Electrophilic addition reactions of alkenes There are some

Electrophilic addition reactions of alkenes. There are some questions in the middle part of the presentation so have a pen and paper ready. There is some narration so turn the sound on!

Electrophilic addition. Ethene and bromine liquid at room temperature.

H H C H Electrophile Polarised

Carbocation H H C C C + H H Br δ+ __ δBr H H H C Brδ+ BrδCurly arrows H

H H H C C+ H H + Br Brδ+ __ δBr Bromide ion H

Electrophilic addition Saturated H H H C C Br Br H 1, 2 -dibromoethane Unsaturated

H H C C Brδ+ H H Mechanism H C C+ Br __ Brδ H C C+ H Br BrδH H __ δ Br H H C C Br Br H

Write down the answers to the questions on a piece of paper. You will be given the answers in the final part of the presentation.

Electrophilic addition. Ethene and bromine liquid at room temperature.

H H C H

H H C C C + H H Br δ+ __ δBr H H H Brδ+ Brδ- C H

H H H C C+ + Brδ+ Br __ δBr H

H H H C C Br Br H

Q 1. From red-brown to colourless (not clear). Ethene and bromine liquid at room temperature.

H H C H Q 2. Ethene is unsaturated because it has a double bond between carbon atoms. Q 3. The δ+ end of the Br 2 acts as an electrophile

Q 5. The carbon only has a single + charge because only one of the shared pair of electrons belonged to this carbon. H H C C C + H H Br δ+ __ δBr H H H Brδ+ Brδ- Q 4. There is a single – charge because one of the shared pair of electrons already belonged to this bromine. C H

Q 6. A carbocation. H H H C C+ + Brδ+ Br __ δBr H Q 7. Curly arrows represent movement of a pair of electrons.

Q 8. The product is saturated. All the bonds between carbon atoms are saturated. H H H C C Br Br H Q 9. 1, 2 -dibromoethane Q 10. Electrophilic addition.

Well done!