6.1.1 - Aromatic Compounds
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What is the structure and formula of Benzene?
C6H6
What is the empirical formula of Benzene?
CH
What is the state of benzene at room temperature?
Liquid
What is the bond angle of benzene?
Bond angle = 120
What are the 3 features of benzene that don’t support kekule’s model?
• Benzene is resistant to addition reactions • Enthalpy change of hydrogenation of benzene is more stable than expected • All the carbon bonds are the same length
What technique was used to find the bond lengths of benzene?
X ray diffraction
What happens to the 4th electron in the p orbital of each carbon atom in benzene?
It delocalises to form rigns of electron density above and below the hexagon
How do the rings of electron density affect the stability of Benzene?
Makes benzene very stable even tough it is unsaturated (aromatic stability)
Draw the skeletal structure of cyclohexa-1,3,5-triene
hexagon with 3 triple bonds and 3 single bonds
Why does benzene have a relatively high melting point?
Close packing of flat hexagonal molecules when solid
Is benzene soluble in water? Explain why
No because it is non-polar
Dangers of benzene - why is it not used in schools?
It is a carcinogen
How do you name compounds containing a benzene ring?
-benzene phenyl- can designate position on ring using numbers if there is more than one substituent
Why is benzene attacked by electrophiles?
High electron density above and below ring due to delocalized electrons.
Draw a general electrophillic substitution mechanism of benzene, using El+ to represent an electrophile
Mechnism
Nitration of benzene is what type of reaction?
Electrophillic substitution reaction
Which ion is used to nitrate benzene?
NO2+
What is the catalyst in nitration of benzene?
Sulfuric acid
How is the NO2+ ion generated (conditions and equations)
Concentrated H2SO4 and concentrated HNO3 H2SO4 + HNO3 —> H2NO3+ + HSO4- H2NO3+ —-> H2O + NO2+ Overall: H2NO4 + HNO3 –> HSO4- + NO2+ + H2O