Olefin types

Like NR, SBR is an unsaturated hydrocarbon polymer. Hence unvulcanised compounds will dissolve in most hydrocarbon solvents and other liquids of similar solubility parameter, whilst vulcanised stocks will swell extensively. Both materials will also undergo many olefinic-type reactions such as oxidation, ozone attack, halogenation, hydrohalogenation and so on, although the activity and detailed reactions differ because of the presence of the adjacent methyl group to the double bond in the natural rubber molecule. Both rubbers may be reinforced by carbon black and neither can be classed as heat-resisting rubbers. 

The olefinic type of TPR is the latest development and is different in that it consists of fine rubber particles in a thermoplastic matrix as shown in Fig. 1.1. 

The addition of various Kolbe radicals generated from acetic acid, monochloro-acetic acid, trichloroacetic acid, oxalic acid, methyl adipate and methyl glutarate to acceptors such as ethylene, propylene, fluoroolefins and dimethyl maleate is reported in ref. [213]. Also the influence of reaction conditions (current density, olefin-type, olefin concentration) on the product yield and product ratios is individually discussed therein. The mechanism of the addition to ethylene is deduced from the results of adsorption and rotating ring disc studies. The findings demonstrate that the Kolbe radicals react in the surface layer with adsorbed ethylene [229]. In the oxidation of acetate in the presence of 1-octene at platinum and graphite anodes, products that originate from intermediate radicals and cations are observed [230]. 

An enormous variety of olefinic types have been found to undergo such solid-state (2 + 2) photocyclodimerizations. These include cinnamic acids (128,132) derivatives of cinnamic acids such as esters (133) and amides (134) styrene derivatives (135) stilbenes (136) aliphatic mono- (137), di- (138), and triene (139) dicarboxylic acids and derivatives 1,4-diarylbutadienes (140) and their vinylogs (141), benzylidene acetones (142) and benzylidene acetophenones (143) ... 

A preliminary rationale for tte steady-state situation of the catalytic system is given in Scheme 3.2-4. The product-controlling ligand association processes are particularly marked. Intermediates of the metal-olefin type are symbolized by SnNi, n being two to four intermediates... 

The epoxidation of unfunctionalized alkenes by dioxiranes was investigated mainly for mechanistic purposes P . Some representative cases are collected in Scheme 3. Although such unfunctionalized alkenes have not been studied as intensively as the other olefin types, the recent asymmetric epoxidations by dioxirane were performed mainly on this substrate class (vide infra) J P. For this purpose, in-situ-generated dioxiranes in carefully buffered aqueous solutions had to be used, since the chiral dioxiranes cannot be readily isolated. Fortunately, the epoxides of unfunctionalized alkenes are more resistant to... 

In spite of those highly favorable stmctural factors, 16a is very ephemeral. Its lifetime in degassed benzene is 0.5 ps, which is shorter even than that of parent triplet DPC. Product analysis smdies have shown that 16a forms a trimer of dianthrylcarbene (116) as the main product (50-60%) (Scheme 9.37). The trimer is the one formed as a result of a threefold coupling at position 10 of the carbene. This observation suggests that delocalization of the unpaired electrons in 16a leads to their leaking out from the carbene center to position 10, where sufficient spin density builds up for the trimerization to take place. At the same time, the lack of formation of olefin-type dimers through coupling of two units of 16a at their carbene centers indicates that the carbene center itself is indeed well shielded and stabilized. 

Section 11.06.4 of this chapter highlights the substrate scope of olefin CM reactions. Based on this survey of the literature, olefins will then be placed into their appropriate category based upon catalyst activity and substrate tolerance, citing specific examples (Section 11.06.4.6). It is important to note that olefin-type characterization can change in response to catalyst reactivity. For example, an olefin may be characterized as a type III olefin in CM... 

The boiling point, refractive index, and density of the olefin derivative of any paraffin were shown, by use of Table III, to stand in the onier of their olefin type. Table X contains the engine data of the olefin derivatives of 2-methylpentane and 3-methylpentane, recorded in the order of their olefin type. No consistent relations between octane numbers or critical compression ratios are obvious—but the blending octane numbers of these branched olefins, as measured by both the research and Motor methods, do generally stand in the order of their type. Two olefins of type III form exceptions, the exceptions being in one case too high and in the other case too low. 

Hydrocarbon Structure Olefin Type Research Octane No. Motor Octane No. Blending Octane No. (Research) Blending Octane No. (Motor) Critical Compression Ratio (600/212° F.) Critical Compression Ratio (600/350° F.)... 

Vapor-phase alkylation of benzene by ethene and propene over HY, LaY, and REHY has been studied in a tubular flow reactor. Transient data were obtained. The observed rate of reaction passes through a maximum with time, which results from build-up of product concentration in the zeolite pores coupled with catalyst deactivation. The rate decay is related to aromatic olefin ratio temperature, and olefin type. The observed rate fits a model involving desorption of product from the zeolite crystallites into the gas phase as a rate-limiting step. The activation energy for the desorption term is 16.5 heal/mole, approximately equivalent to the heat of adsorption of ethylbenzene. For low molecular weight alkylates intracrystalline diffusion limitations do not exist. 

Examples of the disproportionation of dissimilar olefins, Type III reactions, are shown in Table 8. Alpha olefins were produced by disproportionating... 

Table 8. Disproportionation of dissimilar olefins Type III reactions A+B ( 1 P+Q...

FTIR model experiments were performed to reveal the nature of catalyst deactivation in C02. The spectrum taken at 15 bar in a C02/H2 mixture is shown in Fig. 1. The bands at 2060 and 1870 cm 1 indicate considerable coverage of Pt by linearly and bridge-bonded CO [12], formed by the reduction of C02 on Pt (reverse water gas shift reaction). The three characteristic bands at 1660, 1440 and 1235 cm 1 are attributed to C02 adsorption on A1203, likely as carbonate species [13, 14], It is well known [15] that CO is a strong poison for the hydrogenation of carbonyl compounds on Pt, but can improve the selectivity of the acetylene — olefin type transformations. Based on the above FTIR experiments it cannot be excluded that there are other strongly adsorbed species on Pt formed in small amounts. It is possible that the reduction of C02 provides also -COOH and triply bonded COH, as proposed earlier [16]. 

Description DCC is a fluidized process to selectively crack a wide variety of feedstocks into light olefins. Propylene yields over 24 wt% are achievable with paraffinic feeds. A traditional reactor/regenerator unit design uses a catalyst with physical properties similar to traditional FCC catalyst. The DCC unit may be operated in two operational modes maximum propylene (Type I) or maximum iso-olefins (Type II). Each operational mode utilizes unique catalyst as well as reaction conditions. DCC maximum propylene uses both riser and bed cracking at severe reactor conditions, while Type II utilizes only riser cracking like a modern FCC unit at milder conditions. 

One of our earlier attempts to form a cross diperoxide used a variation of olefin types 4 and 5. In this case equimolar amounts of tetra-phenylethylene, 6, and tetramethylethylene, 7, were ozonized together. While ultimately both acetone diperoxide and benzophenone diperoxide could be isolated from the reaction mixture, it became apparent that these olefins have such different reactivities toward ozone that the tetramethylethylene was selectively ozonized. Only after most of the tetramethylethylene had been ozonized was the tetraphenylethylene attacked. The opportunity for cross diperoxide formation in this case is thus minimal. 

Since the Amberlyst XN-IOIO/BF3 catalyst produced an alkylate with quality superior to the other resins tested, additional work was performed with this resin/ BF3 catalyst to explore the effects of particle size and temperature, and sensitivity to olefin type. Olefin space velocity was kept at 2.6 grams C4=/gram resin-hour for all the results reported below. 

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