Chem 334 1nd Edition Lecture 5 Outline of Last Lecture I. Mono and Di substituted nomenclatureOutline of Current Lecture II. Benzylic Radicals and CationsIII. Oxydation of Side ChainsIV. EASCurrent LectureBenzylic radicals and cations:Benzylic positionThis position is reactive because it can form a more stable radical and positive/negative charge. NBS Br Cl2 Cl hv or Br2/hv &ΔCations:Bromination is regioselective. Like with most strong acids when reacting with an alkene, bromination of a benzene molecule typically results in a Markovnikov product, meaning that thebromine is attached to the more substituted carbon.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Br NBS hv Br HBrMethod: HBr Br Oxidation of Side Chains:An alkylbenzene can react with potassium permanganate(KMnO4), resulting in oxidation to form benzoic acid. KMnO4 is such a strong oxidizing agent that it removes the end carbon on the side chain, oxidizing the benzylic position to a carbonic acid and removing the alkyl portion. However, for a reaction to take place, a side chain must be present and there must be at least one hydrogen in the benzylic position.+ - BrNo ReactionEAS:Electrophilic aromatic substitution (EAS) is a reaction in which one hydrogen attached to an aromatic system is replaced with another atom or functional group. These reactions almost always need a catalyst. The catalyst pulls off the proton, leaving the electron behind and leaving you with a core benzene ring. This is a poor nucleophile, so you need a really good electrophile. The main EAS reactions are halogenation, nitration, sulfonation, alkylation, and acylation.Halogenation Nitration Sulfonation E+ Br, Cl NO2 SO3H Cl Cl2 Fe,Cl3 AlCl3 Br Br2 FeBr3ΔThese reactions need a lewis acid catalyst(electron acceptor). H2SO4/ NO2 HNO3/Δ Nitrogen ion is a “super electrophile”. We add the nitro group because we can reduce nitroto auiline (NH2)
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