Pre~arationand S~ectrosco~ic Examination of an
Michael J. Newlands Memorial University of Newfoundland St. John's, Newfoundland, Canada, AlC 5S7 Although organometallic compounds are of increasing importance in both inorganic and organic chemistry on the academic and industrial scales, lahoratory preparations do not appear to be very common in courses taken by the majority of Chemistry Majors. The present example uses cheap materials, introduces the student to the Grignard reaction and to vacuum distillation.. .. eives a .. eood vield. " . and orovides a product u,hose spectra are sufficiently simple to interpret to be useful in introducine the student to the aoolirations of .. spectroscopy to structure determination or structure confirmation. Diphenylmethylsilane, (CeH5)2(CH3)SiH.is prepared on a 0.1 molar scale from bromobenzene and methyldichlorosilane, CH3SiHC12. The bromohenzene is converted into the corresponding Grignard reagent in ether. We have used a 10% excess of the Grignard reagent and have carried out the synthesis under nitrogen, which may not be essential. Methyldichlorosilane is then added to the Grignard in a mixture with ether and the reaction mixture refluxed for a short time. Work-up is standard. The dried ethereal solution has the solvent removed on a rotary evaporator and the product is distilled through a Vigreux column a t about 1mm Hg. The product distils a t about 73°C. I t is sensible to use nitrogen rather than air in the distillation bleed because of the presence of the SiH bond in the product. A yield of around 13g, 67% is easilv ohtained. The produrt can be very well characterized hy its infrared spectrum (ohtained as a liquid film), its 'Hnmr spertrum (we used methyl cyanide as solvent and internal standnrd-tetramethylsilane should not be used for the latter function), and its mass spectrum. If the nmr spectrum is run carefully, satellite peaks resulting from '%-H coupling can he observed on either side of the silane hydrogen resonance (6 5.43 ppm). Coupling between the silane and methyl hydrogens is readily measurable.
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chemical analysis a t the exclusion (at least in part) ofspectral methods. Spectral methods, when employed, are relegated to one or two specific laboratories and are not truly integrated into the laboratory course material. In an attempt to provide a more realistic and relevant laboratow ex~eriencefor students, the qualitative analysis portion of the laboratory has been desipeh u, give the student a "ta$teof what the world is really like." Each student is given an arrount with his instructor which is credited with 5200.00. These monies may he used to purchase ir spectra, uv spectra, and refractive indices (run by the student in the laboratory) or elemental analysis, nmr spectra, or mass spectra (M peak and M 1and M 2 peaks, provided by the instructor). We find this method extremely well received by the students who, once initiated, find the entire laboratory challenging, interesting, fun and a learning experience relevant to the real world. Upon request, we are prepared to provide copies of all handouts designed for this laboratory. Thanks are extended to Mr. David Bernstein for many helpful discussions a t the onset of this project.
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A General Potentiometric Titration Curve Computer Program G. L. Breneman Eastern Washington University, Cheney, 99004
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A Droeram .. has been written in Basic to d. o t ootentiometric . titration curves for a variety of situations. The program will handle all six suhmou~sof' redox titration reactions described by Dick.' This includes cases where the equivalence point potential depends on the concentration of some of the materials in the reaction and where H30+ or OH-enter as part of the reaction. In general overall reactions such as
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The Qualitative Organic Analysis Laboratory: A Real Life Experience Robert L. Caret Towson State University Towson, Maryland 21204 Qualitative organic analysis is an essential part of all Organic Chemistry courses. The bulk of this material is presented in lecture, either lahoratory or recitation, hut the actual hands-on work is of course performed primarily in the laboratory. Though most lecture texts integrate the classical wet qualitative analysis with the more modern spectral methods, lahoratrry texts, in general, tend all toooften to stress the wet 246 1 Journal of Chemical Education
with half reactions
can he handled. Also those whose half reactions both involve H30+ or OH- can he handled. One of three standard reference electrodes (standard hydrogen, saturated calomel, or AgIAgC1) can be picked for the potential calculation or the user can input the potential of any other reference he may wish to use. Concentrations and volumes can he preset by the program or input by the user. For simple cases where there is an equimolar relationship between reactants and products in both half reactions and no H30+ or OH- is involved, input consists of the half cell potential and the number of electrons involved for each half reaction. In the 1
Dick, J. G., "Analytical Chemistry," McGraw-Hill, New York,
1973. pages 350369.
