Semialdehyde

In organic chemistry, a semialdehyde is a compound containing an aldehyde and a carboxylic acid functional groups. Semialdehydes are common in biochemistry. The simplest semialdehydes have the formula HO2C(CH2)_{n}CHO. As illustrated by the behavior of the smallest member, glyoxylic acid, semialdehydes often exist as hydrates (geminal diols) HO2C(CH2)_{n}CH(OH)2.

Some of semialdehydes and their parent dicarboxylic acids are listed below.

Although structurally related to semialdehydes, dicarboxylic acids are rarely biochemical precursors to them.