Which of the following compounds is a structural (constitutional) isomer of 2-methylbutane?A) pentaneB) butaneC) penteneD) cyclopentaneE) cyclobutane

The structural (constitutional) isomer of 2-methylbutane is pentane.

Here's why:

Structural isomers are compounds that have the same molecular formula but different physical structures.

2-methylbutane has the molecular formula C5H12.

Looking at the options:

A) Pentane also has the molecular formula C5H12, but a different structure, making it a structural isomer of 2-methylbutane.

B) Butane has the molecular formula C4H10, so it's not an isomer of 2-methylbutane.

C) Pentene has the molecular formula C5H10, so it's not an isomer of 2-methylbutane.

D) Cyclopentane has the molecular formula C5H10, so it's not an isomer of 2-methylbutane.

E) Cyclobutane has the molecular formula C4H8, so it's not an isomer of 2-methylbutane.

So, the correct answer is A) Pentane.