us to derive lifetimes also for compounds for which OH rate coefficients have not been determined. Specifically, for the alkanes Greiner (1970a,b) has proposed a formula based on his studies of hydrogen abstraction by OH radicals from saturated hydrocarbons. The expression is... 

If the zero-order method of section 2.6 reveals to be efficient, then it should be used to compare fast and slow oxidizing hydrocarbons (alkenes and methane for example). It is expected that the activation energy is constant in a homologous series of hydrocarbons. Then, the ratio of the rates of reaction should Be close to the ratio of the zero-order kinetic constants determined with the LO ciuves. This fortunate situation would enable one to scale the rates of oxidation of various hydrocarbons with respect to a standard hydrocarbon (propylene for example). 

Figure 13.7 shows the recovery of polyolefins (HDPE, LDPE, and PP) from several plastic waste. Very high polymer recovery was observed for all the plastic waste and proven that pure polymer can be easily recovered from plastic waste by this technique. Both solid and liquid fractions of the recovered polymer mainly consist of aliphatic hydrocarbon (a series of alkenes and alkynes) and can be recycled back into the petrochemical industry as a feedstock for the production of new plastics or refined fuels. 

Ethylene (Figure 5.5) contains a double bond between the carbon atoms and single bonds between the hydrogen atoms and the carbon atoms. Ethylene is the first member of the alkene series of hydrocarbons, compounds that have... 

Open chain hydrocarbons which are undersaturated, i.e. having at least one carbon-carbon double bond are part of the olefin series, and have the ending -ene . Those with one carbon-carbon double bond are called mono-olefins or alkenes, for example ethylene CH2 = CH2. 

Lloyd, A.C., Darnall, K.R., Winer, A.M., Pitts, Jr., J.N. (1976) Relative rate constants for reaction of the hydroxyl radical with a series of alkanes, alkenes, and aromatic hydrocarbons. J. Phys. Chem. 80, 189-794. 

The alkenes make up a homologous series of hydrocarbons with the general formula C H2 . Alkenes show two types of structural isomerism, position isomerism and chain isomerism. Geometrical isomerism also exists because of the lack of free rotation about the C=C double bond. 

Among oxo-metals, osmium tetroxide is a particularly intriguing oxidant since it is known to oxidize various types of alkenes rapidly, but it nonetheless eschews the electron-rich aromatic hydrocarbons like benzene and naphthalene (Criegee et al., 1942 Schroder, 1980). Such selectivities do not obviously derive from differences in the donor properties of the hydrocarbons since the oxidation (ionization) potentials of arenes are actually less than those of alkenes. The similarity in the electronic interactions of arenes and alkenes towards osmium tetroxide relates to the series of electron donor-acceptor (EDA) complexes formed with both types of hydrocarbons (26). Common to both arenes and alkenes is the immediate appearance of similar colours that are diagnostic of charge-transfer absorp-... 

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