Hydrocarbon olefinic

The most important olefins used for the production of petrochemicals are ethylene, propylene, the butylenes, and isoprene. These olefins are usually coproduced with ethylene by steam cracking ethane, LPG, liquid petroleum fractions, and residues. Olefins are characterized by their higher reactivities compared to paraffinic hydrocarbons. They can easily react with inexpensive reagents such as water, oxygen, hydrochloric acid, and chlorine to form valuable chemicals. Olefins can even add to themselves to produce important polymers such as polyethylene and polypropylene. Ethylene is the most important olefin for producing petrochemicals, and therefore, many sources have been sought for its production. The following discusses briefly, the properties of these olefmic intermediates. 

Ethylene (ethene), the first member of the alkenes, is a colorless gas with a sweet odor. It is slightly soluble in water and alcohol. It is a highly 

Catalytic oxidation of ethylene produces ethylene oxide, which is hydrolyzed to ethylene glycol. Ethylene glycol is a monomer for the production of synthetic fibers. Chapter 7 discusses chemicals based on ethylene, and Chapter 12 covers polymers and copolymers of ethylene. 

Ethylene is a constituent of refinery gases, especially those produced from catalytic cracking units. The main source for ethylene is the steam cracking of hydrocarbons (Chapter 3). Table 2-2 shows the world ethylene production by source until the year 2000. U.S. production of ethylene was approximately 51 billion lbs in 1997.  

Like ethylene, propylene (propene) is a reactive alkene that can be obtained from refinery gas streams, especially those from cracking processes. The main source of propylene, however, is steam cracking of hydrocarbons, where it is coproduced with ethylene. There is no special process for propylene production except the dehydrogenation of propane. 

Reagent i, WCl6-SnMe4-PhCl, high dilution, 75 C, 12 h 

Cp2TiMe2 and WOCI4 or WCle is an effective catalytic system for the metathesis of olefins. Importantly, the system tolerates carboxylic esters, and this enabled it to be used to effect the key steps in syntheses of civetone and other macrolides. Unsaturated ketones or acetals are not suitable substrates. 

The preparation of strained olefins continues to challenge the synthetic chemist. Although the synthesis of tetra-t-butylethylene remains an elusive goal, the related tetrakis(trimethylsilyl)ethylene has now been prepared and characterized.  

Lenoir and his co-workers have published further syntheses of sterically crowded olefins. Many hindered ketones, l-ethyladamantan-2-one (6) for 

Reagents i, Ti -boiling dioxan, reactant half-life ca. 6 days ii, Ti°-boiling THF, 16 h 

The protonolysis of alkenyldialkylboranes to give -alkenes can be conducted, in most cases, under neutral conditions using methanol. More hindered alkenyldisiamylboranes react less well, unless a small amount of a carboxylic acid is added. A variety of Z-alkenyl pheromones was prepared using this method. The synthesis of trans-alkenes and unsymmetrical ketones was also accomplished using vinylic organoborane chemistry.7 

Cross-coupling reactions are now possible between aryl (or vinyl) halides and trialkylboranes by the use of catalytic 

Warren s examination of the Horner-Wittig reaction continues 

The homologation of esters via a DIBAL reduction and phosphonate extension sequence is a commonly desired transformation. The DIBAL reduction to give an aldehyde suitable for homologation is often plagued by over-reaction problems,so that a reduction-reoxidation procedure is often required. These 

Diiodo alkenes have been prepared via a Wittig-like reaction 17 

Reviews have appeared on the use of the Wittig reaction in industrial practice, the Claisen rearrangement, synthetic applications of the retro-Diels-Alder reaction, organo-palladium intermediates for the alkylation and arylation of olefins, the Prins reaction to give 1,3-dienes, and intramolecular [4 + 2] (Diels-Alder) and [3 + 2] cycloadditions.An interesting discussion of the regiospecificity of the Diels-Alder reaction in terms of frontier orbital overlap favours the Woodward-Katz concept. Useful alkyne and polyene coupling reactions are described in reviews on the chemistry of vitamin the synthesis of insect sex 

New fragmentation and elimination processes are being developed, leading to milder reaction conditions for olefin formation. A novel fragmentation of l-trimethylsilyloxybicyclo(fi,l,0]alkanes (13) with lead tetra-acetate affords the terminal olehnic acids (14) by oxidative cleavage of both cyclopropane bonds a  

Reagents i. BrCH(C02Bu 2-Me2NC(=NH)NMe2 ii, diphenylsulphonium cyclopropylide-KOH iii, NaBH4-Mg(OMe)2 

Reetz has shown that hydride acceptors (e.g. triphenylmethyl tetrafluoroborate) may effect elimination of /8-hydrogen atoms from organolithium and magnesium compounds, to generate olefins under mild conditions.Yields increase from primary through to tertiary metallated compounds. Furthermore, addition of alkyl-lithium reagents to activated olefins (e.g. 1,1-diphenylethylene) followed by hydride abstraction gives the 2-alkyl-l,l-diphenylalkenes.  

Lythgoe and Waterhouse have found that /8-hydroxysulphide-5-methyl-dithiocarbonates (22), chlorosulphides (24), and /3-hydroxythiobenzoate sulphones 

More evidence has appeared showing that the olefin metathesis reaction can tolerate the presence of functional groups. The catalytic system Re207-Al203, promoted by a small amount of tetramethyltin, effects metathesis of olefins in fair yield (17—40%) in the presence of unsaturated ethers and ketones, alkenyl esters, and halogeno-alkenes. The reaction is performed in carbon tetrachloride as solvent at room temperature over 6 h. Electro-reduction of tungsten hexa-chloride with an aluminium anode in halogenated solvents appears to form a complex suitable for a clean metathesis, exemplified by the conversion of pent-2-ene into its equilibrium mixture with but-2-ene and hex-3-ene.  

Substituted vinylsilanes are useful intermediates in the synthesis of stereo-chemically defined olefins. A new synthesis of substituted vinylsilanes (16) from the silylvinyl Grignard reagent (15) has been achieved. An alternative pro- 

The substitution of allylic sulphones by Grignard reagents has been shown to be catalysed by 1% [Cu(acac)2] to give a one-step route to either the a- or the y-coupled products. Primary allylic sulphones favour the y-product, whereas secondary allylic sulphones give a mixture of both a- and y-products. 

Several papers have appeared dealing with the synthesis of strained bridgehead olefins (anti-Bredt olefins). Conditions are described whereby a 10 1 mixture of the olefins (25) and (26) is formed by the vacuum pyrolysis of the bridgehead chloro-compound (24). ° The olefin (25) can form a reversible stabilized complex with [Pt°(PPh3)2], and this same catalyst can also effect irreversible isomerization to (27). The lead tetra-acetate-induced oxidative decarboxylation of the propellane carboxylic acid (28) produces the stable olefin (29) in good yield.  

Becker, P. Engel, and R. Keese, Helv. Chim. Acta, 1979,62, 2181. 

Phosphinothioic amides are highly effective reagents for the alkylidenation of ketones, and the method has been developed as a means of methylenation coupled with optical resolution. The reaction of the anion of the phosphinothioic amide (21) gives the diastereoisomeric mixture (22), which, after separation, can be converted into the optically active olefins (23). The method has been applied to the synthesis of the (+)- and ( —)-iridoid monoterpene hop ether (24), and can be extended to alkylidenation with resolution. 

The reaction of alkenyldi-isobutylalane with titanocene dichloride gives dimetalloalkanes (25), which convert ketones into olefins (26) in good yield (around 65%) but with only poor stereoselectivity the general use of heavy main-group elements in the synthesis of terminal olefins and of (Z)- and ( )-olefins stereospecifically has been reviewed by Kauffmann.  

An interesting method for the introduction of the isopropylidene moiety has been described, using keten thioacetal chemistry. Thus, the reaction of the enolate of ketone (27) with carbon disulphide followed by methylation gives the keten thioacetal (28). Double conjugative addition and elimination, using lithio-dimethyl cuprate, then affords the isopropylidene ketone (29). Similar method- 

Reagents, i, R MgBr ii, ( NiCh iii, Pr MgBr iv, (Ph3P)NiCl2 v, R MgBr 

Further studies on the cationic prenylation of olefins have been published these studies also demonstrate the range of nucleophilicity that is required in the reaction. Nitroalkanes (30) can be C-allylated under Pd catalysis, where the reactivity of the allylic component (31) is in the order X = OPh OAc OH.  

Several factors which influence the rate and yield of the ene reaction have been identified this year. Gladysz and Yu have found that the thermal ene reaction of /3-pinene, which otherwise occurs only at temperatures greater than 150 °C, proceeds readily at room temperature under 40 kbar pressure (39 500 atm). For example, methyl pyruvate and /3-pinene have been reported to react at 165 C to afford the adduct (1) in 55% yield. Since (1) undergoes a rapid retro-ene reaction at this temperature, this yield is believed to represent the maximum equilibrium yield attainable. However, (1) is formed in quantitative yield at room temperature at 40 kbar pressure  

The intramolecular ene reaction of the 1,6-enyne (2) appears to be retarded by a terminal methyl substituent, but significantly accelerated by an electron-withdrawing substituent, such as the methoxycarbonyl group.These observations are pertinent to the conversion (2) — (3) in a synthetic strategy to the iridoid carbon skeleton. 

The eutectic mixture AlCls-NaCl-KCl has been found to be a superior catalyst to AICI3 alone, in the Lewis acid-catalysed ene reaction of methyl acrylate with terminal olefins. Hence an 86 14 mixture of geometrical isomers of (4) is obtained from octene the ester (4) is a useful intermediate in the synthesis of the sex pheromone from the Douglas Fir Tussock moth, and of its biologically active isomer.  

The olefinic ketone (5) is the major component (52%) in a mixture of four products from an apparent ene reaction of an allylic cation with isobutylene the cation is formed by treatment of an a,a -dibromo-ketone with iron carbonyl.  

Reagents i, GHjCCOzMe) or CH2(C02Me)S02R ii, PhSCHjCOR iii, CH2(C02Me)S02R iv, 

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This method follows the ASTM D 1159 and D 2710 procedures and the AFNOR M 07-017 standard. It exploits the capacity of the double olefinic bond to attach two bromine atoms by the addition reaction. Expressed as grams of fixed bromine per hundred grams of sample, the bromine number, BrN, enables the calculation of olefinic hydrocarbons to be made if the average molecular weight of a sufficiently narrow cut is known. 

I H2S reacts in another way with the olefinic hydrocarbons producing thiols and sulfur compounds (Equation 8.3 and 8.4) ... 

The use of silver fluoroborate as a catalyst or reagent often depends on the precipitation of a silver haUde. Thus the silver ion abstracts a CU from a rhodium chloride complex, ((CgH )2As)2(CO)RhCl, yielding the cationic rhodium fluoroborate [30935-54-7] hydrogenation catalyst (99). The complexing tendency of olefins for AgBF has led to the development of chemisorption methods for ethylene separation (100,101). Copper(I) fluoroborate [14708-11-3] also forms complexes with olefins hydrocarbon separations are effected by similar means (102). 

The feedstocks used ia the production of petroleum resias are obtaiaed mainly from the low pressure vapor-phase cracking (steam cracking) and subsequent fractionation of petroleum distillates ranging from light naphthas to gas oil fractions, which typically boil ia the 20—450°C range (16). Obtaiaed from this process are feedstreams composed of atiphatic, aromatic, and cycloatiphatic olefins and diolefins, which are subsequently polymerized to yield resias of various compositioas and physical properties. Typically, feedstocks are divided iato atiphatic, cycloatiphatic, and aromatic streams. Table 2 illustrates the predominant olefinic hydrocarbons obtained from steam cracking processes for petroleum resia synthesis (18). 

Shale oil contains large quantities of olefinic hydrocarbons (see Table 8), which cause gumming and constitute an increased hydrogen requirement for upgrading. Properties for cmde shale oil are compared with petroleum cmde in Table 10. High pour points prevent pipeline transportation of the cmde shale oil (see Pipelines). Arsenic and iron can cause catalyst poisoning. 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

VL sulfonation of olefins requires hydroperoxide catalyst cosdy sulfonation of olefinic hydrocarbons ... 

Coal tar is the condensation product obtained by cooling to approximately ambient temperature, the gas evolved in the destmctive distillation of coal. It is a black viscous Hquid denser than water and composed primarily of a complex mixture of condensed ring aromatic hydrocarbons. It may contain phenoHc compounds, aromatic nitrogen bases and their alkyl derivatives, and paraffinic and olefinic hydrocarbons. Coal-tar pitch is the residue from the distillation of coal tar. It is a black soHd having a softening point of 30—180°C (86—359°F). 

Products from hydrocracking processes lack olefinic hydrocarbons. The product slate ranges from light hydrocarbon gases to gasolines to residues. Depending on the operation variables, the process could... 

When olefin hydrocarbons react with nitrogen dioxide or nitrous and nitric anhydride, they are added to a double bond. .. 

Blumer M (1970) Dissolved organic compounds in seawater. Saturated and olefinic hydrocarbons and singly branched fatty acids. In Hood DW (ed) Organic matter in natural waters. Publication no. 1. Institute of Marine Science, University of Alaska, pp 153-167... 

A similar mechanism of chain oxidation of olefinic hydrocarbons was observed experimentally by Bolland and Gee [53] in 1946 after a detailed study of the kinetics of the oxidation of nonsaturated compounds. Miller and Mayo [54] studied the oxidation of styrene and found that this reaction is in essence the chain copolymerization of styrene and dioxygen with production of polymeric peroxide. Rust [55] observed dihydroperoxide formation in his study of the oxidation of branched aliphatic hydrocarbons and treated this fact as the result of intramolecular isomerization of peroxyl radicals. 

Olefin hydrocarbon Air (oxygen) Formation of explosive organic peroxides... 

Whilst this view was widely accepted as explaining many of the observations, a few workers retained for some time a modified version of Hunter and Yohe s direct initiation mechanism to explain a limited range of phenomena. The point at issue is whether the polymerisation of an olefinic hydrocarbon can be initiated by a metal halide alone, without the participation of a co-catalyst, which might be water, a hydroxylic impurity, or a... 

The important point is that this negative quantum yield is realized only when an olefin (hydrocarbon) is present. Thus, adding the overall step... 

Some work [5] has been performed on the photochemical reaction between sulfur dioxide and hydrocarbons, both paraffins and olefins. In all cases, mists were found, and these mists settled out in the reaction vessels as oils with the characteristics of sulfuric acids. Because of the small amounts of materials formed, great problems arise in elucidating particular steps. When NO and 02 are added to this system, the situation is most complex. Bulfalini [3] sums up the status in this way The aerosol formed from mixtures of the lower hydrocarbons with NO and S02 is predominantly sulfuric acid, whereas the higher olefin hydrocarbons appear to produce carbonaceous aerosols also, possibly organic acids, sulfonic or sulfuric acids, nitrate-esters, etc. ... 

Heinze modified the technique by purifying the solvent by transferring it under high vacuum from the electrochemical cell to superactive alumina in a separate vessel [27, 28]. Such sophisticated methods made it possible to generate reversible polyanions up to octaanions of aromatic and olefinic hydrocarbons [27, 28, 30-33]. 

For the purpose of description, the electrochemistry of hydrocarbons may usefully be classified in three categories benzenoid, nonbenzenoid, and olefinic hydrocarbons. 

Tab. 1 Redox potentials (in volt) for the reduction of aromatic and olefinic hydrocarbons...

The RDA reaction is often observed from steroid molecular ions, and it can be very indicative of steroidal stmcture. [107,110,113,114] The extent of the RDA reaction depends on whether the central ring junction is cis or trans. The mass spectra of A -steroidal olefins, for example, showed a marked dependence upon the stereochemistry of the A/B ring juncture, in accordance with orbital symmetry rules for a thermal concerted process. In the trans isomer the RDA is much reduced as compared to the cis isomer. The effect was shown to increase at 12 eV, and as typical for a rearrangement, the RDA reaction became more pronounced, whereas simple cleavages almost vanished. This represented the first example of such apparent symmetry control in olefinic hydrocarbons. [114]. 

Hydroforming. The use of hydrogen and pressure and a catalyst to convert an olefinic hydrocarbon to a branch-chain paraffin. 

Complete elimination of olefinic hydrocarbons without controlling aldehyde emission will not ensure low oxidant readings in the atmosphere. ... 

Cox, R.A. and Penkett, S.A. Aerosol formation from sulfur dioxide in the presence of ozone and olefinic hydrocarbons, J. Chem. Soc., Faraday Trans. 1., 68 1735-1753, 1972. 

Nitrous oxide Nitric oxide Sulfur dioxide Standardized smoke Saturated and Olefinic Hydrocarbons Ozone... 

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