Alkenes - Topic 6

What is the general formula for alkenes

CnH2n

What are unsaturated hydrocarbons

Molecule containing only carbon and hydrogen with at least one double or triple bond

What is an electrophile

Electron pair acceptor

What two bonds are involved in double bonds

sigma and pi

What are sigma bonds

head-on overlap

What are pi bonds

sideways overlap of p orbitals

which type of bond (sigma/pi) has a higher bond enthalpy

sigma

how does the electron density differ between sigma and pi bonds

Sigma bonds have high electron density whereas electron density is spread above and below the pi bond

what feature that enables optical isomerism is caused by pi bonds

restricted rotation

what are z isomers

high priority groups are on the same side

what are e isomers

high priority groups are on opposite sides of the bond

what are stereoisomers

have the same molecular formula but different spatial arrangement

what reaction of alkenes is used in the production of margarine

hydrogenation

what reaction conditions does hydrogenation of alkenes require

150 degrees, nickel catalyst

what does the hydrogenation of alkenes form

alkanes

what does the halogenation of alkenes form

dihalogenoalkanes

what does the hydrohalogenation of alkenes form

halogenoalkanes

what are the reaction conditions needed for hydration of alkenes

concentrated phosphoric acid (H3PO4), 350 degrees, 60-70 atm

what does the hydration of alkenes form

alcohols

what does the oxidation of alkenes form

diols

what are the reaction conditions for the oxidation of alkenes

acidified potassium manganate (H+/KMnO4), room temperature

What colour change will occur when alkenes are oxidised

purple to colourless

what will combustion of alkenes form

carbon dioxide and water

how can polymers be disposed of

landfill, reusing, burning

what are the disadvantages of burning polymers

can emit toxic gases