 ICI had claimed an average of about three side chains per molecule, but analyses by Prof Scotts lab suggested between three and four.Most of them are at the 2(3) positions, as in the formula and sometimes a cartoon representation uses the methylene bridge criss crossing across the bond between these two positions to indicate that it could bind either of these two positions.A large number of isomers, differing in the positions of the cationic groups, are possible.