February 20, 2013
Oxidation of Cyclohexanone to Adipic Acid
The cyclic ketone cyclohexanone was oxidized to adipic acid using the oxidizing agent nitric acid. The experiment yielded 0.2667 grams of adipic acid, giving a percent yield of 113.97%. Although the product was allowed to dry for one week, residual moisture was still present in the sample and a melting point could not be obtained. This error in the experiment either resulted from adding too much water or not allowing the product to remain in the Hirsch vacuum filtration for long enough to sufficiently dry.
Redox reactions are an important class of reactions in organic chemistry that involve the transfer of electrons from one molecule to another. This experiment focused on an oxidation reaction. In organic chemistry, oxidation reactions occur when a carbon atom becomes bonded to a more electronegative atom, causing the electron density on the carbon atom to decrease (McMurray, 2012). Examples of oxidation reactions in organic chemistry are the breaking of a carbon-hydrogen bond, or the formation of a carbon-oxygen bond (McMurray, 2012). This reaction oxidized a secondary alcohol to a ketone (Williamson, 2003). The oxidation of a ketone, in this case, cyclohexanone, can be accomplished by using various oxidizing agents, however, this experiment made use of the powerful oxidizing agent nitric acid. An intermediate is formed during this oxidation, which is further oxidized to adipic acid (Figure 1) (Williamson, 2003). This reaction is of particular importance, as it breaks the cyclic carbon ring when adipic acid is formed (Williamson, 2003).
The ketone reagent used in this experiment was cyclohexanone, a cyclic six-carbon ring with an attached oxygen group (Figure 1). Cyclohexanone is an oily clear liquid at room temperature. Cyclohexanone is known to have the molecular formula, C6H10O, a molecular weight of 98.14 grams/mole, a melting point of -47
References: Gaivoronskii AN, Granzhan, VA (2005). Solubility of Adipic Acid in Organic Solvents and Water. Russian Journal of Applied Chemistry. 78 pp 404-408. McMurray, JM (2012). Organic Chemistry, 8th Edition. CENGAGE Learning. Williamson, KL (2003). Macroscale and Microscale Organic Experiments, 4th Edition. Houghton Mifflin Custom Publishing. PubChem.com (2012). National Center for BioTechnology Information. http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=944&loc=ec_rcs Accessed February 20, 2013.