Learning The Structure Of Benzene Flashcards
Explain the structure of benzene with reference to demoralised electrons
Explain the structure of benzene molecule with reference to delocalized pi electrons
Each carbon atom is bonded to other carbon atoms and one hydrogen atom the final lone pair of electron is in a p orbital which sticks out above and below
What is delocalisation
The pi electrons are spread over several Atoms
Why are all the carbon-carbon Bonds in the molecule the same length
Due to the delocalized electron structure all the carbon-carbon Bonds in the molecule the same the other same Bond lengths
What do the electrons in the P orbitals combine to form
Delocalized ring of electrons
Draw the kekule structure of benzene molecule
3 alternating bonds,
What is kekule benzene structure wrong
As in benzene all the carbon carbon Bond lengths are equal. Therefore circular structure is wrong as it represents that there are two different types of carbon-carbon bonds in benzene a carbon-carbon double bond and a carbon carbon single Bond.
Why is benzene stable and how can we determine stability
We do this by measuring stability of benzene by comparing the enthalpy change of hydrogenation in benzene and cyclohexane 135 triene
The enthalpy change of hydrogenation benzene in experimental factors is much lower in comparison to therapeutically value
Predicted =-360 REAL -280
Energy required to break bonds and energy is required to release bonds so they suggest more energy is required to break bonds in benzene than cyclo hexene 1,3,5 triene
This suggests benzene is more stable than theoretical value with 3 soluble bonds as this stability of greater energy required to break bonds is due to delivalised electrons. Less exothermic and more endo
The of phenol and phenyl amine
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Why do arenes undergo electrophilic substitution reaction
Benzene has a high electron density . As it has deloclaised electrons. This is attractive to electrophiles- electron loving substances
Why does benzene not undergo electrophilic addition like alkenes
This is because benzene a stable so unlike traditional alkenes do not undergo electrophilic addition reactions as this would disrupt the stable ring of electrons
How does electrophilic substitution take place in a benzene ring
What about a hydrogen or functional group on the benzene ring is substituted for the electrophile
How can benzene be made useful through frediel crafts acylation and what steps are done to allow this to happen?
To add an acyl group (rco) on to the benzene molecule on order to weaken the benzene molecule and make it easier to modify products.
What must be done in order to add onto the benzene ring
Electrophile must have very strong positive charge ACYL groups have positive charge , however it is not positive enough therefore we use a halongen carrier to act as the catalyst example aluminium chloride which will produce a much stronger electrophile with a stronger positive charge
How do we create our strong positive electrophile in Friedel crafts acylation
We have to react an acyl chloride with the halogen carrier example aluminium chloride to create a strong positive electrophile
Explain the reaction of acyl chloride with aluminium chloride
Acyl chloride + aluminium chloride = carbo cation where by the chlorine is removed from the acyl chloride onto the aluminium chloride to form aluminium chloride for