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182 Chapter 9 FURTHER REACTIONS OF ALCOHOLS AND THE CHEMISTRY OF ETHERS Also, for (f) CH₃ CH₃ LiAIH, Finally (g) CH₃ (CH₃)₃COH CH₃ H CH₃ 56. (a) OCH₂CH₃ CH₃ H SN2 by ethanol on protonated oxacyclopropane. Attack at either ring carbon gives same product. H CH₃ HO (b) D H at either ring carbon. CH₃ 57. (a) Cyclopropylmethanethiol (b) 2-(Methylthio)butane, or methyl (1-methyl)propyl sulfide (c) 1-Propanesulfonic acid (d) Trifluoromethylsulfonyl chloride 58. In each case, (1) is the stronger acid and (2) is the stronger base. (a) (1) CH₃SH, (2) CH₃OH (b) (1) (2) (c) (1) H₃S⁺, (2) H₂S SH 59. (a) (b) (SN2) S intermediate) CH₃ SH H (c) (SN2 again) (d) (CH₃CH₂)₃CSCH₃ (SN1) OH H a (e) (f) SO₂ 60. A "road-map" problem. Hint: There is "hidden" information. For example, if you just work out CH₃ the molecular formula of the final product, whose structure is shown, you obtain a useful clue. It is C₆H₁₂SO₂, differing from unknown C by only two oxygens. So we can identify structure C as the cyclic sulfide prior to oxidation (see structure in the margin). S Where do we go next? The reaction that produces C involves treatment of B with Na₂S. Look at Problem 58(a). A butane with leaving groups at each end gives thiacyclopentane on reaction with Na₂S. Do the same thing here, but pay attention to the methyl substituents and their stereochemistry. C must be formed by reaction of Na₂S with a meso-2,3-dimethylbutane with leaving groups at each end: