Arenes
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What are the 3 unusual things about benzene
It’s got delocalised structure The molecule is planar All 6 of its C-C bonds have the same length intermediate between single and double
What gives benzene its stability
The delocalisation of electrons and its ring
Describe the evidence that shows benzene stability
Cyclohexane when hydrogenated the enthaply change is 120 Benzene which is a triene should evolve 3 times this so the enthaply change should be 360 However it’s 208 360-208 = 152 showing benzene has a lower energy and this stability is due to delocalised ring structure
What reactions does benzene undergo
Electrophilic substitution
When benzene reacts with. Nitric and sulphuric acid what is formed and what is the reaction called
Nitro benzene is formed Nitration
What reagents are involved in nitration
Conc H2SO4 and HNO3 Reflux 50-55
Give the equations for the formation of nitric acid in nitration
H2SO4+HNO3-> H2NO3(+) + HSO4- H2NO3->H20+NO2+
What is the catalyst in nitration
Sulphuric acid
What is produced when benzene reacts with acyl chloride
Phenylketones
What is the reaction called when benzene and acyl chloride react
Friedel-Crafts reaction
Give the overall reaction in nitration
C6H6+HNO3-> C6H5NO2 +H2O
Give the equation when alcl3 reacts with and acyl chloride in Friedal crafts
R-CO-CL +AlCL3->R-CO(+) + AlCl4 -
Give the overall reaction in fridel crafts
C6H6+R-COCl->C6H5COR+HCL
In Fridal crafts reaction what does the AlCl3 acts as
Catalyst
What can Nitrobenzene be used to make
Phenylamine
Give the reagents and the reaction name when nitrobenzene is converted to phenylamine
Reduction SN(tin) Concentrated HCl Heating under reflux
Why aren’t LiAlH4 and NABH4 used as reducing agents
As they give other products
Give the overall reaction in the reduction of nitrobenzene
C6H5NO2+6[H]->C6H5NH2+2H2O
What products are made from nitration of benzene
TNT
What can phenylamine be used for
To make dye stuffs when it’s converted
Why is it essential that the reaction temperature isn’t raised about 55 degrees in reactions with arenes
As further substitutions occur