Cyclopentyl ethyl ether

SAMPLE SOLUTION (a) The ether linkage of cyclopentyl ethyl ether involves a primary carbon and a secondary one. Choose the alkyl halide corresponding to the primary alkyl group, leaving the secondary alkyl group to arise from the alkoxide nucleophile. 

Sodium cydopentanolate Ethyl bromide Cyclopentyl ethyl ether... 

Why is the cyclopentyl group chosen for the alkoxide and the ethyl group chosen for the halide Why not use cyclopentyl bromide and sodium ethoxide to make cyclopentyl ethyl ether ... 

Iodide and bromide ions are good nucleophiles but weak bases, so they are more likely to substitute by the Sn2 mechanism than to promote elimination by the E2 mechanism. Mechanism 14-1 shows how bromide ion cleaves the protonated ether by displacing an alcohol. In the following example, cyclopentyl ethyl ether reacts with HBr to produce cyclopentanol by this displacement. Cyclopentanol reacts further with HBr, though, so the final products are ethyl bromide and bromocyclopentane. 

EXAMPLE Cleavage of cyclopentyl ethyl ether by HBr. Step 1 Protonation of the ether to form a good leaving group. 

The elementary analysis is in agreement with the theoretical values. The starting l-amino-4-cyclopentylpiperazine (b.p. 80°-82°C/0.1 mm Hg) is obtained by alkylating N-nitrosopiperazine with cyclopentyl bromide in ethanol in the presence of NaHC03 and reducing the so-obtained l-nitroso-4-cyclopentylpiperazine with LiAIH4 in ethyl ether. 

Seed crystals were also effective for the inclusion complexation of 12 with some other guests. Contact of powdered 12 with gaseous MeOAc and EtOAc for 3 h in the presence of seed crystals of 3 1 inclusion complexes of 12 and MeOAc and EtOAc, respectively, led to the corresponding inclusion complexes in quantitative yields. A pseudo-seed crystal is also effective. For example, contact of powdered 12 with ethyl ether vapor for 3 h in the presence of a seed crystal of the 3 1 complex of 12 and MeOAc gave the 3 1 complex 82 but not 83. Similar conctact of powdered 12 with ethyl ether vapor for 12 h in the presence of a seed crystal of the 1 2 complex of 12 and cyclopentyl methyl ether gave the 1 2 complex 83 but not 82 [47]. 

Introduction of polarity proximal to the cyclopentyl-ethyl function is accommodated by a reduction of the predicted total metabolism observed. Thus, aliphatic ethers were introduced, which are also tolerated by the DGATl pharmacophore. 

Caution Hexanes, cyclopentyl methyl ether, and ethyl acetate are highly flammable. 

CH2CH2—OH (b) CH3CH2C(CH3)2—OH (c) I cyclopentyl-l-butanol. 14.34. (a) The old ether had autoxidized to form peroxides. On distillation, the peroxides were heated and concentrated, and they detonated (b) Discard the old ether or treat it to reduce the peroxides. 14.38. (a) epoxide + PhMgBr (b) epoxide -I- NaOCH3 in methanol (c) epoxide + methanol, H. 14.42. Sodium then ethyl... 

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