Oxdiation of Campgor

An Oxidation-Reduction Scheme: Borneol, Camphor and Isoborneol

H 3C

CH3 H NaOCl CH3COOH

H3C

CH3 NaBH4

H3C

CH3 OH

H 3C

OH

H 3C

O

H 3C

H

Borneol

Camphor

Isoborneol

This experiment will illustrate the use of a "green" oxidizing agent, sodium hypochlo-rite (bleach) in acetic acid, for converting a secondary alcohol (borneol) to a ketone (camphor). This reaction will be followed by TLC to monitor the progress of the oxidation. The camphor is then reduced by sodium borohydride to give the isomeric alcohol, isoborneol. The spectra of borneol, camphor, and isoborneol will be compared to detect structural differences and to determine the extent to which the final step produces an alcohol isomeric with the starting material, borneol.

OXIDATION OF BORNEOL WITH HYPOCHLORITE

Sodium hypochlorite, bleach, can be used to oxidize secondary alcohols to ketones. Because this reaction occurs more rapidly in an acidic environment, it is likely that the actual oxidizing agent is hypochlorous acid, HOC1. This acid is generated by the reaction between sodium hypochlorite and acetic acid. NaOCl + CH3COOH → HOCl + CH3COONa Although the mechanism is not fully understood, there is evidence that an alkyl hypochlorite intermediate is produced, which then gives the product via an E2 elimination:

H3C CH3 H H 3C OH NaOCl CH3COOH H 3C CH3 H H3C O Cl O H H H 3C O H 3C CH3 H3O + Cl

REDUCTION OF CAMPHOR WITH SODIUM BOROHYDRIDE

Metal hydrides (sources of H:-) of the Group III elements, such as lithium aluminum hydride, LiAlH4, and sodium borohydride, NaBH4, are widely used in reducing carbonyl groups. Lithium aluminum hydride, for example, reduces many compounds containing carbonyl groups, such as aldehydes, ketones, carboxylic acids, esters, or amides, whereas sodium borohydride reduces only aldehydes and ketones. The reduced reactivity of borohydride allows it to be used even in alcohol and water solvents, whereas lithium aluminum hydride...