Alkenes Flashcards
Electrophile
Electron pair acceptors that attack regions of high electron density and form dative covalent bonds.
Nucleophile
Electron pair donors that attack regions of low electron density and form dative covalent bonds.
Substitution Reaction
An atom or group of atoms in one molecule is replaced by another atom or group of atoms.
Addition reaction
A reaction in which two molecules react to form a single product.
Elimination reaction
The elements of a simple molecule such as HBr or H2O are removed from the organic molecule and not replaced by any other atom or group of atoms forming >C=C
Aliphatic compounds
Open chain compounds or cyclic compounds that resemble open chain compounds e.g. Alkanes and alkenes.
Primary carbon
A carbon atom bonded to only one alkyl group
Secondary carbon
A carbon atom bonded to two alkyl groups.
Tertiary carbon
A carbon atom bonded to three alkyl groups.
Alkenes
Unsaturated hydrocarbons which contain at least one C=C double bond, do not contain max. no. of H atoms and can undergo +ition reactions.
Test for unsaturation
1) Add Bromine water.
2) Colour change from orange brown to colourless indicates presence of a >C=C
Why are alkenes much more reactive than alkanes?
1) Alkenes have a double bond. As there are 4 electrons found around the 2 C atoms bonded by a double bond: this is an area of high electron density and will be attacked by electrophiles.
2) The >C=C
What are the three different types of reaction alkenes participate in?
1) Combustion in xs O2 to form H2O and CO2
2) Heterolytic electrophilic +ition
3) Polymerisation
Type of reaction: Combustion
Reaction: alkene + O2 ——–> CO2 + H2O
Conditions: Ignite in air or O2
Type of reaction: Heterolytic electrophilic +ition
Reaction: Alkene + H2 ——-> alkane
Reagents: H2
Conditions: a nickel catalyst at 180’C / platinum catalyst at room temperature
