ISOMERISM & AROMATICITY

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  • ISOMERISM & AROMATICITY
    • NAMING COMPOUNDS
      • carboxylic acid
        • R-COOH
        • -oic acid
      • ketone
        • oxo-
        • -one
        • R-CO-R
      • ester
        • R-COO-R
        • -thyl, -oate
      • acid chloride
        • -oyl chloride
        • R-COCl
      • aldehyde
        • R-OH
        • -al
      • alcohol
        • hydroxy-
        • R-OH
        • -ol
      • amide
        • -amide
        • amido-
        • R-COCH2
      • amine
        • amino-
        • -amine
        • R-NH2
      • amino acid
        • R-CH(NH2)COOH
        • -amino acid
      • nitrile
        • cyano-
        • -nitrile
        • R-CN
      • benzene
        • -benzene
        • phenyl-
        • C6H6
      • phenol
        • -ol
        • hydroxy-
        • C6H5OH
    • STEROISOMERISM
      • E-Z isomerism
        • C=C with different atoms
        • one end cannot rotate relative to the other
        • E "trans" = on different sides
        • Z "cis" = on the same sides
      • = same structural formulae but different spacial arrangement
      • optical isomerism
        • chiral carbon cneter with 4 different groups attached
        • mirror images of each other
        • enantiomer = reflect & rotate a plane of polarised light in equal & opposite directions (optically active)
        • racemic mixture = equimolar mixture of both isomers & has no effect on the plane of polarised light (optically inactive)
    • STRUCTURE OF BENZENE
      • flat hexagonal ring of C6H6
      • trigonal planar of 120'
      • made of single sigma covalent bonds
      • unoccupied p-orbitals overlap to form pie bonds
      • electrons are delocalised into the pie electron system leading it to be energetically stable
      • Against Kekule structure
        • all C-C bonds are the same length (0.139nm) which is between single & double bond lengths
        • resists addition reactions as it destroys the stable delocalised pie electron system
        • delocalised resonance energy is 152 kJmol-1 plus difference
    • NITRATION, HALOGENATION & ALKYLATION OF BENZENE
      • electrophilic substitution = replacement of ring of hydrogen atoms by an electron deficient group
      • in situ = reactant made & reacts as it forms
      • nitration of benzene
        • reactants
          • benzene, nitric acid + sulphuric acid
        • products
          • nitrobenzene + water
      • halogenation of benzene
        • reactants
          • benzene + halogen (bromine)
        • catalyst
          • anhydrous iron (III) bromide
            • halogen carrier
            • causes polarisation of Br-Br
            • catalytic action
        • products
          • bromobenzene + HBr
      • alkylation of benzene
        • Friedel-Crafts reaction
        • reactants
          • benzene + alkyl group (ethyl)
        • catalyst
          • aluminium chloride
        • products
          • chlorobenzene + HCl
    • ALKALINE HYDROLYSIS OF CHLOROALKANES & CHLOROBENZENE
      • nucleophilic substitution
      • chloroalkane + NaOH
        • reacts easily when refluxed giving alcohol
        • reflux = evaporation & condensation are occurring & condensed material is returning to flask where reaction is going on
      • cholorobenzene + NaOH
        • stronger C-Cl bond due to stable pie electron-ring system of overlapping lone pairs of electrons
          • needs more energy to be broken (300'C, increased pressures)
            • not economically viable

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