1559T_ch23_409-42210/19/0519:50Pa9e417 EQA Solutions to Problems.417 0 CHO fragments.Simplest interpretation:molecule is CH.CCCH (b)Oxidation.Churning cream mixes it with air,thus allowing O to react with ketoalcohol A to 38.Addition to carbonyl 0 CHaCH +/CHCH2O--CHaC-OCH.CHs Deprotonation of a-carbon 0 Deprotonation of the aldehyde carbon leads to a much poorer anion than the enolate:CHC:electron pair in an sporbital,unable to be stabilized by resonance.Given the two favorable processes shown above. deprotonation of the -CH group is simply not competitive 39 CO.CH: CO.CH 290 -CH;OH -H0 Solutions to Problems • 417 B Molecular weight is reduced by 2 units, so formula is probably now C4H6O2. IR: Ketone signal only. NMR: All H’s equivalent. MS: Molecule breaks in half readily, giving m/z 43, O OO B BB C2H3O fragments. Simplest interpretation: CH3OCO, so molecule is CH3CCCH3 (b) Oxidation. Churning cream mixes it with air, thus allowing O2 to react with ketoalcohol A to make diketone B. (c) You can synthesize A by reaction of acetaldehyde with catalytic N-dodecyl-thiazolium salt (Section 23-4). Oxidation gives B. (d) The diketone is conjugated. 38. Addition to carbonyl: Deprotonation of -carbon: O B Deprotonation of the aldehyde carbon leads to a much poorer anion than the enolate: CH3C), electron pair in an sp2 orbital, unable to be stabilized by resonance. Given the two favorable processes shown above, O B deprotonation of the OCH group is simply not competitive. 39. 1. NaOCH3, CH3OH 2. H, H2O H2O O CO2CH3 1. NaOCH3, CH3OH 2. H, H2O CH3OH CO2CH3 O 1. NaOCH3 2. O O O CO2CH3 Br Br 1. Na CH(CO2CH3)2 2. NaOH, H2O 3. H2SO4, H2O,  2 CH3OH 2 CO2 CH3OH, H CO2H CO2H CO2CH3 CO2CH3 CH3CH2O O O HCCH2 HCCH2 Enolate H HOCH2CH3  CH3CH2O O O CH3CH CH 3C H OCH2CH3 1559T_ch23_409-422 10/19/05 19:50 Page 417