EXPERIMENTAL
Preparation of tosylhydrazine
Scheme 1
Preparation of tosylhydrazine
Scheme 1
As shown in
scheme 1, tosylhydrazide was prepared by the reaction of tosylchloride with
hydrazine. Thus, 85% H2NNH2·H2O (30ml) was added drop-wise into a stirred
solution of tosylchloride in benzene (80ml)
for 40 minutes. The reaction
mixture was left stirring at 60-70°C for additional 50 minutes followed by
laying up. The product, tosylhydrazide, precipitating from the reaction mixture
was isolated by filtration, and was dried at 56°C. It was washed with water
until free from H2NNH2·HCl, then redrying at 50°C for 5h. The
product(15g,80.6%) is a white crystalline solid, mp 105°C(decomposition) as the
literature[10] reported.
Anal. IR (KBr), v=3400, 3255, 1650, 1230, 820cm-1, which is same as Sadtler standard spectrogram.
Anal. IR (KBr), v=3400, 3255, 1650, 1230, 820cm-1, which is same as Sadtler standard spectrogram.
2.2
Synthesis of 1,2,3-triazole
Scheme 2
As shown in
scheme 2, 1,2,3-triazole was prepared by the reaction of tosylhydrazide with
glyoxal followed by treatment with ammonia. Thus, a solution of tosylhydrazine
(20g) and acetic acid(1ml) in methanol(180ml) was added drop-wise into a
stirred solution of glyoxal(31ml of 40% solution) in methanol(100ml). Some solid
was separated out during the addition. The reaction mixture was then stirred
for additional 15 minutes. A stream of ammonia was bubbled through the reaction
mixture for 45 minutes .During the ammonia addition the reaction temperature
rose to 55°C, and then slowly dropped to 30°C. The reaction mixture was left
stirring at room temperature overnight. The reaction mixture was concentrated,
and diluted with 25% methanol in ether(250ml).The separated solid was removed
by filtration, the filtrate concentrated and the residue distilled to isolate
1,2,3-triazole(5.0g,66.8%).The fraction collected at 42°C(0.25mm) was
identified as 1,2,3-triazole, a pale yellow liquid.
2.3 Product analysis
Found: mp, 23-24°C; NMR (CDCl3), =2.33ppm(1H), 7.75ppm (2H);
IR (CCl4), v=3131,2942,1521,1455,1223,1186, 1092,1079, 947,789,701cm-1
Requires: mp, 23°C; NMR (CDCl3), =2.34ppm(1H), 7.76ppm (2H);
IR (CCl4), v=3130,2940,1520,1450,1220,1180, 1090,1080, 950,790,700cm-1
2.3 Product analysis
Found: mp, 23-24°C; NMR (CDCl3), =2.33ppm(1H), 7.75ppm (2H);
IR (CCl4), v=3131,2942,1521,1455,1223,1186, 1092,1079, 947,789,701cm-1
Requires: mp, 23°C; NMR (CDCl3), =2.34ppm(1H), 7.76ppm (2H);
IR (CCl4), v=3130,2940,1520,1450,1220,1180, 1090,1080, 950,790,700cm-1
3. RESULTS AND DISCUSSION
In industry, tosylhydrazide is produced from 40% H2NNH2路H2O, the yield is 76% and the purity is 95%. As the product tends to be hydrolyzed, the product is thermolability and unfit to be material of preparing 1,2,3-triazole. The yield and purity of the product can be raised through properly increasing the dosage of H2NNH2·H2O, thus, high concentration (85%) of H2NNH2·H2O was used as material. The reaction of preparing tosylhydrazine is mainly affected by such factors as mole ratio among materials and reaction temperature. As far as reaction temperature is concerned, 60-70°C is optimal for this reaction. Otherwise, it is inadvisable to lengthen reaction time, since we have obtained high yield (80.6%) of the product after reacting for 1.5h (see Table 1).
While synthesizing 1,2,3-triazole, many experiments to study the influencing factors on the reaction were performed. In experiments, for example, we selected different mole ratios of tosylhydrazide (A) and glyoxal (B). Otherwise, we took three various manners of materials addition: the first, A and B were simultaneously added into a stirred solvent of methanol followed by bubbling a stream of ammonia; the second, a solution of glyoxal in methanol was added into a stirred solution of tosylhydrazide in methanol followed by bubbling a stream of ammonia; the third, a solution of tosylhydrazide in methanol was added drop-wise into a stirred solution of glyoxal in methanol followed by bubbling a stream of ammonia. The results of experiments are shown in table 2.
In industry, tosylhydrazide is produced from 40% H2NNH2路H2O, the yield is 76% and the purity is 95%. As the product tends to be hydrolyzed, the product is thermolability and unfit to be material of preparing 1,2,3-triazole. The yield and purity of the product can be raised through properly increasing the dosage of H2NNH2·H2O, thus, high concentration (85%) of H2NNH2·H2O was used as material. The reaction of preparing tosylhydrazine is mainly affected by such factors as mole ratio among materials and reaction temperature. As far as reaction temperature is concerned, 60-70°C is optimal for this reaction. Otherwise, it is inadvisable to lengthen reaction time, since we have obtained high yield (80.6%) of the product after reacting for 1.5h (see Table 1).
While synthesizing 1,2,3-triazole, many experiments to study the influencing factors on the reaction were performed. In experiments, for example, we selected different mole ratios of tosylhydrazide (A) and glyoxal (B). Otherwise, we took three various manners of materials addition: the first, A and B were simultaneously added into a stirred solvent of methanol followed by bubbling a stream of ammonia; the second, a solution of glyoxal in methanol was added into a stirred solution of tosylhydrazide in methanol followed by bubbling a stream of ammonia; the third, a solution of tosylhydrazide in methanol was added drop-wise into a stirred solution of glyoxal in methanol followed by bubbling a stream of ammonia. The results of experiments are shown in table 2.
Consequently,
we have found out the optimal condition for synthesis of 1,2,3-triazole. The
ratio of (A) and glyoxal(B) 1:2.7 should be selected, and the third manner of
materials addition is the best.
By the way, 1,2,3-triazole should be isolated by vacuum distillation because of
its thermolability at >200°C.
Table
1. The yield of tosylhydrazide at different
reaction time
Reaction time/h
|
1.0
|
1.5
|
2.0
|
3.0
|
5.0
|
Yield/%
|
68.3
|
80.6
|
76.8
|
75.3
|
70.2
|
Table
2. The yield of 1,2,3-triazole at various adding
manner and different mole ratio of A and B
Manner
Ratio |
First
|
Second
|
Third
|
|||
Output(g)
|
Yield
|
Output(g)
|
Yield
|
Output(g)
|
Yield
|
|
1.3
|
2.1
|
28.1%
|
2.3
|
30.7%
|
3.2
|
42.8%
|
2.0
|
2.8
|
37.4%
|
3.2
|
42.8%
|
4.3
|
57.4%
|
2.7
|
3.6
|
48.1%
|
3.8
|
50.8%
|
5.0
|
66.8%
|
3.5
|
2.9
|
38.7%
|
3.4
|
45.4%
|
4.1
|
54.8%
|
5.0
|
2.7
|
36.1%
|
3.2
|
42.8%
|
3.8
|
50.8%
|
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