chapter 14 organometallic compounds. 14.1 organometallic nomenclature

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  • Chapter 14Organometallic Compounds

  • 14.1Organometallic Nomenclature

  • Metal is the parent

  • 14.2Carbon-Metal BondsinOrganometallic Compounds

  • Table 14.1 (p 547)F4.0H2.1O3.5Cu1.9N3.0Zn1.6C2.5Al1.5H2.1 Mg1.2Li1.0Na0.9K0.8

  • Polarity of Bondsorganometallics are a source of nucleophilic carbond+ddd+

  • Polarity of BondsCH3FCH3Li

  • 14.3Preparation of Organolithium Compounds

  • Organolithium Compoundsis an oxidation-reduction reaction: carbon is reduced same for ArXnormally prepared by reaction of alkyl halides with lithium

  • Examples(CH3)3CCl + 2Lidiethyl ether10C(CH3)3CLi + LiCl(75%)Br+ 2Lidiethyl ether35CLi+ LiBr(95-99%)

  • Electron Bookkeeping+ Li+ R+Li

  • 14.4Preparation of Organomagnesium Compounds: Grignard Reagents

  • Grignard ReagentsDiethyl ether is most often used solvent. Tetrahydrofuran is also used.same for ArXRMgXprepared by reaction of alkyl halides with magnesium

  • Examplesdiethyl ether10C(96%)Br+ Mgdiethyl ether35CMgBr(95%)+ Mg

  • Electron Bookkeeping+ Mg+ R+

  • Order of ReactivityI > Br > Cl >> FRX > ArX

  • Forbidden Groupscertain groups cannot be present inthe solventthe halide from which the Grignard reagent is preparedthe substance with which the Grignard reagent reacts

  • Forbidden Groupstherefore cannot use H2O, CH3OH, CH3CH2OH, etc. as solventscannot prepare Grignard reagent from substances such as HOCH2CH2Br, etc.Anything with an OH, SH, or NH group

  • 14.5Organolithium and Organomagnesium Compounds as Brnsted Bases

  • Brnsted basicityGrignard reagents (M = MgX) and organolithium reagents (M = Li) are strong bases. dd+

  • Examplewater is a stronger acid than butane(100%)+ H2O+LiOHCH3CH2CH2CH2LiCH3CH2CH2CH3

  • Examplemethanol is a stronger acid than benzeneMgBr(100%)+ CH3OH+CH3OMgBr

  • Table 14.2Approximate Acidities of HydrocarbonsHydrocarbons are very weak acids.Their conjugate bases are very strong bases.Grignard reagents and organolithium reagents are strong bases.HydrocarbonpKa(CH3)3CH71CH3CH362CH460Ethylene45Benzene43Ammonia36Acetylene26Water16

  • Acetylenic Grignard Reagentsare prepared by an acid-base reactionCH3CH2MgBr+CH3CH3stronger acidweaker acid+



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