4.3 alkenes Flashcards
What are alkenes?
Unsaturated hydrocarbons containing C=C double bonds
Alkene general formula
CnH2n
Sigma bond in alkene
C-C and C-H bonds where there is an overlap of (ss,sp,pp) orbitals between the plane of the C atoms
C=C bonds
sigma-bond and pi-bond, 4 electrons in bond, making area of high localised electron density
Pi bonds in alkene
Sideways overlap of p orbitals above and below the plane of the C atoms
Stereoisomerism
Compounds with the same structural formula but different arrangement of atoms in space
E/Z isomerism
Type of stereoisomerism where there is restricted rotation about the C=C double bond and 2 different groups attached to each C atom in the double bond
E isomer
Highest priority groups on different sides of C=C double bond
Z isomer
Highest priority groups on same side of C=C double bond
Electrophile
Electron pair acceptor (attracted to high e- density)
Which addition reaction do alkenes undergo?
Electrophilic addition, test for unsaturation
Markonikov’s Rule
Major and minor products form when an unsymmetrical alkene reacts to form structural isomers. Major product will form from the most stable carbocation intermediate which has the most alkyl groups attached
Alkene addition reaction with H2
Ni catalyst to form alkanes
Alkene reaction with steam/H2O(g)
(phosphoric) acid catalyst to form alcohols
Addition polymers
Unreactive macromolecules made from small repeating units (monomers)
Disposal of polymers
- Combustion for energy production
- Organic feedstock
