Question

Identities of the components in a mixture may be determined by a technique called spiking. Suppose you had run a gas chromatogram onyour product and had thendeliberately added a drop of a knownsample of 3-methylcyclohexene to a drop of your product. What wouldyou expect the new chromatogram to show you?

Answer 1

The dehydration of 2-methylcyclohexanol gives a mixture of 1-methylcyclohexene and 3 methylcyclohexene, with the expectation that 1-methylcyclohexene (the more substitutted double bond) is the major product.

In any case, a GC chromatogram will show you two products, but doesn't tell you anything about their identities, only relative amounts.

So suppose you run a mixture of the two products and see two peaks in a 10 : 1 ratio (as an example). Then, you add a small drop of 3-methylcyclohexene to the mixture and run it again.

Suppose the new ratio is 3:1. Then, you know that the minor component of the original mixture was 3-methylcyclohexene. If on the other hand the ratio is even larger, say 20:1, then you know that 3-methylcyclohexene was the major product in the original sample.