The Centennial of Systematic Organic Nomenclature Homer A. Smith Jr. Millikin University, Decatur, IL 62522
Most chemists have heard of the "Geneva Rules," but thev mav not realize that the first svstematic rules for orga& nomenclature were formulated 100 years ago at an historic meeting in that Swiss city. Most organic chemists know the basics of current IUF'AC nomenciature and use them in their work, hut many have limited knowledge of the evolution of the rules over the last hundred years and little familiarity with the ongoing nomenclature work of IUPAC. The 100th anniversary of systematic organic nomenclature seems an appropriate time for a careful look a t the nast. nresent. and future of this vital subiect. This article' wiilbut~ine'the development of the G & V ~ Rules, sketch the history of important modifications over the years, discuss recent advances under the auspices of IUPAC, and speculate about future developments. Lavoisier Proposed a Systematic Nomenclatur~l787 Oreanic nomenclature certainlv existed before 1892. ~ a v o k e and r his students f r s t proposed a systematic nomenclature in Methode de Nomenclature Chimique in 1787. Procedures used to formulate names were uncoordinated and often idiosvncratic but sufficed reasonably well in the early days. As the number of organic compounds and their com~lexitvincreased. the need for communication among organiechemists t'hroughout the world became more evident. A number of leading chemists, particularly involving a French contingent ledby ~riede1,-~ouveauli, and Combes, spearheaded a drive toward systematization. At the International Chemistry Conference held in Paris, July 304ugust 3, 1889, Friedel (as president) made reform of organic nomenclature an important agenda item. International Commission of Chemical Nomenclature Although the conference did not publish any nomenclature rules, it established a continuing International Commission of Chemical Nomenclature, with members fmm 14 countries, including Ira Remsen of the United States. Reconvening 8.1889. the commission cre" inParis on Aueust " ated a permanent Subcommission consisting of the members resident in Paris, with Friedel a s chairman. The Subcommission promoted discussions and circulated pronosals on various asnects of nomenclature over the next two years, setting the stage for the convening of a general conference in Geneva. The International Conference of Geneva for the Reform of the Chemical ~orne~clature'took place April 19-22. 1892. with eiaht sessions under the presidency of ~ r i e d e l resulting';n , the formulation (in French, of 60 resolutions for nomenclature. The 34 participants, all Europeans, included such eminent chemists as Fischer, von Baeyer, and Tiemam from Germany; Barbier, Bouveault, Friedel, and LeBel from France; Ramsay from England; Cannizzaro from Italy; and Hantzsch from Switzerland. Given the leadership of Friedel and his French colleagues a t the Paris Conference, a t meetings of the ~omn&sion and Subcommission and a t Geneva, Pieter Verkade, long-time chairman of the IUPAC organic nomenclature commission, asserted that the "beginning of systematic nomenclature had been a French affair" ( I ) . ~
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The Geneva Rules Institute61892 The Geneva Rules, later praised generally as a sound
foundation for nomenclature, enjoyed less than universal acceptance and usage in the years immediately following their issuance. However, they were widely publicized and commented upon (21,a circumstance necessary for permanent impact. As indicated by the titles of the Geneva Conference and its preliminary gatherings, the original subject was to be chemical nomenclature in general. However, the participants at Geneva concentrated exclusively on oreanic nomenclature. where the needs were ~erceivedto he beatest and ~here'~roundwork had been iaid. The basic principles of substitutive nomenclature were established, with the use of a parent structure (called a "radical" at Geneva) modified by prefixes and sdlixes. Choice and numbering of the parent were based on longest continuous carbon chain. renardless of functional -aroups. . . and on proximity df branching. Locants were sometimes placed aRer the prefix or suffix affected. For example, Structure l a is numbered as shown in order to arrive a t the Geneva name methyl-2-butene-3. The numbering shown in l b is used to an&e at the name currently recommended by the IUI'AC Blue Hook (31,soon to be complemented by the new Guide lo the Use of IUI'AC Nompnclature for Orgonic Chemistry (4).
Geneva: Methyl-Bbutene-3
Blue Bwk: 3-Methyl-l-butene Guide: 3-Methylbut-I-ene
Bouveault proposed that the carbon atom associated with a earboxvlic acid or related functional m o u ~not be included in the parent, resulting, for exampik, inathe (anglicized) name shown under Structure 2a.The Geneva Conference rejected this suggestion in favor of the "-oic acid" method (see Structure 2b). but numbered the parent chain without regard to the acid function. The ~ouveault suggestion was later incorporated into conjunctive nomenclature, a n approved alternative for compounds awkward to name by substitutive methods (e.g., benzene-l,2,4-tricarboxylic acid). A German contingent led by von Baeyer argued for names suitable for indexing purposes ("official" or "register" names) rather than names suitable for written and spoken communication, but the conference diplomaticallv resolved to oermit both twes. In these and other controve"rsies, we ha;e the testimiAy of participant Armstrong of Eneland that 'absolute amitv nrevailed throuehout" @), a cogdition that appears to have persisted throigh successor commissions over the next 100 years. International Symposium-Geneva April 22-24,1992
The pioneering work of the Geneva Conference and its ongoing significance are aptly commemorated by an international symposium a t Geneva, April 22-24.1992, almost exactly 100 years after the original conference. Titled "Organic Chemistry: Its Language and its State of the Art, " the symposium features researchers and nomenclature exVolume 69 Number 11 November 1992
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direct impact on the Working Party by the unfortunate circumstance that German membership in IUC, suspended during the War, was not restored until 1930.
2b
Geneva: 2-Methyl4-butanoicacid
Liege Rules-1930 The increased nomenclature activity of the previous two decades set the stage for important reforms a t the 10th conference of IUC, held a t Liege, Belgium, in 1930. Choice and numbering of the parent were reformed essentially to the system in use today, with precedence given to s u f f i functions, then double and triple bonds, then prefix groups. The omission at Geneva of the principle that only one class of function could be represented by a s u f f i was rectified, but no seniority list for functions was promulgated. The concept of official or index names was allowed to die by neglect. The ending ine for the triple bond was chaneed to vne to avoid confusion with common names of amines. Naming for common heterocycles was established. However. several t o ~ i cbroueht s to mature develoomentbv individual publicat~onsor working party report$ were iinored. includine brideed cvclics. " . ~olvcvclic . . " numberine.... conju~ctivcnanycs, and ummr~tics.Equnlly important in the Liczc rcformx was the ohil(lso~hs that strict loeirmust be tempered by flexibility; practieaiity, and acce$ability. On balance, the Liege Rules constituted a major advance in organic nomenclature, providing satisfactory names for most of the 300 thousand or so compounds known at the time. Acceptability of the Liege Rules was enhanced by wide publication in journals and by their use as the basis for CA index names (9). Over the three decades following Liege, more efficient operation enabled the Nomenclature Commission to keep pace with rapid advances in organic chemistry. Selection procedures were modified to ensure that Commission members had interest and expertise in nomenclature, as opposed to past practice when some sewed as substitutes or as ceremonial representatives of their countries. Membership categories were established that remain in effect today, and travel subsidies were authorized for Titular Members. From 1934 to 1971the Commission enjoyed the strong and effective service of Pieter Verkade of t h e Netherlands a s chairman. Following suspension of Commission activity during the wartime years of 1939-1946, he rapidly reconstituted the group to continue its work. Publication of an extensive list of substitutent ("radical") names in 1947 revresented the first Commissi& report in the English language and codified such groups as "isopropyl" for the first time. At its 15th Congress in Amsterdam in 1949, IUC changed its name to the International Union of Pure and A ~ ~ l i eChemistw d (IUPAC).This period culminated in the iiblication, in E;glish, of the Commission's first monograph (lo),covering hydrocarbons ("Section A") and heterocycles ("Section B). In contrast to the bare rules of Geneva and Liege, this publication contained an introduction with glossary and many well-chosen examples to illustrate important principles.
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LiBge, Blue Book, Guide: 3-Methylbutanoic acid pert8 among its 14 speakers. Its title appropriately calls attention to the fact that organic nomenclature has become in effect a language, with its own vocabulary, grammar, and syntax, and that, like other languages, it continues to grow and to be modified by practice. Despite numerous unsettled nomenclature problems, the two decades following the Geneva Conference were periods of stagnation. The lack of established committee structure and procedures made progress excessively dependent on the efforts of a few individuals. The deaths of Combes in 1896 and Friedel in 1899 left voids that were unfilled for years. Editors of some journals showed little interest in further systematization, and the f a d that only about 60 thousand organic compounds were known afforded little Dressure for Dromess. Valuable recommendations that came from a n~mc&lature ronfcrcnce at SalntEtienne (18971were larzcls lanored, illustratme that organizational backing and idequate dissemination are necessary to make recommendations effective For similar reasons, individual proposals by von Baeyer on bridged polycyclics (5) and by Bouveault on replacement nomenclature for heterocyclics (6)had no immediate effect. However. each ~ r o ~ o ssewed al as the basis for an important advance in homenclature many years later. Oreanized nomenclature activitv resumed in 1911when the Lternational Association of khemical Societies was formed in Paris. The 14 member countries, includinz the United States, appointed a permanent working party for the Reform of the Nomenclature of Organic Chemistry. Work was suspended during the 1914-1918 War, and in 1919 the International Association was replaced by the International Union of Chemistry (IUC).United States influence increased with the active participation on the Working Party of A. M. Patterson of Chemical Abstracts, who had coauthored a nomenclature system for CA indexes (7) in 1917. In preparing a system for the naming and num: bering of cyclic systems (81, Patterson consulted extensivelv with a n aooointed United States commission and with the IUC Working Party, portendingthrrxte~l~iveconsultative orocedures develooed luter bv 1I:PAC. Imoortant nomencl&ure ideas from ~ : ~ t e l z n $the er ~eilstek Institute and from other German chemists were deflected from
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Journal of Chemical Education
Commission on Nomenclature of Organic Chemistry During the 60's and 70's the Commission, given the designation 111.1 by IUPAC and renamed the Commission on Nomenclature of Organic Chemistry (CNOC),continued to publish new "sections" of its nomenclature compendium and to revise older ones. In 1979 the latest versions were combined in a monograph (3)that is commonly called the Blue Book due to the color of its cover. The Commission's work was aided bv constructive criticism and bv nomenclature initiatives f k m United States committees appointed bv the ACS and bv its Oreanic Chemistw Division. Above ail, the ~ommissi"onenjoyed the benefiiof nomenclature systems designed for indexing purposes by CA and
Beilstein's Handbuch, and Commission deliberations were enhanced bv the active ~ a r t i c i ~ a t i oofn members drawn from the staffs of these Adex journals. The different missions of CNOC, CA, and Beilstein often lead to disparate names for the same compound, causing some chemists to surmise that friction exists amone them. On the contram. the activities of these organizatio& have always been seen as complementary and mutually supportive by all members of CNOC. Currently, the Commission meets annually for about one week, with much of its work done by mail in the interim. Decisions are made by consensus, with considerable weight given to the potential acceptability of recommendations by the wider chemical community. Typically many are a t various staees of wm~letion.with different ~roiects " a subcommittee (called a "working party") in charge of each. Completion of a project normally requires many years, involving multiple drafts, referee criticism, public a lthe IUPAC hierarchv. This slow comment. and a ~ ~ r o vbv process is the required price for sound nomenclature recommendations that find utilitv and acee~tabilitvamong chemists throughout the world:
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Recent Projects Proieets recentlv wm~letedor in fmal stages include the ~ a & c a l sand Ioils, ~ u s e i - ~Nomenin~ a-coxkention clature. Phane Nomenclature. and A Glossarv of Stereochemical Terms. The most important recent broject is a comprehensive guide to organic nomenclature, due for publication in 1992 (4). The Guide, which makes significant chanees and extensions in several areas, is intended as a compibment to the Blue Bmk, not a replacement of it. Guide recommendationfi of special significance to U. S. of locants immediately bechemists include: (a) fore the suffix designating a characteristic group (See Structure 3) and before the enelyne ending designating a doubleltriple bond (Structure lb);(b) the option of naming alkyl substituents more systematically, as exemplified by the name butan-2-yl for the group called sec-butyl or 1methylpropyl in the Blue Book (see Structure 3).
(1li
Major Project-Preferred Names Just underway is a major project of great complexity called Preferred Names. Its Dumose is to ~rovidea rieorous protocol to generate a single approved name for each substance. In such s ~ e c i a situations l a s reeulation of trade, patent law, and emergency hazard management t to deal uniaue names are necessam to ~ e r m inonchemists un&biguously with chemicai substances. This project will helo set the staee for com~uter-assistedgeneration of names,khich is likzy to be tge next major aivance in nomenclature. The Commission has added computer experts to its membership and is closely monitoring a prototype
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CH3-CH,-CH--CH3 3 Blue Bwk: 3-sec-Butyl-2,4-pentanedione,or 3-(1-~ethylprop~l)-2,4-pentanediane Guide: 3-(ButanPyl)pentane-2,ddione
computer-based system called AUTONOM (12). This system, under development a t the Beilstein Institute, generates a systematic name from structural input in a few seconds using only a PC. Nomenclature Progress over the Past 100 Years Remarkable progress in organic chemistry over the past 100 vears has been facilitated ereatlv " bv " the clear communication provided by sound principles of nomenclature. The rules for naming organic substances devised by an eminent international group of chemists a t Geneva in 1892 have been expanded and improved over the years by scores of dedicated chemists from many countries. Organic nomenclature begins its second hundred vears, with the promise that under the vigorous leadersGp of CNOC the increased Dace and so~histicationof organic research will be continiously matched by appropriate advances in nomenclature.
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Acknowledgment The author thanks James G. Traynham for helpful discussions and for design of the cover for this issue. Travel support for the author's participation in CNOC meetings was provided generously by the Council on Faculty of Millikin University. Literature cited 1. VerLade, P E.A History of the N m n c l a f u r r of O ~ @ ~ nChemistry: ie D. Reidel Pub IishineCo.: Boston. 1985. 2. h a t & , H.E . ~ o i u r e1892.46.5659. 3. Rigaudy, J.; Curran, C. E., Eda. Nomonelatvm of OIgonie Chemistry. Sections A, 8, C, D, E, I? ond H; PergergergnRess:NewYork, 1919. 4. A Guido Lo tho Us. ofIUPACNomnclofurefor Ornanie Chemistry: in mess, 1992. 5. Baeyer,A. Chem BOP lsW.33,3171-3175. 6. Bouveault,L.C. R.Assoc FI Aduonmmenf Sci.,26th Sessim; SsiotiEtienne 1 M , 1.24&264. 7. Patterson,A.M.;Cuman,C.E.J A m . Chem. Soe 1917,39,162-1638, 8. Patterson.A. M.; J A m Chom. Soc. 19%,47,543. 9. The Nomingand Indering of Chemical Compounds by ChemftalAbatmcls (Chem. Absfr l W ,39,5967-59751. 10. IUPACNomclofureofO~g~gieChpmist'y,Soe~lalalaA~ndB, 1st ed.; Buttetworths: landon, 1958. 11. hwU,W.H.PunAppl. Chem. 1988.60,U95-1401. 12. (a) Wisnie-ki, J. L. J Chem. In6 Compuf.Sd.lSB0,30.324332;(h) Geehela, L.; hwson,A. J.; Wianie-ki, J. L. J. Chem. Info Comput. Sci lSB1,31,216225. ~
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