Sulfur trioxide sulfonation of the five alkanonaphthalenes acenaphthene, perinaphthane, 1,2,3,6,7,8-hexahydropyrene, 5,6,7,8-tetrahydrocyclohepta-acenaphthene, and 1,2,3,4,7,8,10-octahydrodicyclohepta[de,ij]naphthalene
The mono- and di-sulfonation of the 1,8-alkano- and 1,8:4,5-dialkano-naphthalenes 1–5 with SO3 in dioxane and nitromethane as solvent have been studied and the results compared with those of 1,8-di- (6) and 1,4,5,8-tetramethylnaphthalene (7). The most reactive position of 1,8-ethano- (1), 1,8-propano-naphthalene (2), and 6 is the 4-position. Sulfonation adjacent to the 1,8-ethano bridge can be effected with SO3 in dioxane as reagent, whereas sulfonation ortho to the longer alkano bridges requires the more reactive reagent SO3 in nitromethane. Disulfonation of the1,8:4,5-dialkanonaphthalenes 3–5 leads to the predominant formation of the "noncrossed" (i.e. the 2,7-) disulfonic acid due to the substituent effect of the 2-sulfonic acid group. The isomer distribution data for the sulfonation of the arenes and their monosulfonic acids show that the steric hindrance increases in the order ethano [Formula: see text] propane ≤ butano and propane < peri dimethyl.