Download Sodium Hypochlorite Oxidation: Preparation of Camphor - Laboratory 9 | CHEM 2130 and more Lab Reports Organic Chemistry in PDF only on Docsity! Lab 9: SODIUM HYPOCHLORITE OXIDATION: PREPARATION OF CAMPHOR From: http://www.wou.edu/las/physci/ch335/preparation%20of%20camphor.doc Oxidation has a somewhat different meaning in organic chemistry than you have been used to in inorganic, where oxidation is defined as a process involving loss of electrons, as in the conversion of Fe+2 to Fe+3. Oxidation of organic compounds also normally involves electron transfer, but because the valence of carbon usually remains at four, it is more useful to define oxidation as either (a) loss of hydrogen atoms or (b) addition of oxygen or other electronegative atoms. Thus, all of the following reactions are classified as oxidations: OH O H CrO3 CH3 C OH O KMnO4 H2O2 OsO4 OH OH Oxidations of alcohols provides one of the most general methods for the preparation of carbonyl compounds; oxidation of primary alcohols affords aldehydes (or carboxylic acids, if oxidation is continued), while oxidation of secondary alcohols affords ketones. Tertiary alcohols cannot be oxidized without breaking carbon-carbon bonds. OHR OR H O R OH Primary alcohol Aldehyde Carboxylic Acid OHR R' OR R' The most common oxidizing agents for the conversion of alcohols to aldehydes and ketones are chromium trioxide (CrO3) 1 and its relatives, chromate and dichromate ions (CrO4-2 and Cr2O7- 2), as well as a series of modified forms of CrO3, such as Collins reagent, in which CrO3 is complexed with pyridine (Collins reagent is used in nonaqueous media, and is especially useful for oxidizing primary alcohols to aldehydes without overoxidation to the carboxylic acid). KMnO4 can also be used to oxidize alcohols. An alternative oxidizing agent for the preparation of ketones, sodium hypochlorite (NaOCl) in acetic acid, was introduced by Stevens, Chapman, and Weller in 1980 (J. Org. Chem. 45, 2030). This reagent offers several advantages: it is cheap (sodium hypochlorite is the reagent in Clorox and "swimming pool chlorine"); it oxidizes secondary alcohols rapidly and in high yield; and it avoids the problem of disposing of toxic wastes associated with chromium and manganese reagents. The example chosen to illustrate the oxidation of alcohols is the sodium hypochlorite oxidation of isoborneol to camphor: H3C CH3H3C OH H3C CH3H3C NaOCl O CH3CO2H Camphor is a bridged bicyclic ketone widely distributed in nature, especially in trees of the Far East. It is used as a plasticizer for the production of celluloid film, for smokeless powders and explosives, as an insect repellent, and for medicinal purposes (you will recognize the characteristics odor of Vicks). Borneol, one of the stereoisomeric related alcohols, is found in certain trees of Borneo, and isoborneol, used in today's experiment, is made commercially from pinenes (the C10 hydrocarbons of turpentine). 2
