code: private void setActiveCenters(IAtomContainer reactant) throws CDKException {
          if (AtomContainerManipulator.getTotalCharge(reactant) > 0) return;
  
          Iterator<IAtom> atoms = reactant.atoms().iterator();
          while (atoms.hasNext()) {
              IAtom atomi = atoms.next(); // Atom pos 1
              if ((atomi.getFormalCharge() == CDKConstants.UNSET ? 0 : atomi.getFormalCharge()) <= 0
                      && reactant.getConnectedLonePairsCount(atomi) > 0
                      && reactant.getConnectedSingleElectronsCount(atomi) == 0) {
                  atomi.setFlag(CDKConstants.REACTIVE_CENTER, true);
  
              }
          }
      }
docs: set the active center for this molecule.
  The active center will be those which correspond with X=Y-Z-H.
  <pre>
  [X-]
  </pre>
  
  @param reactant The molecule to set the activity
  @throws CDKException