Organic chem III

Question 1

benzene structure

Answer 1

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

Question 2

kekule model

Answer 2

structure for Benzene consisting of
alternate single and double covalent
bonds between the carbon atoms

Question 3

issues w kekules model

Answer 3

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

Question 4

combustion of benzene

Answer 4

Benzene will combust with a very sooty flame.

Question 5

reagents and conditions for halogenation of bromine

Answer 5

Change in functional group: benzene -> bromobenzene
Reagents: Bromine
Conditions: Iron(III) bromide catalyst FeBr3

Question 6

Equation for formation of electrophiles in Halogenation of Benzene:

Answer 6

AlCl3 + Cl2 -> AlCl4
– + Cl+

FeBr3 + Br2 -> FeBr4
– + Br

Question 7

reagents and conditions for Nitration of Benzene

Answer 7

Change in functional group: benzene  nitrobenzene
Reagents: conc nitric acid in the presence of concentrated
sulfuric acid (catalyst)

Question 8

equation for electrophile in benzene nitration

Answer 8

HNO3 + 2H2SO4 -> NO2+ + 2HSO4
- + H3O+

Question 9

friedel crafts alkylation reagents and conditions

Answer 9

Change in functional group: benzene -> alkylbenzene
Reagents: chloroalkane in the presence of anhydrous
aluminium chloride catalyst
Conditions: heat under reflux

Question 10

formation of electrophile

Answer 10

AlCl3 + CH3CH2Cl -> CH3CH2
+ AlCl4
-

Question 11

fridel crafts acylation

Answer 11

Change in functional group: benzene -`. phenyl ketone
Reagents: acyl chloride in the presence of anhydrous
aluminium chloride catalyst
Conditions: heat under reflux

Question 12

Equation for formation of the electrophile

Answer 12

AlCl3 + CH3COCl -> CH3CO+ AlCl4-

Question 13

phenol with bromine

Answer 13

Reagents: Bromine water
Conditions: room temp

Question 14

phenol w bromine product

Answer 14

2,4,6 –tribromophenol

white solid

Question 15

uses of phenols

Answer 15

used in the production of plastics, antiseptics, disinfectants and resins for paints.

Question 16

compare contrast bromination of phenol and benzene

Answer 16

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