Chemistry Letters Vol.34, No.11 (2005)
1541
Table 1. Results of the oxidation of diphenylmethanea
O
O
OH
Temperature Reaction Conversion of Selectivity of
Entry
[O]
OH
(1)
/K
time/h
DPM/%
BP/%
1
2
373
373
373
313
323
333
343
353
363
363
363
373
4
8
4.1
36.6
22.2
3.5
90.7
94.0
97.8
57.4
73.0
78.8
80.2
86.0
60.8
78.1
73.7
99.1
OH
H
O
O
OH
OH
Co
3
12
10
10
10
10
10
10
11
11
11
4
Co
[O]
(2)
5
4.8
8.0
6
Scheme 1. Possible mechanism of the product of 2-hydroxy-
benzophenone.
7
7.2
8.7
8
9
27.2
15.8
14.6
23.3
In summary, Co–MCM-41 appears to be an efficient catalyst
for the synthesis of BP. A higher selectivity (99.1%) can be
obtained at 373 K by using acetic acid as solvent.
10b
11c
12b
aReaction conditions: 1–2 mL 30% H2O2, 0.1 g Co/MCM-41.
The authors thank the National Natural Science Foundation
of China (Project No. 20463003), Natural Science Foundation of
Yunnan Province (Project Nos. 2004E0003Z, 2003E0007R,
and 2003E0004Q) for financial support. We thank Li Peng for
GC-MS measurements.
c
b30 mL HAc. 50 mL HAc; all others 10 mL HAc.
(3-HOBP) nor 4-hydroxybenzophenone (4-HOBP). Interesting-
ly, 2-HOBP that was not reported in previous studies for the
oxidation of DPM was also observed. Firstly, the effect of reac-
tion time on the activities was investigated at 373 K that is close
to the boiling point of acetic acid glacial. It was found that the
conversion of DPM decreased, while the selectivity of BP
increased a little, when reaction time increased from 8 to 12 h.
Thus, the optimum reaction time would be between 8–12 h.
These findings are not clearly understood yet, and further experi-
ments are underway. Secondly, at 10 or 11 h, the effect of
reaction temperature on the activities was studied. It is seen from
Table 1 that the conversion of DPM increased with increase in
reaction temperature and passed through a maximum at 363 K.
But the highest selectivity was obtained at 373 K. At 373 K the
selectivity of BP can be over 90% even when the reaction time
and the amount of solvent are different. Thirdly, the effect of the
solvent amount on the activities was examined at 363 K. It is
clear that the selectivity of BP was significantly improved when
the volume of HAC increased from 10 to 30 mL whereas the
conversion of DPM decreased significantly. However, further
increasing the amount of HAc to 50 mL does not change the
activity significantly. Finally, we found that at 373 K, in 30 mL
of HAc the highest selectivity of BP was 99.1% after 11 h reac-
tion. At the optimum reaction condition, the efficiency of reacted
H2O2 for the formation of BP was detected to be 13.7% with
98.2% total consumption of H2O2 by iodometric titration meth-
od. The low efficiency of reacted H2O2 may indicate that the
H2O2 oxidized not only DPM, but also other complexes, such
as a framework silica–peracetic acid complex, when HAc was
used as solvent.16,17
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Published on the web (Advance View) October 15, 2005; DOI 10.1246/cl.2005.1540