Bromination of azobenzenes by acidified hypobromous acid; Orientation, reactivity and mechanism

Abstract

The rate of bromination of azobenzene by acidified hypobromous acid has been measured and compared with those of benzene, toluene, and bromobenzene under the same conditions. Determination of o/m/p ratios for attack on azobenzene show that the rate of attack at the meta position is much lower than expected on the basis of the Hammett σ_m value for the phenylazo substituent. Abnormally low amounts of meta isomer were also observed for the case of bromobenzene, but not toluene. The rates of bromination of two monosubstituted azobenzenes (m-Br, and p-F) were also deter- mined and compared with that of azobenzene.