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Aldehydes and Ketones © E.V. Blackburn, 2011 Structure O O R R H R ketone aldehyde O carbonyl group © E.V. Blackburn, 2011 Structure R o 120 C 'R sp2 O © E.V. Blackburn, 2011 Nomenclature of aldehydes Aldehydes are named by adding the suffix -al to the name of the corresponding hydrocarbon. The carbonyl carbon is given the number 1. H methanal O H or formaldehyde H 3C O ethanal acetaldehyde H © E.V. Blackburn, 2011 Nomenclature of aldehydes OH H H O HOH2C O OH H © E.V. Blackburn, 2011 Nomenclature of aldehydes When -CHO is attached to a ring, the suffix carbaldehyde is used. H O benzenecarbaldehyde benzaldehyde CH 3CH 2CHCH 2CHO 3-methylpentanal CH 3 © E.V. Blackburn, 2011 Nomenclature of aldehydes O H CHO © E.V. Blackburn, 2011 Nomenclature of ketones Ketones are named using the name of the corresponding hydrocarbon followed by the suffix -one. The position of the carbonyl carbon must be indicated. H 3C H 3C propanone acetone O dimethyl ketone One can also name the two radicals, R and R’, followed by the word ketone. © E.V. Blackburn, 2011 Nomenclature of ketones H3CH 2C O butanone ethyl methyl ketone H 3C H3C H2C O 1-phenyl-2-propanone benzyl methyl ketone © E.V. Blackburn, 2011 Nomenclature of ketones O diphenylmethanone benzophenone O CH3 phenylethanone acetophenone © E.V. Blackburn, 2011 Nomenclature of ketones OH O © E.V. Blackburn, 2011 Synthesis of aldehydes oxidation of primary alcohols RCH2OH RCH2OH K2Cr2O7 O R H O PCC in CH2Cl2 R H PCC = pyridinium chlorochromate © E.V. Blackburn, 2011 Rosemund reduction RCOCl or ArCOCl H2, Pd-BaSO 4 quinoline RCHO or ArCHO A special catalyst is used: palladium on barium sulfate which has been deactivated (poisoned) with an amine such as quinoline. © E.V. Blackburn, 2011 Lithium tri-tertbutoxyaluminium hydride O 1. LiAlH(O-t-Bu)3, Et2O, -78C O Cl 2. H2O H © E.V. Blackburn, 2011 Synthesis of ketones oxidation of secondary alcohols RCHOHR' O PCC/CH2Cl2 or K2Cr2O7 or CrO3 or KMnO4 R R' © E.V. Blackburn, 2011 Synthesis of ketones oxidation of secondary alcohols H OH menthol K2Cr2O7 H2SO4 O menthone © E.V. Blackburn, 2011 Synthesis of ketones – hydration of alkynes H H2O H2SO4 HgSO 4 H H 3C OH H H H2O H2SO4 HgSO 4 H2O H2SO4 HgSO 4 H C C H O CH3CHO CH3CCH3 O © E.V. Blackburn, 2011 Keto - enol tautomerism H O - - H+ H OH + H+ H stronger acid - H OH enol structure H C C H O weaker acid O H C C H O keto structure Structural isomers that are formally related only by the shift of a hydrogen and one or more bonds are called tautomers. © E.V. Blackburn, 2011 Friedel-Crafts acylation O R Cl + Lewis O + HCl ArH acid R Ar © E.V. Blackburn, 2011 Reaction of acid chlorides with dialkylcuprates © E.V. Blackburn, 2011 Oxidation of aldehydes Ag(NH3)2+ RCHO or ArCHO KMnO4 RCO2H or ArCO2H K2Cr2O7 © E.V. Blackburn, 2011 Tollens’ test RCHO + + Ag(NH 3)2 colorless solution RCH=CHCHO Tollens' reagent RCO 2- + Ag silver mirror RCH=CHCO 2H © E.V. Blackburn, 2011 Oxidation of ketones - the haloform reaction CH 3 KOCl H3C C CHCCH 3 60C O CHCl 3 + CH 3 - + H3C C CHCO 2 K © E.V. Blackburn, 2011 Reactivity of the carbonyl group R o 120 C 'R sp2 O © E.V. Blackburn, 2011 Nucleophilic addition :Nu R O 'R + Nu R O R' Nu R O R' H2O + Nu R O R' + Nu R OH R' © E.V. Blackburn, 2011 Nucleophilic addition - acid catalysis H+ R R O 'R 'R R 'R :Nu + OH + OH Nu 'R OH R Nu 'R OH R © E.V. Blackburn, 2011 Addition of cyanide cyanohydrin © E.V. Blackburn, 2011 Addition of cyanide © E.V. Blackburn, 2011 Addition of cyanide CH3C=O CN H H+ - OH CH3-C-CN H H2O/HCl OH CH3-C-CO2H H lactic acid © E.V. Blackburn, 2011 Addition of Grignard reagents O R:MgX C R OMgX H 2O C R OH © E.V. Blackburn, 2011 Reduction to alcohols © E.V. Blackburn, 2011 Reduction to alcohols O OCH3 1. NaBH4 OH OCH3 2. H2O O O O OCH3 O 1. LiAlH4 OH 2. H2O HO + CH3OH © E.V. Blackburn, 2011 Reduction to alcohols H 3B H O H - O H 2O H O- H OH hydride transfer © E.V. Blackburn, 2011 Addition of ammonia derivatives O OH C NH-G + H2N-G G N + H2O © E.V. Blackburn, 2011 Addition of ammonia derivatives © E.V. Blackburn, 2011 Addition of ammonia derivatives © E.V. Blackburn, 2011 Addition of ammonia derivatives O O H2NOH H2NNH2 N OH oxime N NH2 hydrazone © E.V. Blackburn, 2011 Addition of ammonia derivatives H N NH2 NO2 O NO2 O2N N N H NO2 © E.V. Blackburn, 2011 Reduction to hydrocarbons Zn(Hg), conc. HCl O H2NNH2, KOH or K t-BuO H C H Clemmensen reduction Wolff-Kishner reduction © E.V. Blackburn, 2011 Reduction to hydrocarbons OH OH CH3(CH2)4COCl AlCl3 OH C(CH2)4CH3 OH O resorcinol Zn(Hg) HCl OH an antiseptic OH CH2(CH2)4CH3 © E.V. Blackburn, 2011 Addition of alcohols dry HCl O H CH3 + CH3OH CH3 OH H OCH 3 hemiacetal CH3 CH3OH OH H OCH -H2O 3 CH3 OCH3 H OCH 3 acetal © E.V. Blackburn, 2011 Addition of alcohols hemiacetal formation O H + R' + OH H R' + H + OH H .. + ROH OH + H C OR R' H R' OH + H C OR R' H OH H C OR + H+ R' © E.V. Blackburn, 2011 Acetal formation H 'R C OR OH2 + H + 'R C OR + H OH H + OR 'R C OR OH2 H R' + + OR .. + ROH H R' H 'R C OR + OR H + H2O H 'R C OR + OR H H + 'R C OR + H OR © E.V. Blackburn, 2011 Reactions of acetals H 'R C OR + H2O OR H + 2ROH + R'-C=O H © E.V. Blackburn, 2011 Acetals as protecting groups O O ? O OH OC2H5 HOCH2CH2OH H3O+ HCl O O O O 1. LiAlH4 OC2H5 2. H2O O OH © E.V. Blackburn, 2011 Wittig reaction P(C 6H5)3 + O an ylid + (C6H5)3PO triphenylphosphine oxide Georg Wittig, University of Heidelberg, Nobel Prize 1979 © E.V. Blackburn, 2011 Wittig reaction - ylid formation CH 2-X Ph3P: + + RCH 2PPh3 + X- R triphenylphosphine + RCH 2PPh3 X + (CH 3)3CO - alkyltriphenylphosphonium halide RCH=PPh 3 + (CH 3)3COH an ylid © E.V. Blackburn, 2011 Wittig reaction + PPh3 R H PPh3 R H O + 'R RH + PPh3 'R O"R R" H R C P Ph3 'R C O R" R R' H R" +Ph3P=O © E.V. Blackburn, 2011 Cannizzaro reaction O strong 2 H base NaOH 2HCHO 50% NO2 -CO 2- + -CH 2OH CH 3OH + HCO 2- Na + NO2 NO2 NaOH + 35% CHO CH2OH CO2 - Na+ © E.V. Blackburn, 2011 Cannizzaro reaction NaOH ArCHO + HCHO conc. ArCH2OH + HCO2- CH2OH CHO NaOH HCHO + + HCO2- conc. OCH3 OCH3 © E.V. Blackburn, 2011 Mechanism H H Ar C OOH O + OH Ar H H Ar C O + Ar OH O Ar HO H O + Ar C OH -H+ ArCO2- H+ ArCH2OH © E.V. Blackburn, 2011 Analysis of aldehydes and ketones • They react with 2,4-dinitrophenylhydrazine. • Aldehydes give a positive Tollens’ test. • Methyl ketones give a positive iodoform test. © E.V. Blackburn, 2011 Spectroscopic properties IR 1705 - 1740 cm-1 - C=O stretching ~2720 cm-1 - C-H stretching in aldehydes NMR chemical shift of aldehyde proton: = 9 - 10 © E.V. Blackburn, 2011