Correlation of Electron Beam and Thermal Electron Attachment Studies for Some Chloro, Bromo, Iodo Aromatic Compounds

The relationship between thermal electron attachment and electron beam studies for chlorobenzene, 0-dichlorobenzene, 0-chlorotoluene, 3′- and 4′-chloroacetophenone, 1-chloronaphthalene, bromobenzene, 0-bromotoluene, 1-bromonaphthalene, and iodobenzene is shown. The empirical negative-ion potential-energy function used to describe electron attachment to aliphatic halides is used for convenience in showing this relationship. Use of the two-dimensional potential-energy function permits a more quantitative representation of the mechanisms previously proposed. In some cases, the mechanisms have been altered from the earlier qualitative interpretation. In general the two types of measurement appear to be essentially in complete agreement. The agreement between the results further supports the empirical potential-energy function for the negative ion. Also, thermal electron attachment to additional aromatic halogen derivatives was investigated by the pulse sampling technique as a function of temperature to further support the mechanism. In particular, the thermal electron attachment of 3′- and 4′-chloroacetophenone shows a unique temperature dependence involving three different phenomena over the temperature range 30°–240°C, which adds further support to the proposed mechanisms. In all the other cases investigated (chlorobenzene, 0-chlorotoluene, 0-bromotoluene), the electron attachment shows only one temperature region, again in complete agreement with the proposed mechanisms.