A periodic table that summarizes a variety of bond energy information.

The mechanism of the palladium-catalyzed carbomethoxylation of bromobenzene to methyl benzoate in the presence of methanol and triethylamine has been investigated with Cylindrical Internal Reflectance Fourier Transform Infrared Spectroscopy (CIR-FTIR). The synthesis of the proposed catalytic intermediate Pd(Br)(C6H5)(P(C6H5)3)2 (1) was carried out, and the reaction of this species with CO to form Pd(Br)(COC6H5)(P(C6H5)3)2 (3) was confirmed. Both complexes were characterized by IR and 31P and NMR spectroscopy. The stability of 3 in the absence of CO suggests that the carbonylation of 1 is irreversible; its stability in the presence of triethylamine establishes that reductive elimination of benzoyl bromide is not facile. In the absence of CO, the conversion of 3 to methyl benzoate was found to be rapid when both methanol and triethylamine were present, but very slow in the presence of methanol alone. A series of experiments in which 3 was allowed to react with methanol and a variety of amines in the absence of CO demonstrated a direct relationship between the rate of reaction and the amine basicity. These observations point to a mechanism in which methanol is initially deprotonated by the amine, and the methoxide ion thus produced attacks the benzoyl complex directly yielding methyl benzoate. When reaction of the benzoyl complex with methanol and triethylamine was carried out with bromobenzene also present, regeneration of 1 was observed via CIR-FTIR and confirmed by IR and proton NMR spectroscopy. The carbomethoxy species, Pd(Cl)(C02CH3)(P(C6H5)3)2, was shown to be stable in the presence of bromobenzene, triethylamine, and methanol at 90 °C, suggesting that this complex is not an active catalytic intermediate. These experiments substantiate the mechanism in Figure 8.

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Our objectives were to develop a model of student portfolios that simultaneously promotes student learning, provides useful outcomes assessment data, and is logistically feasible. From our pilot test of three portfolio models, we conclude that requiring students in selected courses to complete portfolio entries solves most of the logistics problems associated with a large‐scale portfolio plan. Such entries can promote learning by providing a focus for career and educational planning discussions between students and faculty academic advisors. Course faculty are probably in the best position to use the outcomes assessment data obtained from the entries.

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In response to the widely recognized problems with the traditional approach to the introductory chemistry laboratory (1-5), we have initiated the complete restructuring of our program around two major themes. First, our new program incorporates the Discovery approach (6, 7). Second, experiments incorporate the use of modern instrumentation to give students a state-of-the-art laboratory experience that anticipates the workplace experience. We have previously described experiments based on gas chromatography (GC) and electronic absorption spectroscopy (8-10). We here present a headspace GC experiment that enables discovery of the temperature dependence of the vapor pressure of a pure liquid. Articles dealing with the measurement of vapor pressure have appeared in the . The experiment that we discuss here simply and elegantly illustrates liquid-vapor phase equilibrium of pure liquids. The experiment is at a level appropriate for beginning freshmen, yet is challenging, interesting, and informative at the same time. Students discover that

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Description of an experiment that uses both modern instrumentation and the discovery approach to learning with an introductory chemistry lab.