Chem 353-32

Chem 353-32 - Identification of Unknown Ketones This lab is...

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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 were a necessity for organic synthesis before the advent of NMR spectroscopy. These tables, organized by functional group, allowed one to characterize known compounds by comparing the derivative made in the lab with the melting points of derivatives cited in the literature. 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 a 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 in lab. Table 1 . Physical properties and derivative melting points for ten ketones. 1 Ketone MW Lit. bp 2,4-DNPH Derivative mp 9:1 CH 2 Cl 2 /Hexane R f 2-Butanone 72.11 80 116 0.68 2-Pentanone 86.13 100 143 0.69 4-Methyl-2-pentanone 100.16 117 95 0.70 Cyclopentanone 84.12 130 146 0.56 2-heptanone 114.19 151 89 0.71 d,l -3-Methylcyclohexanone 112.17 169 155 0.63 2-Octanone 128.21 173 58 0.74 Cycloheptanone 112.17 181 148 0.65 Acetophenone 120.15 202 238 0.75 Butyrophenone 148.20 229 190 0.80
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Table 2. Reagents, solvents and product.
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Chem 353-32 - Identification of Unknown Ketones This lab is...

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