Alkenes are a group of hydrocarbons that contain at least one carbon-carbon double bond. This double bond gives alkenes unique properties, making them more reactive than alkanes, which only have single bonds. Common examples of alkenes include ethylene, used in the production of plastics, and propene, which is important in making various chemicals. These compounds are typically found in natural sources, such as crude oil, and can also be produced through various chemical reactions. Alkenes play a crucial role in the chemical industry, serving as building blocks for many products, including fuels and synthetic materials.