3.5- dialkyl meta effect

However, there are some contradictory reports on the composition of the products of toluene alkylation or benzene dialkylation at high conversions. In some cases, compositions corresponding to the thermodynamic equilibrium between ortho, meta and para isomers were found, and in other cases, kinetic control of orientation, giving mostly the ortho + para substitution, prevailed. Consecutive isomerisation of the ortho and para isomers to the more stable meta isomer seems to be the cause of the disagreement. More active catalysts gave more meta derivatives than the less active ones [343] and increasing the temperature has the same effect [351]. 

The largest volumes of phenjienediamines are used for the production of polymers, primarily polyurethanes, where the diisocyanates of toluenediamines (meta isomer) are used. For the manufacture of polyamides both meta and para isomers are used. Another significant use for -phenylenediamines is as antioxidants and antiozonants for elastomers, plastics, and petroleum products. The /V-alkyl-/V-aryl- -phenylenediamines are by far the most commonly used and represent the bulk of the volume of the iV-substituted -phenylenediamines reported in Table 3. Some iV iV-dialkyl compounds ate also stiU used as antiozonants, but they oxidize more rapidly and lose activity sooner. The iV,iV-diaryl-/)-phenylenediamines ate used primarily as antioxidants, especially where copper and other harmful metals might be present. -Dinaphthalenyl- -phenylenediamine is especially effective in this application. The... 

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