A single butane
  4
    1BUT     C1    1   1.382   1.573   1.482
    1BUT     C2    2   1.281   1.559   1.596
    1BUT     C3    3   1.292   1.422   1.663
    1BUT     C4    4   1.189   1.407   1.775
   2.46298   2.46298   2.46298