provocative opinion Trivial Names for Chemical Substances Will They be Taught or Forgotten in the Twenty-First Century? Peter A. S. Smith University of Michigan, Ann Arbor, MI 48109
A so-called trivial name is simply a term for identifying a substance without utilizing standardized symbols (mostly syllables ) to designate its structural features. Examples are "ozone", "urea", and "aspirin". Closely allied are semi-trivial names, in which symbols corresponding to a standardized meaning are joined to a trivial stem. "Butane" and "benzoic acid" are examples. They are so universally used that most chemists do not realize that they are not systematic names. The names for the elements are likewise all trivial (with the possible exception of *protium"). Is it reasonable to suppose that "ethanol", "naphthalene", "sodium", and "chlorine" will have disappeared from the respectable scientific vocabulary 10 years from now? If not, some trivial names and many semi-trivial ones will continue to be taught and used. Let's look into these examples a bit more. The GenevdUPAC names for the five smallest saturated aliphatic bydrocarhons are semi-triviat; their only systematic component is the ending -ane, prescribed for saturated systems bearing no functional groups. Only beginning with pentane do we find a feature that explicitly tells us anything more about the structure (i.e., " pent" ). There actually have been proposals over the course of this century to provide truly systematic names for these compounds (e.g., "carbane", "dicarbane", etc., which might even be contracted to "ane", "diane" ) (I),but they seem not to have gathered even a small following. Main Principles of Nomenclature As for "benz-oic acid", that name is obviously not formed according to either of the main principles (2)for forming systematic names for carboxylic acids, namely, adding "-oic acid" to the name of the hydrocarbon having the same skeleton (inthis case, it would be toluene), or adding "-carboxylic acid" to the name of a parent compound in which -H is replaced by -COOH ( i. e., benzene). Namingacids system-
atically was a vexing problem for the participants in the conference in Geneva in 1892, and it continued to be difficult long afterwards. The best that can be done in the framework of the current IUPAC rules is "benzenecarboxylic acid" (or perhaps "phenylformic acid"), but neither of these is actually recommended by IUPAC. One can certainly deduce the structure unambiguously from these names ( if one accepts their trivial components, "benzene" or "phenyl" ) , but they are considerably longer than %enzoic", and for such a commonly mentioned compound, that is a serious disadvantage. Similar remarks can be made about the analogous names "naphthoic", "anthroic", and "phenanthroic" acids, but since they are far less common, the case for retaining them is not so strong. There is no justification for coining new names by this pattern (for example, one bas a right to be horrified by "femcenoic acid" ! ). "Toluic acid" teeters on the brink of ambiguity; a more nearly systematic formation, "toluenoic acid", would strictly denote benzoic acid (-CH3 oxidized to XOOH), but "toluic acid", nevertheless, seems to be understood by everyone and will in all probability survive for a long time. The names of the elements are derived from ancient roots (e.g., gold and silver), from a characteristic (e.g., phosphorus),or the occurrence, geography, or scientists associated with it (e.g., calcium, francium, lawrencium). There is indeed a systematic method for naming them, intended only for hypothetical ones or those so newly discovered that a conventional name has not yet been officially assigned (3).Names such as "ununium" (sodium, atomic number 11)are unlikely to be adopted in the near future (if ever), for more than one reason. If we recognize the fact, exemplified in the foregoing remarks, that trivial names are deeply embedded in nomenclature commonly thought of as fully systematic and are, therefore, unlikely to be abandoned, we could reasonably change the question posed to Wow much trivial nomencla-
Volume 69 Number 11 November 1992
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ture will continue to be taught and used?" To start with, let's have a look at the pros and cons, the rationales for justifying choices of nomenclature. An important place to look is the origins of the nomenclature we use today. In the area of oreanic chemistrv (4).the orkins are the 1892 Geneva ~onference,the 1930 Litge conference, and the considerable amount of published discussion and proposals in . . the years between. Main Functions of Nomenclature
The oartici~antsin the Geneva Conference and in the subsequent developments of organic nomenclature had a clear conception that there &re two kinds of uses for nomenclature, that might require some differences in rules: names for indexing and retrieval, and names for communication (oral or written). For the former, conciseness and simplicity would not be major concerns; whereas, for the lattkr use, short names that are easily comprehended and rules that permit ordered flexibility so as to allow particular features to be emphasized are favored. The task that was originally set was to formulate rules for generating an "official"name for each compound, to be used in indexes. For communication purposes, such as in lectures and in iournals. chemists were to be allowed a meat deal of latiiude in choosing names, as long as the Gdamentals of the rules were not contravened to the point of ambiguity. However, the distinction between the two kinds of use became somewhat blurred in later vears. Stelzner (5)refined this concept of permissiveness in oral and written nomenclature by accepting trivial names as long as they ended with a suffix that corresponded t o the principal functional group present. This concept has been retained to this day, in the IUPAC rules for coining names for natural products. Jacobson (6) favored Ylalf-rational" names, in which a trivial stem is combined with systematic prefixes and suffixes of the general rules ("chloroacetic acid" and "adamantanol" are examples). In 1917, Patterson and Curran (7) in writing about the principles they followed for choosing index names for Chemical Abstmcts, wmte that they had a "tendency toward compact naming, and we have freely used short names for complex compounds as fresh starting points in naming derivatives of them". That is, thev were willine to adopt trivial names into systematic no&enclature wgen the& is substantial advantage to be eained. That ~rinciolealso has been carried down to this ;ay. It is especiallyvaluable when used for stereochemical parent comoounds. such as "glucose", and in steroid nomenclature; which'would be much cl~msierif one did not make use of trivial parent names such as "cholestane". In these instances, the use of trival names has become invaluable not only for communication among scholars, but for indexing as-well. Trivial names are an integral part of NPAC nomenclature for fused-ring compounds, for which the largest system having an approved thvial name is chosen as the fusion parent (thus "ben7.anthracene" is chosen over "dibenz~na~hthalene" ) Some Trivial Names Have Faded
On the other side of the picture, there are trivial names that are not suitable as pirents for a large number of derivatives, do not unambifiuously imply the numbering of substitutable positions, or are not si&ificantly more compact than the corresponding systematic names. wEnanthaldehyde" is clearly less desirable than "heptanal", and the name "nipecotic acid" is not only obscure, but does not assure us about the numbering, whereas "piperidine-3-
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carboxylic acid" (which still has a trivial component) does; albeit at the expense of compactness) . These two names and many like them already have vanished from current use, and I know of no modern textbook that even acknowledges the existence of them. Some of the names that still linger can be expected to die out in the next decade as well. However, read on-life is not so simple ! Other Trivial Names Have Endured
There is a body of trivial names that are part of the general lanmage and are far from being exclusive to chemists. The early &menclaturists were well aware of this fact, and the view was expressed (8)that "none of the stock terms in use in everyday language should be changed". ''Sulfuric acid" is most unlikely to be supplanted by a coordination name for general use ( industry, medicine, art, agriculture, environmental science, ete. ). "Iron" is certainly not going to be given up in favor of "duohexium" or even "ferrum". "Sulfite", "bicarbonate", "acetone", "formaldehyde", "toluene", "ascorbic acid", "cocaine", "styrene", and even "naphthalene", among a host of others, are f m l y entrenched in the eeneral lanzuage. To attempt to do away with such namesin teaching chGmistry wouid at this time result onlv in alienatiw an already suspicious public,who would seLthe new names as unnecessary and &cane, and a means of excluding the layman. The current IUPAC rules (2) recognize this by including statements such as "the name acetic acid is retained." The intent of this statement is that "acetic acid" is the recommended name, rather that "ethanoic acid" (or perhaps "dicarbanoic acid"). " Propionic acid" may be slipping a little, since it is no shorter than "propanoic acid", but interestingly, '%utyric acid" seems to be firmly rooted (perhaps because it is one syllable shorter than "butanoic"). If chemists are to retain an anchor in the "real world". the concession should be made at least to be aware of the terminology in non-scientifie use. We (and our students) should not become so isolated in our scientific cocoon that we become ignorantly mvstified upon encountering a bottle prominently labeled Guriatic acid" on the shelfof the locai hardwareatore! The organic trivial names that best withstand the hardest tests of clarity, brevity, usefulness, and familiarity are listed in a book soon to aooear (91from IIJPAC). These names are sure to be used far into the next century, along with manv that did not make the list. The names for the elements h l also continue to be used (granting the possibilitv that a few. such as "tunesten". could become altered). ~hu;,judiciously selected t r k a l &mes are an important part of general, technical, and scientific communication, and can be expected to remain in use for the foreseeable future.
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Literature Cited
2.Rigandy, J.; I(lewey,S. P . , E d s . N o m e l a t u r e ~f0ganlcChmishy;PergagaganRella Oxford and NewYork. 1979.
7 I ' ~ ~ ~ H ~* r ,~d C~~ n. n n . . C\ . EJ Am C k m . Soc 1817.39. 1623 R C ~ m p r r, s~n l Fr A t u m m n l PI.. 21n S r a m n . Pats. l R P 4 I.:i'?M14 U Pnnico R.: Popell, a' H , K r h w .I X , Ed8 A Cut& the Lire oflUFAC N o m n r l o . r ~ f . r r k ~ , , ,r h , ~e n u w ul p m a . 1992 IUI'.~VI
