Organic Reactions of Alkenes and Related Compounds
Introduction to Organic Compounds
Organic compounds form the basis of all living things and contain carbon atoms as the backbone of their molecules. These compounds are classified into families based on their functional groups, which determine their characteristic reactions. Alkenes, with the general formula CnH2n, are an important family of organic compounds.
Definition: A functional group is a specific arrangement of atoms within a molecule that gives a family of organic compounds their characteristic reactions.
Vocabulary: A homologous series is a family of organic compounds with the same functional group.
Reactions of Alkenes
Alkenes are more reactive than alkanes due to their carbon-carbon double bond. They undergo various reactions, including combustion and addition reactions.
Combustion of Alkenes
Alkenes burn with a smoky, yellow flame due to incomplete combustion. This results in less energy release per mole compared to alkanes, making alkenes less suitable as fuels.
Example: The combustion reaction of alkenes can be represented as:
Alkene + Oxygen → Carbon Dioxide + Water
Addition Reactions of Alkenes
The carbon-carbon double bond in alkenes makes them susceptible to addition reactions. In these reactions, molecules add across the double bond, breaking it in the process.
Highlight: The organic reactions of alkenes are characterized by the breaking of the carbon-carbon double bond to form new compounds.
Reaction with Halogens
Alkenes react with halogens, such as bromine, in a characteristic test. When ethene reacts with bromine water, the orange color of the bromine disappears as it attaches to the alkene.
Hydrogenation Reaction
The hydrogenation reaction process involves the addition of hydrogen to an alkene, converting it to an alkane. This reaction requires a catalyst and elevated temperatures.
Example: Alkene + Hydrogen → Alkane
Reaction with Water (Steam)
Alkenes can react with steam to form alcohols. This reaction is industrially important for producing ethanol.
Highlight: The reaction of alkenes with steam to form alcohols is a reversible process that requires specific conditions: 300°C, 70 atm pressure, and a phosphoric acid catalyst.
