Define Alkene
Unsaturated hydrocarbon
Give general formula of alkenes
CnH2n
What are the steps you take when naming alkanes/alkenes?
- Identify longest chain
- Identify any side chains, name these according to number of carbons
- State location of side chains with number as prefix
- ALKENES ONLY identify position of double bond, number goes in middle of longest chain
How is the sigma bond formed in C=C double bond?
- it is the overlap of s-orbitals
- direct, head on bond containing shared pair of electrons
How is Pi bond formed in C=C double bond?
- p-orbitals overlap above and below carbons
- contain shared pair of electrons, which could be in either orbital
Define electrophile
Substance with partial positive charge that is attracted to region that is negatively charged
Why is the double bond in alkenes susceptible to attacks by electrophiles?
- region of high electron density, therefore negatively charged
Describe basic mechanism of eletrophilic addition with Br
- Br becomes polarised as it approaches negative double bond
- Electrons in Br are repelled by electrons in double bond, move further down molecule
- Electrons in double bond move to partially positive Br, Pi bond breaks and forms bond with 1 Br atom
- Carbocation is formed, quickly forms bond with Br ion
Define carbocation
An ion with positively charged carbon atom
What conditions does hydrogenation (addition of hydrogen) to alkene require?
- nickel catalyst
- 150 degrees Celsius
What conditions does addition reaction between alkene and water (steam) require?
- sulphuric acid catalyst
- high temp and pressure
What is produced when an alkene reacts with water?
Alcohol
