Question

Which of these is not an isomer of (the straight-chained) `"C"_6"H"_14` (hexane)?

Answer 1

The correct answer is B.

Explanation:

All the molecules have the formula `"C"_6"H"_14`.

However, B is not an isomer of hexane.

That structure is hexane.

Answer 2

All isomers of one compound must have the same chemical formula. So, if it doesn't have 6 carbons and 14 hydrogens, it's out. Unfortunately, they all are valid under that condition.

The only differentiating factor then, is whether it is a different atomic connection with respect to:

`"H"_3"C"-"CH"_2-"CH"_2-"CH"_2-"CH"_2-"CH"_3`

which is the straight-chained structure.

`bb(B)` is the one that is the straight-chained structure (rotate the right end `90^@` counterclockwise), so it's not different from the original.

(It technically is an isomer, but it is not an isomer of itself. Not the best-worded question.)