Halogen complexes of heterocyclic amines
Bezjian, Richard M.
MetadataShow full item record
Interest in spectrophotometric study of complexes of aromatic hydrocarbons and halogens started with the studies of Benesi and Hildebrand (l). Their investigation of several different aromatic hydrocarbon-iodine solutions in carbon tetrachloride and hexane showed that, in addition to the known iodine maximum near 500 mn, another maximum existed at about 297 mn. They found convincing evidence that the ultraviolet maximum is a charge-transfer peak, due to a 1:1 complex between the iodine and the aromatic hydrocarbon, and were able to calculate the formation constant of the complex from spectrophotometric data. The addition of methyl groups to benzene increased the stability of the halogen complex; for example, the mesitylene-iodine complex was more stable than the benzene-iodine complex. This observation has been explained by the fact that methyl groups are electron repelling and thus increase the availability of the TT-electrons for complex formation. This gave strong support for the Lewis acid-base explanation of the interaction involved in this type of complex.