code: private boolean isSp3Carbon(IAtom atom, int deg) {
          Integer elem = atom.getAtomicNumber();
          Integer hcnt = atom.getImplicitHydrogenCount();
          if (elem == null || hcnt == null) return false;
          if (elem == 6 && hcnt <= 1 && deg + hcnt == 4) {
              // more expensive check, look one out and see if we have any
              // duplicate terminal neighbors
              List<IAtom> terminals = new ArrayList<>();
              for (IBond bond : container.getConnectedBondsList(atom)) {
                  IAtom nbr = bond.getOther(atom);
                  if (container.getConnectedBondsCount(nbr) == 1) {
                      for (IAtom terminal : terminals) {
                          if (Objects.equals(terminal.getAtomicNumber(),
                                             nbr.getAtomicNumber()) &&
                              Objects.equals(terminal.getMassNumber(),
                                             nbr.getMassNumber()) &&
                              Objects.equals(terminal.getFormalCharge(),
                                             nbr.getFormalCharge()) &&
                              Objects.equals(terminal.getImplicitHydrogenCount(),
                                             nbr.getImplicitHydrogenCount())) {
                              return false;
                          }
                      }
                      terminals.add(nbr);
                  }
              }
              return true;
          }
          return false;
      }
docs: indicates where an atom is a Sp3 carbon and is possibly a stereo-centre