Oxidation Of Cyclododecanol To CyclododecanoneThis print version free essay Oxidation Of Cyclododecanol To Cyclododecanone.
Autor: johnpatrick7 19 November 2012
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John Williamson-Chem 341-Section 007
Oxidation of Cyclododecanol to Cyclododecanone
The goal for the oxidation of cyclododecanol to cyclododecanone is to demonstrate the oxidation of a secondary alcohol to the corresponding ketone using hypochlorous acid. The oxidation of alcohols plays a key role in the transformation of alcohols into ketones, which have a major role in organic synthesis. Preparing aldehydes and ketones from primary and secondary alcohols is important in order to make certain products. The reaction scheme for the oxidation of cyclododecanol to cyclododecanone is shown in figure 1.1.
The mechanism for the oxidation of cyclododecanol to cyclododecanone is shown in figure 1.2.
Some new techniques used in this lab included the starch iodide test, and the Fourier transform infrared spectroscopy.
To start, 0.5 g of cyclododecanol, 1.2 mL of acetone, and 0.5 mL of glacial acetic acid were placed into a 25-mL round-bottom flask. The mixture was then equipped with a stir bar, and heated to a gentle reflux. Using a Pasteur pipette, 8 mL of commercial bleach (ca. 5.3% sodium hypochlorite) was added drop wise to the mixture, and allowed to stay in a state of reflux for 30 minutes. After the allotted time, the mixture was removed from heat, and the layers were allowed to separate. A portion of the aqueous layer was removed and a couple of drops were placed onto a piece of starch/iodide test paper, to determine if enough hypochlorite was added or not. If the test was positive, the test paper would turn a color of blue-black, if the test was negative; 1mL of bleach was added and allowed to reflux for 20 minutes. Once the starch iodide test showed positive, the mixture was allowed to cool to room temperature, and transferred to a seperatory funnel. The round bottom flask was rinsed with 5 mL of Diethyl ether, and the wash was transferred into the seperatory funnel. The mixture was shaken, and an additional 10 mL of diethyl ether was added for extraction. 5mL of saturated sodium bicarbonate was added to the extract, and swirled until the evolution of CO2 dispersed. The mixture was shaken, with proper venting to relieve any pressure, and the organic solution was washed with 5mL portions of saturated aqueous sodium bisulfate and saturated aqueous sodium chloride. The organic solution was then transferred to an Erlenmeyer flask, and dried over several spatula tips full of anhydrous sodium sulfate. After 10-15 minutes of drying, the dried ethereal solution was transferred into a 25-mL round bottom flask, and equipped to a rotary evaporator. 2 mL of methanol was then added to the crystallized extract in the round bottom flask, and heated and stirred. If the solution was not clear, more methanol was added drop wise until it became clear. The solution was then allowed to cool, and 10 mL of water was added. The solution was placed into an ice bath for 10 minutes, and then went through vacuum filtration for 10 minutes. The finalized product was then measured in weight, and went through an FT-IR spectrum. Clean salt plates with dichloromethane (CH2Cl2). For solids, dissolve in CH2Cl2 and place a drop on the salt plate, and let the solvent evaporate to form a thin film. Mount salt plate into the instrument so that the beam passes through your sample. Generally we collect 16 scans.
The limiting reagent in the reaction is cyclododecanol. The results of the experiment are given in table 1. The FT-IR scan can be found on page 5, and page 6 with theoretical results.
compound theoretical yield (g) experimental yield %y melting point exp (deg-C) Melting point lit.
cyclododecanone 0.54398 0.36 66.2% 47-50 60
Results and Observations
The first and second starch iodide test showed negative results. Eventually, the test paper turned a dark blue/black color. The crystals recovered were white in color, and was almost like a powder form. A reason for the low experimental yield could have been caused by human error, where 5mL of sodium bisulfate was used instead of sodium bicarbonate. The organic layer was removed, and redone, but this may have caused some error in the results. The crystals were difficult to acquire a melting point, but easy to use in the FT-IR machine. The transmittance to wavelength of the FT-IR machine is not that great. One reason for this could have been human error, or not enough cyclododenanone added to the dichloromethane salt plate. Overall, the observations and results allowed knowledge to be gained on the oxidation of alcohols.
The significance of this lab was to demonstrate the oxidation of a secondary alcohol, cyclododecanol, to the corresponding ketone, cyclododecanone, using hypochlorous acid. This was achieved by following the procedure, and allowing knowledge to be gained.