4.2 Aromaticity Flashcards
Name all the problems associated with the original structure of benzene.
Lack of reactivity. (Wouldn’t react with bromine water) Thermodynamic stability of benzene (The enthalpy of hydrogenation to cyclohexene was found to be -119kJmol^-1 Bond lengths were found to be different (Different bond lengths in benzene would cause distortion)
What catalyst is used for when benzene reacts with bromine?
iron(III) bromide
What is used as a catalyst for the chlorination of benzene?
anhydrous aluminium chloride.
Describe the halogenation reaction of benzene with bromine.
What type of molecule is benzene?
Planar and aromatic.
What do the rings of p-orbitals overlap to give?
π bonds.
What is the general pattern of the electrophilic substitution of benzene?
Whats’s the overall pattern for the nitration of benzene?
How is Friedel-Crafts alkylation different from halogenation?
It uses a halogenoalkane instead of a halogen.
What do chloroalkanes react with to give alcohols and name the type of reaction.
Sodium hydroxide (aq) in a nucleophilic substitution reaction.
How can we distinguish between 1-chlorobutane and chlorobenzene?
Adding HNO3 followed by AgNO3 gives a white precipitate whereas chlorobenzene does not.
Why is chlorobenzene resistant to nucleophilic substitution?
Its stable π bonds will repell nucleophiles.
Why are the C-Cl bonds in chloroalkanes so strong?
A non-bonding p electron pair on chlorine overlaps with the ring π-system of electrons.
Why are phenols more acidic than alcohols?
They can lose a hydrogen ion as the phenoxide formed is stabilised
Why is phenylamine less basic than alkyl amines?
The lone pair of elecetrons on the nitrogen atom interacts with the delocalised electrons in the benzene ring.
