Trifluralin, fluorinated

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]. 

Fluorinated trifluralin ( oi, Oi, 0 -trifluoro-2,6-dinitro-N,N-dipropyl- -toluidine) was found to contain nitrosamines, and it seems likely that these arose by the nitrosation of the amine used in the condensation with the nitrated chlorobenzene intermediate in the synthesis or by nitration of the product, trifluralin itself. Nitrosamines have also been found in other pesticides prepared by similar nitration processes. 

One of the commercially most successful fluorine-containing herbicides is Trifluralin [12, 13]. Acting by inhibition of root and shoot growth of seedlings immediately after germination it is used as a preplanting herbicide for selective control of armual grasses and broadleaf weeds in cotton and other crops. A newer development is the structurally related Flumetralin [14], which is used to control suckers on tobacco. 

With reference to the molecular structure for trifluralin, the presence of electronegative heteroatoms, such as fluorine eombined with two nitro substituents on the benzene ring, would make the organie eompound highly sensitive to the electron-capture detector (ECD) provided that the substance is sufficiently vaporizable and therefore amenable to GC. With a boiling point of 139°C, trifluralin is appropriately classified as a semivolatile, neutral organic and could be isolated by conventional sample preparation techniques such as liquid-liquid extraction (LLE) (1, 2). 

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