1559T_ch13_247-25811/03/0520:12Pa9e254 EQA 254.Chapter 13 ALKYNES:THE CARBON-CARBON TRIPLE BOND 38.In these,"racemie"means a racemic mixture ofRand S.S stereoisomers ce-B R n (a)meso-RCHDCHDR (a)racemic RCHDCHDR (b)racemic RCDCDR (b)meso-RCDCDR BrBr Br Br (rncemic R pR (e)rocemie RD H OH 仙RAR (d)R D Omea.R号R HO OH (e)racente D HO OH 39.The only high-yield precursor is 3-heptyne(g).which gives cis-3-heptene with both good yield and 3-bepteneSimil (and heptanol are better because at least the regioisomer problem isgone:Onlycand-eptenescan form.Doubl 40.aGH,C,C=CH2 →product bCH,CH.CH.CH.CCH prodct (CHC=CCH, CH CHs 周cHc=ca也Ch。。 HH CH、Br (e)CH;C=CCH; C=C Mainly (f)CH,CH:CH C=CCHCH.CH prodoct 38. In these, “racemic” means a racemic mixture of R,R and S,S stereoisomers. (a) meso-RCHDCHDR (a) racemic RCHDCHDR (b) racemic RCDCDR (b) meso-RCDCDR AA AA Br Br Br Br (c) racemic (c) racemic (d) (d) (e) meso- (e) racemic 39. The only high-yield precursor is 3-heptyne (g), which gives cis-3-heptene with both good yield and selectivity upon hydrogenation over Lindlar’s catalyst. Eliminations of 3-chloroheptane (a) with base and 3-heptanol (d) with acid are the poorest choices because both will give regioisomeric and stereoisomeric mixtures of cis- and trans-2- and 3-heptenes. Similar eliminations of 4-chloroheptane (b) and 4-heptanol (e) are better because at least the regioisomer problem is gone: Only cis- and trans-3-heptenes can form. Double elimination from 3,4-dichloroheptane (c) gives mostly 3-heptyne (g), but other unsaturated regioisomers are obtained as minor products. Finally, addition of chlorine to trans-3-heptene gives 3,4-dichloroheptane. 40. (a) (b) (c) (d) (e) (f) CH3CH2CH2C CCH2CH2CH3 product HgSO4, H2SO4, H2O CH3C CCH3 HBr product Cl2, CCl4 C C H CH3 CH3 Br Mainly CH3C CCH3 product H2, Pd-BaSO4, quinoline, CH3CH2OH Br2, CCl4 C C H CH3 CH3 H CH3C CCH3 product Na, NH3 Br2, CCl4 C C H CH3 CH3 H CH3CH2CH2CH2C 2HI CH product CH3CH2C 1. HCl 2. HBr CH product D R D R HO OH D D R R HO OH D R R D O D D R R O D R D R H OH D D R R H OH C R R D D C C R R D D C 254 • Chapter 13 ALKYNES: THE CARBON–CARBON TRIPLE BOND 1559T_ch13_247-258 11/03/05 20:12 Page 254