Topic 18 Organic III Flashcards
What did Kekule suggest the benzene structure to look like?
Cyclohexa1,3,5-triene
How was Kekule’s benzene structure suggestion proved/disproved?
Supported by
- very sooty after combusting (due to low C:H ratio)
Disproved by
- bromine water does not react, so no C=C bonds
- regular bond lengths
- enthalpy of hydration values
What are chemical evidences for the structure of benzene?
- Bromine water doesn’t decolourise, so no C=C present
- X-ray crystallography, equal bond lengths so same bonds between each C
- Enthalpy of hydration data - much lower than expected
What do you see with HCl / HBr/ HI?
WHITE MISTY FUMES
benzene + O2 →
(complete)
6CO2 + 3H2O
benzene + O2 →
(incomplete)
3H2O + 6C
or
6CO + 3H2O
depending on Q - always 2 products
benzene + bromine with catalyst →
catalyst FeBr3
bromobenzene + HBr
what are the 4 stages of electrophilic substitution?
- formation of electrophile
- attack of electrophile
- reformation of π system
- reformation of catalyst
benzene + conc nitric acid + catalyst →
catalyst conc H2SO4
nitrobenzene + H2O
benzene + halogenoalkanes + catalyst →
catalyst AlCl3
alkyl benzene (or phenyl alkane) + halogenoalkane
in reflux
benzene + acyl chloride + catalyst →
catalyst AlCl3
phenyl ketone + HCl
what are methyl benzene’s properties?
alkyl group is e- pushing
so pushes e- density into pi system
so more easily attacked by electrophiles
what’s another name for methyl benzene?
toluene
is benzene or methyl benzene more reactive?
methyl benzene
has lower activation energy
e- pushing properties
what is a phenol?
benzene with OH attached to one of the C
