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1. The alkyne module in ORGO will give you a good review of some of the fundamental reactions of alkynes. 2. 1-Butyne and 2-butyne can be interconverted with base via their common allene, 1,2-butadiene. Provide a mechanism for this interconversion. Draw an energy diagram that explains why fused KOH (200 oC) gives 2-butyne and NaNH2 (150 oC) gives 1-butyne (after the addition of water). The pKa and heat of formation data on alkynes will be of help. 3. Compound A (C8H14) is reduced to give compound B (C8H16). In a different experiment, compound A is reduced to afford compound C. In separate experiments, both B and C react with H2 in the presence of a Pt catalyst to produce 2,5-dimethylhexane D but B liberates ~1 kcal/mol more heat than C in the hydrogenation. What are the structures of A - D and what are the reduction conditions for A --> B and A --> C? Explain and illustrate. 4. 1-Hexyne A reacts successively with NaNH2 and B (C4H9Br) to produce a single compound C. Hydrogenation of C with Lindlar's catalyst affords D. |
Sterling Chemistry Laboratory Watercolor by Professor H. H. Wasserman |
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Compound D provides a single aldehyde E upon ozonolysis and dimethyl sulfide reduction. What are the structures of A-E? Explain and illustrate. 5. Compound A (C10H20) reacts with O3/dimethyl sulfide to produce B and C. This mixture is the same mixture of compounds obtained by treatment of D (C5H8) with aqueous HgSO4/H2SO4. Upon heating D with NaNH2 at 150 oC, E is formed. Treatment of E with aqueous HgSO4/H2SO4 gives B. What are the structures of A-E? Explain and illustrate. 6. A bottle in a laboratory is labeled "C6-alkyne mixture A and B". A chemist separates the mixture by careful distillation. When she reacts A with Li/NH3, compound C is obtained. When A reacts with HgSO4/aqueous H2SO4, two ketones, D (C6H12O) and D' (C6H12O) are formed. On the other hand, when she reacts B with Li/NH3, compound E is formed, which is different from C. The reaction of E with m-chloroperbenzoic acid provides F (C6H12O), which, when exposed to aqueous acid, gives meso-diol G (C6H14O2). Both A and B give H (C6H14) upon reaction with H2/Pt. Compound H forms three monochlorination products upon free radical chlorination. What are the structures of A-H? Explain and illustrate. 7. Design an efficient synthesis of the ketone 3-hexanone. The only sources of carbon available to you are acetylene and ethylene. You have access to all reagents.
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