Heteroatoms Halogens take the place of hydrogens,so add their number to the number of hs Oxygen doesn,'t change the C: H ratio, So ignore oxygen in the formula Nitrogen is trivalent, so it acts like half a carbon HH H - cCNC > HHH H Chapter 7Chapter 7 8 Heteroatoms • Halogens take the place of hydrogens, so add their number to the number of H’s. • Oxygen doesn’t change the C:H ratio, so ignore oxygen in the formula. • Nitrogen is trivalent, so it acts like half a carbon. C H H C H H N C H H H =>