The one form of branch which does not require parentheses are ring-closing bonds: the SMILES fragment C1N is equivalent to C(1)N, both denoting a bond between the C and the N. Choosing ring-closing bonds adjacent to branch points can reduce the number of parentheses required. For example, toluene is normally written as Cc1ccccc1 or c1ccccc1C, avoiding the parentheses required if written as c1cc(C)ccc1 or c1cc(ccc1)C.
The one form of branch which does not require parentheses are ring-closing bonds: the SMILES fragment C1N is equivalent to C(1)N both denoting a bond between the C and the N Choosing ring-closing bonds adjacent to branch points can reduce the number of parentheses required. For example, toluene is normally written as Cc1ccccc1 or c1ccccc1C, avoiding the parentheses required if written as c1cc(C)ccc1 or c1cc(ccc1)C.