Benzene Flashcards
What did kekulé suggest about the structure of benzene
Hexagonal ring, each C bonded by a sigma bond
Each C had P orbital at right angle to plane
Alternating C-C C=C bonds
Adjacent P orbitals overlap to form PI bonds
Stem for CH3
Methyl
Stem for NO2
Nitro
Stem for OH
Phenol
Stem for NH2
Phenyl
Why was kekule structure proved wrong
Does not readily undergo electrophillic addiction
More thermodynamically stable - hydrogenation enthalpy change less than expected
Double bonds shorter than single, suggests intermediate length
Equation for electrophillic substitution of benzene
C6H6 + X+»_space;» C6H5X + H+
When will benzene react with bromine
In the presence of a suitable catalyst
Conditions needed for nitration of benzene
Conc nitric and sulphuric acid
50 - 55 degrees
Observation when phenol reacts with phenol
Bromine ddecolourises
White precipitate forms
What are delocalised pi electrons
Electrons spread over more than two atoms formed by overlap of P orbitals
Conditions needed for nitration of benzene
Conc HNO3
Conc H2SO4
50 degrees
How does a halogen carrier allow a reaction to take place
It introduces a permenant dipole
