Alkenes are unsaturated hydrocarbons containing at least one double bond. What should be the general formula of alkenes? If there is one double bond between two carbon atoms in alkenes, they must possess two hydrogen atoms less than alkanes.
Hence, general formula for alkenes is CnH2n. Alkenes are also known as olefins (oil forming) since the first member,ethylene or ethene (C2H4) was found to form an oily liquid on reaction with chlorine.