1 Origin and Evolution of Organic Nomenclature A l c h e m i s t s frequently assigned names to substances with the intent o f concealing what they were working on from their fellow workers. This attitude has gradually changed throughout the years, so that chemists now strive to reveal their latest theories or discoveries to others either orally or through the printed medium. T o communicate easily with one another, it has been necessary to devise a special language which we call chemical nomenclature (1,2,3,4,5). We expect this nomenclature not only to define a given compound uniquely but to reveal what atoms are present, how the atoms are arranged within the molecule, and chemical relationships with other compounds as well. Chemical nomenclature as we know it today had its beginning when Guyton de Morveau, Lavoisier, Berthollet, and Fourcroy published their "Methode de Nomenclature Chimique" in 1787. Their chief contributions were to indicate in a name the elements and, so far as possible, the relative proportions o f these elements present in a given compound. Names such as alcohol, ether, and succinic acid were included in their recommenda tions although their primary concern was with inorganic compounds. Organic nomenclature really got its start in the 1830's with Berzelius, Liebig, and Wöhler when names such as benzoyl chloride and ethyl iodide were proposed (6). The first effective consideration o f organic nomen clature on an international basis came about i n 1889 when an Interna tional Commission for the Reform o f Chemical Nomenclature was organized. Three years later, 34 of the leading chemists from 9 European countries met and agreed upon what has become known as the Geneva Rules for nomenclature (7). The objective of this group was to provide names suitable for the systematic indexing o f aliphatic organic com pounds. They introduced the following principles which are still con sidered to be of primary importance i n naming aliphatic compounds: (1) the name of the longest chain is taken as the parent name; (2) the presence of a functional or characteristic group o f atoms is indicated by a suffix. They intended to complete the task b y developing rules for naming cyclic compounds, but this never came to pass. In 1911 an International Association o f Chemical Societies was organized. Nomenclature reform was among the subjects considered by this group, but World War I intervened before any recommendations were 1
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made. It is interesting to note that C . I. Istrati of Bucharest, a participant in the Geneva Congress of 1892, published in 1913 what is probably the most extensive treatise (8) on nomenclature ever written (1210 pages). However, this treatise remained hidden from the rest of the world until long after its publication. International cooperation was again initiated in 1920 when the International Union of Chemistry was organized. A t its meeting in Brussels the following year, three commissions were appointed for the "reform of chemical nomenclature": one for organic, a second for inorganic, and a third for biological chemistry. Reports of these commissions were published thereafter in the Comptes rendus de V Union Internationale de Chimie. The Organic Commission published its Defini tive Report (P), consisting o f 68 rules (the so-called Liege Rules), in 1930, and these were supplemented by less extensive reports of the meetings at Lucerne in 1936 and at Rome in 1938. World War II interrupted the work o f the International Union of Chemistry (IUC) and its commissions once more, and nothing further was done until a meeting was held in London in 1947. A t that time, the name of the Union was changed to the International Union of Pure and Applied Chemistry (IUPAC), and the word "reform" was dropped from the names of its nomenclature commissions. Since 1947, the Commission on the Nomenclature of Organic Chemistry of I U P A C has, in the main, confined its efforts to codifying sound practices that already exist rather than working on the origination of new nomenclature. Thus, in the I U P A C Rules, acceptable alternative methods have been recognized where, for various reasons, limitation to a single method of nomenclature appears undesirable or unfeasible. Since 1947 the Organic Commission of I U P A C has published the following sets of Definitive Rules (10, 11, 12, 13): Nomenclature of Organic Chemistry, 1949 Nomenclature o f Organosilicon Compounds Changes and Additions to the Definitive Report Extended List of Radical Names Nomenclature of Organic Chemistry, 1957 Section A . Hydrocarbons Section B . Fundamental Heterocyclic Systems Nomenclature of Organic Chemistry, 1965 Section C . Characteristic Groups containing Carbon, Hydrogen, Oxygen, Nitrogen, Halogen, Sulfur, Selenium, and/or Tellurium. Nomenclature of Organic Chemistry, 1971 Sections A , B , and C (slightly revised)
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Origin and Evolution
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Today, the path of nomenclature rules from the first proposals to acceptance in definitive form by I U P A C can be a tortuous one, and it must be admitted that the elapsed time for the entire operation can sometimes be painfully long. F o r a proposal originating in the United States the procedure is as follows: (1) A n individual or a group of workers in a particular field of chemistry drafts new or revised rules that seem to fit its needs. Such a group may be made up of experts appointed as an ad hoc subcommittee or an established nomenclature committee, or it may not have any official status at a l l In either case a formal report presenting the proposed rules and the reasons why they should be adopted for general use is prepared. (2) The original report is submitted for review, revision (if necessary), and approval by an officially recognized committee on nomen clature such as that of one of the divisions of the American Chemical Society. Currently, the Organic, Inorganic, Polymer, Carbohydrate, and Fluorine Divisions have active nomenclature committees. (3) The report is then reviewed by the American Chemical Society's Committee on Nomenclature. (4) After approving the report, the A C S Committee submits it to the A C S Council for official acceptance on behalf of the Society. (5) Concurrently, committees of the National Research Council's Division of Chemistry and Chemical Technology may review the report and submit it to I U P A C with their comments and recommendations. Alternatively, the report may be submitted to an I U P A C Commission directly, without review by an N R C Commit tee. (6) The appropriate I U P A C Commission considers the report and its proposals along with any others on the same subject submitted rom other sources. Factors such as past and current usage, adaptability to other languages, and the overall potential utility of the proposed rules are considered. Note is also taken of any relevant actions by other nomenclature committees.
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(7) The I U P A C Commission then submits its recommendations to the I U P A C Council for official adoption and publication. It has been found that the time span between Step 1 and Step 7 can be reduced greatly and the quality of new nomenclature rules improved i f simultaneous attacks are made on the problem from all possible points of
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view. This can be accomplished by inviting experts in the field, irrespective of their nationality, and members of nomenclature commit tees or commissions at all levels to review progress reports and final reports of the initiating group or subcommittee at appropriate stages in the development of the new rules. O n the other hand, premature publication of proposed new nomenclature rules without approval of the appropriate committees not only complicates the process leading to the official adoption of those rules but also leads to confusion among chemists and journal editors as to which kinds of names are considered acceptable for use in published reports of research. Ideally, each I U P A C Commission should be the leader in its particular field of nomenclature and should anticipate the needs of chemists throughout the world. Practically speaking, this is quite impossible. N e w compounds in new fields are being reported in the literature every day. Thus, the burden of providing acceptable names for these compounds necessarily falls upon research workers and journal editors and upon abstracting services such as Chemical Abstracts. T o maintain consistency in its indexing, the latter has published a compilation of its nomenclature rules and practices (14, 15, 16) for the use of its own staff and for the guidance of users. A t its own discretion, Chemical Abstracts revises its rules in the light of new I U P A C recommendations as they become available. A t the same time, I U P A C depends heavily on Chemical Abstracts, on Beilstein's Handbuch, and on journal editors for guidance when considering new nomenclature recommendations. Although it is easy to point out many imperfections and inconsisten cies in today's chemical nomenclature rules, a few words about their advantages and virtues are in order. The language of chemistry is said to involve more terms and to be better ordered than the language of any other scientific discipline. A l l of this has come about despite the fact that until 1949 relatively few nomenclature rules had been agreed upon internationally. The acceptance and codification of many new or revised rules by the I U P A C commissions and by other leaders in nomenclature such as Chemical Abstracts and the A C S nomenclature committees have done much towards maintaining clear and useful communications among chemists. Continuation of these efforts will ensure that improved means for describing and identifying chemical composition and molecular structure will be available for use in our published scientific literature and indexes, in the classroom, and on the lecture platform. Literature Cited 1. Patterson, A. M., Cross, E. J., in "Thorpe's Dictionary of Applied Chemistry," 4th
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ed., I. Heilbron et al., Eds., Vol. VIII, pp. 594-620, Longmans, London, 1947. 2. ADVAN. CHEM. SER. (1953) 8. 3. Crosland, M.P., "Historical Studies in the Language of Chemistry," Harvard University Press, Cambridge, 1962. 4. Capell, L. T., Loening, K. L., in "Treatise on Analytical Chemistry," I. M. Kolthoff, P. J. Elving, Eds., Pt. II, Vol. 11, pp. 1-44, Interscience, New York, 1965. 5. Loening, K. L., in "Kirk-Othmer Encyclopedia of Chemical Technology," A. Standen, Ed., 2nd ed., Vol. 14, pp. 1-15, Interscience, New York, 1967. 6. v. Liebig, J., Wöhler, F., Ann. Pharm. (1932) 3, 249. 7. Tiemann, F., Ber. (1893) 26, 1595. 8. Istrati, C. I., "Studiu Relativ la o Nomenclatura Generala in Chimia Organica," Bucuresti Librariile Soced, 1913. 9. Compt. rend. Conf. IUC, 10th, Liege (1930) 57; J. Amer. Chem. Soc. (1933) 55 3905. 10. Compt. rend. Conf. IUPAC, 15th, Amsterdam (1949) 127; Compt. rend. Con IUPAC, 16th (1951) 100 (reprints available from Chemical Abstracts Service, Columbus, Ohio 43210). 11. IUPAC, "Nomenclature of Organic Chemistry. Definitive Rules for Section A, Hydrocarbons, and Section B. Fundamental Heterocyclic Systems," Butter worths, London, 1958; J. Amer. Chem. Soc. (1960) 82, 5545. 12. IUPAC, "Nomenclature of Organic Chemistry. Definitive Rules for Section C. Characteristic Groups Containing Carbon, Hydrogen, Oxygen, Nitrogen, Halogen, Sulfur, Selenium, and/or Tellurium," Butterworths, London, 1965; PureAppl.Chem. (1965) 11. 13. IUPAC, "Nomenclature of Organic Chemistry, SectionsA,B,and C," 3rd ed., The Butterworth Group, London, 1971. 14. "The Naming and Indexing of Chemical Compounds from Chemical Abstracts," Chem. Abstr. (1962) 56, 1N, 15. "Selection of Index Names for Chemical Substances," Chem. Abstr. (1972) 76, Index Guide. 16. "Chemical Abstracts Service,Chemical Substance Name Selection Manual for the Ninth Collective Period," Chemical Abstracts, 1972.
