Citation: Kk. Laali et al., ELECTROPHILIC CHEMISTRY (PROTONATION, NITRATION, BROMINATION) OF CROWDED (Z)-2,2,5,5-TETRAMETHYL-3,4-DIPHENYLHEX-3-ENE - FORMATION OF PHENANTHRENIUM IONS BY FACIAL RING PROTONATION TRANSANNULAR CYCLIZATION IN SUPERACID MEDIA - P,P-DINITRATION AND P,P-DIBROMINATION WITH NO2(-) AND BR-2-SO2()BF4(), Perkin transactions. 2, (10), 1994, pp. 2169-2173