Alkenes propenes

The important hydrocarbon classes are alkanes, alkenes, aromatics, and oxygenates. The first three classes are generally released to the atmosphere, whereas the fourth class, the oxygenates, is generally formed in the atmosphere. Propene will be used to illustrate the types of reactions that take place with alkenes. Propene reactions are initiated by a chemical reaction of OH or O3 with the carbon-carbon double bond. The chemical steps that follow result in the formation of free radicals of several different types which can undergo reaction with O2, NO, SO2, and NO2 to promote the formation of photochemical smog products. 

The following illustrates the hydrogenation and halogenation, with bromine, of the alkene propene. Notice that the —CH3 group, which is not a functional group, does not change during either reaction. 

The product of an addition reaction depends on the symmetry of the reactants. A symmetrical alkene has identical groups on either side of the double bond. Ethene, CH2 = CH2, is an example of a symmetrical alkene. An alkene that has different groups on either side of the double bond is called an asymmetrical alkene. Propene, CH3CH=CH2, is an example of an asymmetrical alkene. 

Monohaloalkanes can undergo elimination reactions when they are with ethanolic potassium (or sodium) hydroxide, l.e. a solution of potr hydroxide in ethanol. For example, when 2-bromopropane is heated Wi potassium hydroxide, the alkene propene is formed ... 

Other alkene complexes [Re(CO)5(alkene)] [BF4] (alkene = propene, pent-l-ene, buta-1,3-diene) can also be obtained from Re(CO)5(FBF3) and alkene.13... 

Notice that the combination of hydroformylation (Section 16-9F), aldol addition, dehydration, and hydrogenation takes a simple alkene (propene) to an alcohol with more than twice as many carbons. 

Using a relative rate method, rate constants for the gas-phase reactions of O3 with 1- and 3-methylcyclopentene, 1-, 3- and 4-methylcyclohexene, 1-methylcycloheptene, cw-cyclooctene, 1- and 3-methylcyclooctene, cycloocta-1,3- and 1,5-diene, and cyclo-octa-l,3,5,7-tetraene have been measured at 296 2 K and atmospheric pressure. The rate constants obtained (in units of 10-18 cm3 molecule-1 s-1) are as follows 1-methylcyclopentene, 832 24 3-methylcyclopentene, 334 12 1-methylcyclohex-ene, 146 10 3-methylcyclohexene, 55.3 2.6 4-methylcyclohexene, 73.1 3.6 1-methylcycloheptene, 930 24 d.s-cyclooclcnc, 386 23 1-methylcyclooctene, 1420 100 3-methylcyclooctene, 139 9 d.v.d.v-cycloocta-1,3-diene, 20.0 1.4 cycloocta- 1,5-diene, 152 10 and cycloocta-l,3,5,7-tetraene, 2.60 0.19 the indicated errors are two least-squares standard deviations and do not include the uncertainties in the rate constants for the reference alkenes (propene, but-l-ene, d.s-but-2-ene, trans-but-2-ene, 2-methylbut-2-ene, and terpinolene). These rate data were compared with the few available literature data, and the effects of methyl substitution have been discussed.50... 

The behaviour of these catalysts in the oligomerization of higher alkenes, propene and butene has not previously been reported. This paper addresses this aspect, and in addition focuses on the nature of the structure of the oligomers produced by propene dimerization. 

In order to probe this phenomenon quantitatively in an uncharged system where solvation effects are known to be relatively unimportant, the rates of cycloadditions of two relatively electron-deficient 1,3-dipoles, p-methoxy and p-nitro benzonitrile oxides (MBNO and NMBO, respectively) to a series of simple alkenes — propene, 1-butene, 1-pentene, 1-hexene, 3-methyl-l-butene, 3,3-dimethyl-l-butene and isobutene — were measured70. In each of these reactions, only the 5-alkyl-3-aryliso-xazolines were formed. 

A carbocation may lose a proton to form an alkene. For example, 1-propyl carbocation generated from diazonium salt may lose a proton (H+) to form an alkene (propene). Alternatively, 1-propyl carbocation may rearrange to more stable secondary carbocation, which may also lose a proton to give propene (Scheme 2.1). 

Irradiation of the complexes trani -[W(CO)4( ( -alkene)2] (alkene = propene, 1-butene, cyclopentene) in an alkane solution led to the loss of alkene and CO. The liberation of alkene was accompanied by the formation of 16-electron coordinatively unsaturated species trans- and m-[W(CO)4(jj -alkene)(solvent)]. In the case of propene and 1-butene, these species transformed into di-[WH( -allyl)(CO)4]. In the presence of excess alkenes, the 16-electron species bound alkene to give cis-[W(CO)4() -alkene)2]. The CO loss upon irradiation of frani -[W(CO)4() -alkene)2] led to the formation of mer- andyac-[W(CO)3() -alkene)2(solvent)],... 

Palladium clusters have been reported to catalyze the oxidative acetoxy-lation of alkenes Propene reacts with acetic acid and oxygen to give allyl acetate according to... 

The reactions with gaseous alkenes (propene, 2-methylpropene) are conveniently carried out at temperatures of up to — 80 °C, in the presence of powdered potassium hydroxide and a phase-transfer catalyst (solid-liquid variant using bromoform). 

A marked improvement was effected when it was found that the displacement reaction could be operated with trialkyl alanes and ethylene or suitable 1-alkenes (propene, 1-butene, etc.) even at 300°-350°C, if the components were allowed to react for only a very short time at a moderate pressure of alkene. In spite of the high temperature, no decomposition of the trialkyl alanes to aluminum, hydrogen, and alkenes took place. Moreover, in the high temperature reaction with so short a reaction time there were practically no side reactions, i.e., a-branched alkenes and such compounds were hardly detected (314, 326). 

The light alkenes (propene, butene and pentene) are important feedstocks for alkylation, oligomerization and the synthesis of ethers (refs. 1,2). MTBE (methyl tert-butyl ether) and TAME (tert-amyl methyl ether) have research octane numbers of 118 and 112 respectively. These premium blend stocks are synthesised by reaction of methanol with isobutene or isopentene (refs. 3,4). The reaction with methanol is selective towards the branched alkenes so that a mixture may be treated and the straight chain alkenes recovered for other processing such as alkylation. 

For the metallation of propene and homologues the following base-solvent systems are in principle available BuLi TMEDA-hexane [1], BuLi t-BuOK-hexane [2], BuLi t-BuOK-THF + hexane [3], BuLi t-BuOK TMEDA-hexane [4]. In order to maintain a sufficiently high concentration, the metallation of gaseous alkenes (propene, 1- and 2-butene, and isobutene) has to be carried out at relatively low temperatures. As a consequence, reaction times may be long [1]. With the third and fourth base-solvent system the gaseous alkenes can be metallated quickly, while reactions with a number of electrophiles indicate that the metallations have proceeded successfully. 

The Dow Chemical Company also filed several patents [183, 184] on Au-based catalysts for hydro-oxidation (i.e., direct reaction with O2 in presence of Hj) of alkenes (propene and larger). One of them, focused on catalyst prepared starting with atomically precise Au clusters, claims stable catalyst activity over extended hfetime and improved hydrogen efficiency with selectivity of about 90% toward formation of epoxide [184]. 

In the investigation of products and intermediates from the reactions between NO3 and the alkenes (propene isobutene trans- and cis butene 2-methyl-2-butene 2,3-dimethyl-2-butene and isoprene) it was found that all of them followed a similar pattern. The build-up of organic nitrate bands (845, 1280 and 1667 cm ) and peroxynitrate bands (790,1300,1725 cm" ) were observed in the IR-spectra as showed in Fig. 2. The subsequent decay of the peroxynitrate bands was accompanied by a build-up of spectral features attributed to stable products (see Fig. 2). These stable products were identified as aldehydes, alcohol nitrates, carbonyl nitrates and dinitrates [3,4]. 

Perez-Casany, M.P., Nebot-Gil, I., Sanchez-Marin, J. Ab initio study on the mechanism of tropospheric reactions of the nitrate radical with alkenes propene. J. Phys. Chem. A 104,... 

The synthesis and reactions of cationic platinum(II) complexes containing alkenes has been reviewed. New cationic complexes of the type [Pt(T 2-alkene)(X)(tnien)l [C104] (alkene = ethene, propene, styrene, (E)- and (Z)-but-2-ene X = Cl, NO2 tmen = N,N,N, N -tetramethylethylenediamine) have been reported 2 and the intramolecular addition of the oxygen of the nitro ligand onto the cw-alkene described 3 in the case of X = NO2 and alkene = propene or ( )-but-2-ene. 

The dihydroxylatiOTi of terminal aliphatic n-alkenes (propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene) catalyzed by osmium tetroxide, a powerful method to enantioselectively introduce chiral centres into organic substrates, has been computationally studied by the hybrid QM/MM IMOMM-(B3LYP MM3) method. The analysis of the results, in particular the partition of the total IMOMM energy into its components, allows the responsibility for the selectivity to be identified [690]. 

Epoxidation of alkenes with oxygen until recently was possible only on silver catalysts and only in the case of ethylene, while epoxidation of other alkenes (propene, styrene) requires organic peroxides or (in rare cases) hydrogen peroxide. Haruta et al. [130] found that epoxidation of propene using an Au/TS-1 (TS-1 is a titanosilicate with the MFI topology) is catalyzed efficiently only by gold particles with the size not exceeding 1-2 nm, whereas the smaller particles exhibit a poor activity because of their nonmetallic (molecular) nature. 

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