Solvents, types halogenated

Yields of alcohols vary from 45 to 87%, irrespective of solvent or halogen type. However, when crotyl halides are used, 1-methylallyl products are isolated [20], along with occasional diaddition products [Eq. (2)]. 

Copper or iron phthalocyanines encapsulated inX or Y zeolites [25g], which catalyze the oxidation of cyclohexane to Ol/One and to AA with oxygen (in the presence of small amounts of t-BuOOH) at near-ambient conditions. The catalyst remains in the solid phase throughout the reaction, and can be easily filtered off. Moreover, the solvent type affects performance best selectivity to AA (41%) is achieved with methanol [25g], at 12.7% cyclohexane conversion, with a halogen-substituted phthalocyanine of Fe encapsulated in an X zeolite. Cyclohexanone and cyclohex-andione are hypothesized to be the intermediate compounds of the reaction. Incorporation of the zeolite-encapsulated Fe phthalocyanine inside a polymer matrix can serve to enhance catalyst stability and limit leaching phenomena [25h[. 

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. 

Attempts to prepare the mono(cyclopenta-dienyl) derivatives are sometimes frustrated by a Schlenk-type equilibrium (see p. 132), but judicious choice of ligands, solvent etc. occasionally permits the isolation of such compounds, e.g. the centrosymmetric halogen-bridged dimer (t - -C5Me5)Ca(/i-l)(lhf)2 2] which cry.stallizes from toluene solution. The complex is isostruc-tural with the dimeric organosamarium(ll) analogue. - ... 

Two different sets of experimental conditions have been used. Buu-Hoi et al. and Hansen have employed the method introduced by Papa et using Raney nickel alloy directly for the desulfurization in an alkaline medium. Under these conditions most functional groups are removed and this method is most convenient for the preparation of aliphatic acids. The other method uses Raney nickel catalysts of different reactivity in various solvents such as aqueous ammonia, alcohol, ether, or acetone. The solvent and activity of the catalyst can have an appreciable influence on yields and types of compounds formed, but have not yet been investigated in detail. In acetic anhydride, for instance, desulfurization of thiophenes does not occur and these reaction conditions have been employed for reductive acetylation of nitrothiophenes. Even under the mildest conditions, all double bonds are hydrogenated and all halogens removed. Nitro and oxime groups are reduced to amines. 

The distinction between coordination polymerization and ionic polymerization is not sharp. Let us consider for example a C—X bond, X being a halogen or a metal. Winstein54 and Evans14 have demonstrated that in a compound containing this type of bond an equilibrium may be established in a suitable solvent between... 

First of all, the reaction pathways shown in Scheme 1 involve the formation of charge transfer complexes (CTC) between olefin and Br2- The formation of molecular complexes during olefin bromination had been hypothesized often (ref. 2), but until 1985, when we published a work on this subject (ref. 3), complexes of this type had been observed only in a very limited number of circumstances, all of which have in common a highly reduced reactivity of the olefm-halogen system, i.e. strongly deactivated olefins (ref. 4), or completely apolar solvents (ref. 5) or very low temperatures (ref 6). 

Scheme 28 Halide exchange with halogenated solvents during the acetylenic Prins-type cyclization...

Schneemeyer LF, Wrighton MS (1980) n-Type molybdenum diselenide-based photoelectrochemical cells Evidence for Fermi level pinning and comparison of the efficiency for conversion of light to electricity with various solvent/halogen/halide combinations. J Am Chem Soc 102 6964-6971... 

There are numerous examples of cations of the interhalogens, and a great deal is known about the behavior of such species. The species that have been more fully studied involve only one type of halogen such as I3+, Br3+, and Cl3+. In general, the production of these species requires rather stringent conditions that may include nonaqueous solvent systems. For example, a reaction that takes place in anhydrous sulfuric acid can be used to produce I3 +. ... 

The process is represented as a series of steps consisting of the sublimation of the metal, dissociation of the halogen, removal of the electron from the metal and placing it on the halogen, then combining the gaseous ions to form a crystal lattice. These steps lead from reactants to product, and we know the energies associated with them, but the reaction very likely does not literally follow these steps. Reaction schemes in which metal complexes function as catalysts are formulated in terms of known types of reactions, and in some cases the intermediates have been studied independently of the catalytic process. Also, the solvent may play a role in the structure and reactions of intermediates. In this chapter we will describe some of the most important catalytic processes in which coordination chemistry plays such a vital role. 

E = S, Se X = I, Br) cation.20 Whether this cation really forms in solutions, especially in low-polar solvents, is difficult to prove. It has been shown, however, that the calculated NBO charge distribution on [LE-X]+ can be of great help in predicting the most likely product, at least among [LE-EL]2+ dications, C.-T. spoke , and T-shaped hypervalent adducts.21,22 In fact, these three types of products can formally derive from a nucleophilic attack of the appropriate nucleophile on the [LE-X]+ cation at the chalcogen or the halogen site. 

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