C9H7NO

C9H7NO is the molecular formula that can describe several isomeric organic compounds, rather than a single specific molecule. Because the formula contains one nitrogen and one oxygen, a family of structures with a benzene ring fused to a nitrogen-containing heterocycle is commonly encountered. The exact structure depends on how the atoms are arranged, particularly the position of the carbonyl group and the ring fusion pattern.

The best-known representatives of this formula are the quinolinones, also called quinolin-ones. The two principal isomers are 2-quinolinone (quinolin-2-one) and 3-quinolinone (quinolin-3-one). Both are bicyclic heteroaromatic lactams in which a benzene ring is fused to a pyridinone-type ring. In these compounds, the carbonyl group is located at the 2-position or the 3-position of the quinoline system, respectively. These isomers illustrate how a single molecular formula can correspond to different constitutional structures.

In summary, C9H7NO denotes a formula associated with the quinolinone family as its most prominent example, but the name alone does not specify a unique substance. Determination of the exact isomer requires structural data from synthesis, spectroscopy, or crystallography. The formula has a molar mass of approximately 145.16 g/mol and is used in organic synthesis and medicinal chemistry as a scaffold and intermediate for various derivatives. Related terms include quinoline, quinolinone isomers, and other heterocyclic compounds with the same elemental composition.