CA1057774A - Dinitroaniline purification with bromine and chlorine - Google Patents
Dinitroaniline purification with bromine and chlorineInfo
- Publication number
- CA1057774A CA1057774A CA309,416A CA309416A CA1057774A CA 1057774 A CA1057774 A CA 1057774A CA 309416 A CA309416 A CA 309416A CA 1057774 A CA1057774 A CA 1057774A
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- Prior art keywords
- nitrosamine
- bromine
- trifluralin
- dinitro
- ppm
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C211/00—Compounds containing amino groups bound to a carbon skeleton
- C07C211/43—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton
- C07C211/44—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton having amino groups bound to only one six-membered aromatic ring
- C07C211/52—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton having amino groups bound to only one six-membered aromatic ring the carbon skeleton being further substituted by halogen atoms or by nitro or nitroso groups
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C205/00—Compounds containing nitro groups bound to a carbon skeleton
- C07C205/07—Compounds containing nitro groups bound to a carbon skeleton the carbon skeleton being further substituted by halogen atoms
- C07C205/11—Compounds containing nitro groups bound to a carbon skeleton the carbon skeleton being further substituted by halogen atoms having nitro groups bound to carbon atoms of six-membered aromatic rings
- C07C205/12—Compounds containing nitro groups bound to a carbon skeleton the carbon skeleton being further substituted by halogen atoms having nitro groups bound to carbon atoms of six-membered aromatic rings the six-membered aromatic ring or a condensed ring system containing that ring being substituted by halogen atoms
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
- C07C209/04—Preparation of compounds containing amino groups bound to a carbon skeleton by substitution of functional groups by amino groups
- C07C209/06—Preparation of compounds containing amino groups bound to a carbon skeleton by substitution of functional groups by amino groups by substitution of halogen atoms
- C07C209/10—Preparation of compounds containing amino groups bound to a carbon skeleton by substitution of functional groups by amino groups by substitution of halogen atoms with formation of amino groups bound to carbon atoms of six-membered aromatic rings or from amines having nitrogen atoms bound to carbon atoms of six-membered aromatic rings
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C209/00—Preparation of compounds containing amino groups bound to a carbon skeleton
- C07C209/30—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds
- C07C209/32—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups
- C07C209/36—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups by reduction of nitro groups bound to carbon atoms of six-membered aromatic rings in presence of hydrogen-containing gases and a catalyst
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C211/00—Compounds containing amino groups bound to a carbon skeleton
- C07C211/43—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton
- C07C211/44—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton having amino groups bound to only one six-membered aromatic ring
- C07C211/49—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton having amino groups bound to only one six-membered aromatic ring having at least two amino groups bound to the carbon skeleton
- C07C211/50—Compounds containing amino groups bound to a carbon skeleton having amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton having amino groups bound to only one six-membered aromatic ring having at least two amino groups bound to the carbon skeleton with at least two amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton
Abstract
Abstract This invention is directed to a process which comprises contacting a nitrosamine-containing dinitroaniline selected from the group consisting of triflurlain, isopropalin, benefin, butralin, tendimethalin, fluchloralin, profluralin, dinitramine, 4-trifluoromethyl-2,6-dinitro-3-chloro-N,N-diethylaniline, 4-methyl-2,6-dinitro-N,N-bis(2-chloro-ethyl)aniline, oryzalin, and nitralin, (1) in liquid phase, (2) with a reagent selected from the group con-sisting of molecular bromine, molecular chlorine, N-bromosuccinimide, N-chlorosuc-cinimide, bromine chloride, pyridine per-bromide, and pyridinium bromide perbromide, until the concentration of the nitrosamine has been reduced.
Description
~)577'74 The present invention is directed to a process for the removal of nitrosamines from dinitroanilines.
The Russian Chem. Rev. 40 (1) 34-50 (1971 (Eng.) reviews the chemistry of aliphatic N-nitrosamines, generally.
Among other topics, the reactivity of nitrosamines is discribed. The article alludes to the reaction of bromine and sulfuric acid with nitrosamines. Lieb. Ann. 151 366 (1969) article reports that nitrosodibenzylamine was dissolved in bromine; the products were mono- and dibrominated di-benzylamines. Hydrogen bromide is reported to be an effectivedinitrosating agent (Chem. Abst. 6 2434-5 and Arzneimittel Forsch 20 1513). The use of Br2C12 and other compounds uses as dinitrosating agent in this application has not been previously reported.
The dinitroaniline class of compounds includes numerous commercial herbicides. Recently a new analytical device, known as a thermal energy analyzer (TEA), has been developed (J. Chromatogr. 107 (1975), 351 and references there cited; and "N-Nitroso Compounds in the Environment,"
IARC Scientific Publication ~9 (International Agency for Research on Cancer, Lyon, 1974), p. 40). The TEA analyzes specifically for the nitroso (-NO) group, and is capable of detecting the nitroso group at concentrations as low as 0.02 ppm - much lower than prior analytical techniques. Analysis of various dinitroanilines by the TEA reveals that some of the dinitroanilines contain very small amounts of nitrosamines.
The presence of even a very small amount of nitrosamine is viewed as undesirable, because certain of the nitrosa~.ines have been shown to be carcinogenic in animals.
X-49~2A -2-,~
The present invention provides a method forremoving nitrosamines from dinitroanilines. This is deemed a desirable precaution in protecting humans and live~tock from one possible source of dinitrosamines.
This invention provides a process which comprises contacting a nitrosamine-containing dinitro aniline selected from the group consisting of tri1uralin, isopropalin, benefin, butralin, tendimethalin, fluchloralin, profluralin, dinitramine, 4-trifluoromethyl-2,6-dinitro-3-chloro-N,N-diethylaniline, 4-methyl-2,6-dinitro-N,N-bis(2-chloroethyl)aniline, oryzalin, and nitralin, (l) in liquid phase,
The Russian Chem. Rev. 40 (1) 34-50 (1971 (Eng.) reviews the chemistry of aliphatic N-nitrosamines, generally.
Among other topics, the reactivity of nitrosamines is discribed. The article alludes to the reaction of bromine and sulfuric acid with nitrosamines. Lieb. Ann. 151 366 (1969) article reports that nitrosodibenzylamine was dissolved in bromine; the products were mono- and dibrominated di-benzylamines. Hydrogen bromide is reported to be an effectivedinitrosating agent (Chem. Abst. 6 2434-5 and Arzneimittel Forsch 20 1513). The use of Br2C12 and other compounds uses as dinitrosating agent in this application has not been previously reported.
The dinitroaniline class of compounds includes numerous commercial herbicides. Recently a new analytical device, known as a thermal energy analyzer (TEA), has been developed (J. Chromatogr. 107 (1975), 351 and references there cited; and "N-Nitroso Compounds in the Environment,"
IARC Scientific Publication ~9 (International Agency for Research on Cancer, Lyon, 1974), p. 40). The TEA analyzes specifically for the nitroso (-NO) group, and is capable of detecting the nitroso group at concentrations as low as 0.02 ppm - much lower than prior analytical techniques. Analysis of various dinitroanilines by the TEA reveals that some of the dinitroanilines contain very small amounts of nitrosamines.
The presence of even a very small amount of nitrosamine is viewed as undesirable, because certain of the nitrosa~.ines have been shown to be carcinogenic in animals.
X-49~2A -2-,~
The present invention provides a method forremoving nitrosamines from dinitroanilines. This is deemed a desirable precaution in protecting humans and live~tock from one possible source of dinitrosamines.
This invention provides a process which comprises contacting a nitrosamine-containing dinitro aniline selected from the group consisting of tri1uralin, isopropalin, benefin, butralin, tendimethalin, fluchloralin, profluralin, dinitramine, 4-trifluoromethyl-2,6-dinitro-3-chloro-N,N-diethylaniline, 4-methyl-2,6-dinitro-N,N-bis(2-chloroethyl)aniline, oryzalin, and nitralin, (l) in liquid phase,
(2) with a reagent selected from the group con-sisting of molecular bromine, molecular chlorine, N-bromosuccinimide, N-chlorosuc-cinimide, bromine chloride, pyridine per-bromide, and pyridinium bromide perbromide, until the concentration of the nitrosamine has been reduced.
1~3S'7~'74 Dinitroanilines with which the present invention can be practiced (and their generic names where available) are (1) 4-trifluoromethyl-2,5-dinitro-N,N-di-n-propylaniline (trifluralin);
(2) 4-isopropyl-2,6-dinitro-N,N-di-n-propyl-aniline (isopropalin);
1~3S'7~'74 Dinitroanilines with which the present invention can be practiced (and their generic names where available) are (1) 4-trifluoromethyl-2,5-dinitro-N,N-di-n-propylaniline (trifluralin);
(2) 4-isopropyl-2,6-dinitro-N,N-di-n-propyl-aniline (isopropalin);
(3) 4-trifluoromethyl-2,6-dinitro-N-n-b~tyi-N-ethylaniline tbenefir.);
(4) 4-tert-butyl-2,6-dinitro-N-sec-butylaniline (butralin);
(5) 3,4-dimethyl-2,6-dinitro-N-(l-ethylpropyl)-aniline (tendimethalin);
(6) 4-trifluoromethyl-2,6-dinitro-N-propyl-N-(2-chloroethyl)aniline (fluchloralin);
(7) 4-trifluoromethyl-2,6-dinitro-N-propyl-N-(cyclopropylmethyl)aniline (profluralin);
(8) 4-trifluoromethyl-2,6-dinitro-3-amino-N,N-diethylaniline (dinitramine);
(9) 4-trifluoromethyl-2,6-dinitro-3-chloro-N,N-diethylaniline (intermediate to dinitramine);
(10) 4-methyl-2,6-dinitro-N,N-bis(2-chloro-ethyl)aniline;
(11) 4-sulfamoyl-2,6-dinitro-N,N-di-n-propyl-aniline (oryzalin); and
(12) 4-(methylsulfonyl)-2,6-dinitro-N,N-di-n-propylaniline (nitralin).
Preferred dinitroanilines with which the present invention is carried out are trifluralin, isopropalin, and benefin.
Generally, the dinitroanilines are prepared by a reaction route of which the following, for trifluralin, is typical:
1~57774 CF3--/ \~CI HNO3 \ CF3--/ \ CI H=O \ CF ~ ON( C H ) It is believed that small amounts of nitrogen oxides re-maining from the nitration step react with a portion of the amine during the amination step, generating small amounts of nitrosamine which may appear in the final dinitroaniline product. Therefore, any nitrosamine contaminant is expected to be the nitroso derivative of the alkylamine employed.
~owever, it is conjectured that exceedingly small amounts of yet other nitrosamines may also be formed. The removal of nitrosamines, regardless of identity, is desirable, and the present process meets that objective.
The mechanism by which the present process operates is not known with certainty. It is known, however, that the nitrosamine is converted, "denitrosated", to a substance not containing the nitrosamine group; and it is believed but not yet proven that NOBr or NOCl may be generated as part of the denitrosation.
The present process provides substantial reduction in nitrosamine concentration, regardless of the initial amount of nitrosamine. The process has been conducted with dinitroanilines containing from as little as 10 ppm or nitrosamine to as much as several thousand ppm of nitro-samine; nitrosamine concentration is generally reduced to one-tenth of the initial amount, or less. In many cases, the nitrosamine concentration is reduced to less than 1 ppm.
The present process is conducted in a liquid phase. In the case of those dinitroanilines melting at lower temperatures, such as below 140C., this is preferably ~1~15'~774 achieved by heating the nitrosamine-containing dinitro-aniline to its melting temperature or somewhat higher.
Trifluralin melts at 54-55C. and benefin melts at 65-66C.
Isopropalin melts at about 30C. but because of minor impurities is generally liquid at room temperatures.
Additionally, a liquid phase can be achieved by dissolving the nitrosamine-containing dinitroaniline in a solvent.
Suitable solvents include aliphatic alcohols such as methanol and ethanol; and halogenated aliphatic hydrocarbons, such as chloroform, methylene chloride, and carbon tetrachloride.
Solvents which are highly reactive with molecular bromine or chlorine are unsuitable.
Molecular bromine and molecular chlorine are the most suitable reagents, and of these, bromine is especially preferred. However, N-bromosuccinimide, N-chlorosuccinimide, bromine chloride, pyridine perbromide, and pyridinium bromide perbromide can also be employed. The amount of reagent to be employed is not critical, so long as the amount is sufficient to reduce the initial amount of nitro-samine to a lesser amount. When employing bromine, 0.02 to2.0 grams of reagent per 100 grams of dinitroaniline is satisfactory; 0.2 gram of reagent per 100 grams of dinitro-aniline appears to be optimal. When using chlorine, 15 ml/min. to 100 ml/min. of chlorine gas per 100 grams of dinitroaniline is satisfactory; 35 ml/min. of chlorine gas per 100 grams of dinitroaniline appears optimal. When employing N-bromosuccinimide, N-chlorosuccinimide, bromine chloride, pyridine perbromide or pyridinium bromide perbromide, amounts of 0.05 to 5.0 gram of reagent per 100 grams of dinitroaniline are suitable.
1~7774 The reaction can be conducted at temperatures over a wide range. In general, temperatures below 140C. are employed and temperatures below 120C. are preferred because of the greater risk of side reactions at higher temperatures.
When conducting the process neat, the reaction is conducted at temperatures above the melting temperature of the particular dinitroaniline. When conducting the process neat with trifluraLin, isopropalin, and benefin, good results have been obtained at temperatures of from 70 to 90C. for all reagents except chlorine; with chlorine, temperatures of from 90 to 120C. are preferred. The reaction can be conducted at atmospheric pressures or at elevated pressures.
The rate at which the present process proceeds will vary with the concentration of the nitrosamine, tem-perature, the reagent, the rate of its addition, and other factors. Neither the presence of water, alone, nor the presence of water at neutral or acidic pH is deleterious;
however, the presence of water at alkaline pH is disad-vantageous, so that a pH of less than 8 is preferred when a significant amount of water is present in the reaction mixture. The progress of nitrosamine removal can be monitored by gas chromatography or by TEA analysis. Denitrosation is generally complete in less than an hour. Time studies of the present process have shown an early drop in levels of nitrosamine, followed in some instances by a slight rise in levels of nitrosamine upon extended reaction time. It is believed that extended exposure of (1) the dinitroaniline and (2) the denitrosation products, to the reaction conditions may result in further nitrosamine formation. Therefore, minimizing reaction times is desirable.
X-4922A _71 l~)S7774 When the reaction is conducted neat, no workup is required. If desired, workup is conventional and takes the form of bubbling air through the reaction mixture or blowing air over the surface of the reaction mixture, followed by a carbonate wash.
The following examples illustrate the present invention and will enable those skilled in the art to practice the invention.
Unless otherwise noted, determination of nitro-samine concentration in the following examples was done by a gas chromatographic method sensitive down to about 0.5 ppm.
A "non-detectable" reading (reported below as "N.D.") was considered to represent less than about 0.5 ppm of nitro-samine. A Hewlett-Packard Model 5711A gas chromatograph was used but the method can be carried out with any gas chroma-tograph apparatus equipped with a flame ionization detector.
The column was a glass coil 4 ft. x 1/8 inch i.d., packed with 3~ Carbowax 20M on 100/120 mesh AW DMCS Chromosorb G
operated at 100C. After the nitrosamine peak eluted, the column was heated to 230C. and held there for about 15 minutes. The helium flow rate was 60 ml/min. A standard of approximately the same concentration of the nitrosamine expected in the sample was employed. Both standard and sample were prepared in methylene chloride.
Those examples utilizing TEA analysis are so indicated. Analyses by this method were carried out in essentially the same procedures as described at J. Chromatogr.
109 (1975), 271. In the context of the present invention, this method is considered to be sensitive to nitrosamine ~ r~ cJ~,..~k l~S7774 concentrations as low as about 0.05 ppm. Where TEA analysisof the samples reported below showed no nitrosamine, it is reported as "N.D."
EXAMPLE 1: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was melted and 0.2 gram (about 10 drops) of bromine was added. The mixture wa~
heated to 70C. and maintained at that temperature, with stirring, for 30 minutes. A sample was analyzed for nitro-samine; none could be detected.
EXAMPLE 2: NITROSAMINE REMOVAL FROM TRIFLURALIN, LESSER
AMOUNT OF BROMINE
The process of Example 1 was repeated except that only 2 drops (0.04 gram) of bromine were added. ~y gas chromatography, no nitrosamine was detected. TEA analysis showed 0.03 ppm of nitrosamine.
EXAMPLE 3: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE, HIGHER TEMPERATURE, CARBONATE WASH
Trifluralin (30 grams of a sample containing 20 14 ppm of nitrosamine) was heated to 90C. Bromine (0.1 gram) was added and the reaction mixture was maintained at 90C., with stirring, for 30 minutes. The reaction mixture was then washed with 5 ml of a 10% solution of sodium carbonate. The layers were separated and a sample of the organic layer was analyzed for nitrosamine content. It showed 1.4 ppm of nitrosamine. The water layer was extracted with 5 ml of methylene chloride; a sample of the extract was analyzed for nitrosamine content and showed 0.15 ~g/ml.
X-4922A _g_ ~OS~7774 EXAMPLE 4: NITROS~INE REMOVAL FROM TRIFLURALIN, BROMINE, WORKUP WITH AIR
A 27 gram sample of trifluralin containing 1750 ppm of nitrosamine was heated at 70C. and bromine (0.2 - gram) was added. The reaction mixture was maintained at 70C. with stirring, for 55 minutes. During the last 10 minutes, air was blown over the surface. A sample was then taken and analyzed for nitrosamine content. It showed 12 ppm of nitrosamine.
EXAMPLE 5: NITROSAMINE REMOVAL FROM TRIFLURALIN, 8ROMINE, TIME STUDY
A 100 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
and bromine (0.2 gram) was added. The reaction mixture was maintained at 70C., with stirring, for 2 hours. Samples were periodically taken and analyzed for nitrosamine content. The results were as follows:
Time at which Nitrosamine sample taken concentration 5 min 3.2 ppm 15 min 2.8 ppm 30 min 2.2 ppm 1 hour 14 ppm 2 hours 27 ppm Another sample taken at 2 hours was analyzed for trifluralin by vapor phase chromatography and determined to be 97.2% pure.
1~)577'7~
EXAMPLE 6: NITROSAMINE REMOVAL FROM TRIFLURALIN, LARGER
AMOUNT OF BROMINE
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
- and bromine (3.11 grams) was added. The reaction mixture was maintained at 70C., with stirring, for 30 minutes. The reaction mixture turned dark and some dark polymeric material was observed. Samples were analyzed for nitro-samine and~purity of trifluralin. No nitrosamine was detected; purity was 82.5%.
EXAMPLE 7: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE, EFFECT OF WATER
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
and added to 6 grams of water. Bromine (0.2 gram) was added. The reaction mixture was maintained at 70C., with stirring, for 3~ minutes. The layers were separated. A
sample of the organic layer analyzed for nitrosamine content showed <1 ppm.
EXAMPLES 8 AND 9: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE, ACID CONDITIONS
Two reactions were conducted under identical con-ditions except that in one, 0.5 ml of concentrated hydro-chloric acid was used, and in the other, 0.5 ml of 50%
sulfuric acid was used.
In each reaction, a 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine, water (3 ml), and the respective acid were mixed and heated '7'774 to 70C. Bromine (0.2 gram) was added and the mixture main-tained at 70C., with stirring, for 20 minutes. The layers were then separated. The acid layer was neutralized and extracted with an equal volume of methylene chloride.
Samples of the product layer and the methylene chloride extract were analyzed for nitrosamine content. The result~
were as follows:
Nitrosa~lne Concentration product methylene Acid chloride extract Ex. 8 (Concentrated hydrochloric acid) 4.8 ppm 1.4 ~g/ml.
Ex. 9 (50% sulfuric acid) N.D. N.D.
EXAMPLE 10: NITROSAMINE REMOVAL FROM TRIFLURALIN, CHLORINE
- A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
Chlorine gas was bubbled into the trifluralin at a rate of approximately 35 ml/min. for 30 minutes, and air was then bubbled into trifluralin for another 5 minutes. The tri-fluralin was maintained throughout at 70C. A sample was analyzed and showed 16 ppm of nitrosamine.
EXAMPLE 11: NITROSAMINE REMOVAL FROM TRIFLURALIN, CHLORINE
AT ELEVATED TEMPERATURE AND WITH WATER ADDED
Water (1 ml) and a 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine were mixed and heated to 90C. Chlorine gas was bubbled into the mixture at a rate of approximately 35 ml/min for 30 minutes, then air was bubbled through for 10 minutes. The reaction mixture was maintained throughout at 90C. A
sample was analyzed and showed 13 ppm of nitrosamine.
il~5~774 XAMPLE 12: NITROSAMINE REMOVAL FROM TRIFLURALIN, TIME STUDY
OF CHLORINE AT ELEVATED TEMPERATURE WITH
CARBONATE WASH
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated and main-tained at 110C. A 10% sodium carbonate solution (2 ml) was added, and chlorine was bubbled in at a rate of 15 ml/min.
Samples were taken periodically. Of each sample, the layers were separated and the product layer was analyzed for nitrosamine content. The results were as follows:
Time when Nitrosamine sample taken Concentration 30 min 15 ppm l hour 28 ppm 2 hours 1.2 ppm EXAMPLE 13: NITROSAMINE REMOVAL FROM TRIFLURALIN, N-BROMO-SUCCINIMIDE
A 30 gram portion of a lot of tri'luralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
and 0.5 gram of N-bromosuccinimide added. The reactisn mixture was maintained at 70C. for 30 minutes. A sample was analyzed and showed 1.7 ppm of nitrosamine.
EXAMPLE 14: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE
WITH CARBONATE PRETREATMENT OF TRIFLURALIN
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm was melted and washed with 15 ml of 5% sodium carbonate solution. The layers were separated.
3romine (0.1 gram) was added to the trifluralin layer at 70C. and the mixture was maintained at 70C. for 30 minutes.
l~S7774 A sample was analyzed for nitrosamine content. None was detected.
EXAMPLE 15: NITROSAMINE REMOVAL FROM DINITRAMINE, BROMINE
To a 10 gram sample of dinitramine containing 138 ppm of nitrosamine, at 110C., 0.2 gram of bromine was added below the surface. The reaction mixture turned dark. It was stirred for 30 minutes and a 2 gram sample (designated A) removed. The remaining 8 grams was added slowly to 60 ml. of methylene chloride and 15 ml. of 10 percent sodium carbonate solution was added. The organic layer was separated and solvent removed on a rotary e~aporator for 15 minutes at 45C. (Sample B).
Each sample was analyzed for nitrosamine content by TEA. The results were as follows:
Nitrosamine SampleConcentration . _ A <0.2 B 0.3
Preferred dinitroanilines with which the present invention is carried out are trifluralin, isopropalin, and benefin.
Generally, the dinitroanilines are prepared by a reaction route of which the following, for trifluralin, is typical:
1~57774 CF3--/ \~CI HNO3 \ CF3--/ \ CI H=O \ CF ~ ON( C H ) It is believed that small amounts of nitrogen oxides re-maining from the nitration step react with a portion of the amine during the amination step, generating small amounts of nitrosamine which may appear in the final dinitroaniline product. Therefore, any nitrosamine contaminant is expected to be the nitroso derivative of the alkylamine employed.
~owever, it is conjectured that exceedingly small amounts of yet other nitrosamines may also be formed. The removal of nitrosamines, regardless of identity, is desirable, and the present process meets that objective.
The mechanism by which the present process operates is not known with certainty. It is known, however, that the nitrosamine is converted, "denitrosated", to a substance not containing the nitrosamine group; and it is believed but not yet proven that NOBr or NOCl may be generated as part of the denitrosation.
The present process provides substantial reduction in nitrosamine concentration, regardless of the initial amount of nitrosamine. The process has been conducted with dinitroanilines containing from as little as 10 ppm or nitrosamine to as much as several thousand ppm of nitro-samine; nitrosamine concentration is generally reduced to one-tenth of the initial amount, or less. In many cases, the nitrosamine concentration is reduced to less than 1 ppm.
The present process is conducted in a liquid phase. In the case of those dinitroanilines melting at lower temperatures, such as below 140C., this is preferably ~1~15'~774 achieved by heating the nitrosamine-containing dinitro-aniline to its melting temperature or somewhat higher.
Trifluralin melts at 54-55C. and benefin melts at 65-66C.
Isopropalin melts at about 30C. but because of minor impurities is generally liquid at room temperatures.
Additionally, a liquid phase can be achieved by dissolving the nitrosamine-containing dinitroaniline in a solvent.
Suitable solvents include aliphatic alcohols such as methanol and ethanol; and halogenated aliphatic hydrocarbons, such as chloroform, methylene chloride, and carbon tetrachloride.
Solvents which are highly reactive with molecular bromine or chlorine are unsuitable.
Molecular bromine and molecular chlorine are the most suitable reagents, and of these, bromine is especially preferred. However, N-bromosuccinimide, N-chlorosuccinimide, bromine chloride, pyridine perbromide, and pyridinium bromide perbromide can also be employed. The amount of reagent to be employed is not critical, so long as the amount is sufficient to reduce the initial amount of nitro-samine to a lesser amount. When employing bromine, 0.02 to2.0 grams of reagent per 100 grams of dinitroaniline is satisfactory; 0.2 gram of reagent per 100 grams of dinitro-aniline appears to be optimal. When using chlorine, 15 ml/min. to 100 ml/min. of chlorine gas per 100 grams of dinitroaniline is satisfactory; 35 ml/min. of chlorine gas per 100 grams of dinitroaniline appears optimal. When employing N-bromosuccinimide, N-chlorosuccinimide, bromine chloride, pyridine perbromide or pyridinium bromide perbromide, amounts of 0.05 to 5.0 gram of reagent per 100 grams of dinitroaniline are suitable.
1~7774 The reaction can be conducted at temperatures over a wide range. In general, temperatures below 140C. are employed and temperatures below 120C. are preferred because of the greater risk of side reactions at higher temperatures.
When conducting the process neat, the reaction is conducted at temperatures above the melting temperature of the particular dinitroaniline. When conducting the process neat with trifluraLin, isopropalin, and benefin, good results have been obtained at temperatures of from 70 to 90C. for all reagents except chlorine; with chlorine, temperatures of from 90 to 120C. are preferred. The reaction can be conducted at atmospheric pressures or at elevated pressures.
The rate at which the present process proceeds will vary with the concentration of the nitrosamine, tem-perature, the reagent, the rate of its addition, and other factors. Neither the presence of water, alone, nor the presence of water at neutral or acidic pH is deleterious;
however, the presence of water at alkaline pH is disad-vantageous, so that a pH of less than 8 is preferred when a significant amount of water is present in the reaction mixture. The progress of nitrosamine removal can be monitored by gas chromatography or by TEA analysis. Denitrosation is generally complete in less than an hour. Time studies of the present process have shown an early drop in levels of nitrosamine, followed in some instances by a slight rise in levels of nitrosamine upon extended reaction time. It is believed that extended exposure of (1) the dinitroaniline and (2) the denitrosation products, to the reaction conditions may result in further nitrosamine formation. Therefore, minimizing reaction times is desirable.
X-4922A _71 l~)S7774 When the reaction is conducted neat, no workup is required. If desired, workup is conventional and takes the form of bubbling air through the reaction mixture or blowing air over the surface of the reaction mixture, followed by a carbonate wash.
The following examples illustrate the present invention and will enable those skilled in the art to practice the invention.
Unless otherwise noted, determination of nitro-samine concentration in the following examples was done by a gas chromatographic method sensitive down to about 0.5 ppm.
A "non-detectable" reading (reported below as "N.D.") was considered to represent less than about 0.5 ppm of nitro-samine. A Hewlett-Packard Model 5711A gas chromatograph was used but the method can be carried out with any gas chroma-tograph apparatus equipped with a flame ionization detector.
The column was a glass coil 4 ft. x 1/8 inch i.d., packed with 3~ Carbowax 20M on 100/120 mesh AW DMCS Chromosorb G
operated at 100C. After the nitrosamine peak eluted, the column was heated to 230C. and held there for about 15 minutes. The helium flow rate was 60 ml/min. A standard of approximately the same concentration of the nitrosamine expected in the sample was employed. Both standard and sample were prepared in methylene chloride.
Those examples utilizing TEA analysis are so indicated. Analyses by this method were carried out in essentially the same procedures as described at J. Chromatogr.
109 (1975), 271. In the context of the present invention, this method is considered to be sensitive to nitrosamine ~ r~ cJ~,..~k l~S7774 concentrations as low as about 0.05 ppm. Where TEA analysisof the samples reported below showed no nitrosamine, it is reported as "N.D."
EXAMPLE 1: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was melted and 0.2 gram (about 10 drops) of bromine was added. The mixture wa~
heated to 70C. and maintained at that temperature, with stirring, for 30 minutes. A sample was analyzed for nitro-samine; none could be detected.
EXAMPLE 2: NITROSAMINE REMOVAL FROM TRIFLURALIN, LESSER
AMOUNT OF BROMINE
The process of Example 1 was repeated except that only 2 drops (0.04 gram) of bromine were added. ~y gas chromatography, no nitrosamine was detected. TEA analysis showed 0.03 ppm of nitrosamine.
EXAMPLE 3: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE, HIGHER TEMPERATURE, CARBONATE WASH
Trifluralin (30 grams of a sample containing 20 14 ppm of nitrosamine) was heated to 90C. Bromine (0.1 gram) was added and the reaction mixture was maintained at 90C., with stirring, for 30 minutes. The reaction mixture was then washed with 5 ml of a 10% solution of sodium carbonate. The layers were separated and a sample of the organic layer was analyzed for nitrosamine content. It showed 1.4 ppm of nitrosamine. The water layer was extracted with 5 ml of methylene chloride; a sample of the extract was analyzed for nitrosamine content and showed 0.15 ~g/ml.
X-4922A _g_ ~OS~7774 EXAMPLE 4: NITROS~INE REMOVAL FROM TRIFLURALIN, BROMINE, WORKUP WITH AIR
A 27 gram sample of trifluralin containing 1750 ppm of nitrosamine was heated at 70C. and bromine (0.2 - gram) was added. The reaction mixture was maintained at 70C. with stirring, for 55 minutes. During the last 10 minutes, air was blown over the surface. A sample was then taken and analyzed for nitrosamine content. It showed 12 ppm of nitrosamine.
EXAMPLE 5: NITROSAMINE REMOVAL FROM TRIFLURALIN, 8ROMINE, TIME STUDY
A 100 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
and bromine (0.2 gram) was added. The reaction mixture was maintained at 70C., with stirring, for 2 hours. Samples were periodically taken and analyzed for nitrosamine content. The results were as follows:
Time at which Nitrosamine sample taken concentration 5 min 3.2 ppm 15 min 2.8 ppm 30 min 2.2 ppm 1 hour 14 ppm 2 hours 27 ppm Another sample taken at 2 hours was analyzed for trifluralin by vapor phase chromatography and determined to be 97.2% pure.
1~)577'7~
EXAMPLE 6: NITROSAMINE REMOVAL FROM TRIFLURALIN, LARGER
AMOUNT OF BROMINE
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
- and bromine (3.11 grams) was added. The reaction mixture was maintained at 70C., with stirring, for 30 minutes. The reaction mixture turned dark and some dark polymeric material was observed. Samples were analyzed for nitro-samine and~purity of trifluralin. No nitrosamine was detected; purity was 82.5%.
EXAMPLE 7: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE, EFFECT OF WATER
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
and added to 6 grams of water. Bromine (0.2 gram) was added. The reaction mixture was maintained at 70C., with stirring, for 3~ minutes. The layers were separated. A
sample of the organic layer analyzed for nitrosamine content showed <1 ppm.
EXAMPLES 8 AND 9: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE, ACID CONDITIONS
Two reactions were conducted under identical con-ditions except that in one, 0.5 ml of concentrated hydro-chloric acid was used, and in the other, 0.5 ml of 50%
sulfuric acid was used.
In each reaction, a 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine, water (3 ml), and the respective acid were mixed and heated '7'774 to 70C. Bromine (0.2 gram) was added and the mixture main-tained at 70C., with stirring, for 20 minutes. The layers were then separated. The acid layer was neutralized and extracted with an equal volume of methylene chloride.
Samples of the product layer and the methylene chloride extract were analyzed for nitrosamine content. The result~
were as follows:
Nitrosa~lne Concentration product methylene Acid chloride extract Ex. 8 (Concentrated hydrochloric acid) 4.8 ppm 1.4 ~g/ml.
Ex. 9 (50% sulfuric acid) N.D. N.D.
EXAMPLE 10: NITROSAMINE REMOVAL FROM TRIFLURALIN, CHLORINE
- A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
Chlorine gas was bubbled into the trifluralin at a rate of approximately 35 ml/min. for 30 minutes, and air was then bubbled into trifluralin for another 5 minutes. The tri-fluralin was maintained throughout at 70C. A sample was analyzed and showed 16 ppm of nitrosamine.
EXAMPLE 11: NITROSAMINE REMOVAL FROM TRIFLURALIN, CHLORINE
AT ELEVATED TEMPERATURE AND WITH WATER ADDED
Water (1 ml) and a 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine were mixed and heated to 90C. Chlorine gas was bubbled into the mixture at a rate of approximately 35 ml/min for 30 minutes, then air was bubbled through for 10 minutes. The reaction mixture was maintained throughout at 90C. A
sample was analyzed and showed 13 ppm of nitrosamine.
il~5~774 XAMPLE 12: NITROSAMINE REMOVAL FROM TRIFLURALIN, TIME STUDY
OF CHLORINE AT ELEVATED TEMPERATURE WITH
CARBONATE WASH
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm of nitrosamine was heated and main-tained at 110C. A 10% sodium carbonate solution (2 ml) was added, and chlorine was bubbled in at a rate of 15 ml/min.
Samples were taken periodically. Of each sample, the layers were separated and the product layer was analyzed for nitrosamine content. The results were as follows:
Time when Nitrosamine sample taken Concentration 30 min 15 ppm l hour 28 ppm 2 hours 1.2 ppm EXAMPLE 13: NITROSAMINE REMOVAL FROM TRIFLURALIN, N-BROMO-SUCCINIMIDE
A 30 gram portion of a lot of tri'luralin with an average assay of 68 ppm of nitrosamine was heated to 70C.
and 0.5 gram of N-bromosuccinimide added. The reactisn mixture was maintained at 70C. for 30 minutes. A sample was analyzed and showed 1.7 ppm of nitrosamine.
EXAMPLE 14: NITROSAMINE REMOVAL FROM TRIFLURALIN, BROMINE
WITH CARBONATE PRETREATMENT OF TRIFLURALIN
A 30 gram portion of a lot of trifluralin with an average assay of 68 ppm was melted and washed with 15 ml of 5% sodium carbonate solution. The layers were separated.
3romine (0.1 gram) was added to the trifluralin layer at 70C. and the mixture was maintained at 70C. for 30 minutes.
l~S7774 A sample was analyzed for nitrosamine content. None was detected.
EXAMPLE 15: NITROSAMINE REMOVAL FROM DINITRAMINE, BROMINE
To a 10 gram sample of dinitramine containing 138 ppm of nitrosamine, at 110C., 0.2 gram of bromine was added below the surface. The reaction mixture turned dark. It was stirred for 30 minutes and a 2 gram sample (designated A) removed. The remaining 8 grams was added slowly to 60 ml. of methylene chloride and 15 ml. of 10 percent sodium carbonate solution was added. The organic layer was separated and solvent removed on a rotary e~aporator for 15 minutes at 45C. (Sample B).
Each sample was analyzed for nitrosamine content by TEA. The results were as follows:
Nitrosamine SampleConcentration . _ A <0.2 B 0.3
Claims (10)
1. A process which comprises contacting a nitro-samine-containing dinitroaniline selected from the group consisting of triflurlain, isopropalin, benefin, butralin, tendimethalin, fluchloralin, profluralin, dinitramine, 4-trifluoromethyl-2,6-dinitro-3-chloro-N,N-diethylaniline, 4-methyl-2,6-dinitro-N,N-bis(2-chloro-ethyl)aniline, oryzalin, and nitralin, (1) in liquid phase, (2) with a reagent selected from the group con-sisting of molecular bromine, molecular chlorine, N-bromosuccinimide, N-chlorosuc-cinimide, bromine chloride, pyridine per-bromide, and pyridinium bromide perbromide, until the concentration of the nitrosamine has been reduced.
2. The process of claim 1 wherein the temperature is between room temperature and 140°C.
3. The process of claims 1 or 2 wherein the temperature is between 70°C. and 90°C.
4. The process of claim 1 wherein the temperature is between 90°C. and 120°C.
5. The process of claim 1 wherein the molten dinitroaniline constitutes the liquid.
6. The process of claim 1 wherein the process is conducted with an aliphatic alcohol, or halogenated aliphatic hydrocarbon.
7. The process of claim 1 wherein the reagent is molecular bromine.
8. The process of claim 1 wherein the reagent is molecular chlorine.
9. The process of claim 1 which comprises con-tacting molten trifluralin with molecular bromine at 70° to 90°C. until the concentration of the nitrosamine has been reduced.
10. The process of claim 1 which comprises con-tacting molten trifluralin with molecular chlorine at 90° to 120°C. until the concentration of the nitrosamine has been reduced.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US82534577A | 1977-08-17 | 1977-08-17 | |
| US05/878,835 US4127610A (en) | 1977-08-17 | 1978-02-17 | Dinitroaniline purification with bromine and chlorine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1057774A true CA1057774A (en) | 1979-07-03 |
Family
ID=27124896
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA309,416A Expired CA1057774A (en) | 1977-08-17 | 1978-08-15 | Dinitroaniline purification with bromine and chlorine |
Country Status (21)
| Country | Link |
|---|---|
| JP (1) | JPS5822101B2 (en) |
| AR (1) | AR221489A1 (en) |
| AU (1) | AU518675B2 (en) |
| BG (1) | BG34332A3 (en) |
| BR (1) | BR7805279A (en) |
| CA (1) | CA1057774A (en) |
| CS (1) | CS222270B2 (en) |
| DD (1) | DD138312A5 (en) |
| DE (1) | DE2835530C2 (en) |
| DK (1) | DK152116C (en) |
| ES (1) | ES472550A1 (en) |
| FR (1) | FR2400503A1 (en) |
| GB (1) | GB2003148B (en) |
| HU (1) | HU179460B (en) |
| IE (1) | IE47178B1 (en) |
| IL (1) | IL55354A (en) |
| IT (1) | IT1098023B (en) |
| MX (1) | MX5204E (en) |
| NL (1) | NL180100C (en) |
| PL (1) | PL120364B1 (en) |
| RO (1) | RO75536A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4335260A (en) * | 1980-05-15 | 1982-06-15 | Montedison S.P.A. | Process for the preparation of N-di-n-propyl-2,6-dinitro-4-trifluoromethylaniline having a low content of nitrosamines |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0019281B1 (en) * | 1979-05-21 | 1982-12-29 | Hoechst Aktiengesellschaft | Process for the removal of nitrozation agents from nitrated aromatic compounds |
| DE2920448C3 (en) * | 1979-05-21 | 1982-02-11 | Hoechst Ag, 6000 Frankfurt | Process for removing nitrosating agent (s) from nitrated aromatic compounds |
| DE2926947C2 (en) * | 1979-07-04 | 1982-03-18 | Hoechst Ag, 6000 Frankfurt | Process for removing nitrosating agent (s) from nitrated aromatic compounds |
| IT1195822B (en) * | 1986-08-12 | 1988-10-27 | I Pi Ci Spa | TRIFLURALINE PURIFICATION PROCEDURE |
| US5922915A (en) * | 1998-05-11 | 1999-07-13 | Srm Chemical, Ltd., Co. | Process for removing N-nitroso compounds from organo-amine compositions including dinitroaniline herbicides |
| WO2016110965A1 (en) * | 2015-01-07 | 2016-07-14 | 三菱日立パワーシステムズ株式会社 | Method and device for treating nitroso compound |
-
1978
- 1978-08-10 GB GB7832840A patent/GB2003148B/en not_active Expired
- 1978-08-14 MX MX787310U patent/MX5204E/en unknown
- 1978-08-14 HU HU78EI804A patent/HU179460B/en not_active IP Right Cessation
- 1978-08-14 PL PL1978209046A patent/PL120364B1/en unknown
- 1978-08-14 IL IL55354A patent/IL55354A/en unknown
- 1978-08-14 ES ES472550A patent/ES472550A1/en not_active Expired
- 1978-08-14 IT IT26768/78A patent/IT1098023B/en active
- 1978-08-14 AR AR273298A patent/AR221489A1/en active
- 1978-08-14 DE DE2835530A patent/DE2835530C2/en not_active Expired
- 1978-08-14 RO RO7894976A patent/RO75536A/en unknown
- 1978-08-15 CA CA309,416A patent/CA1057774A/en not_active Expired
- 1978-08-15 CS CS785322A patent/CS222270B2/en unknown
- 1978-08-16 DK DK362578A patent/DK152116C/en not_active IP Right Cessation
- 1978-08-16 FR FR7823852A patent/FR2400503A1/en active Granted
- 1978-08-16 BR BR7805279A patent/BR7805279A/en unknown
- 1978-08-16 DD DD78207319A patent/DD138312A5/en unknown
- 1978-08-16 IE IE1649/78A patent/IE47178B1/en not_active IP Right Cessation
- 1978-08-16 NL NLAANVRAGE7808479,A patent/NL180100C/en not_active IP Right Cessation
- 1978-08-16 BG BG7840680A patent/BG34332A3/en unknown
- 1978-08-17 AU AU39028/78A patent/AU518675B2/en not_active Expired
- 1978-08-17 JP JP53100850A patent/JPS5822101B2/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4335260A (en) * | 1980-05-15 | 1982-06-15 | Montedison S.P.A. | Process for the preparation of N-di-n-propyl-2,6-dinitro-4-trifluoromethylaniline having a low content of nitrosamines |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2835530A1 (en) | 1979-03-01 |
| DK152116B (en) | 1988-02-01 |
| GB2003148A (en) | 1979-03-07 |
| GB2003148B (en) | 1982-02-10 |
| CS222270B2 (en) | 1983-06-24 |
| JPS5441826A (en) | 1979-04-03 |
| IL55354A0 (en) | 1978-10-31 |
| FR2400503B1 (en) | 1980-10-31 |
| BG34332A3 (en) | 1983-08-15 |
| MX5204E (en) | 1983-04-25 |
| BR7805279A (en) | 1979-04-10 |
| RO75536A (en) | 1980-11-30 |
| DK362578A (en) | 1979-02-18 |
| IE47178B1 (en) | 1984-01-11 |
| PL120364B1 (en) | 1982-02-27 |
| IL55354A (en) | 1981-05-20 |
| ES472550A1 (en) | 1979-10-16 |
| HU179460B (en) | 1982-10-28 |
| NL7808479A (en) | 1979-02-20 |
| PL209046A1 (en) | 1979-05-07 |
| AU518675B2 (en) | 1981-10-15 |
| JPS5822101B2 (en) | 1983-05-06 |
| FR2400503A1 (en) | 1979-03-16 |
| IE781649L (en) | 1979-02-17 |
| DD138312A5 (en) | 1979-10-24 |
| AU3902878A (en) | 1980-02-21 |
| DK152116C (en) | 1988-06-20 |
| NL180100C (en) | 1987-01-02 |
| DE2835530C2 (en) | 1982-10-21 |
| IT7826768A0 (en) | 1978-08-14 |
| IT1098023B (en) | 1985-08-31 |
| NL180100B (en) | 1986-08-01 |
| AR221489A1 (en) | 1981-02-13 |
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