Chemical classification
Chemical classification systems attempt to classify as elements or compounds according to certain chemical functional or structural properties. Where as the structural properties are largely intrinsic, functional properties and the derived classifications depend to a certain degree on the type of chemical interaction partners on which the function is exerted. Sometimes other criteria like purely physical ones (e.g. molecular weight) or - on the other hand - functional properties above the chemical level are also used for building chemical taxonomies.
Some systems mix the various levels, resulting in hierarchies where the domains are slightly confused, for example having structural and functional aspects end up on the same level. Whereas chemical function is closely dependent on chemical structure, the situation becomes more involved when e.g. pharmacological function is integrated, because the QSAR can usually not be directly computed from structural qualities.
Physico-chemical classification
- by molecular weight
- by electrical charge: uncharged, positively, negatively, partially charged
- solubility
- pH value
Structural classification
Usually binary classifications and combinations thereof:
- radicals, non-radicals
- cyclic vs. linear
- type of major bond: ionic (salts) vs. covalent, metallic
- organic vs. inorganic compounds (depends on whether carbon is the main constituent or not)
- (in organic chemistry)
- aliphatic vs. aromatic compounds
Functional classification
Chemical function
Pharmacological/biological function
Mostly appropriate only for large biological molecules (as at least one interacting partner), in particular enzymes, depends on chemical functions of their constituent amino acids.
- ligand vs. receptor, coenzyme
- EC number
- TC number
- pharmacophore vs. non-drug
See also: biological activity
Mixed systems
- Anatomical Therapeutic Chemical Classification System
- Gene Ontology
See also
- Chemical Safety: Globally Harmonized Classification System
External links
- http://www.ebi.ac.uk/chebi/ Chemical Entities of Biological Interest