- Email: [email protected]
Separation of pyrazoles by gas chromatography
Jomzal of Chromatography, 174 (1979) 221-223 0 Ekevier Scientific Publishing Company, Amsterdam CHROM.
-
Printed in The Netherlands
11,799
Separation af pyrazoles by gas chromatography D. D. WARD Department
and M. R. GRIMMETT
of Chemistry,
University
of Otago,
Dunedin
(New
Zealand)
(Received February 2nd, 1979)
Although there have been reports1-3 of the use of gas chromatography for the separation of pyrazoles, no systematic study has yet been presented. We had found earlier4 that a wide range of imidazoles is separable using OV-17 as liquid phase, provided that the compounds are either N-substituted or can be N-acetylated prior to introduction on to the column. Such polar compounds as the azoles require silanized glass columns packed with a relatively inert support such as Chromosorb W. EXPERIMENTAL
Chemicals The pyrazole derivatives were prepared in this laboratory by standard methods and checked for purity by microanalytical
and spectrophotometric
techniques.
Gas chromatography ’ GC analysis was performed on a Varian Aerograph Model 1400-10 gas chromatograph equipped with a flame ionisation detector. The glass columns were 2.5 m x 1.5 mm I.D., packed with silanized 100-120 mesh Chromosorb W coated with 12% OV-17 or OV-225. The carrier gas was nitrogen with a flow-rate of 20-25 cm3 min-‘; the inlet temperature was 130-140”; and the detector temperature 300-350”. The column oven was temperature programmed to increase in temperature by 10” min-l from 50”. RESULTS
AND DISCUSSION
We found that, in contrast to the imidazoles, N-unsubstituted pyrazoles are susceptile to direct GC, and no prior acetylation is required. However, in order to separate a wide range of pyrazole derivatives, which in some instances required high t,:mperatures, isothermal operation of the columns proved unsatisfactory. The use c f linear temperature-programmed techniques overcame the problem of long retention Imes, but required the results to be quoted in the form of relative retention indices, 1 -DY(relative to pyrazole), and, in addition, linear programmed retention indices, iP ( ef. 5). These are listed in Table I. When using the method for quantitative analysis 1 f mixtures of pyrazoles, the flame ionisation detector requires that response factors I -1ative to pyrazole be calculated (see Table II). Although both N-substituted and
222
TABLE
NOTES I
RELATIVE INDICES
RJXENTION (1,)
INDICES
(R,,,)
AND
LINEAR
PROGRAMMED
FOR PYRAZOLES
Corqpouzzd
AlkyIpyr~~o1e.s Pyrazole 1-Acetyl-3,5-dimethylI-AllylI-r-Butyl I-Ethyl3-Etbyl3,PDimethyl3,5-Dimethyll-Methyl3-MethylCMethylbBromopyrazoles Unsubstituted l-Acetyl-3,5-dimethyl1-r-ButylI-Ethyl 3-Ethyl3,5-Dimethyll-Methyl3-Metbyl3-Phenyl4,5-Dibromo-l-methylI-Nitropyrazoles Unsubstituted 4_Bromo3,5-Dimethyl3-EthylS-Ethyl3-Methyl3-Phenyl3-Methyl-l&dinitro 3,5-Dimethyl-l&dinitro C-Nitropyrazoles 3-Nitro4-Nitro1,4-Dimethyl-3,5_dinitro1,4-Dimethyl-S-nitro3,5-Dimethyl&nitro3,4-Dinitro-l-methyl3,4-Dinitro-lethylI-Etbyl4nitro3-Ethyl4nitro3-Ethyl-S-nitroI-Methyl4nitro3-MethyI4nitro3-Methyl-5-nitro-
ov-17
0 v-225
R PI
A+
1.00
1050
1.00 1.01 0.83 1.48 1.61 1.46 0.69 1.25 1.36
1050 1080 985 1205 1270 1215 910 1155 1165
1.94
1400
1.78 1.89 2.23 2.19 1.08 2.03 5.65 1.91
1315 1365 1515 1500 1070 1435 1800 14Gtl
t
l
1.85
1333
1.73 *
1300 *
1.50 6.80 I
1233 2100 *
2.58 2.44 2.81 1.79 2.80 3.15 3.35 2.30 2.79 2.85 2.20 2.71 2.78
1820 1730 1870 1320 1840 2051 2100 1575 1840 1885 1520 1800 1832
R PI
1,
0.42
870 775
1.88
1170
1.68
1130
2.28 0.93
1250 830
3.11 2.75
1495 1412
1.65 1.83 2.25 I
1080 1145 1245
4.72
2030
4.40 4.30
1835 1825
4.42
1980
4.38 4.52
1915
1.00
.
RETENTION
223
Brwm~itrop~azo~ 4-Bmmo-3.%dimethyI-1-nitro- 2.03 4-Bromo-3,54iinitro-l-ethyl3.13 4-Bromo-3,5-dinitro-l-methyl- 1.93 4-Bromcl-l-ethyl-3-&m260 4-Bromo-3ethykkkkm3.63 4-Bromo-3-methyl-l-nitro* 4-Bromo-5-methyl-l-nitml 4-Brom~3-methyl-5-nitro3.12 * De&r&ion
and/or
1435
2.29
1315
2070 1380 1725 2265 * * 2155
5.42
2270
rearrangement takesplace on injectioo.
TABLE 11 DETECTCZR SENSITIVE
FACTORS
(RELATIVE
TO PYRAZOLE)
Pyrawk
Sensitivityfactor Pyrazde
unsubstituted 4-Bromo4-Bromo-3,%iimethyl4-Brom*3-ethylCFsmmo-3-methyl4-Bmmo-3-methyl-5-nitmCBmmo-l-nitro3,EDim&hyE 3,5-Dimethy~4nit 3-Ethyl-
1.00 6.14 9.72 2.83 17.65 3.12 6.30 0.96 1.06 0.83
3-Ethyl-L-nitro3-Ethy&l-nitm3-Ethyl-5-&m3-Methyl3-Methyl-l-&m3-Meffiyl4nitro3-Methyl-5-1&o3-N&m4NitrcE
Sensitivityfactor 1.30
0.60 6.68 0.88 129 1.68 1.73. 1.86 1.3r
N-unsubstituted pyrazoles co&i be separated on the Sqme coin there were problems experienced with I-nitropyrazoles which were some’Sruessusceptible-to de&ration or rearrangementat the elevati teempe~atures used. REFERENCES
’
1 U. Rydberg and J. C. Buijten, 1. Cfzromatogr~,6+ (1972) 170. 2 J. W. A. M. Jansen, H. J. Koeners, C. 6. Knxe and 4Z. L. Habraken, .i- Org. Chem., 38 (1973) 1777. 3 J. W. A. M. Jcs.nsxn and C. L. Habraken, J. Org. Cheni., 36 (1971) 3USI. 4 C. G. Begg and M. R. Grimmett, /. Cluomtu~., 73 (1972) 238. 5 H. van den Dool, and P. D. Kratz, J. Chnmxafugr...11 (1%3) 463.
-
Printed in The Netherlands
11,799
Separation af pyrazoles by gas chromatography D. D. WARD Department
and M. R. GRIMMETT
of Chemistry,
University
of Otago,
Dunedin
(New
Zealand)
(Received February 2nd, 1979)
Although there have been reports1-3 of the use of gas chromatography for the separation of pyrazoles, no systematic study has yet been presented. We had found earlier4 that a wide range of imidazoles is separable using OV-17 as liquid phase, provided that the compounds are either N-substituted or can be N-acetylated prior to introduction on to the column. Such polar compounds as the azoles require silanized glass columns packed with a relatively inert support such as Chromosorb W. EXPERIMENTAL
Chemicals The pyrazole derivatives were prepared in this laboratory by standard methods and checked for purity by microanalytical
and spectrophotometric
techniques.
Gas chromatography ’ GC analysis was performed on a Varian Aerograph Model 1400-10 gas chromatograph equipped with a flame ionisation detector. The glass columns were 2.5 m x 1.5 mm I.D., packed with silanized 100-120 mesh Chromosorb W coated with 12% OV-17 or OV-225. The carrier gas was nitrogen with a flow-rate of 20-25 cm3 min-‘; the inlet temperature was 130-140”; and the detector temperature 300-350”. The column oven was temperature programmed to increase in temperature by 10” min-l from 50”. RESULTS
AND DISCUSSION
We found that, in contrast to the imidazoles, N-unsubstituted pyrazoles are susceptile to direct GC, and no prior acetylation is required. However, in order to separate a wide range of pyrazole derivatives, which in some instances required high t,:mperatures, isothermal operation of the columns proved unsatisfactory. The use c f linear temperature-programmed techniques overcame the problem of long retention Imes, but required the results to be quoted in the form of relative retention indices, 1 -DY(relative to pyrazole), and, in addition, linear programmed retention indices, iP ( ef. 5). These are listed in Table I. When using the method for quantitative analysis 1 f mixtures of pyrazoles, the flame ionisation detector requires that response factors I -1ative to pyrazole be calculated (see Table II). Although both N-substituted and
222
TABLE
NOTES I
RELATIVE INDICES
RJXENTION (1,)
INDICES
(R,,,)
AND
LINEAR
PROGRAMMED
FOR PYRAZOLES
Corqpouzzd
AlkyIpyr~~o1e.s Pyrazole 1-Acetyl-3,5-dimethylI-AllylI-r-Butyl I-Ethyl3-Etbyl3,PDimethyl3,5-Dimethyll-Methyl3-MethylCMethylbBromopyrazoles Unsubstituted l-Acetyl-3,5-dimethyl1-r-ButylI-Ethyl 3-Ethyl3,5-Dimethyll-Methyl3-Metbyl3-Phenyl4,5-Dibromo-l-methylI-Nitropyrazoles Unsubstituted 4_Bromo3,5-Dimethyl3-EthylS-Ethyl3-Methyl3-Phenyl3-Methyl-l&dinitro 3,5-Dimethyl-l&dinitro C-Nitropyrazoles 3-Nitro4-Nitro1,4-Dimethyl-3,5_dinitro1,4-Dimethyl-S-nitro3,5-Dimethyl&nitro3,4-Dinitro-l-methyl3,4-Dinitro-lethylI-Etbyl4nitro3-Ethyl4nitro3-Ethyl-S-nitroI-Methyl4nitro3-MethyI4nitro3-Methyl-5-nitro-
ov-17
0 v-225
R PI
A+
1.00
1050
1.00 1.01 0.83 1.48 1.61 1.46 0.69 1.25 1.36
1050 1080 985 1205 1270 1215 910 1155 1165
1.94
1400
1.78 1.89 2.23 2.19 1.08 2.03 5.65 1.91
1315 1365 1515 1500 1070 1435 1800 14Gtl
t
l
1.85
1333
1.73 *
1300 *
1.50 6.80 I
1233 2100 *
2.58 2.44 2.81 1.79 2.80 3.15 3.35 2.30 2.79 2.85 2.20 2.71 2.78
1820 1730 1870 1320 1840 2051 2100 1575 1840 1885 1520 1800 1832
R PI
1,
0.42
870 775
1.88
1170
1.68
1130
2.28 0.93
1250 830
3.11 2.75
1495 1412
1.65 1.83 2.25 I
1080 1145 1245
4.72
2030
4.40 4.30
1835 1825
4.42
1980
4.38 4.52
1915
1.00
.
RETENTION
223
Brwm~itrop~azo~ 4-Bmmo-3.%dimethyI-1-nitro- 2.03 4-Bromo-3,54iinitro-l-ethyl3.13 4-Bromo-3,5-dinitro-l-methyl- 1.93 4-Bromcl-l-ethyl-3-&m260 4-Bromo-3ethykkkkm3.63 4-Bromo-3-methyl-l-nitro* 4-Bromo-5-methyl-l-nitml 4-Brom~3-methyl-5-nitro3.12 * De&r&ion
and/or
1435
2.29
1315
2070 1380 1725 2265 * * 2155
5.42
2270
rearrangement takesplace on injectioo.
TABLE 11 DETECTCZR SENSITIVE
FACTORS
(RELATIVE
TO PYRAZOLE)
Pyrawk
Sensitivityfactor Pyrazde
unsubstituted 4-Bromo4-Bromo-3,%iimethyl4-Brom*3-ethylCFsmmo-3-methyl4-Bmmo-3-methyl-5-nitmCBmmo-l-nitro3,EDim&hyE 3,5-Dimethy~4nit 3-Ethyl-
1.00 6.14 9.72 2.83 17.65 3.12 6.30 0.96 1.06 0.83
3-Ethyl-L-nitro3-Ethy&l-nitm3-Ethyl-5-&m3-Methyl3-Methyl-l-&m3-Meffiyl4nitro3-Methyl-5-1&o3-N&m4NitrcE
Sensitivityfactor 1.30
0.60 6.68 0.88 129 1.68 1.73. 1.86 1.3r
N-unsubstituted pyrazoles co&i be separated on the Sqme coin there were problems experienced with I-nitropyrazoles which were some’Sruessusceptible-to de&ration or rearrangementat the elevati teempe~atures used. REFERENCES
’
1 U. Rydberg and J. C. Buijten, 1. Cfzromatogr~,6+ (1972) 170. 2 J. W. A. M. Jansen, H. J. Koeners, C. 6. Knxe and 4Z. L. Habraken, .i- Org. Chem., 38 (1973) 1777. 3 J. W. A. M. Jcs.nsxn and C. L. Habraken, J. Org. Cheni., 36 (1971) 3USI. 4 C. G. Begg and M. R. Grimmett, /. Cluomtu~., 73 (1972) 238. 5 H. van den Dool, and P. D. Kratz, J. Chnmxafugr...11 (1%3) 463.