Double bond reaction with

The reaction with bromine is very rapid and is easily carried out at room temperature, although the reaction is reversible under some conditions. In the case of bromine, an alkene-Br2 complex has been detected in at least one case. Bromine is often used as a test, qualitative or quantitative, for unsaturation. The vast majority of double bonds can be successfully brominated. Even when aldehyde, ketone, amine, so on functions are present in the molecule, they do not interfere, since the reaction with double bonds is faster. 

The role of reactive centers is performed here by free radicals or ions whose reaction with double bonds in monomer molecules leads to the growth of a polymer chain. The time of its formation may be either essentially less than that of monomer consumption or comparable with it. The first case takes place in the processes of free-radical polymerization whereas the second one is peculiar to the processes of living anionic polymerization. The distinction between these two cases is the most greatly pronounced under copolymerization of two and more monomers when the change in their concentrations over the course of the synthesis induces chemical inhomogeneity of the products formed not only for size but for composition as well. 

The radical-induced cleavage of a,/ -aziridino alcohols proceeds in analogy to that of a,/ -epoxyalcohols, leading regiospecifically to allyl amines (a). By successive reactions with double bond systems, pyrrolidines are formed (b) [68]... 

Diazomethane is capable of addition reactions with double bonds. Pyrazoline rings are formed. Studebaker et al. (38) saw in this reaction an indication of quinone groups ... 

An interesting variant of reactions with double bonds is the action of [ F]F2 or other electrophilic [ F]reagents on enol structures. 

The most popular type of photosensitive functionality is the aryl azide derivative. On photolysis, phenyl azide groups form short-lived nitrenes that react rapidly with the surrounding chemical environment (Gilchrist and Rees, 1969). Nitrenes can insert nonspecifically into chemical bonds of target molecules, including undergoing addition reactions with double bonds and insertion reactions into active hydrogen bonds at l"l C—H and N—H sites. Abundant evidence, however, indicates that the photolyzed... 

Desulfurization or sulfoxide elimination of the adducts effects addition of the nitrogen nucleophile to an olefin or a substitution reaction with double-bond migration. 

The active centers in this process are free radicals, whose reaction with double bonds of monomers leads to the growth of a polymer chain. In the framework of the ideal kinetic model, the reactivity of a macroradical is exclusively governed by the type of its terminal unit. According to this model, the sequence distribution in macromolecules formed at any moment is described by the Markov chain with elements controlled by the instantaneous composition of the monomer mixture in the reactor as... 

The physical properties, preparation and reactions of ruthenium tetroxide have been reviewed by Lee and van den Engh, Rylander," Haines and Hetuy and Lange. A more vigorous oxidant than osmium tetroxide, its reaction with double bonds produces only cleavage products. " Under neutral conditions aldehydes are formed from unsaturated secondary carbons while carboxylic acids are obtained under alkaline or acidic conditions. For example, Shalon and Elliott" found that ruthenium tetroxide reacted with compound (11) to give the corresponding aldehyde under neutral conditions, but that a carboxylic acid was formed in acidic or alkaline solvents (equation 23). 

Selective epoxidMion. van Tamelen and Curphey noted that NBS in an aqueous polar solvent (1,2-dimeihoxyethane)generated HOBr, and that this reagent showed some selectivity in reaction with double bonds. The method was used for selective epoxida-tion of the terminal double bond of famesyl acetate (I) to give 10,11-epoxyfamesyl acetate (4). Complete details of this transformation have been described by Hanziik. ... 

Substitution reactions with double bond shift... 

Foirmation of nitroxide and iminoxy radicals is enhanced by ultraviolet radiation. This indicates that the photochemical dissociation of NO2 into nitric oxide and oxygen atoms plays an important role in the reaction with double bonds. 

Razumovskii, S. D. and Zaikov, G. E. Kinetics and mechanism of ozone reaction with double bonds. Uspekhi Khimii. 1980, 49, 2344. 

Radical reactions with double bonds usually give the more stable (more substituted) radical. Because additions are biased in this fasWon, the polymerizations of vinyl monomers tend to yield polymers with head-to-taU linkages. Vinyl polymers made by radical processes generally have no more than l%-2% head-to-head linkages. 

J.1.1 Intermolecular Reactions with Allylic Rearrangement 4.5.1.J.l Substitution reactions with double bond shift... 

Hydrosilanes undergo addition to carbon-carbon multiple bonds under catalysis by transition metal complexes. Nickel, rhodium, palladium, and platinum were used as catalytically active metals. By incorporating chiral ligands into the metal catalyst, the hydrosilylation can be performed analogously to other addition reactions with double bonds, for example, asymmetric hydrogenation to obtain optically active alkylsilanes. 

The double bond possesses high reactivity therefore, olefins enter into various reactions with double bond opening. In particular, olefins react with halogens X2 and with HX via the ionic and chain-radical mechanisms (see Chapters 7 and 8). Along with these multistage mechanisms, the addition of X2 and HX at the double bond under certain conditions occur by the molecular route. The reaction is preceded by the formation of a molecular complex. 

FIGURE 5.1 Chemical reactions in the modification of fatty acids. (A) in situ formation of per-formic acid and its reaction with double bond to facilitate an epoxide, (B) simplified scheme of acrylation of epoxy group (Wool and Sun, 2005), and (C) simplified mechanisms of ozonolysis of the double bonds. 

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