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Is there a chemical or historical significance in the fact that 'ethane' is just 'methane' without the 'm'?

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meth vs eth

[OP] Why is '-ethane' in 'methane'?

This is a coincidence.

Methyl is

ultimately from Greek methy "wine" + hylē "wood.

Source: https://www.etymonline.com.

The terminology was created by Dumas and Péligot in 1834 to distinguish wood alcohol from ethanol, and was published first in the French language:

https://gallica.bnf.fr/ark:/12148/bpt6k6569005x/f15.item

Source: https://gallica.bnf.fr/ark:/12148/bpt6k6569005x/f15.item

Ethyl is from

Greek aithēr "upper air; bright, purer air; the sky" (opposed to aēr "the lower air"), from aithein "to burn, shine," from PIE *aidh- "to burn"

Source: https://www.etymonline.com.

Liebig had argued in 1834 that what now is known to be $\ce{-C2H5}$ is a "radical", i.e. a reoccuring group in molecules such as diethyl ether, ethanol and ethyl ethanoate, and gave it the name ethyl.

enter image description here

Source: https://babel.hathitrust.org/cgi/pt?id=uva.x002457887&view=1up&seq=30

Using the ending -yl for both the methyl and the ethyl group is a suggestion by Berzelius from 1835 (the correct atomic weight of carbon was not know yet, so the chemical formulas are off by a factor of two):

enter image description here

Source: https://books.google.com/books?id=1DM1AAAAcAAJ&pg=PA376#v=onepage&q&f=false, see Wikipedia entry on Ethyl group.

methane vs ethane

That these both end in -ane is not a coincidence - all alkanes end in -ane. As stated in M. Farooq's answer, this nomenclature was introduced by A. W. Hofmann in 1865.

Acknowledgements

Maurice's answer inspired me to find the first work by Dumas that led to the methyl terminology. I have edited my answer to incorporate information from the excellent answers by M. Farooq and Jan and the insightful comments. In trying to figure out the sequence of events in the 1830s, I made use of this account by Frederick E. Ziegler.

References

Dumas, J.-B, Mémoire sur l'esprit de bois et sur les divers composés éthérés qui en proviennent. lu à l'Académie des Sciences les 27 Octobre et 3 novembre 1834, Paris, 1834

Jean-Baptiste Dumas et Eugène Péligot, Mémoire sur l’Esprit de Bois et sur les divers Composés Ethérés qui en proviennent, Annales de chimie et de physique, 58 (1835) p. 5-74

Justus Liebig (1834) "Ueber die Constitution des Aethers und seiner Verbindungen" (On the composition of ethers and their compounds), Annalen der Pharmacie, 9 : 1–39

Jacob Berzelius, Årsberättelsen om framsteg i fysik och kemi [Annual report on progress in physics and chemistry] (Stockholm, Sweden: P.A. Norstedt & Söner, 1835), p. 376

A. W. Hofmann 1866, in Monatsbericht der Königl. Preuss. Akad. der Wissenschaften zu Berlin, 1865 653

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    $\begingroup$ Karsten, You are making it more and more like a Journal of Chemical Education article. Worth thinking about it a formal article. $\endgroup$ – M. Farooq Dec 9 '20 at 0:21
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It’s worth pointing out how much of a coincidence it is that the modern ethyl and methyl are identical but for one letter. While Karsten already outlined the general bits of etymology behind these two words one can go a little bit deeper and find out how different they are.

Methane’s derivation traces itself back to Greek μέθυ (méthy) and ὕλη (hýlē with a long e) via the intermediate methyl. As the first component included Greek epsilon (ε), it was rendered e in all languages that are based on the Latin alphabet.

Ethane can be traced back directly to ethyl and was introduced to chemistry via German. However, when introduced the German spelling was actually Äthyl, sometimes (especially in the day) rendered Aethyl. The German letter ä represents a sound similar to the vowel in English bear – more open than the e spelling (which corresponds approximately to English here) would suggest. The German spelling changed sometime during the last century and nowadays the pronunciation of Ethyl and Ethan has the closed e-type vowel (while older non-chemists might still write ä and pronounce it with the more open vowel).

The Ä (or Ae) spelling in German was actually systematic, as it traces back to Latin aethēr that already featured ae; practically all Latin ae combinations are pronounced as ä in modern German. Latin borrowed this term from Greek (hence the th) where it was written αἰθήρ (aithḗr). Both the Greek and Latin terms were probably originally pronounced with an /ai/ diphthong (approximately as in high).

The term ethyl may have also entered English more directly, being derived from the already established and borrowed term ether (which came to English via French as a direct descendent of Latin aethēr; French had already dropped the leading a in spelling). The corresponding German term used to be written Äther or Aether exclusively. Nowadays, the chemical term is only Ether while the non-scientific term may be either but is more likely to remain Äther.

Thus, the two terms only began sharing most of their letters by accident and in late stages of their etymology; and had German remained a primary language of chemistry we might still be writing aethane or some derivative.

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    $\begingroup$ In the word-origin of methane and ethane, you have to consider both French and German as important languages of chemistry in the 1830s, see the edit to my answer. $\endgroup$ – Karsten Theis Nov 18 '20 at 12:42
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    $\begingroup$ @KarstenTheis In all honesty, I just didn’t go back at all with methyl because wherever one would go the form would be written with e. It’s ethyl that’s interesting because it did not develop from Greek epsilon (or eta). $\endgroup$ – Jan Nov 18 '20 at 13:46
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    $\begingroup$ In English, "ethyl" is still pronounced with a sound closer to "ä". (More like an "eh", actually, because most English speakers are also lazy about pronunciation.) It is not the same vowel sound as is used in the English word "here". ("Ether", on the other hand, is pronounced with the same vowel sound as "here".) $\endgroup$ – Cody Gray Nov 18 '20 at 22:53
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    $\begingroup$ @CodyGray Actually, both pronunciations exist according to Wiktionary and I believe I heard the closed e more often. But that’s probably irrelevant for a number of reasons including English spelling and the letter e being a written form for both. I tried not implying that I was talking about the English pronunciation anywhere. $\endgroup$ – Jan Nov 19 '20 at 11:09
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For word-history lovers...It is all gifted from the German language. Hope that satisfies the OP's curiosity.

The suffix -ane, was chosen by a chemist and it was not random or accidental. It was a well thought-out suggestion by Hofmann.

Current sense.

In sense 2 after German -an (A. W. Hofmann 1866, in Monatsbericht der Königl. Preuss. Akad. der Wissenschaften zu Berlin, 1865 653, translated by the author in quot. 1867). In this passage, Hofmann proposes a series of five such suffixes, one with each vowel (German -an , -en , -in , -on , -un ), and the systematic application of these to specific types of hydrocarbons, or their analogues. Of these (and their English equivalents), only -an -ane suffix2, -en -ene comb. form, and -in -ine suffix5 were adopted by others. As influences on his nomenclature, Hofmann cites (in the same paper) A. Laurent (compare -ene comb. form) and C. Gerhard (compare discussion at -ol suffix and -one suffix).

Methane

Origin: Formed within English, by derivation; modelled on a German lexical item. Etymons: meth- comb. form, -ane suffix. Etymology: < meth- comb. form + -ane suffix, after German Methan (A. W. Hofmann 1866, in Monatsbericht der Königl. Preuss. Akad. der Wissenschaften zu Berlin, 1865 653).

Ethane

Etymology: < eth- comb. form + -ane, after German Aethan (A. W. Hofmann 1866, in Monatsbericht der Königl. Preuss. Akad. der Wissenschaften zu Berlin, 1865 653; also Äthan and (now usually) Ethan).

Ref: Oxford's Unabridged Dictionary (behind subscription).

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    $\begingroup$ @KarstenTheis, OED traces back to Swedish work (cf 1835 French), same year. Origin: A borrowing from German. Etymon: German Methyl. Etymology: < German Methyl (F. Wöhler 1836, in Jahres-Bericht über die Fortschritte der physischen Wissensch. 15 381), shortened < Methylen methylene n., after Swedish metyl (Berzelius 1835, in Årsberättelser om vetenskapernas framsteg, afgifne af Kongl. Vetenskaps-Academiens embetsmän 376), itself shortened < metylen methylene n., after etyl ethyl n. (compare -yl suffix). Compare French méthyle ( A. J. L. Jourdan tr. Berzelius Traité de chim. (1839) III. 403). $\endgroup$ – M. Farooq Nov 18 '20 at 12:48
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    $\begingroup$ Your reference is from 1835. Not sure who published first. $\endgroup$ – M. Farooq Nov 18 '20 at 12:51
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    $\begingroup$ Dumas gave two talks at the French Academy of Sciences in 1834, and subsequently published with Péligot in 1835. I think the work by Berzelius is an annual report of progress in science to the Swedish crown. I added more references to my answer. $\endgroup$ – Karsten Theis Nov 18 '20 at 14:50
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    $\begingroup$ This seems like only a partial answer (and arguably the less important part, at that). Good answers on Stack Exchange are generally meant to be complete, or at least to explicitly acknowledge any intentional omissions. I feel this answer would be significantly improved if you added at least a brief mention of the origins of the meth- and eth- roots, even if you choose not to go into as much detail about them as some of the other answers have. $\endgroup$ – Ilmari Karonen Nov 18 '20 at 20:24
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    $\begingroup$ @IlmariKaronen I think you are mainly criticizing Oxford's dictionary for not digging deeper. I am glad this answer exists because it contains the origin of the suffixes -ane and friends, something lacking from other answers. $\endgroup$ – Karsten Theis Nov 18 '20 at 21:56
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Yes. It is a prefix and a way to make a distinction for the number of carbon atoms in a molecule as such Meth: 1 carbon, Eth: 2 carbons, Prop: 3 carbons, Βut: 4 carbons, Pent: 5 carbons, Hex: 6 carbons, etc

The next part relates to the number of links between those carbon atoms as such: -an- single link, -en- one double link, -in- one tripple link, -dien- two double links, etc

Finally the suffix goes like this: -ic acid COOH, -cn nitrile, -ale CH=O, -one CO, -ol OH, etc

CΗ3 ― CΗ = CΗ2 : προπ-έν-ιο propane

CΗ3 ― CΗ2― CΗ2 ― CΗ3 : βουτ-άν-ιο butane

CH ≡ C―CH=O: προπ-ινά-λη propinal

Η―CH=O: μεθ-αν-άλη methanol

Η―CΟOΗ: μεθ-αν-ικό οξύ methanic acid

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