Now, if the compound is relatively simple, you can figure out what the molecular structure of that compound is using your molecular formula. But if the compound is relatively complicated and the molecular formula contains lots of different atoms, then it becomes very difficult at determining what the molecular structure is using only your molecular formula. Now, one tool that we can use to figure out what the molecular structure is is known as degree of unsaturation. So degree of unsaturation, given by the Greek letter omega, gives us the total number of pi bonds and or ring structures for that given molecular formula. And the formula to find degree of unsaturation is given by this guy here. So two N plus two minus x, and the whole thing divided by two, where N represents your number of carbons and x represents your number of hydrogen atoms.