What is a polycyclic aromatic hydrocarbon?
The place to start is with the simplest PAH: benzene. It’s a hydrocarbon because it consists entirely of hydrogen and carbon (C6H6). The carbon atoms are arranged in a hexagonal structure with one hydrogen atom attached to each carbon atom. Because benzene has only one ring, it’s not really polycyclic (does this make it monocyclic a MAH?). Each carbon atom has four electrons to share. One goes to the hydrogen atom, and one each to the two neighboring carbons. This leaves one to share with one of its two neighboring carbon atoms, which is why the benzene molecule is drawn with alternating single and double bonds around the hexagon. But at any time, there’s no way to know which bonds are single and which are double. Many chemists just draw a circle around the inside of the ring to show that there are six electrons floating around. Hydrocarbons with this structure are called aromatic (because they generally stink no kidding!) The electrons float above and below the ring, and the electroma
