Organic 2 Review Problem 432

Organic 2 Review Problem 432 - noted that the...

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PART IV QUANTITATIVE ANALYSIS THE analyses which follow are arranged in the order in which they would be applied to a newly discovered substance, the estimation of the elements present and molecular weight deter- minations (i.e., determination of empirical and molecular formulae respectively) coming first, then the estimation of particular groups in the molecule, and finally the estimation of special classes of organic compounds. It should be noted, however, that this systematic order differs considerably from the order of experi- mental difficulty of the individual analyses. Consequently many of the later macro-analyses, such as the estimation of hydroxyl groups, acetyl groups, urea, etc., may well be undertaken by elementary students, while the earlier analyses, such as estimation of elements present in the molecule, should be reserved for more senior students. The estimation of carbon and hydrogen, of nitrogen and of methoxy groups has now however been transferred to Section B (Semi-rnicroanalysis) (p. 465). In this connection it should be
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Unformatted text preview: noted that the macro-estimation of nitrogen in foodstuffs, etc., by the Kjeldahl method is still often employed because of the low nitrogen content and the non-homogeneous nature of the material. Full details of this method on the macro-scale will be found in An Introduction to Practical Organic Chemistry by Mann and Saunders, 4th ed., p. 148 (Longman Group Ltd.). SECTION A MACROANALYSIS Estimation of Halogens. Carius's Method. Principle. A known weight of the substance is heated with fuming nitric acid and silver nitrate in a sealed tube. The organic material is thus oxidised to carbon dioxide and water, whilst the halogen is converted quantitatively into the corresponding silver halide. The latter is subsequently washed out of the tube, filtered and weighed. The method is general for all organic halogen compounds and is the standard method for almost all such compounds, except of course 416...
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This note was uploaded on 09/19/2011 for the course CHM 2211 taught by Professor Castalleano during the Fall '06 term at University of Florida.

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