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Solutions to Problems 275 1. BH 2 2. NaOH, H₂O₂ 45(i) C=C H OH 47. In these, "racemic" means a racemic mixture of and S,S stereoisomers. R R R D C=C D D D R (a) meso-RCHDCHDR (a) racemic RCHDCHDR (b) racemic RCDCDR (b) meso-RCDCDR Br Br Br Br D D D R R R R D (c) racemic (c) racemic H OH H OH D D D R R R D (d) (d) O O D D D R R D (e) meso- (e) racemic OH HO OH 48. 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 stereoiso- meric 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 unsatu- rated regioisomers are obtained as minor products. Finally, addition of chlorine to trans-3-heptene gives 3,4-dichloroheptane. 1. HCI 2. HBr 49. (a) CH₃CH₂C=CH product 2HI (b) product CH₃ H Na, NH₃ Br₂, (c) product H CH₃ CH₃ CH₃ H₂, Pd-BaSO4, quinoline, CH₃CH₂OH (d) product H H