RESIDUE   BUO     12
CONECT      O1     1 C1  
CONECT      C1     3 O1   C4   C2  
CONECT      C4     4 C1   H1   H2   H3  
CONECT      C2     3 C1   C3   O2  
CONECT      C3     4 C2   H4   H5   H6  
CONECT      O2     1 C2  
CONECT      H1     1 C4  
CONECT      H2     1 C4  
CONECT      H3     1 C4  
CONECT      H4     1 C3  
CONECT      H5     1 C3  
CONECT      H6     1 C3  
END   
HET    BUO             12
HETNAM     BUO butane-2,3-dione
FORMUL      BUO    C4 H6 O2