How acidic are aldehydes like formaldehyde?

The C-H bond is very stable, so, no not acidic. This is to say the H in the COH2 is not likely to come off, which is the Arrhenius definition. read more

The Mannich reaction is the aminoalkylation reaction, involving the condensation of an enolizable carbonyl compound (α-CH acidic compound) with a nonenolizable aldehyde (like formaldehyde) and ammonia; or a primary or a secondary amine to furnish a β-aminocarbonyl compound, also known as Mannich base. read more

An aldehyde /ˈældɪhaɪd/ or alkanal is an organic compound containing a functional group with the structure −CHO, consisting of a carbonyl center with the carbon atom also bonded to hydrogen and to an R group, which is any generic alkyl or side chain. The group—without R—is the aldehyde group, also known as the formyl group. Aldehydes are common in organic chemistry. Many fragrances are aldehydes. read more