CHEM 121 glossary

Heteroatom

Any atom in an organic molecule other than carbon or hydrogen, most often O, N, S or a halogen. In a skeletal structure heteroatoms are always written, together with any H atoms on them; only carbon gets implicit hydrogens.

Highlighted atoms (shaded band)

Ethyl acetate: the two oxygen heteroatoms are written; the carbons are not.

Example

Ethyl acetate, $\ce{CH3COOCH2CH3}$ , has two O heteroatoms: the C=O oxygen and the chain –O–, which is drawn without H because it has none. In ethanol the O is written as OH.