Crops protection

DIFLUOROBENZENES Interest in the commercialization of difluoroaromatics in crop protection chemicals and dmgs (Table 5) continues to be strong. Numerous liquid crystals containing the 1,2-difluorobenzene moiety have been synthesized. Table 6 lists physical properties of commercially significant intermediates such as o-, m-, and -difluorobenzene, 2,4-difluoroaniline and 2,6-difluorobenzonitrile. The LD q values for the three isomeric difluorobenzenes are identical 55 g/m for 2 h (inhalation, mouse) (127). 

Trifluoromethyl aromatics are used widely ia the production of dmgs, crop-protection chemicals, germicides, dyes, etc. 

Crop Protection Cbemic ls. Ben2otrifluoride derivatives have gained wide acceptance as herbicides, iasecticides, and fungicides (Table 10). 

Applications. Table 12 Hsts crop-protection chemicals and pharmaceuticals containing the aryl fluoroaLkyl ether group. 

Ring- or side-chain fluoriaated nitrogen heterocycHcs have been iacorporated iato crop-protection chemicals, dmgs, and reactive dyestuffs. Key iatermediates iaclude fluoriaated pyridines, quiaolines, pyrimidines, and tria2iaes. Physical properties of some fluoriaated nitrogen heterocycHcs are Hsted ia Table 13. 

Applications. Until recently, haloxydine, a herbicide, was one of the few early examples of crop-protection chemicals containing riag-fluofinated pyridines. Fluroxypyr-(l-methylheptyl) and pyroxofop are new herbicides that are being commercialized (Table 14). 

PERFLUOROALKYLPYRIDINES New developments ia trifiuoromethylpyridine technology are associated with the commercialization of numerous crop-protection chemicals as herbicides, fungicides, and iasecticides (Table 15). Physical properties for representative trifiuoromethylpyridines are fisted ia Table 13. 

Table 15. Trifluoromethylpyridine-Based Crop-Protection Chemicals ...

A significant development ia trifluoromethylpyridine synthesis strategy is the use of fluoriaated aUphatic feedstocks for the ring-constmction sequence. Examples iaclude the manufacture of the herbicide dithiopyr, utilising ethyl 4,4,4-trifluoroacetoacetate [372-31-6] CF2COCH2COOC2H (436,437). 2,3-Dichloro-5-trifluoromethylpyridine [69045-84-7], a precursor to several crop-protection chemicals (see Table 15), can be prepared by conversion of l,l,l-trichloro-2,2,2-trifluoroethane [354-58-5], CF CCl, to 2,2-dichloro-3,3,3-trifluoropropionaldehyde [82107-24-2], CF2CCI2CHO, followed by cycUzation with acrylonitrile [107-13-1] (415). 

J. Dekker and S. G. Georgopoulos, eds.. Fungicide Resistance in Crop Protection, Centre for Agdcultural Publishing and Documentation, Wageningen, the Nethedands, 1982. 

Technical Informationsfor Crop Protection, E. Merck, Darmstadt, Germany, 1964. 

Between 1979 and 1991, the amounts of herbicide apphed in the United States have remained constant, but the expenditures on herbicides have increased 54%. Agricultural costs accounted for ah. of this increase and more, since herbicide user expenditures in the government/commercial and home sectors combined dropped 3 to 4% during that period. Increased weed control costs related to crop protection have also contributed to the 37% increase, since 1988, in total annual user expenditures for pesticides in general, ie, herbicides, fungicides, and insecticides. In the United States, agricultural uses (ca 1993) account for more than 67% of total pesticide user expenses and 75% of the quantity used annually. Herbicides are now the lea ding type of pesticides in terms of both user expenditures and volumes used (1). 

P. A. Hedin, J. J. Menn, and R. M. HoUiugworth, eds.. Biotechnologyfor Crop Protection, ACS Symposium Series 379, American Chemical Society, Washington, D.C., 1988. 

L. G. Coppiug and P. Rodgers, eds., "Biotechnology and its AppHcation to Agriculture." British Crop Protection Conference, Croydon, U.K., Monograph 32,1985. 

T. H. Thomas, ed. Plant Growth Regulator Potential and Practice, Bnt. Crop Protect. Conf. Publ., Croydon, U.K., 1982, p. 117. 

E. Y. Spencer, Guide to the Chemicals Used in Crop Protection, 7th ed.. Research Branch Agriculture, Ontario, Canada, 1980. 

B. E. Greenwold, F. Pereiro, T. J. PumeU, and H. B. Scher, Proceedings of the 1980 British Crop Protection Conference on Weeds, British Crop Protection Society, London, p. 185. 

Crop Protection, insects and weeds in fields, gardens, greenhouses, nurseries Disinfection, bacteria in homes, hospitals, on medical and dental equipment... 

C. A. Edwards, in G. Ekstrom, ed.. World Directory of Pesticide Control Organisations, 2nd ed.. The British Crop Protection Council and the Royal... 

Society of Chemistry, Crop Protection Publications, Cambridge, U.K., 1994, pp. 1—23. 

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