Aromatic substitution. XXVIII. Mechanism of electrophilic aromatic substitutions

Metal Ions Associated to the Molecular Sieve Framework: Possible Catalytic Oxidation Sites

This paper reviews the various reactions used to sulfonate polymers, especially polystyrene. The mechanisms for the sulfonation of low molar mass compounds are also discussed. The commonly used sulfonation reagents are described, with an emphasis on SO3 and its physical and chemical properties. Polymer sulfonations can be grouped into two general routes: one involving homogeneous sulfonation and the other heterogeneous reactions.

Homogeneous and heterogeneous sulfonation of polymers: A review

*Reprinted from Polymer Modification: Principles, Techniques, and Applications; Meister, J. J., Ed.; Marcel Dekker, Inc.: New York; 2000, 67–144.

Modification of lignin

Publisher Summary This chapter deals with reactions involving carbocationic transition states, in most cases forming intermediates having carbocationic centers at the conjugative position in the side chain. Yukawa–Tsuno (Y–T) introduced the concept of the varying resonance demand of reactions into substituent effect analysis. Nevertheless, the correlation results were always compared with those of the Brown equation implying constant resonance demand. The Y–T equation has been used extensively in studies of electrophilic substitution in the aromatic ring, and aliphatic nucleophilic substitution and related reactions forming a carbocation or a carbocationic (electron-deficient) center at the conjugative position (mostly benzylic position) in the side chain. The Y–T equation has proved to be one of the most fundamental and essential equations for understanding structure–reactivity relationships in chemical reactions using the language of the physical organic chemist.

R F Taylor

Papers

Electrophilic Substitution in Benzenoid Compounds