3.3.10- aromatic Chemistry Flashcards
What does benzene look like
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Molecular formula of benzene
C6H6
Structure of benzene
Planar
Bond length of benzene
Intermediate between single and double
Explain the bonds in benzene
Each C bonded to 2 other C and a H so 1 unused electron
Unused electron is perpendicular to plane in p orbital
P orbitals overlap to form pi binds = negative charge above and below
What makes benzene even more stable
Electrons are delocalised so travel through whole system repelling each other makes even more stable
What was the proposed structure of benzene and what would it be called
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Triene
Evidence against triene
1) C-C bond length - all the bonds are same length on triene benzene not
2) addition reactions - benzene does not undergo these reactions where as triene would
3) enthalpy of hydrogenation - expect triene to react with 3H2 to form cyclohexane releasing 360kjmol only releases 208 showing benzene is 152 more stable than triene extra stability because of delocalised electrons
What is extra stability called in benzene
Delocalisation stability
What is aromatic ring attacked by and why ?
Electrophile because is very electron rich
What reaction does and dosent benzene go through and why
Does go through substitution because H atoms relaxed but not addition as would lose stability delocalisation
Reagents and condition needed for nitration
Conc HNO3 and Conce H2SO4
50c
Nitration generation of electrophile
HNO3 +H2SO4– NO2+ + 2HSO4- + H3O+
Nitration mechanism
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Nitration regeneration of catalyst
H+ + HSO4- —- H2SO4
