code: public MoleculeProperty getCapMoleculeInfo(String label) throws 
         CTKException, ChemistryException, IOException {
      for (Attachment attachment : attachmentList) {
        if (attachment.getLabel().equalsIgnoreCase(label)) {
          String capSmi = attachment.getCapGroupSMILES();
          org.helm.chemtoolkit.MoleculeInfo info = Chemistry.getInstance().getManipulator().getMoleculeInfo(Chemistry.getInstance().getManipulator().getMolecule(capSmi, null));
          MoleculeProperty moleculeinfo = new MoleculeProperty();
          moleculeinfo.setExactMass(info.getExactMass());
          moleculeinfo.setMolecularFormula(info.getMolecularFormula());
          moleculeinfo.setMolecularWeight(info.getMolecularWeight());
          return moleculeinfo;
        }
      }
      return null;
    }
docs: This method returns the MoleculeInfo for the input R group label of this
  monomer
  
  @param label - R1, R2...
  @return MoleculeInfo for the cap group, R group will contribute nothing
  @throws CTKException general ChemToolKit exception passed to HELMToolKit
  @throws ChemistryException if chemistry could not be initialized
  @throws IOException if molecule can not be read