Question

question 12 (1 point)
which of the following is not a constitutional (structural) isomer of pentane?
2 - methylbutane
2,2 - dimethylpropane
cyclopentane
all of the above are constitutional isomers of pentane.
question 13 (1 point)
what is the classification of each labeled carbon atom in this structure?

Explanation:

Constitutional isomers have the same molecular formula but different connectivity of atoms. Pentane has the molecular formula $C_{5}H_{12}$. 2 - methylbutane and 2,2 - dimethylpropane have the same molecular formula as pentane and different connectivities. Cyclopentane has the molecular formula $C_{5}H_{10}$, so it is not a constitutional isomer of pentane.

Answer:

C. cyclopentane