Benzene Flashcards
Describe the structure of benzene.
One un-bonded electron is left on each carbon atom in a p-orbital.
The six electrons are delocalised in a ring structure above and below the plane of carbons
Is benzene planar or non-planar?
Planar
Why is the theoretical enthalpy of formation for benzene greater than the true value?
The delocalised ring provides stability
What reactions does benzene usually carry out?
Electrophilic substitution due to the high electron density.
Describe the reactivity of of methylbenzene.
Reacts more readily than benzene because the methyl side group releases electrons into the delocalised system making it more attractive to nucleophiles.
Describe any observations as benzene burns in oxygen.
Very sooty flame because of the low C:H
What’s the reagent and conditions for halogenating of benzene
Reagent = Halogen
Conditions = FeBr3 catalyst
What’s the conditions and reagent for nitration of benzene?
Reagent = conc nitric acid in conc sulfuric acid
Conditions = 60 degrees
What’s the mechanism for halogenating of benzene?
- Arrow from inside of benzene to halide ion
- carbon bonded to both Cl and H, horseshoe with + inside facing the bond
- arrow from H bond to +
- Benzene with halide substituted on
What’s the side reaction of nitric acid and sulfuric acid for form a NO+ ion for nitration of benzene?
HNO3 + 2H2SO4 —> NO+ + 2HSO4- + H3O+
What’s the reagent and conditions for hydrogenation of benzene?
Reagent = Hydrogen
Conditions = Nickel catalyst at 200 degrees and 30 atm
What does hydrogenation of benzene form
Cyclohexane
What’s the reagent and conditions for Friedel Crafts Alkylation of benzene?
Reagent = Chloroalkane in the presence of anhydrous aluminium chloride catalyst
Conditions = Heat under reflux
How do you form phenylamine from nitrobenzene?
Tin and HCl needed
