While alkenes can burn, they often undergo incomplete combustion , resulting in a smoky flame due to unburnt carbon particles. Key Concepts for Exam Success
Alkenes react with halogens like bromine ( Br2cap B r sub 2 ) or chlorine ( Cl2cap C l sub 2
in the presence of a catalyst (like nickel) converts an alkene into an alkane. chemsheets 1232 answers
). The reaction with bromine water is a standard test for unsaturation: the orange-brown liquid turns . Reaction with Hydrogen (Hydrogenation): Adding H2cap H sub 2
Alkenes are a homologous series of that contain at least one carbon-to-carbon double bond ( While alkenes can burn, they often undergo incomplete
). This double bond is their functional group and is responsible for their high chemical reactivity compared to alkanes. The general formula for alkenes is CnH2ncap C sub n cap H sub 2 n end-sub Key Examples: Common alkenes include ethene ( C2H4cap C sub 2 cap H sub 4 ), propene ( C3H6cap C sub 3 cap H sub 6 ), and butene ( C4H8cap C sub 4 cap H sub 8
Reacting an alkene with water (steam) in the presence of a phosphoric acid catalyst produces an alcohol (e.g., ethene becomes ethanol). The reaction with bromine water is a standard
The worksheet emphasizes the various that alkenes undergo. In these reactions, the double bond breaks to form a single bond, allowing new atoms to join the carbon atoms.
Be prepared to draw displayed formulas (showing all bonds) and molecular formulas for the first four alkenes.