A disclaimer: This problem does not assume any knowledge of chemistry:


The formulae for chemical molecules and their names are given below in mixed order:
C₃H₈, C₄H₆, C₃H₄, C₄H₈, C₇H₁₄, C₂H₂;
Heptene, Butyne, Propane, Butene, Ethyne, Propyne.

1.Match the formulae with the names.
Explain your solution.

2.Write the names corresponding to the following formulae: C₂H₄, C₂H₆, C₇H₁₂.

3.Write the formulae for the following molecules: Propene, Butane.

Source: Russian contest

1.

Prefixes:

There's one "hept-" (which also sounds like it has to do with seven).

There are two "bu-"'s, and two "pro-"'s, as well as a single "eth-".

Suffixes:

There are two "-ene"'s, three "-yne"'s and one "-ane".

Carbon numbers:

Two 3's, two 4's, one 7 and one 2.

Hydrogen numbers:

Two 8's, one 6, one 14, one 4 and one 2.

Apparently there's no direct relation between the hydrogen-atom counts and either suffixes or prefixes.

We can do something with the carbons, however. Hept is so 7-like, I'd say:

Heptene is C7H14.

Perhaps -ene means there are twice as many H's as C's. If that's the case then:

Butene is C4H8.

If that's the case, then bu- would be associated with 4 carbon atoms, and fortunately there are two bu-'s and two formulae with four carbon atoms, so:

Butyne is C4H6.

That leaves Propane, Propyne and Ethyne to be matched against C3H8, C3H4 and C2H2.

Well, just based on carbon-atom numbers their uniqueness equates:

Ethyne is C2H2.

We're left with Propane and Propyne to be somehow matched with C3H8 and C3H4. Neither has the hydrogen-atom count match the carbon-atom count as in Ethyne.

But, following from Chris's idea, together with what I noted in the reply thereto, Propyne would be C3H4 and Propane C3H8.

2. If the above is correct insofar as it goes, C2H4 would be Ethene. C2H6 would be Ethane, C7H12 would be Heptyne.

3. Propene = C3H6; Butane = C4H10.

Posted by Charlie on 2012-08-16 11:59:37