2formyl

2formyl refers to a formyl substituent (-CHO) attached at the second position of a parent molecule, typically an aromatic ring. In this usage, the label denotes ortho substitution relative to a reference group on the ring and is employed in both systematic (IUPAC) and common nomenclature to describe 2-formyl substitution.

In aromatic chemistry, formyl groups can be introduced at the 2-position through formylation reactions such as the Gattermann–Koch process, or by directed metalation followed by carbonyl insertion. The exact outcome depends on the substituents already present on the ring, which influence directing effects and regiochemistry.

Common examples of 2formyl-containing compounds include 2-formylbenzene derivatives and heteroaromatic analogs such as 2-formylpyridine. When the parent structure is a benzoic or other polyfunctional ring system, 2formyl is used to specify the ortho formylation relative to a reference group, as in compounds described as 2-formylbenzoic acid or related heterocycles.

Reactivity: The formyl group is an aldehyde and thus undergoes typical aldehyde chemistry, including oxidation to a carboxyl group, reduction to an alcohol, and condensation with amines or hydrazines to form imines and related products. The ortho (2-) position can influence both the rate and outcome of subsequent functionalization due to steric and electronic effects from neighboring substituents.

Applications: 2formyl-containing molecules are valuable as intermediates in organic synthesis, enabling construction of more complex polyfunctional compounds, dyes, fragrances, and pharmaceutical scaffolds. They also serve as building blocks in the preparation of fused-ring systems.

See also: formyl group, formylation, o-formyl, aldehyde, Gattermann–Koch reaction.