- Photochemical Bromination of Anilides by Benzenehexabromide
-
Benzenehexabromide was found to afford photochemical bromination of substituted acetanilide in the p-position.The rates of bromination were found to follow the order predicted on the basis of inductive effect of the substituents and similar to the sequence of reactivities observed for bromination of acetanilides with N-bromosuccinimide.Similar results were obtained in the case of p-substituted benzanilides and the reaction shows a good Hammett correlation with the ?+ values for the substituents with a ρ value -0.266.
- Aly, M. M.,Awad, I. M. A.,Fahmy, A. M.
-
-
- Photochemical Bromination of Simple Arenes
-
Photochemical bromination of benzene, fluorobenzene, chlorobenzene, t-butylbenzene, α,α,α-trifluorotoluene, and (in tetrachloromethane) biphenyl and naphthalene gives substitution products and adducts such as 1,2,3,4,5,6-hexabromocyclohexane (1).The decomposition of (1) and of the analogous chlorobenzene adduct (3) under photochemical conditions gives the parent arene, the monobrominated halogenobenzene, and bromine which may be scavenged by toluene to give benzyl bromide or by benzene to give bromobenzene and dibromobenzenes.Addition is a kinetically controlled process, so that the mechanism of formation of these aryl bromides must be largely through the reversible formation of these adducts.This is consistent with the unusual orientation of apparent attack by bromine upon the arene substrates, since the relative amounts of the isomeric aryl bromides is a consequence of the relative stabilities and ease of elimination of HBr and Br2 from a family of adducts. The range of isomer distribution found within the reaction of each arene with bromine is consistent with two competing processes involved in the formation of the aryl bromides; one of these might by the direct homolytic substitution by bromine atoms upon the arene.
- Bolton, Roger,Bhangar, Muhammad Iqbal,Williams, Gareth H.
-
p. 893 - 896
(2007/10/02)
-
- Bromination of Methyl Substituted 1,2,5-Thiadiazoles with N-Bromosuccinimide
-
Bromomethyl-1,2,5-thiadiazoles 2a-c were prepared by bromination of methyl-1,2,5-thiadiazoles 1a-c by NBS in refluxing carbon tetrachloride.When bromination of 1a and 1b was carried out under irradiation of tungsten lamp, mixtures of cis-5a and b and tran
- Mataka, Shuntaro,Kurisu, Masayoshi,Takahashi, Kazufumi,Tashiro, Masashi
-
p. 1157 - 1160
(2007/10/02)
-