Polyens

Polyenes are organic compounds that contain multiple carbon-carbon double bonds. The number of double bonds determines the specific class of polyene. For example, a compound with two double bonds is a diene, three is a triene, and so on. The arrangement of these double bonds is significant. If the double bonds are separated by a single bond, they are called conjugated polyenes. Conjugated systems often exhibit distinct chemical and physical properties due to the delocalization of pi electrons across the multiple bonds. Alternatively, if the double bonds are separated by two or more single bonds, they are referred to as isolated polyenes. A less common arrangement is cumulative polyenes, where the double bonds are adjacent to each other, such as in allenes. Polyenes are found in various natural products, including pigments like carotenoids, which are responsible for the colors of many fruits and vegetables, and vitamin A. Their chemical reactivity is often associated with the double bonds, making them susceptible to addition reactions. The extended conjugation in some polyenes leads to absorption of visible light, resulting in their colored appearance.