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Influence of energy input on the oxidation of anilines with KMnO
4
and Al
2
O
3
.
a
Table 3.5
Conversion of amine (%)/selectivity for the azo product (%)
b
Solvent-free
Solution (30 mL; H
2
O/acetonitrile, 1 : 1 v/v)
Planetary ball mill
c
Vibration ball mill
d
Conventional heating
e
Multimode microwave
f
Monomode microwave
g
Ultrasound
h
Amine
Aniline
93/95
71/89
83/88
90/91
58/91
88/94
m-Anisidine
70/90
40/91
53/89
22/91
27/90
73/96
o-Toluidine
94/89
81/97
89/88
39/87
63/88
82/87
m-Toluidine
95/91
87/2
84/72
54/81
84/72
67/87
p-Toluidine 499/96
499/95
96/90
91/93
96/90
97/97
a
Standard batch size: amine (2 mmol), KMnO
4
(4 mmol), g-Al
2
O
3
(4 g; activity 90, neutral).
b
Determined by GC-FD measurements of extracted products in relation to amine.
c
Fritsch Pulverisette 7 classic line: two agate beaker (45 mL), six agate milling balls per beaker (15 mm), 800 rpm, 20 min.
d
Retsch MM301: two agate beaker (50 mL), six agate milling balls per beaker (15 mm), 800 rpm, 20 min.
e
Round-bottom flask (100 mL); 80 1C, 60 min.
f
MLS ETHOS Plus: 80 1C(P
max
¼
300 W), 30 min.
g
CEM Discover: 80 1C(P
max
¼
130 W), 30 min.
h
Hielscher UP200 s: 33% of standard batch size; 100% P
max
,201C, 20 min.
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