C9H9N

C9H9N is the molecular formula for a family of nitrogen-containing organic compounds that together contain nine carbon atoms, nine hydrogen atoms, and one nitrogen atom. It is not a single substance but a set of possible constitutional isomers, meaning many different structures can share this same formula. The formula has a degree of unsaturation of six, which commonly indicates aromatic rings or multiple rings and double bonds in the structures.

A representative isomer is 1,2-dihydroquinoline, a hydrogenated derivative of quinoline. This bicyclic structure comprises a benzene ring fused to a saturated six-membered ring containing nitrogen, giving the formula C9H9N. Other possible isomers fall into different categories of nitrogen-containing aromatics and heterocycles, such as ring systems in which the nitrogen is part of a pyridine-like ring or where the nitrogen appears as part of an amine substituent on a benzene ring. The exact physical properties and reactivity depend on the specific arrangement of atoms.

In practice, C9H9N is used as a laboratory shorthand in chemical databases and mass spectrometry to describe molecules that share this composition. To identify a particular compound, researchers provide structural information such as SMILES, InChI, or a systematic name that specifies connectivity and stereochemistry where applicable.

Applications of C9H9N compounds span organic synthesis, pharmaceutical research as potential scaffolds, and dye- or pigment-related chemistry. Accurate data require knowledge of the exact isomer involved.