Electrophilic Substitution

Question 1

what are the catalysts used in step 1 of electrophilic substitution called?

Answer 1

• halogen carriers
• FeCl3 or AlCl3
• FeBr3 or AlBr3

Question 2

what always happens in step 3 of electrophillic substitution?

Answer 2

the catalyst is regenerated

Question 3

why is step 1 of electrophillic substitution done?

Answer 3

make the electrophile very reactive

Question 4

what is the reaction of benzene with haloalkanes called?

Answer 4

friedel-craft alkylation

Question 5

what is the reaction of benzene with acyl chlorides called?

Answer 5

friedel-craft acylation

Question 6

compare the reactivity of alkenes and benzene.

Answer 6

alkenes react with bromine much more readily than benzene does

Question 7

explain cyclohexene(alkenes) and bromine water reaction.

Answer 7

• the pi bond in cyclohexene contains localised electrons which is a region of high electron density
• the electrons in the pi bond repel the electrons in the Br-Br bond and polarises the Br2 molecule
• alkenes polarises the electrophile more

Question 8

explain benzene and bromine water reaction.

Answer 8

• benzene has delocalised electrons which spread over all 6 carbons in the ring, creating a lower electron density than in an alkene
• there is insufficient pi electron density above or below any 2 carbon atoms to polarise the X-X bond
• make benzene resistant to reactions with non-polar halogens

Question 9

what is needed for the reaction of bromine and benzene?

Answer 9

a halogen carrier to generate a more powerful electrophile

Question 10

what is an electrophile?

Answer 10

an electron pair acceptor