An aldehyde /ˈaeldɨhaɪd/ ˈældɨhaɪd or alkanal is an organic compound containing a formyl. Group the formyl group is a functional, group with the Structure-R, cho consisting of a carbonyl (center a carbon double bonded to) oxygen bonded to hydrogen and An r, group which is any generic alkyl or side. chainecause of resonance stabilization of the conjugate base, an α-hydrogen in an aldehyde (not shown in the picture above) is far more acidic, with a pKa near 17, than a C-H bond in a typical alkane (pKa about 50).