Question

Which of the following molecules are chiral?

• A. Methane
• B. Benzene
• C. Ethene
• D. None of the above

Answer 1

The correct option is D None of the above

Visualize the three-dimensional structure of each of the given molecules and see if the mirror image is identical to the original. Alternatively, if the image is superimposable on the original, the original molecule is achiral.
Let us start with methane:

Now draw a plane that passes through a Hydrogen atom (any one) and the central Carbon atom such that the plane splits the methane molecule internally into two mirror images. Like this:

We see that the mirror image is identical to the original. As in, it is superimposable on top of the original molecule. Hence, methane is achiral.
Now, let us take benzene:

Clearly it is a planar molecule. If a molecule is strictly planar, then the molecule could be assumed to in just the one plane. When you take a mirror image of such a compound, the image will be identical to the original molecule. The image will be superimposable.
Similarly, ethane is also planar. You know the drill. So, none of the given molecules are chiral. All are achiral.