Chemistry: Benzene
simplestarene
BENZENE Qwhy notaccurate
GHG 1 L I V L L I V L All e to Cbondssamelength
Explaindirtarrangere
aliphatic straight1branchedchainorgsubs 1716 e ofC Ddoc
aromatic i haveplanarunsatring pleasentsmell inbenzene
arene 31 ring 6C atoms w delocalised bonding
aromatichydrocarbon
STRUCTURE
CGH6 Actualstruct
6 Catoms hexring oneHbondedeachC
planarMol deloc e system
e delocaroundring overlap porbitals H C C bondangle
9 1200
Kekule model evidence to proveWRONG
Kbenz
ring largenonpolar
hydrophobic
delocalised model
G p e deloc inringabove t below
p plane carbon ring
6 orbitalsoverlap 317 bonds
17bonds clouds deloc e
e constantmove shared equally bet 6 C atoms
stability
EVIDENCE AGAINST KEKULE
1 x decor 13hwater Clackreactivity ofbenzene as not normalalkene
giverforbenzenethanexp
2 Thermodyn stability OHhydrogenation
f delocalization is stable ordecoct
E req breakbonds in benzene
t Hz f OH 120KJmol kendo texovalue
cyclohexane
If Kekulecorrect OHF benzene SHOULD be 3 X 360
BUT NET is 208
benzene stable by152KTmol
G n e deloc notas 3 C c
Benzene stableby15215mi
difference delocalisationenthalpy onbonde Deloc
sub rxns insteadaddn
maintains delocsyst
Ivexothanexpected
duedelocstabringfromringe