Sublimation will begin to occur in 5-10 minutes. Continue swirling for about 5 minutes after all the dichromate is added. Avoid allowing ice to fall into the stopper where it connects to the cold finger and to the flask. The layers that form may be very hard to distinguish, as in the image below. Clamp the 125 mL vacuum flask to the monkey bars. Reaction Scheme Mechanism 2 In step 1 Oxone oxidizes the chloride forming hypochlorous acid. Which purpose does this step serve? In addition, one major source of error was the loss of crude product prior to purification which resulted in losing two-thirds of the product.
Determine the melting point of your camphor. You may also wish to review Chapter 8 of the Vollhard and Schore text. The peak differences show that isoborneol was preferred over borneol, due to the steric strain caused by the two geminal methyl groups on one side of the cyclohexane. Place paper towels around the stopper of the cold finger. The impurities were likely to be the unreacted alcohol present in the product mixture, which was further confirmed by the analysis of infrared spectrum. Chemical Information Name Structure 2-D.
Following this was the workup which included purification through sublimation and drying with desiccation. During this the flask became foggy which indicated that crystals were forming 4 on the sides of the glass. The integration of this borneol peak was 1. Fountainhead Press: Southlake, Texas, 2015, pp. Also, the sublimation apparatus consisted of a 250-mL round-bottom flask and beaker versus the cold finger method. Stir 2 minutes and repeat the test. Shut off the vacuum at the aspirator.
Place the stopper with the hollow glass rod into the vacuum flask. If the test tube needs to be adjusted, remove it from the flask before adjusting the test tube. Also ensure that the steam lines do not have condensed water in them as you will need to set up a steam bath. To a stirred solution of ketone 1. The gas chromatography also shows evidence of the reaction proceeding when reducing camphor into borneol and isoborneol. In camphor, however, the top and bottom faces of the carbonyl group are different, and we will attempt to take advantage of this to selectively reduce the ketone to the other diastereomer of the alcohol. Answer to the questions1 Stepwise reaction mechanism of hypochlorite oxidation of endo-borneol to camphor:2 To determine the amount of endo-borneol present in a sample of camphor, one possible way to look for the intensity of the peak at a specific absorption frequency that was characteristic of endo-borneol but absent in camphor.
Written by Kevin Abstract: This experiment will reduce camphor into isobornel with sodium borohydride. The crude product was purified under sublimation using a 250-mL round-bottom flask with a 250-mL beaker covered with parafilm. While it is less commonly used than dichromate, it is much less expensive we make it by treating sodium hypochlorite household bleach with acetic acid and much less toxic. A new green oxidation procedure was developed for the undergraduate organic teaching laboratories using Oxone and a catalytic quantity of sodium chloride for the conversion of borneol to camphor. These weak peaks indicate that there was only a small amount of starting material in the final product. This solid is then collected over a Hirsh funnel and allowed to dry.
In acidic solution, iodide is oxidized by hypochlorite to iodine: The iodine then reacts with the starch in the test paper to produce the characteristic purple colour of the starch-iodine complex. The spectrum shows three methyl singlet peaks in the upfield region of around 1. In the second part, we will employ sodium borohydride to reduce the ketone obtained in the first step back to an alcohol. Using this information the percent purity was calculated to be 86. Place a Buchner filter equipped with a filter paper into the vacuum flask. If you activate the vacuum too quickly some camphor might be lost.
Keep the ether layer in the filter flask and add a boiling chip. In the first step, Cl+ was added to the alcohol but in the following step Cl- was lost. Overall, this reduction reaction of camphor into isoborneol was completed relatively successfully. Evaporate the ether on a gentle steam bath until a foamy residue remains. While the product is drying, begin setting up the by obtaining a 1 L filter flask, a stopper with a hollow glass rod, and a cold finger. To make sure there was an excess of hypochlorite oxidizing agent so that the reaction could go to complete, starch-iodide test paper was used at regular time intervals.
This is because when the sodium borohydride attacks the camphor, it would attack in the endo-phase due to the steric strain caused by the two geminal methyl groups on one side of the cyclohexane ring. The use of steric effects to control reactivity in this way is termed steric approach control. Dry the organic layer with magnesium sulfate. Dissolve this solid in methylene chloride then add anhydrous sodium sulfate to remove any water in solution. Slowly add the sulfuric acid to the Erlenmeyer flask.