## A Russian Internet Linguistics Olympiad

I just discovered a Russian Internet Linguistics Olympiad. Even though most linguistics problems are not translatable, this time we are lucky. My favorite problem from this Olympiad is related to chemical elements — their names in Russian have the same logical structure as in English. Keep in mind, the problem doesn’t assume any knowledge of chemistry. Here is the problem:

The formulae for chemical elements and their names are given below in mixed order:
C3H8, C4H6, C3H4, C4H8, C7H14, C2H2;
Heptene, Butine, Propane, Butene, Ethine, Propine.

1. Match the formulae with their names. Explain your solution.
2. Write the names of the elements with the following formulae: C2H4, C2H6, C7H12.
3. Write the formulae for the following elements: Propene, Butane.
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1. #### Anonymous Rex:

I believe that the ending -yne is (significantly) more common than -ine. I can’t find the latter attested very much online.

2. #### ano:

An attempt, by someone who remembers no chemistry:

We can classify the names as follows:
* -ine versus -ene versus -ane: {Butine, Ethine, Propine}, {Heptene, Butene}, {Propane} (sizes 3, 2, 1)
* Prefixes: {Butine, Butene}, {Propane, Propine}, {Heptene}, {Ethine} (sizes 2, 2, 1, 1)

We can classify the formulae as follows:
* Number of Cs: {C3H8, C3H4}, {C4H6, C4H8}, {C7H14}, {C2H2} (sizes 2, 2, 1, 1)
* Number of Hs: {C3H8, C4H8}, {C4H6}, {C3H4}, {C7H14}, {C2H2} (sizes 2, 1, 1, 1, 1). Er, does not correspond to anything, so we’re stuck here.

Ok, let’s cheat and resort to using linguistic knowledge (it’s a linguistic olympiad anyway), namely that “heptene” suggests something to do with the number 7. So by making the guess (based on sizes) that prefixes correspond to number of Cs, we get:
Heptene = C7H14
Ethine = C2H2
{{Butine,Butene},{Propane,Propine}} = {{C3H8,C3H4},{C4H6,C4H8}}.

We need to figure out what the suffixes stand for. The *number* of Hs hasn’t been useful, so let’s try *ratios*. For “Heptene” with an “-ene”, the ratio of Hs to Cs is 2. Among the undetermined ones, there’s only one “-ene” (Butene) and only one with a ratio of 2 (namely C4H8), so let’s map them:
Butene = C4H8
Butine = C4H6
{Propane, Propine} = {C3H8,C3H4}

Since the number of Hs is always even, we should probably look at *half* the number of Hs. And since the number by itself wasn’t useful, let’s compare half the number of Hs to the number of Cs:
Heptene = C7H14 (7,7)
Butene = C4H8 (4,4)
Ethine = C2H2 (2,1)
Butine = C4H6 (4,3)
{Propine, Propine} = {C3H8 (3,4), C3H4 (3,2)}
Since both -ine’s we know have the second coordinate as one less than the first (and there’s exactly one unknown -ine name and exactly one such unknown formula), that’s probably what *-ine* means.
Propine = C3H4 (3,2)
Propane = C3H8 (3,4) So -ane means #H/2 = #C + 1.

Summarizing our knowledge so far:
Prefixes:
Hept: #C = 7
But: #C = 4
Eth: #C = 2
Prop: #C = 3
Suffixes:
ene: #H/2 = #C
ine: #H/2 = #C – 1
ane: #H/2 = #C + 1.

Cool. So C2H4 (2,2) = Ethene, C2H6 (2,3) = Ethane, C7H12 (7,6) = Heptine, Propane = (3,4) C3H8, Butane = (4,5) C4H10.

3. #### animesh:

Really nice puzzle…and a very logical solution. Loved it!
I approached it similarly…but just remembered C2H6 = ethane from chemistry days….so thought C2H2 must be ethine…although I am pretty sure (now googled it!) there is no such thing as ethine…so well that was my cheat!

4. #### GW:

Those are molecules, not elements!

5. #### Tanya Khovanova:

I apologize.

Seems I consulted a wrong website for spelling of chemical names. “ine” should be replaced with “yne”. The problem works anyway. Also, “chemical elements” was a direct translation for Russian.

6. #### Daniel McArdle:

Let’s see, looks like Greek prefixes to me, which is lucky as I was terrible at chemistry.

Ah, Hept-\$. That’s got to be 7 as in heptagon. Turns out that was all I needed!

I got the same answers as ano above so I think I am correct. I also had no recollection that -ines did not exist, (absence of evidence not being…etc.) and the problem worked out okay.

Hurrah! I did so poorly at my first problem on here, I am relieved.

Thanks for sharing Tanya – a cool propblem indeed!