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IDENTIFICATION OF UNKNOWN KETONES Organic Chemistry 222: Section 0210 Experiment #11 Gifty Asare I.D: 1968165 Experiment conducted on September 24 th , 2010 Report submitted on October 8 th , 2010
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INTRODUCTION An ex-employee is the prime suspect regarding a machine shop incident suggesting arson. Two cans of flammable liquids containing ketones were found in the employee’s garage. The assignment brought to us is to identify the ketones in the liquid and to see if they match those in the residue (methyl ethyl ketone solvent) recovered at the site of the fire. Two different methods have been suggested to identify the ketones. Thin-layer chromatography (TLC) is a popular method in laboratories for separating the components of compounds. It also has the advantage of being fast and efficient because of the variety of absorbents available to it. TLC is used to monitor the progress of a reaction,   identify compounds present in a given substance, determine the purity of a substance and is performed on a sheet of glass, plastic, or aluminum foil, which is coated with a thin layer of adsorbent material. The layer of adsorbent is known as the stationary phase. The liquid solvent is the mobile phase that creeps up the absorbent layer via capillary action. In this case, the absorbent on the TLC plate is silica gel and the liquid solvent is 3:1 toluene petroleum. The ratio to front (R f ) value of components visualized on a TLC plate can be compared to known R f values and thus identified. Nuclear magnetic resonance (NMR), another method for identifying compunds, is widely used to study molecular physics, crystals and non-crystalline materials through NMR spectroscopy. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI). NMR is a property that magnetic nuclei have a magnetic field and applied EM pulses which cause the nuclei to absorb energy radiate it back out with a specific resonance frequency which depends on the strength of the magnetic field and other factors. This allows the observation of specific quantum mechanical magnetic properties of a proton’s nucleus in our case. In the conducted experiment, our unknown ketone was converted to 2,4- dinitrophenylhydrazone (DPNH) by combining the ketone with DPNH reagent in order to be able to distinguish the spots clearly after the TLC. The derivative was then purified by recrystallization after washing it with sodium bicarbonate and vacuum filtrating it. The derivatives of known ketones will be prepared by combining them with DNPH reagent as well for
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This note was uploaded on 10/20/2010 for the course CHEMISTRY 202 taught by Professor Ta during the Fall '10 term at Concordia University Irvine.

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