A REAÇÃO DE SUBSTITUIÇÃO ELETROFÍLICA AROMÁTICA E OS EFEITOS DOS GRUPOS NITROSO E FLÚOR: CORREÇÃO DE IMPRECISÕES EM LIVROS TEXTO

THE ELECTROPHILIC AROMATIC SUBSTITUTION REACTION AND THE EFFECTS OF NITROSO AND FLUORINE GROUPS: CORRECTION OF INACCURACIES IN TEXTBOOKS. The nitroso (NO) and fluorine (F) groups are rarely addressed in electrophilic aromatic substitution (SEAr) reactions of undergraduate organic chemistry textbooks, and when they are, textbook misconceptions about their reactivity and regioselectivity often arise. Experimental data from the literature and molecular orbital calculations for nitrosobenzene and its dimer indicate that the nitroso group is deactivating and does not have significant reactivity. When nitrosobenzene undergoes SEAr, the reactive species responsible for its reactivity and regioselectivity is its dimer, containing the azodioxy group. This intermediate is ortho/para-directing and dissociates at the end of the reaction to yield the substituted nitrosobenzene. Therefore, describing the behavior of the NO group as simply deactivating and ortho/para-directing is inaccurate. The behavior of the fluorine group is more complex: it acts as an activating group at the para position through resonance, and as a deactivating group at the ortho and meta positions through its inductive effect. Similarly, simplifying the behavior of fluorine as deactivating and ortho/para-directing is also inaccurate. To rationalize the experimental behavior of fluorobenzene, one must consider the partial rate factors for each position of the monosubstituted benzene. The kinetic data should be normalized to reflect the actual reaction rate at each position, minimizing the influence of statistical factors and enabling analysis based on the energy term of the Eyring equation. The complexity of NO and F in SEAr, combined with discrepancies between experimental data and textbook, compromises the effective teaching of the reactivity and regioselectivity of nitrosobenzene, fluorobenzene, and their derivatives in undergraduate courses. It is recommended that the effects of NO and F be reserved for advanced courses, such as organic reaction mechanisms or advanced organic chemistry, to prevent the spread of misconceptions.