Лако-красочные материалы — производство

Diphenyl-DPP 2 was smoothly sulfonated to the corresponding disulfonic acid and acid salts 23 according to Scheme 11.7. Group II metal and ammonium salts of 23 proved to be thermally highly stable compounds and also useful pigment surface treating agents frequently warranting rheological improvement of DPP pigment dispersions in various paint media [29, 30].

2

Scheme 11.7

The aromatic halogenation of diphenyl-DPP 2, however, did not proceed as unambiguously as the sulfonation reaction. Bromination of the unsubstituted DPP 2 gave the electrophilic aromatic substitution product 4,4′-dibromophenyl DPP 24 whereas the corresponding chlorination afforded the fairly unstable addi­tion product 25 (Scheme 11.8) [5, 31].

The different reaction pathways of bromine and chlorine were explained by a preequilibrium addition reaction to the double bonds allowing for a differentia­tion between the bromine being a better leaving group and a better nucleophile compared to the chlorine [5].

11.4.2