Module 6

• Aromatic: containing one or more benzene rings
• Cis-trans isomerism: A special type of E/Z isomerism in which there are two non-hydrogen groups and two hydrogen atoms around the C=C double bond
• Electrophile: An electron pair acceptor
• Nucleophile: An electron pair donor
• Optical isomers: Stereoisomers that are non-superimposable mirror images of each other about a chiral centre; also called 'enantiomers'
• Stereoisomers: compounds with the same structural formula but with a different arrangement in space
• Structural isomers: molecules with the same molecular formula but with a different structural formula
• Differences between Kekule and delocalised model:

  • delocalised: p orbitals overlap + form delocalised π system
  • Kekule: 3π bonds, each localised at carbon to carbon bond
• For gas chromatography components in a mixture can be identified from their retention time
• For gas chromatography, the relative peak areas give the proportion of components in a mixture
• For gas chromatography, calibration curves are used to confirm concentrations of components in a mixture
• 2 optical isomers: 1 chiral centre, 4 optical isomers: 2 chiral centres
• Solvents that do not produce NMR signal: deuterated solvents (D) as they do not have spin
• What produces a peak at 0 on NMR spec: TMS
• Why do deuterated solvents not produce a NMR peak?

  Does not have any protons.
• Limitations of gas chromatography:

  • reference retention times impossible for unknown substances
  • times dependent on temperature, pressure + machine
  • similar compounds have similar retention times
• Limitations of thin layer chromatography:

  • 2 different compounds may have same Rf value (similar polarities/functional groups)
  • dependent on temperature + solvent
• Gas chromatography based on relative solubility
• TLC works by adsorption
• Gas Chromatography:

  • mobile phase: inert gas (He)
  • stationary phase: high bp liquid absorbed onto inert solid
• TLC:

  • mobile phase: organic liquid (solvent)
  • stationary phase: solid
• Condensation polymer: monomers react together + release a small molecule (e.g water)