Alkenes alkane olefination

Among these examples, probably the most notable case is the dehydrogenation of linear alkanes to their corresponding terminal alkenes (a-olefins), this being the kinetically favored process over the production of the internal alkenes. However, the same complex slowly catalyzes an isomerization of the terminal alkene to internal alkenes, as the latter are the thermodynamic products (Scheme 13.15) [33]. 

Aliphatic hydrocarbons such as n-alkanes and n-alkenes have been successfully used to distinguish between algal, bacterial, and terrestrial sources of carbon in estuarine/coastal systems (Yunker et al., 1991, 1993, 1995 Canuel et al., 1997). Saturated aliphatic hydrocarbons are considered to be alkanes (or paraffins) and nonsaturated hydrocarbons which exhibit one or more double bonds are called alkenes (or olefins)—as indicated in the simple structures of hexadecane and 1,3-butadiene, respectively (figure 9.7). It should also be noted that, n-alkanes tend to be odd-numbered as they result from enzymatic decarboxylation of fatty acids. Long-chain n-alkanes (LCH) (e.g., C27, C29, and C31) are generally considered to be terrestrially derived, originating from epicuticular waxes... 

The FTS converts synthesis gas into mostly liquid hydrocarbons [12-15]. Depending on the origin of the synthesis gas, the overall process from carbon feedstock to liquid product is called gas-to-liquids (GTL), coal to liquids (CTL), or biomass to liquids (BTL). The product spectrum, however, is broader than liquid hydrocarbons alone and can include methane and alkanes, C H2 +2 (with n from 1 — 100), alkenes or olefins (C H2 n > 2), and to a lesser extent, oxygenated products such as alcohols. Hence the FTS offers the opportunity to convert gas, coal, or biomass-derived syngas into transportation fuels, such as gasoline, jet fuel, and diesel oil, and chemicals, such as olefins, naphtha, and waxes. The reactions need a catalyst, which in commercial applications is either based on cobalt or iron. 

Open-chain aliphatic hydrocarbons constitute alkanes, alkenes, alkynes, and their isomers. Alkanes have the general formula C H2 +2, where n is the number of carbon atoms in the molecnles, snch as methane, propane, n-pentane, and isooctane. Alkenes or olefins are nnsaturated compounds, characterized by one or more double bonds between the carbon atoms. Their general formula is C H2 . Examples are ethylene, 1-butene, and... 

The acronym FIONA, which is often used, means Paraffins (n-alkanes). Isoparaffins (iso-alkanes). Olefins (alkenes), Naphtenes (cyclanes). Aromatics. 

Aliphatic alkylation is widely used to produce high-octane gasolines and other hydrocarbon products. Conventional paraffin (alkane)-olefin (alkene) alkylation is an acid-catalyzed reaction it involves the addition of a tertiary alkyl cation, generated from an isoalkane (via hydride abstraction) to an olefin. An example of such a reaction is the isobutane-ethylene alkylation, yielding 2,3-dimethylbutane. 

Today, the majority of ethylene is produced by thermal cracking of hydrocarbon feedstocks ranging fi-om ethane to heavy vacuum gas oils. Over 60% of the world s propylene is produced as a by-product of thermal cracking, with the balance being supplied from refinery sources and others. Raw materials are mosdy natural gas condensate components (principally ethane and propane) in the US and Mideast and naphtha in Europe and Asia. Alkanes/olefins are broken apart at high temperatures, often in the presence of a zeolite catalyst, to produce a mixture of primarily aliphatic alkenes and lower molecular weight alkanes. The mixture is feedstock and temperature dependent and separated by fractional distillation. 

The separation of hydrocarbons is one of the most important chemical processes routinely carried out in the petrochemical industry. Hydrocarbons, as the name suggests, are exclusively made up of carbon and hydrogen atoms that can be broadly classified based on their chemical nature alkanes or paraffins (general formula C H2 +2 example ethane, C2Hg), alkenes or olefins (general formula example ethene,... 

Additioneilly, "classes" or types of hydrocarbons were and still are determined based on the capability to isolate them by separation techniques. The four types usually sought eue paraffins, olefins, naphthenes, and aromatics. Paraffinic hydrocarbons include both normal and branched alkanes. Olefins refer to normal and branched alkenes that contain one or more double or triple carbon-carbon bonds. Naphthene (not to be confused with naphthalene ) is a term of the petroleum industry that refers to the saturated cyclic hydrocarbons or cycloalkanes. Finally, aromatics include all hydrocarbons containing one or more rings of the benzenoid structure. These general hydrocarbon classifications are complicated by many combinations of the above types, for example, olefinic aromatics (styrene) or alkylbenzenes (cumene). Table 4 presents a summary of the hydrocarbon types usually found in specific petroleum fractions. 

Microorganisms that use gaseous olefins as a carbon source are widely exist in nature, and they typically produce nonheme iron-dependent alkene/alkane monooxygenases. Although in a lot of cases, the identification of the key enzyme hasn t been attempted many of those alkene-utilizing bacteria have been used in the asymmetric epoxidation of aliphatic alkenes with high stereoselectivities [26]. 

A straight- or branched-chain alkane, with formula C H2 +2, has the maximum number of H atoms possible for its number of C atoms. In other classes of hydrocarbons, compounds with the same number of C atoms but fewer H atoms, the C atoms must join into rings, form carbon-to-carbon multiple bonds, or do both to ensure that each C atom forms a total of four bonds. We have already discussed some aspects of ring structures (in Section 26-3). In this section, we focus on hydrocarbons whose molecules contain some double or triple bonds between C atoms. Such molecules are said to be unsaturated. If the molecule has one double bond, the hydrocarbons are the simple alkenes, or olefins they have the general formula C H2 . Simple alkynes have one triple bond in their molecules and have the general formula C H2n-2-... 

Alkane (Section 2 1) Hydrocarbon in which all the bonds are single bonds Alkanes have the general formula C H2 +2 Alkene (Section 2 1) Hydrocarbon that contains a carbon-car bon double bond (C=C) also known by the older name olefin... 

Fischer-Tropsch Process. The Hterature on the hydrogenation of carbon monoxide dates back to 1902 when the synthesis of methane from synthesis gas over a nickel catalyst was reported (17). In 1923, F. Fischer and H. Tropsch reported the formation of a mixture of organic compounds they called synthol by reaction of synthesis gas over alkalized iron turnings at 10—15 MPa (99—150 atm) and 400—450°C (18). This mixture contained mostly oxygenated compounds, but also contained a small amount of alkanes and alkenes. Further study of the reaction at 0.7 MPa (6.9 atm) revealed that low pressure favored olefinic and paraffinic hydrocarbons and minimized oxygenates, but at this pressure the reaction rate was very low. Because of their pioneering work on catalytic hydrocarbon synthesis, this class of reactions became known as the Fischer-Tropsch (FT) synthesis. 

In general, hydroboration—protonolysis is a stereoselective noncatalytic method of cis-hydrogenation providing access to alkanes, alkenes, dienes, and enynes from olefinic and acetylenic precursors (108,212). Procedures for the protonolysis of alkenylboranes containing acid-sensitive functional groups under neutral or basic conditions have been developed (213,214). 

Hydrocarbons, compounds of carbon and hydrogen, are stmcturally classified as aromatic and aliphatic the latter includes alkanes (paraffins), alkenes (olefins), alkynes (acetylenes), and cycloparaffins. An example of a low molecular weight paraffin is methane [74-82-8], of an olefin, ethylene [74-85-1], of a cycloparaffin, cyclopentane [287-92-3], and of an aromatic, benzene [71-43-2]. Cmde petroleum oils [8002-05-9], which span a range of molecular weights of these compounds, excluding the very reactive olefins, have been classified according to their content as paraffinic, cycloparaffinic (naphthenic), or aromatic. The hydrocarbon class of terpenes is not discussed here. Terpenes, such as turpentine [8006-64-2] are found widely distributed in plants, and consist of repeating isoprene [78-79-5] units (see Isoprene Terpenoids). 

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. 

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