Unsaturated hydrocarbons the alkenes

An alkene is a hydrocarbon that has one carbon-to-carbon double bond in each molecule. The general molecular formula for this class of hydrocarbons is C H2k- The two electrons involved as the second pair of the double bond are not shared with hydrogen atoms, so each molecule of an alkene has two fewer hydrogen atoms than that of the corresponding alkane. Alkenes are therefore said to be unsaturated hydrocarbons. The alkenes are also named systematically ... 

Saturated hydrocarbons have only single bonds unsaturated Ihydrocarbons have one or more multiple bonds. Alkanes are saturated hydrocarbons. Alkenes and alkynes are unsaturated hydrocarbons the former have carbon-carbon double bonds and the latter have triple bonds. 

In most palladium-catalyzed oxidations of unsaturated hydrocarbons the reaction begins with a coordination of the double bond to palladium(II). In such palladium(II) olefin complexes (1), which are square planar d8 complexes, the double bond is activated towards further reactions, in particular towards nucleophilic attack. A fairly strong interaction between a vacant orbital on palladium and the filled --orbital on the alkene, together with only a weak interaction between a filled metal d-orbital and the olefin ji -orbital (back donation), leads to an electrophilic activation of the alkene9. 

Markownikoff rule In the addition of hydrogen halides to unsymmetrically constituted (unsaturated) hydrocarbons, the halogen atom becomes attached to the carbon bearing the lesser number of hydrogen atoms. Originally formulated by Markownikoff (Markovnikov) to generalize the orientation in additions of hydrogen halides to simple alkenes, this rule... 

Alkenes and alkynes are unsaturated hydrocarbons. The characteristic functional group of an alkene is the carbon-carbon double bond. The functional group that... 

Oxidation of Alkenes and Other Unsaturated Hydrocarbons. The epoxidation of double bonds has been the major area for the application of DDO methodology and a wide range of alkenes are effectively converted to epoxides by solutions of DDO. Epoxidation is stereospecific with retention of afkene stereochemistry, as shown by the reactions of geometrical isomers for example, ( -1-phenylpropene gives the cw-epoxide cleanly (eq 2), whereas the (E) isomer yields the corresponding trans-epoxide. Rate studies indicate that this reagent is electrophilic in nature and that alkyl substitution on the double bond enhances reactivity Interestingly, cw-disubstituted alkenes react 7-9 times faster than the trans isomers, an observation that has been interpreted in terms of a spiro transition state. ... 

An unsaturated hydrocarbon contains one or more carbon-carbon double or triple bonds. The term unsaturation indicates that fewer hydrogens are bonded to carbon than in an alkane, C 2n+i- three most important classes of unsaturated hydrocarbons are alkenes, alkynes, and arenes. Alkenes contain a carbon-carbon double bond and, with one double bond and no rings, have the general formula C 2n- Alkynes contain a carbon-carbon triple bond and, with one triple bond and no rings, have the general formula CJi2 2- The simplest alkene is ethylene, and the simplest alkyne is acetylene. 

A hydrocarbon containing one or more carbon-carbon double or triple bonds. The three most important classes of unsaturated hydrocarbons are alkenes, alkynes, and arenes. 

Alkenes and alkynes contain fewer hydrogen atoms than alkanes with the same number of carbons. Because they are not saturated with hydrogen, they are called unsaturated hydrocarbons. The structures and some of the properties of the families of alkenes and alkynes are discussed in this chapter. 

In discussing the propetties of hydrocarbons in general there are two other terms that it is important to understand cleatly. These are the terms saturated and unsaturated. The alkanes are saturated hydrocarbons as all the C to C bonds in the chain are single bonds. The molecules have as much hydrogen as possible attached to the carbon chain. If there is a C=C bond in the chain then additional hydrogen atoms could be attached to the chain, and the molecule is said to be unsaturated. Thus the alkenes ate a series of unsaturated hydrocarbons. The same is true for the alkynes. They are also unsaturated hydrocarbons. 

Table 21.3 gives the names and formulas of some of the simpler unsaturated hydrocarbons. The lUPAC nomenclature system for the alkenes matches that of the alkanes. The suffix designating the alkene hydrocarbon series is -ene, just as -ane identifies an alkane. For example, pentene is CjHjq, hexene is QHj2, and octene is CgHjg. The common names for the alkenes are produced similarly, except that the suffix is -ylene. These names for the smaller alkenes are often used instead of the lUPAC names C2H4 is often called ethylene, CjHg is propylene, and C4H8 is butylene. 

It has been known for more than a century that hydrocarbons containing double bonds are more reactive than their counterparts that do not contain double bonds. Alkenes are, in general, more reactive than alkanes. We call electrons in double bonds 71 electrons and those in the much less reactive C—C or CH bonds Huckel theory, we assume that the chemistry of unsaturated hydrocarbons is so dominated by the chemistry of their double bonds that we may separate the Schroedinger equation yet again, into an equation for potential energy. We now have an equation of the same fomi as Eq. (6-8), but one in which the Hamiltonian for all elections is replaced by the Hamiltonian for Ji electrons only... 

Alkenes are commonly described as unsaturated hydrocarbons because they have the capacity to react with substances which add to them Alkanes on the other hand are said to be saturated hydrocarbons and are incapable of undergoing addition reactions... 

Alkenes are unsaturated hydrocarbons and react with substances that add to the dou... 

The butane-containing streams in petroleum refineries come from a variety of different process units consequently, varying amounts of butanes in mixtures containing other light alkanes and alkenes are obtained. The most common recovery techniques for these streams are lean oil absorption and fractionation. A typical scheme involves feeding the light hydrocarbon stream to an absorber-stripper where methane is separated from the other hydrocarbons. The heavier fraction is then debutanized, depropanized, and de-ethanized by distillation to produce C, C, and C2 streams, respectively. Most often the stream contains butylenes and other unsaturates which must be removed by additional separation techniques if pure butanes are desired. 

Alkenes — Also known as olefins, and denoted as C H2 the compounds are unsaturated hydrocarbons with a single carbon-to-carbon double bond per molecule. The alkenes are very similar to the alkanes in boiling point, specific gravity, and other physical characteristics. Like alkanes, alkenes are at most only weakly polar. Alkenes are insoluble in water but quite soluble in nonpolar solvents like benzene. Because alkenes are mostly insoluble liquids that are lighter than water and flammable as well, water is not used to suppress fires involving these materials. Because of the double bond, alkenes are more reactive than alkanes. 

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. 

The above discussions have concentrated on hydrocarbons, both saturated and unsaturated, with the unsaturated hydrocarbons containing only one multiple bond. The unsaturated hydrocarbons are the alkenes with one double bond and the alkynes... 

Saturated hydrocarbons are stable. Only cycloalkanes with a tight ring are unstable. Alkenes and alkynes have a strong endothermic character, especially the first homologues and polyunsaturated conjugated hydrocarbons. This is also true for aromatic compounds, but this thermodynamic approach does not show up their real stability very well. Apart from a few special cases, the decomposition of unsaturated hydrocarbons requires extreme conditions, which are only encountered in the chemical industry. 

Hydrocarbons are the simplest organic compounds, containing only carbon and hydrogen. There are three families of hydrocarbons. The alkanes have only single bonds and are said to be saturated. Alkanes are very stable and generally unreactive. Alkenes and alkynes have multiple bonds between two adjacent carbon atoms and are said to be unsaturated. This unsaturation makes alkenes and alkynes more reactive than alkanes. 

The gas-phase reaction of cationic zirconocene species, ZrMeCp2, with alkenes and alkynes was reported to involve two major reaction sequences, which are the migratory insertion of these unsaturated hydrocarbons into the Zr-Me bond (Eq. 3) and the activation of the C-H bond via er-bonds metathesis rather than /J-hydrogen shift/alkene elimination (Eq. 4) [130,131]. The insertion in the gas-phase closely parallels the solution chemistry of Zr(R)Cp2 and other isoelec-tronic complexes. Thus, the results derived from calculations based on this gas-phase reactivity should be correlated directly to the solution reactivity (vide infra). 

Alkanes, with the general formula C H2 +2, are saturated hydrocarbons, in which each carbon atom is singly bonded to four other atoms. These atoms are either carbon atoms or hydrogen atoms. Alkenes, C H2 , and alkynes, C H2 2, are unsaturated hydrocarbons in which there is a carbon-carbon double bond or a carbon-carbon triple bond, respectively. 

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