Olefins in solvents

Neither for olefins nor for heterocyclic monomers do we yet have a sufficiently extensive body of activation energies of the kp-s to make a detailed discussion profitable. It is worth noting, however, that for the cationic (as opposed to the pseudo-cationic) polymerisation of olefins in solvents of DC greater than about 10, it is likely that a reduction of the temperature does not affect the rate except through its effect on k p, since these reactions are mainly carried by free ions only. 

For cationic polymerisation of olefins in solvents of DC appreciably less than ca. 10 and for those of heterocyclic monomers in all solvents of DC up to perhaps 15-20, this is not so. For such systems the polymerisations are probably at least dieidic (free ions and ion-pairs) and a lowering of the temperature will increase the DC of the ion pairs. Thus in such systems the change of temperature affects not only k p and k"p, but also the relative abundance of the different types of chain-carriers therefore the proper interpretation of the apparent activation energies is difficult and by no means obvious. 

Aryl radicals obtained directly or through mediation of aromatic anion radicals react with olefins in solvents such as liquid NH3, DMSO, CH3CN or DMF to give the arylated products. The electrochemically generated aryl radicals react with styrene or its derivatives in aprotic media to give arylated addition products (225). The reaction, shown in equation 120, has been optimized to be synthetically useful. The rate constants of the key step, i.e. addition of the radical to the olefin, were determined by cyclic voltammetry177. 

In the third article of the series the authors set out to determine the kinetic initiation parameters and the lifetime of the ionic chain carriers. The values of kj were cmnputed frmn the measured rates of carbenium icm formation assuming bimolecular initiation. This assumption is unacceptable a priori since the interaction between Brjinsted acids and olefins in solvents like the one used in this work has been shown to involve kinetic patterns whidi are almost always more complicated than a simple first order in each reactant (see Sect. III-B). As for the calculation of the mean lifetime of the active species based on the expression... 

Structural Isomerization Reactions.—In earlier work Kropp and his co-workers19 suggested that the unsaturated and cyclopropane products formed by the irradiation of olefins in solvents of low nucleophilicity were produced by initial rearrangement to carbenes. In a later study Kropp and Fields20 have demonstrated that carbene intermediates are indeed formed in the irradiation of olefins... 

Acetyl chlotide reacts with aromatic hydrocarbons and olefins in suitably inert solvents, such as carbon disulfide or petroleum ether, to furnish ketones (16). These reactions ate catalyzed by anhydrous aluminum chlotide and by other inorganic chlotides (17). The order of catalytic activity increases in the order... 

Chloroacetate esters are usually made by removing water from a mixture of chloroacetic acid and the corresponding alcohol. Reaction of alcohol with chloroacetyl chloride is an anhydrous process which Hberates HCl. Chloroacetic acid will react with olefins in the presence of a catalyst to yield chloroacetate esters. Dichloroacetic and trichloroacetic acid esters are also known. These esters are usehil in synthesis. They are more reactive than the parent acids. Ethyl chloroacetate can be converted to sodium fluoroacetate by reaction with potassium fluoride (see Fluorine compounds, organic). Both methyl and ethyl chloroacetate are used as agricultural and pharmaceutical intermediates, specialty solvents, flavors, and fragrances. Methyl chloroacetate and P ionone undergo a Dar2ens reaction to form an intermediate in the synthesis of Vitamin A. Reaction of methyl chloroacetate with ammonia produces chloroacetamide [79-07-2] C2H ClNO (53). 

The dipolar ion can react in several ways according to the solvent and the stmcture of the olefin. In inert solvents, if the carbonyl compound is highly reactive (eg, an aldehyde), the dipolar ion can be added to the carbonyl fragment to give the normal ozonide or 1,2,4-trioxolane (7) for example, 1,1-and 1,2-dialkylethylenes react in this manner. Tri- or tetraalkyl-substituted olefins produce a smaH, if any, yield of an ozonide when the ozonolysis is... 

Mercury(II) trifluoroacetate is a good electrophile that is highly reactive toward carbon-carbon double bonds [52, 53, 54] When reacting with olefins in nucleophilic solvents, it usually gives exclusively mercurated solvoadducts, but never products of skeletal rearrangement Solvomercuration-demercuratton of alkenes with mercury(II) trifluoroacetate is a remarkably effective procedure for the preparation of esters and alcohols with Markovnikov s regiochemistry [52, 5J] (equation 24)... 

It is appropriate to point out that when the enamine was allowed to react with the olefin in nonpolar solvents such as benzene, cyclohexane, or ethyl... 

No direct detection of CTC s had instead been reported for fast reacting systems of olefins and Bt2 in solvents of moderate or high polarity, where the existence and the kinetic role of these complexes had been only a matter of speculation. 

Monflier et al. (1997) have suggested Pd catalysed hydrocarboxylation of higher alpha olefins in which chemically modified P-cyclodextrin (especially dimethyl P-cyclodextrin) is u.sed in water in preference to a co-solvent like methanol, acetone, acetic acid, acetonitrile, etc. Here, quantitative recycling of the aqueous phase is possible due to easy phase separation without emulsions. A similar strategy has been adopted by Monflier et al. (1998) for biphasic hydrogenations for water-in.soluble aldehydes like undecenal using a water-soluble Ru/triphenylphosphine trisulphonate complex with a. suitably modified p-cyclodextrin. 

The thermally activated addition of HC1 to simple olefins in polar solvents has been well known for many years. Corresponding additions in the gas phase have high activation energies and over temperature ranges at which the reaction can conveniently be measured, the equilibrium lies largely on the side of elimination... 

This and other work indicates that HC1 is largely undissociated in nitromethane for [HC1]>- 0.015 M and that there is little association either. There is evidence that a corresponding addition occurs to olefins in theimally degraded PVC. Results carried out in a variety of solvents (26) are consistent with elimination of HC1 occurring by a/3 -elimination of the Ex type favored by polar solvents. The same authors showed that at least in nitrobenzene containing dissolved HC1, the reverse reaction, i.e. addition of HC1, takes place. The fact that this may be interpreted as a retardation of the degradation process may have contributed to the confusion which has arisen and emphasizes the care which must be taken to disentangle the possible catalytic effect of HC1 when concurrent addition of HC1 to the polyenes is possible. 

Anions of the type [M(C2B9H11)2] (M = Fe, Cp, Ni) were also used as noncoordinating anions with [Cp2ZrMe] +, which are active for the polymerization and copolymerization of ethylene and oc-olefins in non-polar solvents such as toluene and hexane [54]. By using the same anions, cationic actinide complexes have also been prepared [110]. 

Polywax 500 and 655 (polyethylene fraction with average molecular weights of 500 and 655, respectively), purchased from Baker Petrolite, Inc., was used to prepare simulated FT wax (i.e., solvent) for the evaluation of flltration performance with and without the presence of aliphatic alcohol and mono-olefin in the FT wax. 1-dodecanol (ACS reagent, > 98%, Sigma-Aldrich, Inc.) and 1-hexadecene (GC standard grade reagent, > 99.8%, Sigma-Aldrich, Inc.) were used as model... 

Reaction of 30.5 ml of olefin in 75 ml of benzene solvent at 400 psi total pressure, H2/ CO = 2. Catalyst charge 1.28 g Co2(CO)3 and 2.56 g Bu3P. Reaction run overnight (about 17 hours). Table reprinted with permission from Ind. Eng. Chem., Prod. Res. Dev. 7, 226 (1968). Copyright by the American Chemical Society. 

Loop A continuous process for polymerizing aqueous emulsions of olefinic compounds such as vinyl acetate. Polymerization takes place in a tubular reactor (the loop) with recycle. Invented by Gulf Oil Canada in 1971 and further developed by several United Kingdom paint companies. It is now used for making copolymers of vinyl acetate with ethylene, used in solvent-free paints and adhesives. 

Scheme 3. The mechanism of Rh-catalyzed hydrogenation of functionalized olefins in the presence of a bidentate P,P-ligand (S = solvent, P = phosphine unit, R = alkyl).

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