Halobenzenes bromobenzenes, iodobenzenes

The dimerization of ethylene is selectively catalyzed by halotrisftriphenyl-phosphine)Co(I) in halobenzene containing boron trifluoride etherate [144,145]. The catalytic activity is significantly affected by the solvent, bromobenzene being the most effective. The rate of ethylene absorbtion decreases in the order bromobenzene > iodobenzene > o-dichlorobenzene > chlorobenzene > o-chlorotolene. The optimum ratio of boron to cobalt for the borontrifluoride etherate/bromo-tris(triphenylphosphine)Co(I) system is 1. This suggests a strong 1 1 interaction between the two components ... 

Exercise 14-19 The intervention of benzyne in the amination of chlorobenzene, bromobenzene, and iodobenzene with sodium amide in liquid ammonia originally was demonstrated by J. D. Roberts using 14C-labeled halobenzenes. Show explicitly how the use of a chlorobenzene-14C label could differentiate between amination by addition-elimination (Section 14-6B) versus amination by elimination-addition (benzyne mechanism). 

Many different heteroatoms or functional groups may be attached to a benzene ring, and the presence of a certain functional group often imparts a unique name to that family of compounds. Perhaps the simplest heteroatom derivatives are halobenzenes such bromobenzene (18). The halogens do not constitute a formal functional group with respect to nomenclature, but rather are treated as substituents. Therefore, the halobenzenes are named fluorobenzene, chlorobenzene, bromobenzene, and iodobenzene. 

---