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Combination techniques, such as gas chromatographymass spectroscopy (GC-MS) or gas chromatography-infrared spectroscopy (GC-IR), are widely used throughout the chemical community to simultaneously separate and identify components of mixtures. The pedagogical value of introducing students to these techniques has been recognized by funding agencies such as the NSF-ILI program, who are making them available for undergraduate instruction (1). To illustrate, in 1988, The National Council for Undergraduate Research determined that 92 of the 224 public and private undergraduate institutions surveyed (43%) had a GC-MS. However, few experiments have been designed to use this instrument (2-4) and most of the experiments that have been presented were designed for use in instrumental analysis or biochemistry. Although mass spectrometers usually are mentioned in general chemistry texts (5-7) and often students are introduced to mass spectrometric analysis in organic chemistry (8-10), recent lab manuals for organic chemistry rarely contain mass spectrometry experiments. As part of our sophomore-level integrated inorganic/organic laboratory, the syntheses of ferrocene and acetylferrocene are carried out (11). In addition to common purification and characterization techniques (sublimation, thin-layer and column chromatography, FTIR, and ^sup 1^H and ^sup 13^C NMR), the progress of these reactions is monitored using GC-MS and GC-FTIR. Because the student response from the sophomores was extremely favorable, we also have ineluded GC-MS in our introductory chemistry majors laboratory as part of the 2,4-pentanedionato complex synthesis and spectroscopy experiment (12). Both reaction systems are well suited for introductory MS experiments because these compounds give clear parent peaks and simple fragmentation patterns that can be correlated readily to the structure of the complex.
Experimental Procedure
During the first several weeks of the second semester in the sophomore-chemistry majors' laboratory, the students synthesize ferrocene and acetylferrocene following preparation procedures given previously (11). The students prepare, purify, and characterize the ferrocene using UV/visible spectroscopy, FTIR, FT-NMR, and GC-MS. They use this product to prepare the acetylferrocene. The acetylferrocene is purified using column chromatography and checked for purity using thin-layer chromatography (TLC). Identical fractions are combined, evaporated, and analyzed using GC-MS.
The three-week 2,4-pentanedionato complex synthesis and spectroscopy experiment used in the freshman laboratory has been presented in this Journal previously (12). The students synthesize tris(2,4-pentanedionato-O,O')aluminum, tris(2,4-pentanedionato-O,O')chromium (III), or tris(2,4-pentanedionato-0,O')iron(III) using synthesis procedures found in the literature. In addition to...