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.  Observe prefixes.  Hept is the prefix for the number 7, and I thus postulate that Heptene is associated with C7H14 as this is the only molecule with 7 C's or H's.

There are two molecules starting with Prop. (Propyne, Propane)There are two molecules starting with But. (Butyne, Butene)There are 2 molecules with 3 C's, and 2 molecules with 4 C's.There is only 1 molecule with 2 C's.  Therefore Ethyne matches with C2H2.

Next observe there are three suffixes:  -ene, -yne and -ane.

I postulated that Heptene is associated with C7H14.  Here 14 is twice 7, so I assume this is the rule for the suffix -ene.

There is one other molecule with suffix -ene.  This is Butene.  Also C4H8 is the only structure where H's are twice C's.  Therefore Butene = C4H8, and the prefix But- refers to the 4 C's.  There is only one other molecule with 4 C's, which is C4H6.  Therefore C4H6 = Butyne.

Therefore -yne refers to the combination where H = 2C - 2.

Finally Prop- must correspond to 3 C's.  Propyne must be C3H4.  Leaving Propane = C3H8.

 

Edited on August 16, 2012, 10:11 pm

Posted by Chris, PhD on 2012-08-16 11:19:47