code: @Override
      public void addReactant(IAtomContainer reactant, Double coefficient) {
          reactants.addAtomContainer(reactant, coefficient);
          notifyChanged();
      }
docs: Adds a reactant to this reaction with a stoichiometry coefficient.
  
  @param reactant    Molecule added as reactant to this reaction
  @param coefficient Stoichiometry coefficient for this molecule
  @see   #getReactants