Our laboratory is
interested in developing greener and safer Oxidations of Alcohols. Using an environmentally friendly and
inexpensive reagent for the oxidation of alcohols will (1) produce a safe
environment in an undergraduate lab and (2) teach students that greener
reactions are critical to our stewardship of our environment. Traditional reagents such as Chromic acid
are very efficient in oxidizing alcohols.
But chromium is toxic and an environmental hazard. And its waste requires expensive
disposal. Clorox is safe to use, its
by-products are harmless as they are sodium chloride (table salt) and water.
And Clorox is inexpensive as it
costs less than a dollar from supermarkets.
This oxidation, however, is quite inefficient and produces many
by-products. Our studies supported by
an ACA Mellon grant for the GreenLab project and Faculty Research and
Curriculum Development grants from E&H have shown that known methods of Clorox
oxidation of cyclohexanol gave not only a low yield of cyclohexanone but also
produced chlorocyclohexanone, dichlorocyclohexanone and many others as major
by-products. Others have reported the
use of expensive, exotic and sometimes difficult to separate catalysts such as
phase transfer catalysts. In our
laboratory, we have established an optimal set of conditions for the oxidation
of cyclohexanol and for the recovery of products. By monitoring reaction with
GC-MS, we have studied this oxidation with various catalysts and under
different reaction conditions. Under
one set of conditions, cyclohexanol was oxidized efficiently to cyclohexanone
by Clorox at 0 to 5 C with dilute hydrochloric acid as catalyst. The small quantity of product from
small-scale reaction, the water solubility of product, and the large amount of
aqueous solution make high yield recovery of product a challenge. We have also developed efficient work-up and isolation procedures to recover
the products. Student researchers obtained
actual yields of 96% of product with purity of 94% by GC-MS with about 5% 2-chlorocyclohexanone
as major impurity. We have tested this procedure in my second semester
organic lab and initial results indicate that this procedure is reproducible even
by unskilled undergraduates.
Other compounds oxidized in
excellent yields by similar methods are 3-pentanol, 2-hexanol, fluorenone and
benzophenone. We are continuing with
the evaluation of the scope of Clorox oxidation of various other alcohols. Our preliminary studies showed that some
other primary and secondary alcohols and diols were not easily oxidized without
producing serious by-products. These
alcohols may well require different oxidizing conditions.
Students under my close
supervision have done all the work in this research project. The students did all the reactions, operate
the instruments (GC/MS, NMR, IR), collect and analyze data and draw
conclusions. They have learned
important theories, skills and practices of research. They have gained important knowledge and experience in
research. They were an integral part of
the discoveries and problem-solving processes. And students will continue in such roles in the future of this
project.