Substituent Effects in Fluorobenzenes, Phenols, and Anilines

Calculations were carried out on a variety of possible conformations of substituted fluorobenzenes, phenols, and anilines the total energies, relative energies, and dipole moments are presented in Tables 3-5. Table 6 lists interaction energies, based on the lowest energy conformation of each molecule. These are calculated as energies of reaction 3  

From the discussion on monosubstituted benzenes, it is apparent that there is a pronounced interaction between the substituents F, OH, and NH2 with the ring. These substituents were found to be a acceptors and ir donors. The effect of an additional substituent on the interaction between the first substituent and the ring (and vice versa) will now determine whether substituent-substituent interactions are favorable or unfavorable. 

The substituents CH3, NH2, OH, OCH3, and F all interact favorably with the group of a acceptors and tt donors at the meta position but unfavorably at the para position. This behavior may be accounted for in terms of changes in the two-electron interaction between the x-donor substituent and tt ring orbitals of the monosubstituted benzene. Relevant orbitals for the monosubstituted benzene (generated in Fig. 8) and the lone pair of the second substituent are shown in Fig. 12. 

Substituent (X) Conformation Dipole moment (debyes) Total energy (hartrees) Relative energy (kcal mole ) 

Energy Data and Dipole Moments for Substituted Phenols 

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