Borneol; An Oxidation-Reduction Scheme
Lab Time: Tuesday 11:30 am
In this experiment, the main objective was to synthesize a ketone from borneol via an oxidation reaction and secondly, to produce a secondary alcohol from camphor via a reduction reaction. Therefore, the hypothesis of this lab is that camphor will be produced in the oxidation reaction and isoborneol will be the product of the reduction reaction because of steric hindrance. For the oxidation step, a reflux will be done and then a microscale reflux for the reduction step. The products will be confirmed using Infrared spectroscopy, the chromic acid test, 2,4-DNP test and 13C NMR spectroscopy. The results of this experiment show that camphor was produced during oxidation (0.6576 g). The IR spectrum shows a strong peak at 1740 cm-1 representing a carbonyl compound, which was concluded to be a ketone by the 2,4-DNP test and the deshielded peak at 218.4 ppm in the 13C NMR spectrum. The product of the reduction reaction was isoborneol (0.1591 g). The IR spectrum indicates a medium, broad peak from 3000-3500 cm-1 representing a hydroxyl group. The hydroxyl group is confirmed from the chromic acid test and the peak in the 13C NMR spectrum with a chemical shift of 80 ppm. These results support the hypothesis. Steric approach control states that steric hindrance will control the stereoselectivity of a reaction and direct the reducing agent to the less hindered face. In this case the endo face is the least hindered and will produce isoborneol. Further evidence from comparing the 13C NMR spectrum of borneol to isoborneol will show a difference in chemical shifts of one of the methyl bridge carbons that will conclude in what position the hydroxyl group is situated.
This laboratory experiment focuses on the procedures of oxidation and reduction reactions. Oxidation is a reaction that results in a loss of electron density around a carbon due to either the bond formation between a carbon and a more electronegative atom or bond breakage between carbon and a less electronegative atom1 (John McMurry, 2008). The element whose atoms lose electrons during oxidation is said to be oxidized and the atom that gains electrons is called the oxidizing agent. In this experiment a secondary alcohol, borneol, is oxidized to a ketone using the oxidizing agent, hypochlorous acid (HOCl). Hypochlorous acid is generated by the reaction of sodium hypochlorite and acetic acid (Fig. 1). The oxidation mechanism is not completely understood but an alkyl hypochlorite intermediate is produced which undergoes E2 elimination reaction to produce a ketone2 (Fig. 1).
Figure 1: Oxidation reaction of a secondary alcohol, borneol, to produce a ketone On the other hand, a reduction is the opposite reaction of oxidation. Reduction results in a gain of electron density around a carbon caused by either the bond formation between a carbon and a less electronegative atom or bond breakage between carbon and a more electronegative atom1 (John McMurry, 2008). The element whose atoms gain electrons during reduction is said to be reduced and the atom that loses electrons is called the reducing agent. In the second part of this experiment, camphor is reduced to a secondary alcohol using the reducing agent, NaBH4 (Fig. 2).
Figure 2: Reduction reaction of a ketone, camphor, to produce a secondary alcohol, isoborneol.
The main objectives of the lab were to synthesize a ketone from borneol via an oxidation reaction and in part 2, to synthesize a secondary alcohol from camphor via a reduction reaction. This experiment incorporated Infrared spectroscopy, the chromic acid test, the 2,4-DNP test and 13C NMR spectroscopy. These four tests will give indication of functional groups present or not present in the product, as well as...
References: 1. University Of Winnipeg Organic Chemistry 2203 Lab Manual, 2014, Pages 7-11.
2. McMurry J.; Organic Chemistry, 8th edition.; Brooks/Cole Cangage Learning., 2012, Pages 277,281,437,440-441,465,473 and 645.
3. Zubrick, J.W.; The Organic Chem Lab Survival Manual, 8th edition.; John Wiley & Sons Inc., New York, 2011, Pages 281-283.
4. McMaster University: Department of Chemistry. Isomerization of an Alcohol by Oxidation-Reduction: Borneol, Camphor, and Isoborneol. http://www.chemistry.mcmaster.ca/~chem2o6/labmanual/expt7/2o6exp7.html (accessed March 5, 2014).
5. University of Texas. Oxidation-Reduction Scheme: Borneol – Camphor – Isoborneol. http://www.utdallas.edu/~scortes/ochem/OChem_Lab2/recit_notes/exp35_ox_borneol.pdf (accessed March 6, 2014)
6. Chemical Book. L(-)-Borneol(464-45-9)13CNMR. http://www.chemicalbook.com/SpectrumEN_464-45-9_13CNMR.htm (accessed March 9, 2014).
7. Chemical Book. DL-Isoborneol(124-76-5)13CNMR http://www.chemicalbook.com/SpectrumEN_124-76-5_13CNMR.htm (accessed March 9, 2014).
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