4
92
S. AMIRIAN et al.
Experimental
Chlorine gas that is generated from 20 g of KMnO and 120 mL of concentrated HCl (37%)
4
was slowly bubbled through a solution of KOH (36 g) in 100 mL of water for one hour
period, with stirring. Simultaneously, this system is chilled in an ice bath. To the resulting
yellow solution of KClO, was added 11.63 g (0.04 mol) of Ni(NO ) .6H O portion-wise in
3
2
2
2
0 min while stirred in an ice bath. A fine black precipitate formed which was filtered and
washed with deionized water and dried by means of a vacuum desiccator under calcium
chloride. The yield is 95% (3.42 g of NiO2).
Oxidation of alcohols
To a homogeneous mixture of 2 mmol of nickel peroxide and 0.5 g of silica gel (grinding for
about 2 min), 1 mmol of an alcohol was added. The mixture is ground very well and the
reaction is monitored by TLC. When the reaction completed, the product was washed with
CH Cl . Then, the CH Cl was evaporated in a rotary system. After removing of the solvent
2
2
2
2
the product was isolated and characterized by comparing its spectroscopic data with an
authentic sample.
Recovery of nickel peroxide
The spent nickel peroxide was first washed with acetone and then with water to remove the
adhered organic compounds and often impurities. The solid was then stirred with KClO
solution (about ten times the quantity of NiO ) for 30 min. The recovered NiO was filtered,
2
2
washed with water and kept dried for new oxidation process.
Results and Discussion
1
12
Nickel peroxide is prepared by Nakagawa et al. method, with some modification . We
examined various mineral supports such as alumina, wet alumina and silica gel 60 and found
that silica gel 60 provided the best result in terms of grinding and the reaction time. All of
the alcohol oxidation reactions herein were carried out in silica supported nickel peroxide
and the grinding time is less than 10 min (Table 1).
1
-Phenyl ethanol is selected as a probe substrate and after examination, the magnitude
of silica gel 60 is determined. Thus, 1-phenyl ethanol (1mmol), nickel peroxide (2 mmol)
and various magnitude of silica gel 60 (0.25, 0.5, 1, 1.5 and 2 g) is mixed. The mixture is
grinding and the reaction was monitored by TLC. The products were then isolated and
characterized by comparison of their spectroscopic data with those reported in the literature.
The stoichiometric oxidation is expressed as follows:
All of the alcohols (Table 1) are converted to carbonyl derivative when treated with nickel
peroxide in the presence of silica gel. When the reaction occurred in a solution, 1-7 hours is
1-3,12
needed to complete it. Also the yield of the product is fairly good
method, the reaction time is very short (5-10 min) and the yield is high (71-93%).
. But in solvent free
After oxidation process, the nickel peroxide is converted to nickel oxide that can be
easily recoverable by washing in acetone. Thus, after oxidation no material remains in the
environment and this case is very important to green chemistry.
OH
O
NiO / Silica
2
+
NiO + H O
2
Kooti, Mohammad
