117. The kinetics of halogen addition to unsaturated compounds. Part XI. The halogeno-ethylenes

Abstract

Whereas bromine addition to vinyl bromide in acetic acid solution is catalysed by both hydrogen bromide and lithium chloride, CHPhXHBr and CMe,:CHCl behave differently, bromine addition being decelerated by hydrogen bromide and accelerated by lithium chloride to a relatively small extent. This is further evidence that electrophilic addition of HBr, may take place to compounds in which there is considerable electron-accession to the ethylenic system. The rates of chlorine addition to cis-and trans-1 : 2-dichloroethylene and t o trichloroethylene have been measured in aqueous acetic acid solution. The velocity of bromine addition to s.-dichloroisobutylene is low owing to steric hindrance, and with this compound there is very marked catalysis by hydrogen bromide and lithium chloride. The theoretical significance of these various results is discussed. (Bull. SOC. chim. Belg., 1914, 28, 234). It was found that the relative rates were tvans > cis, d[BrJ/dt = k,[A][Br,]X-+ R,[A][Br,] + k,[A][Br,]Y

The Decomposition of Bis(o-iodophenylacetyl) Peroxide

“…Soc., 79,501 (1957). (6) For the general behavior of peroxycarbamates see E. L. O'Brien, F. M. Beringer, and R. B. Mesrobian, J. Am.…”

“…The general method of O'Brien, Beringer, and Mesrobian was used. 6 Freshly prepared o-iodobenzoylazide (0.01 mole) was separated from the aqueous acetone by addition of water and decantation. It was then treated with 0.01 mole or less of -butyl hydroperoxide in benzene.…”

“…® Yields from a run in which air was carefully excluded. 6 Some of the o-iodobenzyl alcohol is formed during the isolation of the ester, which partially hydrolyzes during chromatography on alumina. The acid moiety of the ester remains on the alumina and is not recovered.…”

“…Gentle heating of 4-i-butyl-2,6-diiodophenol with benzoyl peroxide in benzene produces a transient blue color, probably because of the aryloxy free radical.5 6 The blue color fades and is replaced by red, but no quinonoid product is readily isolable from the reaction mixture.…”

Kinetics of Aromatic Halogenation. IV. The Bromination of Naphthalene in 50% Aqueous Acetic Acid1

“…In addition, since bromide ion is formed during the reaction, some of the bromine is continuously removed from the reaction as tribromide ion or HBrs, which have either no, or only very weak, brominating properties. Highorder bromination has also been observed in other solvents of low dielectric constant, such as 75% and 90% aqueous acetic acid,3•4 carbon tetrachloride,5 chlorobenzene,4 methanol2b or benzene.6 Following Robertson,7 it is customary to regard bromination as a composite reaction of the type -dx/dt = ¿,(ArH…”