Module 6 Electrophilic substitution reactions

why does benzene not undergo electrophilic addition

the delocalised ring of electrons is too stable and would be disrupted

what substitution reactions does benzene undergo

reactions in which a hydrogen atom on the benzene ring is replaced by another atom. the delocalised ring is briefly disrupted and then restored during the process

what is this

electrophilic substitution of benzene

what is the reaction rate increased by in nitration of benzene

heating to 50 degree, using a sulfuric acid catalyst

what will benzene do in nitration of benzene

react slowly with nitric acid to form nitro benzene

what happens to one of the hydrogen atoms around the benzene ring in nitration of benzene

it is replaced by a nitro group NO2

what happens at higher temps in the nitration of benzene

further substitutions around the ring producing dinitrobenzene

what is nitrobenzene used in

dyes, pharmaceuticals, pesticides

what is this

nitration of benzene

what happens in step one of nitration of benzene

nitric acid reacts with sulfuric acid to produce the electrophile nitronium ions NO2+. HNO3 + H2SO4 -> NO2+ + HSO4- + H2O

what happens in step 2 of nitration of benzene

nitronium ions attack the benzene ring forming an unstable intermediate. the intermediate loses and H+ ion to restore the delocalised ring forming nitrobenzene

what happens in step 3 of nitration of benzene

the hydrogen ion reacts with the HSO4- ions from step 1 to reform the catalyst H2SO4. H+ + HSO4- -> H2SO4

when will the halogen not react with benzene in halogenation of benzene

if there is no halogen carrier catalyst used

what are the common halogen carriers especially for halogenation of benzene

AlCl3, FeCl3, AlBr3, FeBr3

where are the halogen carriers often generated

as part of the overall reaction by adding the metal and halogens separately. 2Fe + 3Cl2 -> 2FeCl3

what is this

halogenation of benzene

what happens in step one of halogenation of benzene

halogen reacts with halogen carrier to produce a bromonium ion Br+. Br2 + FeBr3 -> FeBr4- + Br+

what happens in step 2 of halogenation of benzene

the positive ion attacks the benzene ring forming unstable intermediate. the intermediate loses a H+ ion to restore the delocalised ring forming bromobenzene

what happens in step 3 of halogenation of benzene

the hydrogen ion reacts with the halogen carrier ion from step 1 to reform the carrier and hydrogen bromide. H+ + FeBr4- -> FeBr3 + HBr

why is the intermediate unstable

because electrons have been removed from the benzene ring

what is alkylation of benzene

reacting a haloalkane with benzene in the presence of a halogen carrier. nearly always doe with chloroalkanes and AlCl3

what is alkylation of benzene nearly always done with

chloroalkanes and AlCl3

what is this

alkylation of benzene

what is step 1 in alkylation of benzene

haloalkane reacts with halogen carrier to produce alkyl ion

what is step 2 in alkylation of benzene

the positive ion attacks the benzene ring forming an unstable intermediate. the intermediate loses an H+ ion to restore the delocalised ring forming alylbenzene

what is step 3 in alkylation of benzene

the hydrogen ion reacts with the halogen carrier ion from step 1 to reform the carrier and a hydrogen halide

what is acylation of benzene

reacting an acyl chloride with benzene in the presence of a halogen carrier. this is almost always done with an acyl chloride and AlCl3

what is acylation of benzene almost always done with

acyl chloride and AlCl3

what is this

acylation of benzene

what always has to happen to the O

always has to be double bonded to first C

what is step 1 in acylation of benzene

acyl chloride reacts with halogen carrier to produce acyl ion

what is step 2 in acylation of benzene

the positive ion attacks the benzene ring forming an unstable intermediate. the intermediate loses an H+ ion to restore the delocalised ring forming alkylbenzene

what is step 3 in acylation of benzene

the hydrogen ion reacts with the halogen carrier ion from step 1 to reform the carrier and a hydrogen halide