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benzene

structure
1. C6H6 =mr
2. kekulé structure
  1. low reactivity
    1. -didn't react with Br water
    2. -not contain C=C bonds
    3. -not take part in other electrophilic additions
  2. C-C bond lengths
    1. C-C & C=C different lengths
    2. benzene- C-C bonds only as all same lengths
    3. kekulé structure wrong
  3. hydrogenation
    1. cyclohexene (1 C=C) -120 KJ mol-1
    2. cyclo-1,3,5-triene (3 C=C) -360 KJ mol-1
    3. benzene -208 KJ mol-1
      1. more stable then cyclo-1,3,5-triene
relative ease of bromination
1. easy- ethene
  1. middle- phenol
    1. hard- benzene
      1. -π e' delocalised in benzene ring -e' density low -can't polarise Br2 -halogen carrier needed for reaction
    2. -lone pair of OH partially delocalised in ring -e'density higher than benzene -can polarise Br2
  2. -e' localised C=C -e' density is high -can polarise Br2
2. points for the answer
  1. order of reactivity (hexene>phenol>benzene)
  2. benzene- π e' are delocalised
  3. phenol- lone pair is partially delocalised into ring
  4. hexene- e' localised between 2 carbons
  5. benzene lower e' density than phenol which is lower than hexene
  6. benzene can't polarise Br2
properties
1. common start of aromatic compounds
2. carsinogen
3. colourless & flamable
reactions
1. nitration of benzene
  1. conc HNO3 conc H2SO4 50'c
    1. C6H6 + HNO3 = C6H5NO2 + H2O
2. halogenation
  1. -requires halogen carrier -used as catalyst -carrier same as halogen
3. reducing reaction
  1. propanal + reducing agent ( [H] ) = propan-1-ol
  2. reducing agent (NaBH4)
    1. generates hydride ions (H-)
4. nucleophilic addition

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benzene

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	Created by becca.dodd over 10 years ago