In functional groups, how can you distinguish between hexylamine (C6H13NH2) and aniline (C6H5NH2)?

Answer 1

You would want to look at the degrees of unsaturation (DOU) from the listed formulas, which is going to tell you if and how many pi bonds or rings are present. For each pi bond or ring, you have 1 degree of unsaturation (or you can say you are deficient 2 total hydrogen atoms that would be present on a saturated molecule). The formula for DOU is (2(n)+2-H+N-X)/2, where n is the number of carbon atoms in your molecule, H is your number of hydrogen atoms, N is any nitrogen atoms present, and X represents any halogens. So, two times the number of carbons, plus two, minus any hydrogens and halogens and add any nitrogen atoms present. Structures, which have benzene rings present are generally pretty easy to identify because they will have 4 or more degrees of unsaturation (3 pi bonds and 1 ring). The hexylamine should only have none. Also, C6H5 is almost always going to be the formula for a benzene ring.