Herbicides trifluralin

The discovery of nitrosamines in pesticide formulations, Ross et al (1976), led to remarkable public and regulatory reaction. The widely used herbicide, trifluralin, because of the inadvertent nitrosamine impurity, received the most attention. All dinitroaniline herbicides have similarities therefore, trifluralin, with appropriate exceptions, will serve as a suitable exan le. 

The herbicide trifluralin undergoes a photochemical reaction in which the n-propyl side chain of the amine reacts with the vicinal nitro group to form the benzopyrazine (Figure 1.7) (Soderquist et al. 1975). 

A. Szekacs, N. Trummerb, N. Adanyi, M. Varadi, and I. Szendro, Development of a non-labeled immu-nosensor for die herbicide trifluralin via optical waveguide lightmode spectroscopic detection. Anal. Chim. Acta 487, 31-42 (2003). 

Kearney et al. [254] in a study of persistence, binding and metabolism of six dinitroaniline herbicides (Trifluralin, Profluralin, Dinitramine, Butralin, Fluchloralin and Chlornidine) showed that the parent herbicide was the major compound extracted from herbicide-treated soil after three, five and seven months. Trifluralin, Fluchloralin and Profluralin were the most persistent of the six pesticides. 

The work reported in this paper was part of a larger project whose principal objective was to measure the rate of volatilization of the herbicide trifluralin to the atmosphere from a field soil after surface application and incorporation to a depth of 7.5cm by cultivation with a disc harrow. In this experiment it was necessary to measure as accurately as possible the amount of the trifluralin residue in the soil on several days during the growing season and to calculate the rate of disappearance of the... 

A kinetic smdy of the formation of zwitterionic adducts (28) from 1,3,5-trinitrobenzene and diazabicyclo derivatives indicates that reactions are surprisingly slow, with rate constants many orders of magnitude lower than those for related reactions with primary or secondary amines. The use of rapid-scan spectrophotometry was necessary to study the kinetics of reaction of 4-substimted-2,6-dinitro-A -n-butylanilines (29) with n-butylamine in DMSO the two processes observed were identified as rapid deprotonation to give the conjugate base and competitive a-adduct formation at the 3-position. The reactions of MAf-di-n-propyl-2,6-dinitro-4-trifluoromethylaniline (30), the herbicide trifluralin, and its A -ethyl-A -n-butyl analogue with deuteroxide ions and with sulfite ions in [ H6]DMS0-D20 have been investigated by H NMR spectroscopy. With deuteroxide a-adduct formation at the 3-position is followed by... 

The herbicide trifluralin is prepared by the following sequence of reactions. Identify compound A and deduce the structure of trifluralin. 

Hegedus, G., I. Belai, and A. Szekacs. 2000. Development of an enzyme-linked immunosorbent assay (ELISA) for the herbicide trifluralin. Anal. Chim. Acta 421 121-133. 

Dinitroaniline herbicides. Trifluralin (Treflan ), a 4-trifluoromethyl substituted 2,6-dinitroaniline derivative, was the first main fluorine-containing herbicide to be marketed, with 18,000 tons sold in 1982 in the United States alone [16]. Trifluralin, which was introduced in 1960 by Eli Lilly, is a pre-emergence herbicide used in soybean for the control of a variety of grass and broadleaf weeds [17]. It is prepared from the nitration of 4-chlorobenzotrifluoride, followed by nucleophilic displacement of chlorine with di-n-propyl amine (Fig. 3). Following the success of trifluralin, a number of related A/,A/-dialkyl 4-trifluoromethyl 2,6-dinitroaniline herbicides were later introduced [18]. 

In the past seven years N-nitrosamines have attracted wide attention due to their carcinogenic properties. In 1977, Ross et al. (67) reported the presence of N-nitrosodipropylamine in the formulation of dinitroaniline herbicide, trifluralin, at the 154 ppm level. Subsequent studies by other laboratories showed that nitrosamine impurities are common to all dinitroaniline-based herbicides. Nitrosamines contamination resulted from the nitration of dipropylamine by the excess nitrosating agent. 

The dinitroaniline herbicides, trifluralin and pendimethalin, have been utilized in greater than 80% of the cotton acreage in the Southern United States because of their very effective weed control in this crop (1). Many of these fields are essentially in cotton monoculture and hence the continued use of these herbicides has constantly selected out those weeds most tolerant of these herbicides. Under such a selection pressure, the appearance of weed biotypes resistant to dinitroaniline herbicides is expected (2). The first report of a resistant biotype did not appear until 1984, Mudge si gl. (3) described the occurrence of dinitroaniline-resistance in Eleusine indica in counties in South Carolina where cotton is extensively cultivated. Since that initial report, dinitroaniline-resistant Eleusine has been detected throughout the midsouth (H. LeBaron, personal communication). 

It appears that resistance to the aryloxyphenoxypropionate herbicides, the cyclohexanedione herbicides and to the sulfonylurea herbicides is unlikely to be due to reductions in the sensitivity or increases in the amounts of their respective target enzymes (Figures 2 3). Studies have not yet been performed to examine if die resistance to the dinitroaniline herbicide trifluralin is associated with any change at the tubulin polymerization site. 

In the third experiment, rotation away from continuous EPTC + dietholate in 1984 to no herbicide, trifluralin (2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine) + metribuzin (4-amino-6-(l, l-dimethylethyl)-3-(met.hylthio)-l, 2,4 -triazin-5(4H) one), alachlor + atrazine, or cycloate + atrazine increased the persistence of EPTC + dietholate at 14 and 21 DAT in 1985. Rotation with trifluralin + metribuzin or alachlor + atrazine was more effective than rotation with weedy check or cycloate + atrazine. However, the differences were not statistically significant. All rotated herbicide treatments had higher EPTC recoveries than the untreated plot (Table III). The results indicated that 1 year rotations resulted in partial to complete elimination of enhanced biodegradation for this herbicide. 

Chan MMY, Fong D. Inhibition of leishmanias but not host macrophages by the antitubulin herbicide trifluralin. Science 1990 249 924-926. 

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