Benzene Flashcards
Who came up with the original structure of benzene?
Kekule
What were the 3 problems with benzene?
Xrays showed bond lengths were all equal as double bonds were thought to be shorter.
Benzene didn’t decolourise bromine water which an alkene should.
Hydrogenation took less due to low bond enthalpy
Name some structural features of benzene
Planar
Trigonal planar, 120°
Aromatic
Contains pi bonds and sigma bonds
6 delocalised electrons
How is the delocalised model of benzene different to kekule structure?
Shows p orbitals on each carbon atom crossing over sideways to create a pi bond above and below the plane
When does the benzene ring become the substitute group?
When there are 7 or more carbons or a functional group
What is the name used when the benzene ring is substitute group?
Phenyl
Outline the mechanism for nitration
Outline the mechanism for halogenation
Outline the mechanism for alkylation
Outline the mechanism for asylation
What is the molecular formula for phenol?
C6H5OH
How is phenol a weak acid?
Partially dissociates to give off H+ ions
Give the equation for phenol Reacting with sodium hydroxide
C6H5OH + NAOH > C6H5O-NA+ + H+
Give the reaction for phenol Reacting with sodium
2C6H5OH + 2NA > 2C6H5O-NA+ + H2
What is the name of C6H5O-NA+ ?
Sodium phenoxide
Why is phenol more reactive than benzene?
A lone pair of electrons from the oxygen moves into the ring making ut more negative activating ring
Outline the mechanism for the relation of phenol and bromine and what would you observe?
C6H5OH + Br3 > C6H2OHBR3 + 3HBr
White precipitate forming
Outline the mechanism for nitration of phenol
C6H5OH > C6H4OHNO2
Nitrate group on either carbon 2 or 4
Nitric acid with water at 25°c
How does phenol form an electrophile?
Sufficiently electron dense to induce a dipole in a neighbouring molecule
