C6H4CHO2

C6H4CHO2 refers to a chemical formula that can represent several isomers of phthalaldehyde. Phthalaldehyde is an aromatic dialdehyde, meaning it contains two aldehyde functional groups attached to a benzene ring. The chemical structure consists of a benzene ring with two aldehyde groups (-CHO) positioned on adjacent carbon atoms. This arrangement gives it the specific name "phthalaldehyde."

There are technically three possible positional isomers for a benzene ring with two substituents, but the term "phthalaldehyde" almost exclusively refers to the ortho-isomer, where the two aldehyde groups are on adjacent carbons (positions 1 and 2). The other isomers, where the aldehyde groups are on positions 1 and 3 (isophthalaldehyde) or 1 and 4 (terephthalaldehyde), are generally referred to by their specific names. Therefore, C6H4CHO2 most commonly and implicitly signifies 1,2-benzenedicarboxaldehyde.

Phthalaldehyde is a white to pale yellow crystalline solid. It is soluble in many organic solvents and slightly soluble in water. Its reactivity is characteristic of aldehydes, undergoing reactions such as oxidation, reduction, and condensation. A notable reaction is its use in the detection of primary amines, forming fluorescent isoindole derivatives, which is employed in analytical chemistry. It can also be used as a cross-linking agent.