Aromatic Chemistry Flashcards
Due to benzenes delocalised ring off electrons what type of reactions will it rarely undergo?
Addition reactions
What is a common misconception about the bonds within benzene?
That they are alternating double and single bonds.
What length are the bonds in a benzene ring?
The bonds are an intermediate between a single c-c bond and a double c=c bond, all bond lengths are the same.
What are the bond angles in a benzene ring?
120 degrees
how many bonds does every carbon atom make in a benzene ring?
3
what happens to the 4th electron of every carbon that is not part of a bonding pair?
It can be found in the p orbitals which are adjacent to the benzene ring.
What does the overlapping of each carbons P orbital cause?
The overlapping of the 6s carbons p orbitals cause the electrons to delocalise and form a region of electron density above and bellow the benzene ring.
What provides benzene with its stability
The delocalisation of each carbons 4th electron/ the delocalised system.
What is more stable the theoretical molecule
cyclohexa-1,3,5-triene or benzene and why is this the case
Benzene , the delocalised system of electrons provide it with its aromatic stability.
What evidence supports the idea that benzene is more stable than cyclohexa-1,3,5-triene?
The enthalpy of hydrogenation is higher for benzene than it is for cyclohexa-1,3,5-triene this shows that more energy is required to break the existing bonds in benzene which demonstrates its greater stability.
If benzene is not the main functional group how can it be referred to?
phenyl
What type of reactions do benzene rings commonly undergo ?
Electrophilic Substitution
What is an electrophile?
Electrophiles are electron sir acceptors
Why do benzene rings attract electrophiles?
They have regions of high electron density.
Explain electrophilic substitution of a benzene ring?
The electron dense region of the benzene ring attracts the electrophile
The electrophile takes electrons from the from the electron dense region of the ring and uses the electrons to bid to one of the carbon atoms
This partially breaks the electron ring and gives the molecule a positive charge
To regain stability the benzene ring bound to the electrophile loses a hydrogen.
The electrophile is thus substituted for a H
