Chapter 25 Reactions With Benzne

Question 1

1) Electrophilic substitution with nitric acid

Answer 1

BENZENE + Nitric acid —> nitro benzne and water
Requires = H2SO4 CATALYST AND 50°c

1) formation of electophile 
H2so4 + HNO3–> HSO4- + H2O + No2+
2) substition happens 
3) reformation of catalyst 
HSO4- + H+ —> H2SO4

Question 2

What’s actually happening with the electrophokic subsitionn

1) how does the first step happen
2) why positive in the horseshoe?

Answer 2

1) - slightly electo dense ring attracts the electrophile ish
a pair of electrons from the benzene ring is donated to the electrophile such that a DATOVE bond can be formed
2) this BREAKs the benzne ring- the top carbon is no longer part of the delocalised system , and as you have 4 electrons for 5 carbons, you have a positive charge
3) now aromatic compounds always move to REGAIN THAT STABILITY THATS NICE . Thus bond for hydrogen breaks and both electrons are donated back to the benzne ring
4) this makes it stbale again and also a H+ ion
5) finally this joins back with HSO4- to become H2SO4 reformation of catalyst again

Overall just h29 made

Question 3

Why does subsition with nitric acid require 50°?
Why this need to be controlled?
What happens if it goes above 70?

Answer 3

Nitro groups are very unreavtive so it needs 50° for a good rate of reaction
2) this needs to be controlled because if it rises above 50 then further subsition of another nitro group may occur.

For example at 70 another happens making dinitrobenzene !

Question 4

What is Nitorbenzne used for in real life

Learn

Answer 4

Importsnt starting material in preparation of dyed , pharmaceuticals and pesticides

For example can make paracetamol !

Question 5

2) halogenation if benzene?

What conditions
What produced

Answer 5

Electrophilic subsition again

Again reacts with Br2 or Cl2 ti make broom chloro benzne, but in the presence of a HALOGEN CARRIER CATALYST = FeBR3 or Al
- this because too stbale to react with unpolarised bromine molecule, so electrophile must be made first , and then catalyst again

Gives HBR or HCL

Question 6

ALKYLATION of benzene
Reaction
Conditions + SPECIAL REACTANT

What’s so special about this

Answer 6

Electrophilic subsition

• requires a HALOGEN CARRIER CATALYST
• AND substitution with a HALOALKANE

One of first reactions that involves carbon to carbon bonding!

Question 7

How does ACYLATION WORK
A) what mechanism
B) what reactants and what PRODUCT PRODUCED
C) what conditions

Answer 7

A) Electrophilic subsition
B) reactants include benzne and an ACYL CHLORIDE , products are a phenylketone and HCl or something
C) conditions are a HALOGEN CARRIER
same subsition as before

Question 8

What even is an Acyl chloride homologous seriös

Answer 8

Same as aldehyde instead of the h it’s a cl

Question 9

Summary 4 reactions

Answer 9

1) nitro sub (H2so4 + 50)
2) halogenation (halogen carrier)
3) alkylation (need haloalkane to sub and halogen carrier)
4) ACYLATION (need Acyl chlroide to sub and halogen carrier)

Question 10

Why do we do ACYLATION more over alkylation?

Answer 10

Alkohaltion not reliable and really only works for tertiary, Acyl chldoird much more reactive