edited by MARY VIRGINIAORNA.O.S.U College of New Rochelle New Rochelle. NY 10801
thumbnail /ketche/ The Official Rules for Organic Chemical Nomenclature: Emergence, Evolution, Emphases, and Errors James G. Traynham LOUISI~MSlate University &ton Rouge. LA 70803
An accurate, appropriate characterization of organic chemical nomenclature is probably a resonance hybrid of the well-known canonical expressions "fits and starts", "all deliberate speed", and "don't rock the boat". Significant efforts toward an orderly organic nomenclature emerged in England during the 1860's and 1870's. The Journal of the Chemical Society published lengthy abstracts of chemical papers that had appeared in other journals, and the 1879 volume carried Instructions to Abstractors ( I ) that included some rules about names of comoounds that were an auproach to standardization of nomenclature. The influence of these Instructions spread beyond the abstractors to whom they were addressed. Two years later, Henry Watts, the editor of that journal, was able to write to H. E. Armstrone, a member of the Journal's Committee on Publication, that "Our system of nomenclature is making its way beyond the seas. In Remsen's 'American Chemical journal' our 'Instruetions' are followed almost to the letter and to a considerable extent also in the Proceedings of the Royal Soc. of New South Wales" (2). Several vears later. in 1889. oreanic chemical nomenclature problems were s"fficiently w;('lely acknowledged for the International Chemical Coneress - meetinr in Parig that summer to appoint a special commission "to consider the unification of chemical nomenclature". The work of the commission led to the first international conference on chemical nomenclature, which convened in Geneva, Switzerland, on Easter Monday in 1892. The Geneva Conference was attended by 34 prominent chemists from nine European countries (3). Although Ira Remsen had been amemher of the commission, neither he nor any other person from the United States was uresent a t the Conference. ~ i Conference e memhers adopted the idea of adding a systematic suffix to indicate the functional class of the compound being named, and although not all classes were considered and some of the endings adopted were changed later, the idea has remained central to organic nomenclature practice. Some other adoptions, just as firm, have also persisted through the near century of revisions of the rules but continue to be flouted by authors of textbooks and journal articles. The prefix n- with names of unbranched dkanes and the name mercaptan were abandoned by the 1892 Conference (3). They havenever had an official status, hut they continue to he used and taught today. One can understand the hesitance of uracticine chemists to abandon their own use of familiar but newlyproscribed nomenclature in the 1890's; it is more difficult to account for the continued use of antiquated terminology several generations later, particularly by those writing the books and teaching the classes for the newest generation of chemistry students. The resolutions adopted by the Conference were not comprehensive even for the kinds of organic compounds known in 1892, but 30 years lapsed before the International Union ~
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of Chemistry appointed a committee of editors of major chemical publications to develop new recommendations on organic nomenclature. Their re~ommeudationswere adopted in 1930 at Liege as the "Definitive Report" with 67 rules (. 4.) . After 1930 suuolemental renorts on nomenclature rules .. appeared rather regularly under the auspices of the lnternational Union of Purt. and Applied Chemistry (IL'PAC, surressor to IUC). A much longer set of rules was adupted in 1957, hut the emphasis in it was on "codifving sound practices which already existed, rather than . . . originating new nomenclature" 151. The rules were exuanded sirnificantlv to additional classes of compounds and nomenclaiure issues in the 1960'sand 1970's. The last official IUPAC set of rules for Nomenclature of Organic Chemistry was adopted in 1979 (6).In 87 years, the page and a half of 46 resolutions adopted by the 1892 Geneva Convention had grown t o a hook of 559 pages. The committee responsible for the 1930 rules explicitly abandoned one specific goal of the Geneva Conference, namely, to have one official name for each compound. Several styles of nomenclature for the same compound were now allowed. Some textbook authors and manv teachers. relvinp on the textbooks, have mistakenly identified the 'ori&a! Geneva Conference resolution for a single official name with the current IUPAC rules. A texthookmay identify 2-methyl2-propanol as an IUPAC name and tert-butyl alcohol as not; both, however, are approved IUPAC names for that comuound, illustratine different stvles (substitutive and func~ j . IUPAC rules are truly tional class n a m e s ~ r e s p e c t i ~ e lhe permissive among styles, although the narrative with the 1957 (and subsequent) rules faintly revealed a preference away from trivial names. But firmer choices were soon being made. While earlier editions had permitted citations of suhstituent side chains either in order of complexity (specified first in the rule) or in alphabetical order, after 1968 the rules specified only alphabetical order. Acceptable styles for heterocvclic svstems were similarlv restricted. Generating a proper name for a complex compound probahlv will require us to refer to the "Blue Book" of rules.' t o examine il1;strative examples. But persistent, widespiead errors with simple svstems . . -governed bv simule. straiahtforward, easily learned and follou,ed instructions are puzzling. Alksl groups are named substitutivelv on the l~asis01' the longest chain beginning a t the carbon atom with the free valence (point of attachment). That seems simple enough. Just start numbering on the carbon atom with the free valence (number 1) and let all the locants for substituents follow. But how often have you seen 2-butyl instead of 1methylpropyl for CH&H2-CH-CH3? "2-Butyl" is not a cor-
An abridged version of a paper (HIST 26) presented at the 189th National Meeting of the American Chemical Society, Division of History of Chemistry Symposium on Chemical Nomenclature. Miami Beach, FL, April 30, 1985. Reference 6 is bound in blue cloth and is referred to colloquially as the "Blue Book"; similarly, the volume of rules of the IUPAC Commission on Nomenclature of Inorganic Chemistry is called the "Red Book".
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Volume 64
Number 4
Aprll 1987
325
rect name for anything, but i t is widely used even by prestigious chemists in prestigious journals. Does it matter? Is anyone going to be uncertain about the intended identity? Probably not any more than about the intended meaning of the sentence, "When we seen the data, the interpretation came quickly to Shirley and I." As a referee of a manuscript, would you as quickly object to "2-hutyl" as to the sentence? Both are unacceptable because of the same kinds of rules governing language, and a chemist ought to know better on both items. A central theme of organic chemical nomenclature-and in a large measure, its inspiration-lies in its extension heyond mere identification to illuminate the chemical behavior to expect of the compound being named. For example, butanal rather than 1-oxobutane. The first name tells us to expect aldehyde behavior; the second, based on some but not all anorooriate IUPAC rules. hides that behavior. We mav. z. at first reading or hearing, expect slightly modified d k a i d behavior. The IUPAC rules for oreanic comoounds have, since the 1930Definitive Report, emphasized the functional group and a priority of functional groups. A compound with butyl, hydroxy, and methyl groups on a benzene ring (used
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Journal of Chemical Education
as an inhibitor of radical reactions) is properly named as a suhstituted ohenol. not as a substituted toluene. but a widely used a c r & n f i r it (BHT) is based on t h e improperly generated name. How helpful can an improperly based acronym be in prompting our memory about compound identity or function? The development of organic nomenclature, like the development of organic synthetic methods, is impressively advanced but is continuing. The ideal is complete banishment of ambiguity in transfer of chemical information. The rules are extensive, because organic chemistry is so extensive. The rules change, partly because chemistry changes, partly because the chemists get better ideas. Meanwhile, the rules are the rules, and flouting them, intentionally or not, may well make our communication precarious. 1. J.Chzm.Soc. 1879,35.276281. 2. Letter from Watts, H.. to Armstmng, H. E., dated 13 Sept, '6L;item 514 in Henw Edward Alrnsfrone Archives collection. Colleee Archives. 1rnneria1 Colleae,London. 6. Armstrong, H.E. ~ Z u r e 1892,46(1177l.5659.. 4. J. Chem.Sac. 1931.1607-1616. 5. J.Am.Chem.Soe. 1960.62.554&5574. Chsmb6, lnternstionalUnianofPureandAppliedChemiatw.Nom~ncloturro/Orgonir try. Saeliona AB,C,D. E, F o n d H . Pergarnon: Oxford, England, 1979.
