Aromatics Flashcards
Outline the structure and bonding of benzene
- Cyclic, planar molecule,
- Formula: C6H6
- -Final lone pair electron is in a p orbital which sticks out
- this causes a delocalised electron structure
- have the same bond length (139 pm)
Draw the kekule structure
add pic
How is benzene drawn usually
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Why is benzene more stable than cyclohexa,1-3.5 triene
- compared the hydrogenation of benzene and cyclohexa 1-3-5 triene
- in theory the hydrogenation of benzene should be -360 kjmol-1
- but for benzene it is -208kjmol-1
- this suggests that more energy is required to break the bonds in benzene than cyclohexa1-3-5 triene (bond breaking is endothermic)
- which means it is more stable due to delocalised electron structure
What is an arene
a molecule that contains a benzene ring
When do we add benzene at the end when naming aromatic compounds
halogen
methyl group
nitro (nitrate group)
When do we use phenyl (C6h5) when naming benzenes
- alcohols (phenol)
- amines (phenylamine)
What reactions does benzene go under
electrophilic substitution
Why are electrophiles attracted to benzene
it has a high electron density
Why don’t electrophilic addition reactions happen with benzene
because it would disrupt the stable ring of electrons
What is substituted in benzene reaction
one of the hydrogen in the delocalised structure
What are the uses benzene
pharmaceutical
dyes
What is the first step of fridel crafts acylation and why do we do this
- to add an electrophile onto the benzene, the electrophile must have a strong positive charge
- we react an acyl chloride, with a halogen carrier to create a strong electrophile
Acyl chrloide+ ALCL3 -> R-C=O (+) +ALCL4-
What is the equation for the nitration of benzene (forming the electrophile)
HNO3 + 2H2SO4 -> NO2+ + 2HSO4- + H3O+
What is the equation for the nitration of benzene (Reforming the catalyst)
H+ + HSO4- -> H2SO4
