| Nitrous oxide | Inorganic compounds | Homogeneous non-metal compounds | Homogeneous other non-metal compounds | Not Available | Details |
| O-Acetyl-rhamanosyl-N-acetylglucosamyl-undecaprenyl diphosphate | Organic compounds | Lipids and lipid-like molecules | Prenol lipids | Polyprenols | Details |
| O16 antigen undecaprenyl diphosphate | Organic compounds | Lipids and lipid-like molecules | Prenol lipids | Polyprenols | Details |
| Octadecanoyl-phosphate (n-C18:0) | Organic compounds | Organophosphorus compounds | Organic phosphoric acids and derivatives | Organic phosphoric acids | Details |
| Octadecanoyl-phosphate (n-C18:1) | Organic compounds | Organophosphorus compounds | Organic phosphoric acids and derivatives | Organic phosphoric acids | Details |
| Octadecenoyl-CoA (N-C18:1CoA) | Organic compounds | Lipids and lipid-like molecules | Fatty Acyls | Fatty acyl thioesters | Details |
| Oxamate | Organic compounds | Organic acids and derivatives | Carboxylic acids and derivatives | Amino acids, peptides, and analogues | Details |
| P1,P4-Bis(5'-guanosyl) tetraphosphate | Organic compounds | Nucleosides, nucleotides, and analogues | (5'->5')-dinucleotides | Not Available | Details |
| PG(12:0/12:0) | Organic compounds | Lipids and lipid-like molecules | Glycerophospholipids | Glycerophosphoglycerols | Details |
| PG(14:1(7Z)/14:1(7Z)) | Organic compounds | Lipids and lipid-like molecules | Glycerophospholipids | Glycerophosphoglycerols | Details |
| PG(18:0/18:0) | Organic compounds | Phenylpropanoids and polyketides | Stilbenes | Not Available | Details |
| PGP(12:0/12:0) | Organic compounds | Lipids and lipid-like molecules | Glycerophospholipids | Glycerophosphoglycerophosphates | Details |
| PGP(14:0/14:0) | Organic compounds | Lipids and lipid-like molecules | Glycerophospholipids | Glycerophosphoglycerophosphates | Details |
| PGP(14:1(7Z)/14:1(7Z)) | Organic compounds | Lipids and lipid-like molecules | Glycerophospholipids | Glycerophosphoglycerophosphates | Details |
| PGP(16:0/16:0) | Organic compounds | Lipids and lipid-like molecules | Glycerophospholipids | Glycerophosphoglycerophosphates | Details |
| PGP(16:1(9Z)/16:1(9Z)) | Organic compounds | Lipids and lipid-like molecules | Glycerophospholipids | Glycerophosphoglycerophosphates | Details |
| PGP(18:0/18:0) | Organic compounds | Lipids and lipid-like molecules | Glycerophospholipids | Glycerophosphoglycerophosphates | Details |
| PGP(18:1(11Z)/18:1(11Z)) | Organic compounds | Lipids and lipid-like molecules | Glycerophospholipids | Glycerophosphoglycerophosphates | Details |
| Peroxyaminoacrylate | Organic compounds | Organic acids and derivatives | Carboxylic acids and derivatives | Peroxycarboxylic acids and derivatives | Details |
| Phosphotyrosine | Organic compounds | Phenylpropanoids and polyketides | Phenylpropanoic acids | Not Available | Details |
| Propanal | Organic compounds | Organooxygen compounds | Carbonyl compounds | Aldehydes | Details |
| Quinate | Organic compounds | Organooxygen compounds | Alcohols and polyols | Cyclic alcohols and derivatives | Details |
| Reduced riboflavin | Organic compounds | Organoheterocyclic compounds | Pteridines and derivatives | Alloxazines and isoalloxazines | Details |
| S-Adenosyl-4-methylthio-2-oxobutanoate | Organic compounds | Organooxygen compounds | Carbohydrates and carbohydrate conjugates | Glycosyl compounds | Details |
| Selenodiglutathione | Organic compounds | Organic acids and derivatives | Carboxylic acids and derivatives | Amino acids, peptides, and analogues | Details |
| Stearoyl-CoA | Organic compounds | Lipids and lipid-like molecules | Fatty Acyls | Fatty acyl thioesters | Details |
| Superoxide anion | Inorganic compounds | Homogeneous non-metal compounds | Non-metal oxoanionic compounds | Non-metal superoxides | Details |
| Tetradecanoyl-phosphate (n-C14:0) | Organic compounds | Organophosphorus compounds | Organic phosphoric acids and derivatives | Organic phosphoric acids | Details |
| Tetrahydromonapterin | Organic compounds | Organoheterocyclic compounds | Pteridines and derivatives | Pterins and derivatives | Details |
| Thiocyanate | Organic compounds | Organosulfur compounds | Thiocyanates | Not Available | Details |
