434 ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP 17.16 Ylides are prepared by the reaction of an alkyl halide with triphenylphosphine, followed by treat ment with strong base. 2-Bromobutane is the alkyl halide needed in this case (C6H5)3P CH3 CHCH, CH3-(CH5)3P-CHCH2CH3 Br CH3 2-Bromobutane (1-Methylpropyl)triphenyl (C HS)P-CHCH,CH, Br NaCH,SCH (C6H5)2P—CCH2CH2 Sodiomethyl 17.17 The overall reaction is CCH3+ C COOH OCCH3+ C6HS COH Cyclohexyl methyl Peroxybenzoic Cyclohexyl Benzoic In the first step, the peroxy acid adds to the carbonyl group of the ketone to form a peroxy monoester CCH CHCOOH CCH OOCCSH Peroxy monoester The intermediate then undergoes rearrangement. Alkyl group migration occurs at the same time as cleavage of the o-o bond of the peroxy ester In general, the more substituted group migrates HC H-C O+ HOCC6Hs SOCC.H 17.18 The formation of a carboxylic acid from Baeyer-Villiger oxidation of an aldehyde requires o COCC.H Back Forward Main Menu TOC Study Guide Toc Student OLC MHHE Website17.16 Ylides are prepared by the reaction of an alkyl halide with triphenylphosphine, followed by treat￾ment with strong base. 2-Bromobutane is the alkyl halide needed in this case. 17.17 The overall reaction is In the first step, the peroxy acid adds to the carbonyl group of the ketone to form a peroxy monoester of a gem-diol. The intermediate then undergoes rearrangement. Alkyl group migration occurs at the same time as cleavage of the O@O bond of the peroxy ester. In general, the more substituted group migrates. 17.18 The formation of a carboxylic acid from Baeyer–Villiger oxidation of an aldehyde requires hydrogen migration. C6H5COOH O O CH O2N m-Nitrobenzaldehyde O COH O2N m-Nitrobenzoic acid OH C H O OCC6H5 O O2N H3C O C O O HOCC6H5 C OCC6H5 O OH O H3C O C6H5COOH O CCH3 Peroxy monoester OH OOCC6H5 O CCH3 Peroxybenzoic acid O C6H5COOH Cyclohexyl methyl ketone O CCH3 Benzoic acid O C6H5COH Cyclohexyl acetate O OCCH3 Br CH3 CHCH2CH3 (C6H5)3P (1-Methylpropyl)triphenyl￾phosphonium bromide Sodiomethyl methyl sulfoxide O NaCH2SCH3 Ylide CH3 CCH2CH3 (C6H5)3P Br CH3 CHCH2CH3 (C6H5)3P (1-Methylpropyl)triphenyl￾phosphonium bromide CH3CHCH2CH3 Br 2-Bromobutane (C6H5)3P Triphenyl￾phosphine 434 ALDEHYDES AND KETONES: NUCLEOPHILIC ADDITION TO THE CARBONYL GROUP Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website