This paper describes work done to develop a meaningful undergraduate organic lab activity that illustrates chemistry of the real world while utilizing reactions typically included in the organic lecture and lab. We show how a common plastic can be converted into several compounds using ester hydrolysis and SN2 reactions.Contributing to the critical shortage of landfill space faced by many communities is the large quantity of plastic refuse. Thus, there is a real need to recycle plastic products. One way to recycle plastics such as polyethyleneterephthalate (PET), the polyester from which numerous consumer products such as 2-liter soda bottles are made, is to depolymerize them and then to use the resulting monomers to produce new products. PET is industrially depolymerized via an acid-catalyzed transesterification reaction conducted under conditions of high temperature and pressure that are not feasible in the undergraduate lab. Despite literature reports that PET is remarkably resistant to hydrolysis, we found that PET can be readily hydrolyzed by refluxing with potassium hydroxide or potassium tert-butoxide in amyl alcohol to give terephthalic acid in high yield. It is then possible to readily synthesize terephthalate diesters via SN2 reactions of ammonium terephthalate salts with alkyl halides. Fischer esterification can also be used to prepare the diesters, but yields are significantly lower.

A kinetics experiment is found in virtually all undergraduate physical chemistry laboratory texts and indeed is even common in many organic laboratory texts. Furthermore, increasing applications of various spectrophotometric methods, particularly nuclear magnetic resonance, are being made a part of the laboratory experience in both of these courses. Thus, a kinetics experiment utilizing NMR spectroscopy to obtain rate data should be particularly attractive to instructors in these laboratories. Advantages of the ExperimentThe experiment presently discussed also offers the following advantages:1. The reactant, p-methoxyphenylacetylene, is easily synthesized from readily available starting materials.* 1 2. As little as 30 mg of compound is required per student or pair of students. 3. Other than the NMR spectrometer, the only required apparatus includes an analytical balance, syringe, NMR tube in which the entire reaction is conducted, and a temperature controlled water bath (optional). 4. The reaction involved, the hydration of an alkyne, is simple and should be known to all students who would be conducting the experiment. 5. The experiment gives reproducible data from which a rate expression is easily extracted which is consistent with the accepted mechanism of the reaction.6. The reaction is conveniently run at elevated temperatures of one's choosing and thereby permits the calculation of the energy of activation for the reaction.

Reduction of a«» heptan-3-one (8). Lithium aluminum hydride reduction of pure 8 gave a mixture of 16 and 17 in 89 % yield.Reduction of iyn-7-Methoxytricyclo[2.2.1.02'6]heptan-3-one (18). Lithium aluminum hydride reduction of pure 18 gave pure 15. Identification was made by a comparison of infrared spectra and vpc retention times. Reaction of 7,7-Dimethoxybicyclo[2.2.1]hepta-2,5-diene (6) with Methanoiic Sulfuric Acid. The ketal 6 (194 mg) was treated with 10% methanoiic sulfuric acid for 21 hr at room temperature. Hydrolytic work-up as described for reactions of 4 gave benzene and no residue after removal of ether and benzene by distillation at reduced pressure.Equilibration of 3,3-Dimethoxytetracycio[2.2.0.02'7.04'6]heptane (4) with Ethanol via Acid Catalysis. A sample of 177 mg of 4 was dissolved in 249 mg of dry ethanol (distilled from magnesium ethoxide). The nmr spectrum was recorded and showed the spectrum of 4 superimposed on the spectrum of ethanol. The triplet observed for ethanol's hydroxyl proton demonstrated that the sample was acid free.A solution was prepared from 19 mg of sulfuric acid and 3.34 g of dry ethanol, and 86 mg of this solution was added to the nmr tube containing 4 and ethanol. The tube was shaken vigorously and the nmr spectrum was recorded (total elapsed time 100 sec).In addition to showing the simplified ethanol spectrum (due to acid-catalyzed exchange of the hydroxyl proton), the spectrum showed a drastic decrease in the relative intensity of the absorption due to the dimethyl ketal and the presence of a new absorption due to methanol. This spectrum of equilibrated material did not undergo further change on rerunning.

No abstract

No abstract