Quaternary ammonium herbicide

The ring-chiorinated benzyl chlorides are used ia the preparation of quaternary ammonium salts and as iatermediates for pharmaceuticals and pesticides. p-C. orohen zyl chloride is an iatermediate ia the manufacture of the rice herbicide, Saturn ((S-4-chlorobenzyl)-N,N-diethylthiolcarbamate [28249-77-6] (75). The o- and -chlorobenzal chlorides (l-chloro-2-and 4-dich1 oromethylhenzenes) are starting materials for the manufacture of o- and p- chlo rob enz aldehyde s. 

Diquat and paraquat are quaternary ammonium compounds largely used as contact herbicides and crop desiccants. When systemic absorption occurs, paraquat and diquat are rapidly distributed into the body. Paraquat primarily accumulates in the lungs and kidneys, while the highest diquat concentrations have been found in the gastrointestinal tract, liver, and kidneys (WHO, 1984). Urine is the principal route of excretion for both diquat and paraquat, which are primarily eliminated as unmodified compounds. Occupationally exposed workers can be monitored by measuring paraquat and diquat concentrations in urine samples (Table 6). Blood concentrations are useful to monitor acute poisoning cases. 

Nunez, O., Moyano, E., and Galceran, M. T. (2002). Capillary electrophoresis-mass spectrometry for the analysis of quaternary ammonium herbicides.. Chromatogr. A 974, 243—255. 

Herbicides are used widely throughout the world to control weeds and exist in a wide variety of different types. Examples of classes of herbicide include the triazine, sulfonylurea, phenoxy, and quaternary ammonium herbicides. 

Paraquat (1,1 dimethyl, 4,4 bipyridyl) is a nonselective contact herbicide. It is used almost exclusively as a dichloride salt and usually is formulated to contain surfactants. Both its herbicidal and toxicological properties are dependent on the ability of the parent cation to undergo a single electron addition, to form a free radical that reacts with molecular oxygen to reform the cation and concomitantly produce a superoxide anion. This oxygen radical may directly or indirectly cause cell death. Diquat, l,T-ethylene-2,2 -dipyridylium, is a charged quaternary ammonium compound often found as the dibromide salt. The structure of diquat dibromide and that of the closely related herbicide paraquat can be seen in Fig. 4.5. 

The quaternary ammonium compounds paraquat and diquat are widely used non-selective contact herbicides, which are extremely toxic to humans. Fee et al. [112] established an HPLC-MS-MS procedure for the determination of these herbicides in whole blood and urine using ethyl paraquat as internal standard. After extraction with Sep-Pak C18 cartridges, analytes were separated using ion pair chromatography with heptafluorobutyric acid in 20 mM ammonium acetate and acetonitrile gradient elution. Detection was carried out in ESI MS-MS SRM mode. Using similar separation and detection conditions, paraquat, diquat, difenzoquat, and a number of structurally related quaternary nitrogen muscle relaxants (see Section 20.2.1.3) were determined in whole blood by Ariffin and Anderson [113]. 

Rocuronium bromide, other quaternary ammonium drugs and herbicides Column Atlantis dC18 (100 mm x 2.1 mm) Mobile phase (A) 15 mM HFBA-20 mM ammonium formate buffer adjusted to pH 3.30 by formic acid (B) MeOH 100%. Linear gradient run from 5% to 90% of solvent B within 18 min. Detector MS/MS using ESI in the positive mode m/ z 529 487.2... 

The chloride is used to manufacture silicones, tetramethyl lead and triptane (2,2,3 trimethylbutane). Lesser uses include the manufacture of butyl rubber, higher halogenated methanes, methyl cellulose, quaternary ammonium compounds, methyl mercaptan, methionine, fungicides and pesticides (primarily the Me-arsenate herbicides). Recently the chlorinated fluorocarbons have replaced CH3CI as high volume refrigerants and propellants (ref. 32) Tables 12 and 13 list the chemical and physical properties and potential numbers of workers exposed to the monohalomethanes. 

Ariffin MM, Anderson RA (2006) LC/MS/MS analysis of quaternary ammonium drugs and herbicides in whole blood. J Chromatogr B 842 91-97... 

Paraquat, a bipyridyl quaternary ammonium salt, was introduced by ICI in 1965 (Fig. 3). It is a non-selective, contact herbicide on plant foliage, but is immediately inactivated when applied to soil. It is used in minimum tillage programs and as a postemergence directed spray in sugarcane and in fruit tree crops. 

Methyl chloride is the only chlorinated methane with good growth. The principal use for methyl chloride is in the manufacture of chlorosilanes (89%) for the silicone industry. Other smaller uses are for methyl cellulose ether, quaternary ammonium compounds, herbicides, and butyl rubber. 

Quaternary Ammonium Herbicides Paraquat and diquat are the most important members of this class and are readily available in various proprietary formulations. Their analysis is complicated by the fact that they are not extractable by conventional liquid/liquid extraction procedures, nor can they be gas chromatographed in their original form. Ingestion of large amounts (several grams) of paraquat leads rapidly to death, and in these cases ultraviolet spectrophotometry may be used. However, death can occur even with smaller doses (300 mg), and the concentrations in body fluids are consequently much lower. Specific radioimmunoassay methods have been developed (T. Levitt, Proc. Analyt Div. Chem. Soc., 1979, 16, 72-76, and D. Fatori and W. M. Hunter, Clinica chim. Acta, 1980, 100, 81-90). 

Note. Unless otherwise stated, the analytical information given below refers to diquat dibromide. For information on the monoene and diene reduction products for GC-MS analysis, see under Quaternary Ammonium Herbicides, p. 80. 

Quaternary ammonium compounds, thin-layer chromatography, 175 Quaternary ammonium herbicides, 80... 

Positive-ion ESI is the obvions mode-of-choice in the analysis of quaternary ammonium herbicides and plant growth regulators, although APCl data were reported as well. ESI mass spectra of paraquat and diquat were reported by Song and Budde [54], obtained nnder CE-MS conditions. The appearance of the mass spectra depended on the solvent compositiom In acetic acid or sodium acetate, the base peak was due to the doubly-charged ions at m/z 92 [M] " for diquat and at m/z 93 for... 

O. Nunez, E. Moyano, M.T. Galceran, High mass accuracy in-source CE)-MS-MS and multi-step MS as complementary tools for fragmentation studies of quaternary ammonium herbicides, J. Mass Spectrom., 39 (2004) 873. 

The field of research was then extended to nontensioactive quaternary ammonium compounds, and in the reaction product of 2,2-bipyridyl, prepared for other purposes, with ethylene bromide a herbicide (diquat, 1) was discovered which proved efficient in greenhouses at a rate of 125 g/ha (Brian et at.. 1958). This compound was followed by paraquat (2) (Jeater, 1963) and other isomeric bipyridyls and their substituted derivatives. 

A number of developmental methodologies which are of interest in the herbicidal field have been examined for the formation of carbamates and related intermediates. Phosgene and phenol reacted in the presence of triphenylphosphine and a quaternary ammonium salt catalyst at 120-125°C over a total period of 10 hours gave phenyl chloroformate in 89% yield (ref.26). 

This discussion emphasizes the need to understand the nature of the compound to interpret its sorption behavior. Many compounds of environmental significance are nonpolar and one tends to relate sorption to aqueous solubihty. The herbicide, Paraquat, by contrast shows a A oc of 1 x 10 despite having a high aqueous solubility (>600 gL ). This compound is a bipyridinium salt and the high tendency to sorb would be due to cation exchange not partitioning. A comparable response would be expected with quaternary ammonium detergents. 

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