Paradox t-shirt

Leonard wears a t-shirt with a 'paradox' molecule on it.

The molecule on the [shirt] is a "Paradox" - why? D,O and X represent atoms and molecule fragments, while "Para" represents the way they are connected. Therefore we call this molecule "Paradox". The hexagonal structure in the center of the Paradox molecue is a Benzene ring. The position of the groups (represented by letters) connected to the benzene ring is described using the Greek words "Ortho","Meta" and "Para". "Orthos" means straight, upright, correct. Groups in adjacent positions on a Benzene ring are referred to as being "Ortho" one to the other. "Meta" means "after". Groups that are separated by one position are said to be "Meta" one to another. "Para" means "beside". Groups on opposite sides of the benzene ring are referred to as being "Para" one to the other.

This explanation is used by permission from the MolecularShirts website: http://www.molecularshirts.com/