Aromatic compound group influencing reactivity

This chapter deals with anodic oxidation of saturated hydrocarbons, olefins, and aromatic compounds. Substituted hydrocarbons are included, when the substituents strongly influence the reactivity. Anodic functional group interconversions (FGI) of the substituents are covered in Chapters 6, 8-10 and 15. 

The nitro group has a considerable influence on the properties of the whole molecule of an aromatic compound. For example, owing to the presence of the nitro group, nitrobenzene does not take part in the Friedel-Crafts reaction. The reactivity of a chlorine atom, brought about by the presence of a nitro group in the ortho or para position, may be represented by a diagram based on the induction effect (la). 

Yagupolskii, L., Bystrov, V., Stepanyants, A., and Fiatkov, Y., Influence of substituents with trifluoromethyl group on the reactivity of aromatic compounds, Z. Obshchei Khimii, 34, 3682-3690, 1964. 

The reactive moieties themselves may influence the reaction products obtained for reasons other than the reaction selectivity just discussed. For example, a hydrophobic probe will tend to bind to any hydrophobic region that is available to it. Thus, it will most likely react while in this region, and the reaction products will be biased. This is of particular concern in photoaffinity experiments that use substituted aromatic compounds as reactive groups. 

In the scientific sector, the understanding of the generally higher reactivity of heteroaromatic diazo components relative to that of aromatic diazonium salts has increased. The number of heterocyclic nitrogen atoms in azolediazonium ions has a marked influence on the N-H acidity of these ions. The pvalues of a series of such ions in aqueous solution at 0 °C (Scheme 12-4) indicate that the electrophilicity of the diazonio group in these compounds increases with the number of nitrogen atoms in the ring. ... 

In various heterocyclic compounds two types of C F bonds are hydrogenolyzed. In fluoromethyl groups, which are attached to the aromatic heterocyclic ring, the C-F bonds arc activated similarly to benzylic C-F bonds, but the degree of activation is influenced by the position relative to the heteroatom the reactivity of aromatic C-F bonds in six-membered heterocyclcs is strongly influenced by their positions relative to the heteroatom(s). 

This method is mainly restricted to the synthesis of amino acids with aromatic side-chains since the required unsaturated azlactones [e.g. (30)] are most readily prepared using aromatic aldehydes. Typically, benzaldehyde condenses under the influence of base with the reactive methylene group in the azlactone (29) which is formed by the dehydration of benzoylglycine (28) when the latter is heated with acetic anhydride in the presence of sodium acetate (cf. Expt 8.21). The azlactone ring is readily cleaved hydrolytically and compounds of the type (30) yield substituted acylaminoacrylic acids [e.g. (31)] on boiling with water. Reduction and further hydrolysis yields the amino acid [e.g. phenylalanine,... 

Anisole is the most popular compound for the assessment of the influence of an activating substituent on aromatic reactivity. The difficulties in the evaluation of the relative rate of bromination and other reactions have already been discussed. An entirely different problem is encountered in the study of the influence of the p-methoxy group through the polymethylbenzene approach (Illuminati, 1958b). Methoxydurene (8) is not activated to the anticipated extent. Illuminati... 

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