Development of Systematic Names for the Simple Alkanes

(I compiled this page partly because I was embarrassed in class by not knowing their etymology.
It is not a crucial part of Chem 125 and is presented for your amusement and enrichment.)

The nomenclature of organic chemistry is both a tool and a symbol of the chemist's mastery over molecules of modest size. Lavoisier set a high standard in 1789 when he suggested that a compound's name should clearly describe its nature. Of course one had to know something of its nature before being able to give it an appropriate name, and the nature had to be simple enough to name. Otherwise only a nickname was possible, perhaps one describing its source, or color, or use. Such a name might be useful, unambiguous, and unique, but it could never be systematic in a way that would allow it to conjure up the structure for a chemist who had not previously encountered it. The complexity of very large organic molecules, and practically all large biochemical molecules, prevents their nomenclature from becoming usefully systematic and encourages the use of nicknames, leaving communication of structural detail to pictures. For most large molecules the power of organic nomenclature for aiding thought and communication remains a dream.

Organic structure was a meaningless concept until 1858 when Couper and Kekulé proposed valence. Over the next three decades a large number of constitutional structures were determined, and there arose a clear need for a structure-based system of nomenclature. In 1892 the International Congress of Chemists, meeting in Geneva, approved a report on the subject that had been developed over the three years since the previous meeting of the Congress in Paris. This "Geneva Nomenclature" contained the core of the system that, as IUPAC nomenclature (International Union of Pure and Applied Chemistry), remains in use after more than 100 years and is constantly being updated to deal with the latest challenges in structural chemistry. Much of the financial support for this effort is supplied by industries affected by the patent and legal implications of how we name molecules.

The Geneva system is based on identifying hydrocarbon chains, most of which are named systematically with a Greek numerical prefix denoting the number of carbons and the suffix -ane if they contain no multiple bonds. It is instructive to see how the unsystematic names for the simplest chains developed, because it underlines how small the community of academic chemists was, and it reinforces what we know about the development of organic chemistry. In chemical as in human families, names provide a link to our heritage.

Two ancient word roots entered into the naming of simple hydrocarbons. One was HYLE from the Greek υλη (üleh, where the ü is pronounced as in German or as in "lune" in French) meaning wood or matter. Aristotle and other Greek philosophers had used υλη πρωτυ (üleh proteh) to denote the fundamental matter of the universe from which all things are made. When in 1815 William Prout had the idea that all elements were composed of hydrogen atoms, he followed the Greek lead by calling this atom protyle.

The other is ETHER the root of which (αιθο, etho) means to shine and was related in the ancient tongues to fair weather, clear sky, and the space beyond the clouds. Already in the 1700s it was firmly associated with the colorless, light, volatile liquid formed by treating alcohol with acid. "The subtile fluid, prepared from vinous spirits with the vitriolic acid, called by the chemists æther..." (1757) was of course what we call diethyl ether. As additional clear, volatile liquids were discovered, they also came to be called ethers.

The first 19th Century coinage related to the simple hydrocarbons arose in 1826 when Michel Eugène Chevreul, who was purifying fatty acids (and would propose using melting point as a criterion of purity) gave the name BUTYRIC acid to the acid from rancid butter, using the Latin root butyrum for butter and Lavoisier's -ic suffix to denote acid.

Michel Chevreul

Chevreul also discovered and named creatine,
which has been faddish as a body-building
dietary supplement - Note that he lived
to the age of 103, presumably without
consuming any dietary supplements.

Chevreul is said to be the
only centennarian scientist
who was born before 1864.

In 1832, when Liebig and Wöhler discovered the benzoyl radical, they proposed the suffix -YL for naming radicals to evoke the sense of ultimate matter or hyle. The German pronunciation of the suffix is much closer to the Greek "üleh" than is the American "uhl" or the British "isle".

In 1834 Liebig proposed that ether was based on the radical he called ETHYL, using as root the word ether and the suffix -yl. Remember that the archetypal ether was diethyl ether

In the next year, 1835, Dumas proposed the METHYLENE radical (CH2) from Greek μεθυ (methü) for wine and hyle for wood (hyle's other meaning), with -ene, a Greek feminine patronymic tossed in to give the meaning "daughter of the spirit of wood" (remember that the formula of wood alcohol is CH3OH or for Dumas CH2 H2O). By 1840 the French chemist Regnault was already calling the CH3 radical METHYL, where the meth part comes from Dumas's methylene and the yl does double duty representing both the yl in methylene, where it means wood, and the -yl radical suffix, where it means matter.

In 1847 Dumas named the three-carbon acid PROPIONIC, from Greek proto (πρωτο, first) and pion (πιον, fat) again with the Lavoisier -ic suffix. The physical properties of the smaller acids, formic (from Latin formica, ant) and acetic (from Latin acetum, vinegar) were not considered fat-like. By 1850 the three-carbon radical was being referred to as PROPYL. (Click for Dumas's rationale.)

The name ether was being used widely for clear, volatile liquids, so in 1848 Leopold Gmelin proposed that nomenclature achieve greater specificity by naming those "ethers" that come from an acid and an alcohol, as ESTER, a sort of contraction of essig and ether based on the archetypal essigäther (German for vinegar ether, our ethyl acetate).

By 1852 the olefiant (oil making) gas C2H4 was being referred to as ETHYLENE, presumably because it is related to ethyl C2H5 in the same way as methylene CH2 is related to methyl CH3, i.e. "daughter of ethyl", even though methylene first meant "daughter of wood alcohol" not "daughter of methyl".

By 1866 the Greek feminine patronymic suffixes -ene, -ine, and -one were in scattered use as hydrocarbon suffices meaning "daughter of this or that", so August Wilhelm Hofmann, a former Liebig student who had a way with languages, suggested systematizing nomenclature by using the whole sequence of vowels a e i o u to create suffixes -ane, -ene, -ine (or -yne), -one, -une, for the hydrocarbons CnH2n+2, CnH2n, CnH2n-2, CnH2n-4, CnH2n-6. Only the first three caught on for naming hydrocarbons with single, double and triple bonds. Hofmann's "quartone" and "quartune" never made it. One reason is that -one was already being used since 1839 for acetone (" daughter of acetum", because it was synthesized by heating vinegar, the previous name had been "pyro-acetic spirit") and since 1848, through the Germanized version of acetone Keton, as the generic suffix for, and the functional group name of, the ketones.

In 1866 Hofmann suggested that the first four alkanes be called methane, ethane, propane, quartane. By the mid-1870s Butane, from butyl, from Chevreul's 1826 butyric, had overcome quartane, and Hofmann's other Latin numerical prefixes had been replaced by Greek ones, except that the Latin non for nine was never replaced by Greek ennea. Perhaps this is because enneaene does not trip as lightly off the tongue as nonene.

August Wilhelm Hofmann

Click to read Hofmann's original scheme

Greek Feminine Patronymic Suffix

Many feminine names in Greek end in -ene (ηνη, -ine (ινη), or -one (ονη) meaning "daughter of". Here are some examples:

-ene Esmene (Ισμηνη) : daughter of wisdom (ισμη = wisdom)

-ine Mersine (Μυρσινη) : daugher of myrtle (μυρτια = myrtle)

-one Hermione (Ερμιονη) : daughter of Hermes (Ερμησ) ; Antigone (Αντιγονη): daughter that goes against her parentage (αντι, anti = against ; γενια, genia = generation) ; Persephone (Περσεφονη) : daughter of Perseus (Περσεασ) ; Dione (Διονη) : daughter of Zeus (Διασ, Dias = Zeus)

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Much of the information for this page came from the Oxford English Dictionary or the fascinating book on the source of common names in organic chemistry Alex Nickon and Ernest F. Silversmith, The Name Game, Pergamon Press, New York 1987. The postage stamp is reproduced from E. Heilbronner and F.A. Miller, "A Philatelic Ramble through Chemistry", Verlag Helvetica Chimica Acta, Basel (1998). The Greek roots and examples were kindly supplied by Sotiria Palioura, a Chem 125 student. I thank Anthony L. Almada for pointing out the following reference on centennarian scientists: S. Sri Kantha, Medical Hypotheses, 57, 750-753 (2001).

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copyright 1999 J.M.McBride