Alkenes and their derivatives

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)- 

Among the cycloalkenes, cyclobutene, cyclopropene and cylcohexene are most common. Cyclobutene is about 4 kcal/mol more strained than cyclopentene. The smaller bond angles mean more deviation from 120°, and this makes cyclobutene more reactive than cyclopentene. 

The systematic name of an alkene originates from the name of the alkane corresponding to the longest continuous chain of carbon atoms that contains 

For branches, each alkyl group is given a number, but the double bond still gets preference when numbering the chain. 

A cyclic alkene is named by a prefix cyclo- to the name of the acyclic alkene. Double bonded carbons are considered to occupy positions 1 and 2. 

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The uses to which ethylene and its relatives are put are summarized in an article entitled "Alkenes and Their Derivatives The Alchemists Dream Come True/ in the August 1989 issue of the Journal of Chemical Education (pp. 670-672). 

In the presence of an organic peroxide Initiator, the alkenes and their derivatives undergo addition polymerisation or chain growth polymerisation through a free radical mechanism. Polythene, teflon, orlon, etc. are formed by addition polymerisation of an appropriate alkene or Its derivative. Condensation poiymerisation reactions are... 

In conclusion, we can say that the liquid-phase carboxidation of alkanes can be applied to various substrates, induding linear, cyclic, heterocydic alkenes and their derivatives, yielding the corresponding ketones and aldehydes with selectivities in many cases of >90%. 

The yield varies from 40 to 60% no matter what size the ring is. The separation of the alkenes and their derivatives is difficult because of the closeness of their boiling points. Furthermore, one obtains, probably as the result of partial isomerization during reaction of the methylenecycloalkanes to 1-methylcycloalkenes, small amounts of secondary compounds, such as the corresponding methylbicyclo[n.l.O] alkanes. 

Highly synthetically demanding (. -hisubstituted alkenes and their derivatives (useful advanced intermediates for archazolid A and B, (+)-discodermolide and (—)-callystatin A) are prepared from 1-haloalkyne via hydroboration-migratory insertion-Zn-promoted iodinolysis-Pd-catalyzed organozinc cross-coupling (eq 27). ... 

Cycloalkenes and their derivatives are named by adapting cycloalkane termmol ogy to the principles of alkene nomenclature... 

The classification of hydrocarbons as aliphatic or aromatic took place m the 1860s when It was already apparent that there was something special about benzene toluene and their derivatives Their molecular formulas (benzene is CgHg toluene is C7Hj ) indicate that like alkenes and alkynes they are unsaturated and should undergo addition reac tions Under conditions m which bromine for example reacts rapidly with alkenes and alkynes however benzene proved to be inert Benzene does react with Bi2 m the pres ence of iron(III) bromide as a catalyst but even then addition isn t observed Substitu tion occurs instead ... 

Generally, unsaturated compounds, eg, alkenes and natural fats and their derivatives, are much more reactive toward sulfur than alkanes. Sulfur reacts with unsaturated compounds at temperatures of 120—215°C, forming products that are usually dark and often viscous cross-linked mixtures of dithiole-3-thiones (eq. 4) (2) and sulfides (Table 1) (3). 

Several alkenes are converted to aziridines by treating with oxaziridine (52) at elevated temperatures. Styrene, a-methylstyrene and their derivatives substituted in the benzene ring react smoothly, and so do 1,1-diphenylethylene, indene and acrylonitrile (74KGS1629). 

Alkenes and alkynes are similar in structure to the alkanes except the alkenes contain a carbon-to-carbon double bond (C=C) and the alkynes contain a carbon-to-carbon triple bond (C=C). The name prefixes are exactly the same as for the alkanes with the same number of carbons, but the endings are -one for compounds with double bonds and their derivatives and -yne for compounds with triple bonds... 

As in the alkanes, it is possible for carbon atoms to align themselves in different orders to form isomers. Not only is it possible for the carbon atoms to form branches which produce isomers, but it is also possible for the double bond to be situated between different carbon atoms in different compounds. This different position of the double bond also results in different structural formulas, which, of course, are isomers. Just as in the alkanes, isomers of the alkenes have different properties. The unsaturated hydrocarbons and their derivatives are more active chemically than the saturated hydrocarbons and their derivatives. 

Reactions and Properties of Phosphonic and Phosphinic Acids and their Derivatives.-A free radical mechanism has been proposed to account for the cleavage of the phosphorus-carbon bond in the alkylphosphonic acids (155) by E coli to give a mixture of alkane (methane only, from methylphosphonic acid) and terminal alkene. 

Esters of [1-(diethoxyphosphinyloxy)perfluoro-l-alkene]-phosphonic acid appear to be effective reagents for the synthesis of perfluoro-a,B-unsaturated carboxylic acids and their derivatives presumably an initially-generated perfluoroketene (166 ) is acted upon by a nucleophile (NuH=RNH2, I NH, or ROH). The ( E) / (Z) ratio of the product components increases with increasing length of R. 2 ... 

Nitro compounds have been converted into various cyclic compounds via cycloaddition reactions. In particular, nitroalkenes have proved to be useful in Diels-Alder reactions. Under thermal conditions, they behave as electron-deficient alkenes and react with dienes to yield 3-nitrocy-clohexenes. Nitroalkenes can also act as heterodienes and react with olefins in the presence of Lewis acids to yield cyclic alkyl nitronates, which undergo [3+2] cycloaddition. Nitro compounds are precursors for nitrile oxides, alkyl nitronates, and trialkylsilyl nitronates, which undergo [3+2]cycloaddition reactions. Thus, nitro compounds play important roles in the chemistry of cycloaddition reactions. In this chapter, recent developments of cycloaddition chemistry of nitro compounds and their derivatives are summarized. 

Baranov, G.M., Perekalin, V.V., Ponamarenko, M.V., and Orlovskii, I.A., Synthesis, properties, and structure of nitro- and aminoalkyl(alkene)phospho-nates and their derivatives, Khim. Primen. Fosfororg. Soldin., Tr. Konf., 4th, 228, 1969. 

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