RESIDUE   C2H      4
CONECT      C      2 C1   H2  
CONECT      C1     2 C    H4  
CONECT      H2     1 C   
CONECT      H4     1 C1  
END   
HET    C2H              4
HETSYN     C2H ethyne
HETNAM     C2H acetylene
FORMUL      C2H    C2 H2