Aldehyde
A compound containing a carbonyl group bonded to at least one hydrogen atom, so it lies at the end of a chain.
Formula / equation
R–CHO
Unit
Dimensionless
In depth
The terminal position leaves the carbonyl carbon accessible to nucleophiles and easily oxidised further to a carboxylic acid, which is what distinguishes aldehydes from ketones in the classic silver mirror and Fehling's tests. They are typically pungent and volatile.
Examples in the real world
Methanal as a preservative, ethanal from ethanol metabolism, and benzaldehyde smelling of almonds.