I am wondering what is developers' and users' perspective on handling hydrogens of a structure when matching a SMARTS pattern. For example, C-[!#6] pattern usually does not match “C” (methane), although methane has implicit C-H bond, which literally is a carbon connected to non-carbon. It does not match C([H])([H])([H])[H] either. The C[*] pattern also usually does not match methane, not depending of explicit or implicit hydrogens.
It looks like a rule everybody is used to, am I right? In this case, what is the rule, speaking formally? SMARTS format description does not say much on this topic.
Fredrik Wallner [ Editor ]
From the perspective of one user, I would say that I always think of hydrogens as non-existing when working with SMILES and SMARTS, so I would be very surprised if C-[!#6] matched methane.