Lecture 2 not finished (copy)

What is an arene?

aromatic hydrocarbons

What is an aryl group?

aromatic hydrocarbon with one hydrogen atom removed

what is an electrophile

electron - loving or electron deficient species

What is a phenyl group?

Benzene ring with 1 hydrogen atom removed

What can an electrophile do?

React with a benzene ring and substitute for one of the hydrogen atoms

What reaction does benzene undergo?

Substitution reactions

What do electrophiles attack the π system of benzene form?

A delocalised non-aromatic carbocation

What happens in the first step of electrophilic substitution?

The electrophile takes 2 electrons from the system to form a σ bond in 1 of the carbon atoms

What happens in step 2 of electrophilic substitution?

The arenium ion loses a proton from the carbon with the electrophile.

What is the carbocation generated by in Friedel-Crafts alkylation?

AlCl3

In FC alkylation what are the 3 steps?

Formation of carbocation

Formation of arenium ion

Loss of proton from the arenium ion

What are examples of Friedel-Crafts alkylation(2)?

A mixture of an alkene and Bronsted acid

A mixture of an alcohol and Lewis acid

What happens to aromatic alkyl halides in Friedel-Crafts alkylation reaction

They do not react

When does the Friedel-Crafts alkylation reaction not take place(2)?

If rings contain electron withdrawing substituents

N group present

What is rearranged in Friedel-Crafts alkylation reaction?

Carbocation

Which multiple reactions often take place in Friedel-Crafts alkylation reaction?

Substitution

What does the primary alkyl halide-AlCl3 complex undergo?

A proton shift rearrangement to generate a more stable 2^o carbocation

What happens in the halogenation of benzene?

In the presence of a Lewis acid, benzene reacts with Br or Cl to produce a halobenzene

What are examples of halobenzene?

Bromobenzene or chlorobenzene

What happens in the nitration of benzene?

Benzene reacts slowly with hot HNO3 to form nitrobenzene

What can make the nitration of benzene faster?

If a mixture of HNO3 and H2SO4 is used

How does H2SO4 increase the rate of reaction?

By increasing the concentration of NO2+