Unknown A - Identification of an Unknown Ketone

Unknown A - Identification of an Unknown Ketone -...

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Identification of Unknown Ketones This lab is an exercise in determining the identity of two unknown ketones using derivatives and proton NMR. The reaction below is a generic example of a derivative formed from a ketone. Your task will be to determine the R groups, and thus the identity of your unknowns from the list of possibilities provided in Table 1. Historically, the chemical reaction above has been widely used to characterize both ketones and aldehydes due to the fact that hydrazone derivatives are relatively easy to form, and are solids at room temperature. Compiled derivative tables with melting point data were a necessity for organic synthesis before the advent of NMR spectroscopy. These tables, organized by functional group, aided the student and researcher alike to characterize known compounds by duplicating the derivative and comparing the melting points. The chemistry and techniques behind derivative formation can be quite interesting and useful in developing laboratory skills. NMR spectroscopy has largely antiquated the use of derivatives for characterizing organic compounds. To highlight the reasons why, you will determine the identity of the second unknown ketone using a proton NMR alone. The second unknown will also be limited to the compounds in Table 1, and the proton NMR will be provided to you. Table 1 . Physical properties and derivative melting points for ten ketones. 1 Ketone MW Lit. bp 2,4-DNPH Derivative mp 2-Butanone 72.11 80 116 2-Pentanone 86.13 100 143 4-Methyl-2-pentanone 100.16 117 95 Cyclopentanone 84.12 130 146 Cyclohexanone 98.14 155 160 d,l -3-Methylcyclohexanone 112.17 169 155 2-Octanone 128.21 173 58 Acetophenone 120.15 202 238 Propiophenone 134.18 218 191 Butyrophenone 148.20 229 190
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Table 2. Reagents, solvents and product. hydrazone
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This note was uploaded on 03/08/2012 for the course CHEM 353 taught by Professor Bronson during the Fall '11 term at BYU.

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Unknown A - Identification of an Unknown Ketone -...

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