Organic chem III Flashcards
benzene structure
molecular formula C6H6
Each C atom is bonded to two other C atoms and one H atom by
single covalent σ-bonds. This leaves one unused electron on each
C atom in a p orbital, perpendicular to the plane of the ring.
The Six p electrons are delocalised in a ring structure above and
below the plane of carbon atoms
kekule model
structure for Benzene consisting of
alternate single and double covalent
bonds between the carbon atoms
issues w kekules model
Benzene is a planar molecule.The evidence suggests all the C-Cbonds are the same and have a length and bond energy between a
C-C single and C=C double bond
enthalpy of hydrogenation is less exothermic than expected: The 6 pi
electrons are delocalised and
not arranged in 3 double bonds there more thermodynamically stable
combustion of benzene
Benzene will combust with a very sooty flame.
reagents and conditions for halogenation of bromine
Change in functional group: benzene -> bromobenzene
Reagents: Bromine
Conditions: Iron(III) bromide catalyst FeBr3
Equation for formation of electrophiles in Halogenation of Benzene:
AlCl3 + Cl2 -> AlCl4
– + Cl+
FeBr3 + Br2 -> FeBr4
– + Br
reagents and conditions for Nitration of Benzene
Change in functional group: benzene nitrobenzene
Reagents: conc nitric acid in the presence of concentrated
sulfuric acid (catalyst)
equation for electrophile in benzene nitration
HNO3 + 2H2SO4 -> NO2+ + 2HSO4
- + H3O+
friedel crafts alkylation reagents and conditions
Change in functional group: benzene -> alkylbenzene
Reagents: chloroalkane in the presence of anhydrous
aluminium chloride catalyst
Conditions: heat under reflux
formation of electrophile
AlCl3 + CH3CH2Cl -> CH3CH2
+ AlCl4
-
fridel crafts acylation
Change in functional group: benzene -`. phenyl ketone
Reagents: acyl chloride in the presence of anhydrous
aluminium chloride catalyst
Conditions: heat under reflux
Equation for formation of the electrophile
AlCl3 + CH3COCl -> CH3CO+ AlCl4-
phenol with bromine
Reagents: Bromine water
Conditions: room temp
phenol w bromine product
2,4,6 –tribromophenol
white solid
uses of phenols
used in the production of plastics, antiseptics, disinfectants and resins for paints.
compare contrast bromination of phenol and benzene
phenol does not need halogen carrier
phenol needs room temp but benzene needs heat under reflux
oxygen lone pair on phenol interacts w delocalised electrons therefore electrophilic attack is more likely
