Give the atom a name with a number following it, with the number in the range of 1-5. For example, if you named one atom C5 and another atom H5, the fifth constraint would be used for this atom pair. Make sure no more than two atoms have the same constraint number. If you use a charged atom or a stereo atom in a constraint, make sure to put the constraint number last. For example, a constraint with a carboxyl atom would be specified as O-2, and the second constraint would be applied to this atom and the other atom labeled with a 2.
Atoms can only be tetravalent, sorry.
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