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Solutions to Problems 177 42. Ethers lack hydrogens attached to oxygen, and therefore. unlike alcohol molecules. ether molecules cannot hydrogen bond to one another. Ethers can hydrogen bond to the hydrogens of water, however, and therefore are more soluble in water than the analogous alkanes but still less soluble than alcohols of comparable molecular weight. 43. The usual options are Williamson ether synthesis (if at least one of the components is a good SN2 substrate) or acid-catalyzed reaction in the case of symmetrical ethers or ethers containing one fragment suit- able for solvolysis (SN1) chemistry (usually tertiary). (a) 2 CH₃CH₂CH₂OH NaH 0 (b) NaH (c) CH₃CH₂CH₂CH₂OH (d) (CH₃)₂CHCH₂OH NaH NaH CH₃CH₂CH₂Br (e) (CH₃)₂CHOH NaH (f) A Williamson ether synthesis would also be usable to synthesize propoxypropane (a), but the mineral acid method is simpler. All the rest are Williamson methods. In the cases of the ethers in (b), (c), and (f), the syn- thesis would work as well if carried out in the complementary manner, reversing the starting materials' roles, because both alkyl groups are suitable for use as SN2 substrates. Such is not the case in (d) and (e): Branched primary and secondary haloalkanes are poorer substrates in SN2 reactions and undergo elimination to a significant degree. 44. (a) (SN2 okay on 1° haloalkane.) (b) CH₃CH₂CH₂OH + CH₃CN=CHCH₂CH₃ (Basic alkoxide gives mainly E2 with 2° haloalkane.) CH₃ (c) (d) OCH₃ (e) Cyclohexanol + cyclohexene [Same situation as (b).] (f) CH₃ OH + 45. The products are shown above. As in the solutions for Problem 30. only the mechanisms and interme- diates (if any) will be presented here.