An alpha-beta unsaturated ketone is an organic molecule that contains a ketone carbonyl group and a double bond between the alpha and beta carbons in the chain. The carbons in the chain are named based on their proximity to the carbonyl group of the ketone.
A carbonyl group is a carbon atom that has a double bond to an oxygen atom. Carbonyl groups can occur as parts of other types of organic molecules.
Ketones are molecules that contain a carbonyl group inside of a chain of carbon atoms. To be a ketone, the carbonyl carbon must have at least one other carbon on either side before the end of the chain. As a result, the shortest carbon chain that can be a ketone has three carbon atoms and the middle carbon is the carbonyl carbon.
When labeling the carbon atoms with Greek letters, the carbonyl carbon does not get a letter. The carbon atoms to either side of the carbonyl group are named alpha carbons, and the next carbon that is bound to the alpha carbon is the beta carbon. Depending on the length of the carbon chain attached to the ketone, the unsaturated double bond could occur at any point, which would change the name of the molecule. For example, if the double bond occurred between the beta and gamma carbons, then it would be a beta-gamma unsaturated ketone.