The two crystalline products of the non-steam volatile fraction from t
he reaction of acetophenone and methane-sulfonic acid have been identi
fied, by single-crystal strucure analysis, as 6a-methyl-5-phenyl-5,7-m
ethano-5H-benzo[c]fluorene and 9-methyl-1,3,9-triphenylfluorene. The m
echanism leading to their formation is not obvious.