Dienes removal from olefins

Regioisomerism in azide additions is also evident in unsymmetrical dienes with two unequally strained double bonds.89,92,144 Reaction occurs preferentially at the angle-strained double bond,25,81,89-92 and two isomeric exo-monotriazoline adducts are obtained.81,93 The ratios of the triazoline isomers from the reaction of phenyl azide and bicycloocta-2,6-diene, as deduced from their NMR spectra, indicate that the major isomer is the one that results from the terminal azido nitrogen attacking the olefinic carbon more removed from the unreactive double bond (Scheme 10).92 Similar reactions... 

It seems that soluble catalysts can be fairly easily removed from polymers. As the color, the stability to light, or the general stability of the polymer depends on the degree to which catalysts have been removed, soluble systems have received more technical attention. In addition, in some cases the diene and copolymerization of a-olefins show extremely high stereoselectivity and activity. On the other hand, there are examples known where residues of even the homogeneous bis(cyclopentadienyl) metal systems lead to coloring of the product. 

Based on the principles of n-complexation, we have already developed a number of new sorbents for a number of applications. These include sorbents for (a) olefin/paraffin separations [9-12], (b) diene/olefin separation or purification (i.e., removal of trace amounts of dienes from olefins) [13], and (c) aromatics/aliphatics separation and purification (i.e., removal of trace amounts of aromatics from aliphatics [14]. Throughout this work, we have used molecular orbital calculations to obtain a basic understanding for the bonding between the sorbates and sorbent surfaces, and further, to develop a methodology for predicting and designing n-complexation sorbents for targeted molecules (e.g. Ref 11). 

Dienes can undergo olefin metathesis reactions of two types (i) intermolecular, and (ii) intramolecular, as illustrated by the reactions of hexa-1,5-diene and octa-1,7-diene, respectively, eqns. (1) and (2). If necessary, reaction can be driven from left to right by the removal of ethene. 

Removal of dienes from olefins (to oxides TT-complexation sorbents such as Cu(I)Y,... 

For the reasons above, the w-complexation sorbents hold a tremendous potential for future applications in purification, some of which will be inclnded for discnssion. The removal of dienes from olefins by AgY and CuY has already been demonstrated and applied in the field (Padin et al., 2001). Other promising applications inclnde ... 

The sorbent that forms a 7r-complexation bond with molecules of a targeted component in a mixture is named 7r-complexation sorbent. The r-complexation bond is a type of weak and reversible chemical bond, the same type that binds oxygen to hemoglobin in our blood. This type of sorbent has been developed in the past decade, largely in the author s laboratory. Because they have shown a tremendous potential for a number of important applications in separation and purification, they are discussed separately in Chapter 8. This chapter also presents their applications for olefin/paraffin separations, olefin purification (by removal of dienes to <1 ppm, separation of CO, as well as aromatics from aliphatics. The particularly promising application of 7r-complexation sorbents for sulfur removal from transportation fuels (gasoline, diesel, and jet fuels) is discussed in Chapter 10. 

Based on the empirical results/ X-ray-diffraction data/ and solution-phase NMR experiments/ a transition state model (6) has been advanced to explain the observed enantioselectivity. The presence of an ortho substituent in the A arylmaleimide reactant directs aluminum coordination to occur with the lone pair of electrons anti to the nitrogen atom. A 3,5-dimethylphenyl moiety present on the ethylenediamine framework blocks one face of the dienophile, resulting in approach of the diene from the backside. A considerable amount of spectroscopic evidence, most notably that obtained fromNOE (nuclear Overhauser effect) experiments, has been accumulated to support this model. A -arylmaleimide derivatives that lack an ortho substituent and other dienophiles (e.g., maleic anhydride) can coordinate to the aluminum catalyst in alternative modes such that the reactive olefin is far removed from the chiral environment of the ligand scaffold, thereby resulting in cycloaddition reactions that exhibit little or no enantioselectivity. 

CH3 storage H3 storage N3/CH3 separation CO3 adsorption CO removal from (to <10 ppm) NO removal Removal of dienes from olefins (to <1 ppm) Super-activated carbon and activated carbon fibers Carbon nanotubes Clinoptilolite, Sr-ETS-4 MCM-41-polyethylenimine composite 7t-Complexation sorbents such as CuCl/y-Al O, CuY, and AgY Fe-Mn-li oxides, Fe-Mn-Zr oxides, Cu-Mn oxides tc-Complexation sorbents such as Cu(I) and AgY... 

As stated above, olefin metathesis is in principle reversible, because all steps of the catalytic cycle are reversible. In preparatively useful transformations, the equilibrium is shifted to one side. This is most commonly achieved by removal of a volatile alkene, mostly ethene, from the reaction mixture. An obvious and well-established way to classify olefin metathesis reactions is depicted in Scheme 2. Depending on the structure of the olefin, metathesis may occur either inter- or intramolecularly. Intermolecular metathesis of two alkenes is called cross metathesis (CM) (if the two alkenes are identical, as in the case of the Phillips triolefin process, the term self metathesis is sometimes used). The intermolecular metathesis of an a,co-diene leads to polymeric structures and ethene this mode of metathesis is called acyclic diene metathesis (ADMET). Intramolecular metathesis of these substrates gives cycloalkenes and ethene (ring-closing metathesis, RCM) the reverse reaction is the cleavage of a cyclo-... 

The stream from the cryogenic unit which is rich in C /C-olefins can be fractionated and selectively hydrogenated (to remov traces of dienes) to yield the pure olefins. Common uses of propene are the production of polypropylene, acrylonitrile, cumene etc. Butene can be catalytically dehydrogenated to butadiene which is used in the production of synthetic rubbers. 

Hydroformylation of Other Lower Olefins and Dienes - Lower olefins such as 1-butene or 1,3-butadiene are hydroformylated with acceptable rates using Rh/tppts catalysts according to the RCH/RP process. Hoechst AG Werk Ruhrchemie has developed an attractive new process350 for the hydroformylation of raffinate II, a mixture of 1-butene, cis- and /rbutane derived from the C4 stream of naphtha crackers (after removal of 1,3-butadiene... 

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