ketone reduction report.docx - Experiment 5B Ketone...

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Experiment 5B: Ketone Reduction by usage of Sodium Hydride: cis-and-trans-4-tert- Butylcyclohexanol Objective The main objective in this experiment was to take 4-tert-butylcyclohexanone and add a metal hydride, sodium borohydride, in the presence of methanol. This mechanism allows the ketone on the 4-tert-butyl cyclohexanone to be reduced to the corresponding alcohol (cis or trans conformer). In analyzing the reaction, we monitored the resulting solution by TLC. In using ethyl acetate:hexanes, we were able to distinguish spots that were corresponding to the ketone standard, crude reaction, and the crude spot. In doing so, we were able to determine the presence of the cis and or trans conformation. P-anisaldehyde was used in order to stain the TLC plate, so that the spots would appear. Subsequently, the final product was used in order to characterize it via an IR spectrum. Experimental Procedure: The procedure was carried out as described in Mayo, pages 158-163, with the modifications posted in the Canvas document. No melting point was acquired. Reaction Scheme:
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Data and Results: Data and Results Table: 4-tert- butylcyclohexanon e Methanol Sodium Borohydride Hydrochloric Acid (3.0M) Methylene Chloride 4-tert-butyl cyclohexanol mol. Formula C 10 H 18 O CH 3 OH NaBH 4 HCl CH 2 Cl 2 C 10 H 20 O amount (mg) 100 --- --- --- --- (TY) 101 (EY) 29 amount (mL) --- 0.100 0.200 1.0 1.5 mmoles 0.65 --- --- --- --- (TY) 0.65 (EY) 0.18 molar mass (g/mol) 154.25 32.04 37.83 36.46 84.93 156.296* Density (g/mL) --- --- 1.07* --- 1.33* --- Lit. Bp ( C) --- 65 500* --- 39.6* 110-115* Lit. mp ( C) 47-50 -97.8 400* --- -96.7* 62-70* *www. pubchem.ncbi.nlm.nih.gov Observations: Adding 4-tert-butylcyclohexanone with methanol created a relatively clear solution. The addition of sodium borohydride created the production of bubbles, with a resulting cloudy mixture. The addition of p-anisaldehyde, to reveal the TLC spots, was a dark pink color. The ketone spot was a dark purple spot. The cis-isomer was a lighter purple spot, higher on the TLC plate. The trans-isomer was a slightly darker purple, than the cis, a little lower on the TLC plate. The vial, without any material, weighed 11.503 g. The vial as evolved at ~80 ( C). The final product was really small white, transparent, crystals. The vial, after crystals had formed, weighed 11.532 g. The following image depicts the TLC plate:
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Calculations: 1. Theoretical yield of alcohol products: The limiting reagent is 4-tert-butylcycloheaxnone = 0.1 g 4 tert butylcyclohexanone 1 x 1 mol 154.25 g 4 tert butylcyclohexanone x 1 mol product 1 molreactant x 156.269 g 4 tert butylcyclohexanol 1 mol = 0.101 g 4-tert- butylcyclohexanol 2. TLC data: TLC Plate 1:4 Ethyl Acetate:Hexanes Spot Sample Solvent Front Distance (mm) Spot(s) Distance (mm) Color R f value 1 Ketone Standard 70 46 Dark purple/pink 0.66 2 Co-spot 24,31,48,54 Dark puple/pink,light purple/pink,purpl e 0.34,0.44,0.69,0.7 7 3 Crude 26,32,49,56 Dark 0.32,0.46,0.70,0.8
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product puple/pink,light
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  • Spring '09
  • FLEMMING
  • Cyclohexane conformation, sodium borohydride

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