The Negative-Ion States of Benzene and Naphthalene

TABLE 7.4 Morse Parameters, Dimensionless Constants, and Experimental Data for Nentral and Ionic I2 

For naphthalene there should be nine negative-ion states the polarization state, four bonding states, and four antibonding states. The ground state has a positive electron affinity of 0.16 eV and dissociates via the 1—C-H bond. The polarization state and a state dissociating via the 2-C-H bond have positive electron affinities of 0+ and 0.13 eV respectively. The excited-valence-state curve dissociating to H(—) 

The dimensionless constants for the ground state for I2(—) correspond to an increase in the attractive term but a larger increase in the repulsive term to give a smaller bond dissociation energy. In the case of bonds for aromatic hydrocarbons the attractive terms are decreased and the repulsive terms increased, but by a smaller amount than for I2(—) or H2(—). Notice that the relative bond order is given by BO = D,.(A 2( j)/De Xi) = [k /kR], Thus, the bond orders for the aromatic hydrocarbons are larger than for the diatomic molecules. If there are no experimental data for the construction of negative-ion states of aromatic hydrocarbons, then these values can be used as first approximations or the theoretical values could be used. 

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