Isol. from various plant sources, e.g. hops, banana, sweet or sour cherry, blackcurrants, melon, pineapple, bread, chesses, coffee, cooked rice and strawberry or apple aroma. Flavouring agent In organic chemistry, propanal or propionaldehyde is the aldehyde of the 3 carbon propyl group. It has a chemical formula of CH3CH2CHO, and is a structural isomer of propanone. At room temperature, it is a colourless liquid with a slightly irritating, fruity odour.; It is principally used as a precursor to trimethylolethane (CH3C(CH2OH)3) through a condensation reaction with methanol; this triol is an important intermediate in the production of alkyd resins.; Propionaldehyde or propanal is the organic compound with the formula CH3CH2CHO. It is a saturate 3-carbon aldehyde and is a structural isomer of acetone. It is a colourless liquid with a slightly irritating, fruity odour.; Researchers have recently discovered two new interstellar molecules one of which is propanal. It was located within the Milky Way Galaxy inside an interstellar cloud known as Sagittarius B2. The identity of the carbon-containing molecule, propanal, was discovered by , Jan M. Hollis of the NASA Goddard Space Flight Center in Greenbelt, Md., and his colleagues. For the team to identify the propanal they looked for the emission of specific frequencies of radio waves from the cloud. They did this because different types of molecules emit energy at different frequencies, each producing a unique signal that researchers can detect with powerful telescopes. Located in the July 20th Astrophysical Journal Letters, researchers reported that they had recorded the frequencies associated with two aldehydes called propenal and propanal. Although researchers have found other organic molecules in space before this, the evidence of the two aldehydes will assist them in the understanding of how molecular building blocks are assembled into more-complex organic molecules; in space.