chemical name

A chemical nomenclature is a set of rules to generate systematic names for chemical compounds. The nomenclature used most frequently worldwide is the one created and developed by the International Union of Pure and Applied Chemistry (IUPAC).

The IUPAC's rules for naming organic and inorganic compounds are contained in two publications, known as the '' Blue Book''. . and the '' Red Book'',. respectively. A third publication, known as the '' Green Book'',. recommends the use of symbols for physical quantities (in association with the IUPAP), while a fourth, the '' Gold Book'',''Compendium of Chemical Terminology, IMPACT Recommendations (2nd Ed.)'', Oxford:Blackwell Scientific Publications. (1997) defines many technical terms used in chemistry. Similar compendia exist for biochemistry''Biochemical Nomenclature and Related Documents'', London: Portland Press, 1992. (the ''White Book'', in association with the IUBMB), analytical chemistry (the '' Orange Book''), macromolecular chemistry''Compendium of Macromolecular Nomenclature'', Oxford: Blackwell Scientific Publications, 1991. (the ''Purple Book''), and clinical chemistry. (the ''Silver Book''). These "color books" are supplemented by specific recommendations published periodically in the journal ''Pure and Applied Chemistry''.

Aims of chemical nomenclature

The main goal of chemical nomenclature is to disambiguate the spoken or written names of chemical compounds: each name should refer to one compound. Secondarily: each compound should have only one name, although in some cases some alternative names are accepted.

Preferably, the name should also reflect the structure or chemistry of a compound. This is achieved by the International Chemical Identifier (InChI) nomenclature. However, the American Chemical Society's CAS numbers nomenclature reflects nothing of the compound's structure.

The nomenclature used depends on the needs of the user, so no single correct nomenclature exists. Rather, different nomenclatures suit different circumstances.

A common name will successfully identify a chemical compound, given context. Without context, the name should indicate at least the chemical composition. To be more specific, the name may need to reflect the three-dimensional arrangement of the atoms.This requires adding more rules to the standard IUPAC system (the CAS system is the most commonly used in this context), at the expense of having longer and less familiar names.

The IUPAC system is often criticized for the failing to distinguish relevant compounds (for example, in differing reactivity of sulfur allotropes, which IUPAC does not distinguish). While IUPAC has a human-readable advantage over CAS numbering, IUPAC names for some larger, relevant molecules (such as rapamycin) are barely human-readable, so common names are used instead.

Differing aims of chemical nomenclature and lexicography

It is generally understood that the aims of lexicography versus chemical nomenclature vary and are to an extent at odds. Dictionaries of words, whether in traditional print or on the web, collect and report the meanings of words as their uses appear and change over time. For web dictionaries with limited or no formal editorial process, definitions —in this case, definitions of chemical names and terms— can change rapidly without concern for the formal or historical meanings. Chemical nomenclature on the other hand (with IUPAC nomenclature as the best example) is necessarily more restrictive: It aims to standardize communication and practice so that, when a chemical term is used it has a fixed meaning relating to chemical structure, thereby giving insights into chemical properties and derived molecular functions. These differing aims can have profound effects on valid understanding in chemistry, especially with regard to chemical classes that have achieved mass attention. Examples of the impact of these can be seen in considering the examples of:
* resveratrol, a single compound clearly defined by this common name, but that can be confused, popularly, with its ''cis''-isomer,
* omega-3 fatty acids, a reasonably well-defined chemical structure class that is nevertheless broad as a result of its formal definition, and
* polyphenols, a fairly broad structural class with a formal definition, but where mistranslations and general misuse of the term relative to the formal definition has led to serious usage errors, and so ambiguity in the relationship between structure and activity (SAR).
The rapid pace at which meanings can change on the web, in particular for chemical compounds with perceived health benefits, rightly or wrongly ascribed, complicate the monosemy of nomenclature (and so access to SAR understanding). Specific examples appear on the polyphenols article, where varying web and common-use definitions conflict with any accepted chemical nomenclature connecting polyphenol structure and bioactivity).

History

The nomenclature of alchemy is rich in description, but does not effectively meet the aims outlined above. Opinions differ about whether this was deliberate on the part of the early practitioners of alchemy or whether it was a consequence of the particular (and often esoteric) theoretical framework in which they worked.

While both explanations are probably valid to some extent, it is remarkable that the first "modern" system of chemical nomenclature appeared at the same time as the distinction (by Lavoisier