ascii alanine aliphatic compound amino acid aromaticity atom benzene biphenyl carbon dioxide chemical bond chemical database chemical element chemical file format chemistry chemistry development kit cis cyclohexane david weininger depth-first search dimension enantiomer ethanol filename extension fluoroform furan gold graph theory hydrogen cyanide hydroxide imidazole international chemical identifier international union of pure and applied chemistry isomorphism isotope joelib molecular query language molecular configuration molecule molecule editor oelib openbabel open standard propionic acid pyridine pyrrole query language sybyl line notation smiles arbitrary target specification trans tree traversal water wildcard character wiswesser line notation