alkenes Flashcards
What is present in alkenes?
C=C double bond
what is alkenes also known as?
unsaturated hydrocarbons
Why is alkenes also known as unsaturated hydrocarbons?
they contain one or more C=C double bonds
what is the general formula of alkenes?
CnH2n
what are the chemical properties of alkenes?
- combustion
- undergoes addition reaction due to C=C bond -> polymerisation
- b.p of alkene increases as no. of carbon increases
what does addition reaction mean?
one molecule combines with another molecule to form a larger molecule with no other products
what are the 5 types of addition reaction?
- addition of halogens (halogenation)
- addition of hydrogen halide
- addition of hydrogen (hydrogenation)
- addition of water (steam) - hydration
- addition of alkenes (addition polymerisation)
what is the equation for halogenation?
ethene + Br2 (orange-red) -> 1,2-dibromoethane (colourless)
why is the end product of halogenation colourless?
bromine is removed and added to ethene
what is the test halogenation good for?
distinguishing alkenes from alkanes as alkenes will undergo addition reaction while alkanes dont
what is the equation for addition of hydrogen halide?
ethene + HBr -> bromoethane
what is the equation of hydrogenation?
ethene + H2 -> ethane (occurs through nickel catalyst in the presence of heat)
what is the equation for hydration?
ethene + H-OH -> ethanol
what is the catalyst for hydration?
H2SO4
what does addition of alkenes mean?
many molecules of alkenes join tgt to form giant molecular structure called polymers
