Hofmann's Proposal for Systematic Nomenclature of the Hydrocarbons

"On the Action of Trichloride of Phosphorus on the Salts of the Aromatic Monamines"

By A. W. Hofmann, LL.D., F.R.S., &c.

received March 3, 1866
Proc. Roy. Soc. London, 15, 55-62 (1866)

Footnote on pp. 57-58

The term ethenyl proposed for the group C2H3, which in the new compound functions with the value of 3 atoms of hydrogen, is framed according to a sysem of nomenclature to which I have occasionally resorted, in the boundless confusion of names now prevailing in organic chemistry, as a means of communication with my pupils. Perhaps this system is capable of further development.

It is a peculiar feature of the development of modern chemistry that more than ever before is felt the necessity of grouping the organic compounds round the hydrocarbons. The question therefore may be said to reduce itself to the discovery of a good principle of nomenclature for the compounds of hydrogen and carbon. Many attempts have been made in this direction, as yet without any acceptable results.

For the purpose of framing my names I fuse the method originally employed by Laurent with the principle proposed by Gerhardt, and more or less adopted by his successors. [I have not yet located these sources. Charles Gerhardt's four volume Traité de Chimie Organique (1853-1856) calls methane "hydrure de méthyl" (methyl hydride) or "gaz des marais" (marsh gas). But in the preface he writes," I have held to the customary nomenclature, preferring to modify the sense of the names rather than their form; I have even sacrificed my notation in order to keep the previous formulae, so as better to demonstrate by example the extent to which use of these latter is irrational, and to leave to time the responsibility of carrying out a reform that chemists have not yet generally adopted."]

An example will illustrate my mode of proceeding. Let us consider the most important of all the series of hydrocarbons, the homologues of marsh-gas. All the members of this series I make terminate in ane, distinguishing the order of succession by prefixing the first syllable of the Latin numeral corresponding to the number of carbon atoms in the molecule. From this rule the first three members of the series are conveniently excepted, their names having been so long in use as to render it desirable to embody them in the system. [Note that we have subsequently adopted Greek roots, except that non is retained for nine rather that the Greek ennea.]

By the removal of 1 atom of hydrogen from the hydrocarbon, the latter ceases to be a saturated compound, and the remaining group of atoms becomes univalent. The termination yl now takes the place of ane. A second atom of hydrogen is removed, the group becomes bivalent and now terminates in ene; a third hydrogen atom is separated, the group is again raised in value by one becoming in fact trivalent, and acquires the termination enyl. By the removal of the fourth and fifth atom of hydrogen the quadrivalence of the residuary group again increases, the groups becoming quadrivalent and quintivalent, and acquiring the terminations ine and inyl, &c.

According to this principle the following names are formed:

Methane, (C H4

Sextane, (C6 H14

Ethane, (C2H6

Septane, (C7 H16

Propane, (C3H8

Octane, (C8 H18

Quartane, (C4H10

Nonane, (C9 H20

Quintane, (C5H12

Decane, (C10H22

And further:

Methane, (CH4

Ethane, (C2H6

Propane, (C3H8

Quartane, (C4H10

Methyl, (CH3)'

Ethyl, (C2H5)'

Propyl, (C3H7)'

Quartyl, (C4H9)'

Methene, (CH2)''

Ethene, (C2H4)''

Propene, (C3H6)''

Quartene, (C4H8)''

Methenyl, (CH)'''

Ethenyl, (C2H3)'''

Propenyl, (C3H5)'''

Quartenyl, (C4H7)'''

Ethine, (C2H2)iv

Propine, (C3H4)iv

Quartine, (C4H6)iv

Ethinyl, (C2H) v

Propinyl, (C3H3) v

Quartinyl, (C4H5) v

Propone, (C3H2)vi

Quartone, (C4H4)vi

Proponyl, (C3H) vii

Quartonyl, (C4H3) vii

Quartune, (C4H2)vii

Quartunyl, (C4H) ix

This is not the place to develope this subject further. The short notice I have given must suffice. A superficial examination of the system shows, however, how large a number of groups of atoms may be clearly and succinctly expressed in it.

It appeared convenient to submit the plan to a provisional test by framing some of the names required for the substances which were furnished by the above experiments.

Bodies containing oxygen may be as simply nominated according to this plan.

The acid derived from ethylic alcohol is ethoxylic acid (acetic acid), the first acid corresponding to ethenic alcohol would be ethoxenic acid (glycolic acid), the second being ethdioxenic acid (oxalic acid). We speak of the oxylic, oxenic, and dioxenic acids of a series, of the quartane series, for instance, and any one would understand that by these expressions are meant butryric, butylactic, and succinic acids.

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