Aromatic Chemistry Flashcards
What is Benzene?
A cyclic planar molecule with the formula C6H6
Why is Benzene so stable?
This is because Carbon has 4 electrons, each being bonded to 2 other arbons and 1 hydrogen; so the final one is in a p orbital which sticks about and below the planar ring and this allows the molecule to be more stable
How is Benzene more stable than theoretical alternative cyclohexa-1,3,5-triene (alternating single bonds / double bonds model)?
If you hydrogenate cyclohexane (1 double bond) the enthalpy change is -120kJmol-1 so youd expect benzene to be -360 kJmol-1, however, benzene actually is -208kJmol-1 (152 kJmol-1 more stable) and this is due to the delocalised electron structure
What are Arenes?
These are aromatic compounds which are molecules that contain a benzene ring. Named in 2 different ways: Benzene at end, phenyl at the start
What kind of do Arenes undergo?
Electrophilic Substitution
Why are arenes attacked by electrophiles?
This is due to the high electron density due to the delocalised ring of electrons
What is Electrophilic Substituition?
A reaction where a hydrogen or functional group on the benzene ring is substituted for an electrophile
Why doesn’t benzene undergo electrophilic addition?
This is because benzene is stable and if it occurred, it would disrupt the stable ring of electrons
How does benzene have a ring of delocalised electrons?
Final unpaired electron on each carbon is located in a p orbital that sticks out above and below the plane of the ring, so, the p orbitals on each atom combine to form a ring of delocalised electrons
What is Friedel Crafts Acylation used for?
This is when acyl groups are added to benzene to make it weaker and easier to modify into useful products like pharmaceuticals amd dye stuffs as initially, benzene is too stable to react to form these products
What halogen carrier used as a catalyst in Friedel Crafts Acylation and why?
AlCl3 and this will produce a much stronger electrophile with a stronger positive charge
What is the first stage in Friedel Crafts Acylation?
React acyl chloride with the halogen carrier to create a strongly positive electrophile
What is the second stage in Friedel Crafts Acylation?
Electrophilic Substitution and it forms a phenylketone
What type of reaction is Nitration of Benzene?
Electrophilic substitution
Why is Nitrating Benzene useful?
Can be used to make dyes and explosives
