Olefinic double bond, radical added

The antioxidant may lose a hydrogen atom to an attacking free radical and thus render it less capable of adding to an olefinic double bond. 

In the previous sections polyolefin reactions were shown to occur by addition of a free radical across a double bond or by adding across a double bond in an organometaUic complex. This creates an unpaired electron at the end of the chain that reacts with another double bond. The olefin molecules are considered to be inert in reactions with each other, and the process terminates when reactive free radicals are quenched by reaction with each other or by other reactions that produce stable molecules. In these processes the growing polymer can react only with the monomer. 

The groups R2N and Cl can be added directly to olefins, allenes, conjugated dienes, and alkynes, by treatment with dialkyl-N-chloroamines and acids.663 These are free-radical additions, with initial attack by the R2NH + radical ion,664 N-Halo amides RCONHX add RCONH and X to double bonds under the influence of uv light or chromous chloride.665 For an indirect way of adding NH2 and I to a double bond, see 5-32. 

ArX can be added across double bonds, in a free-radical process, by treatment of olefins... 

The addition of HX to double bonds in the dark and in the absence of free-radical initiators is closely related to hydration The orientation of the elements of HX in the adduct always rnrrrsponds to Markownikoff addition 16 no deuterium exchange wish solvent is found in unreacted olefins recovered after partial reaction, nor is recovered starting material isomerized after partial reaction.17 However. the addition of HX apparently can proceed by a number of different mechanisms depending on the nature Ol the substrate and on the reaction conditions. Thus when HC1 is added to f-butylethylene in acetic acid, the rate is first-order in each reactant and the products are those shown in Equation 7.5.le Since 4 and 6 were demonstrated to be stable to the reaction conditions, the rearranged product (5) can be formed only if a carbocationic intermediate is formed during reaction. However, the carbocation exists almost solely in an intimate ion pair, and the rate of collapse of the ion pair to products must be faster than, or comparable to, the rate of diffusion of Cl- away from the carbocation. This must be so because the ratio of chloride to acetate products is unaffected by... 

In cathodic addition reactions solvated electrons, radical anions or anions are generated at the cathode and added to activated or unactivated double or triple bonds. This broad spectrum of reactions is partially treated a) in section 8.2 when group conversion generates a reactive intermediate which undergoes addition reactions 1 S5a,b and b) in section 12.2 when olefins are coupled via addition of a cathodically generated radical anion to an activated double bond. 

In agreement with Balandin s theory it was assumed by Eidus (79,80) that methylene radicals adsorbed on two adjacent centers of the catalyst are dimerized to ethylene which remains adsorbed on a doublet subsequently a new methylene group is added to one of the carbon atoms with a hydrogen atom migrating to the carbon atoms of the ethylene which is then desorbed further growth with formation of 1-olefins proceeds similarly a shift of the double bond inside of the molecule may occur. The view of Craxford and co-workers that all polymerizing methylene radicals remain adsorbed to the surface was contradicted by Eidus as inconsistent with experimental evidence (84b). 

Aqueous solutions of bisulfites react with olefins in the presence of oxygen or certain oxidizing agents. Addition of the bisulfite takes place by a free-radical mechanism contrary to Markownikoff s rule. The yields of sulfonates are usually low (12-62%). Styrene gives mainly 2-hydroxy-2-phenylethanesulfonic acid. Bisulfite has also been added to the double bonds in allyl and cinnamyl alcohols. /3-Sulfocarboxylic acids are prepared in this way from a,/3-olefinic acids. /3,/3-Disulfopropionic acid is made in 80% yield by the addition of two molecules of bisulfite to... 

Since the S-H bond is only slightly polarized and heterolysis to a proton and a mercaptide ion is thus difficult,19 the addition to olefins is preferably carried out by a radical route induced by benzoyl peroxide12 by irradiation with UV light.13 Alkanethiols and thiophenols can be added under the influence of basic catalysts to strongly polar double bonds such as those in unsaturated carbonyl compounds, nitriles, and carboxylic acids, the C-S bond then being formed to the cationic / -carbon atom ... 

Benzoyloxy radicals are electrophilic and show higher reactivity towards electron-rich (c.. S, VAc) than electron-deficient e.g. MMA, AN) monomers (Table 3.7). Product studies on the reactions of benzoyloxy radicals with simple olefins and monomers show that they have remarkably poor rcgiospccifieity when adding to carbon-carbon double bonds. Their reactions invariably give a mixture of products from head addition and tail addition (Scheme... 

Energy distributions of alkyl radical dissociation products, as measured by crossed molecular beam and infrared chemiluminescence experiments, show deviations from the predictions of statistical theories such as the RRKM or phase space theory. In these experiments an atom X is added to a C=C double bond of an olefin RY to form... 

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