The sulfonation of a series of methylphenanthrenes (MPs) and two bromophenanthrenes with SO3 in nitromethane has been studied at 0" C. From the substitution pattern it is evident that steric factors play an important role. Substitution of the 4-and 5-H peri to the methyl does not occur, and that ortho to the 9-methyl is severely reduced. Provided that allowance is made for the steric factors, the positional order of substitution for monosulfonation of a ...
