dihydroxybenzaldehyde 3,4-dihydroxybenzaldehyde 1,2-dihydroxy-4-formylbenzene 138.032 138.12074 3,4-dihydroxybenzaldehyde 3,4-dihydroxybenzenecarbonal 4-formyl-1,2-benzenediol 4-formyl-1,2-dihydroxybenzene Beilstein:774381 C7H6O3 CAS:139-85-5 CHEBI:50205 Drug_Central:4612 Gmelin:123001 IBGBGRVKPALMCQ-UHFFFAOYSA-N InChI=1S/C7H6O3/c8-4-5-1-2-6(9)7(10)3-5/h1-4,9-10H KEGG:C16700 KNApSAcK:C00018099 Protocatechualdehyde [H]C(=O)c1ccc(O)c(O)c1 chebi_ontology protocatechualdehyde protocatechuic aldehyde