Protective chemicals

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. 

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). 

Crop Protection Chemicals Reference (CPCR), 6th ed.. Chemical and Pharmaceutical Press, John Wiley Sons, Inc., New York, 1990. Includes brand names and product labels. 

Sustainable Agriculture. The third factor that will influence the future of pesticide sales is the emphasis on sustainable agriculture systems that rely on more natural pest control methods and reduced pesticide usage. These are integrated systems that requke nutrients and crop protection chemicals from on-farm natural sources and cultural methods. Many current sustainable farms are site-specific systems that may depend on the soils in a... 

Bakery Products. Sorbates are used in and/or on yeast-raised and chemically leavened bakery products. The internal use of sorbates in yeast-raised products at one-fourth the amount of calcium—sodium propionate that is normally added provides a shelf life equal to that of propionate without adversely affecting the yeast fermentation. Sorbates added at one-tenth the propionate level reduce the mix time by 30% (126). This internal treatment combined with an external spray of potassium sorbate can provide the same or an increased shelf life of pan breads, hamburger and hot-dog buns, English muffins, brown-and-serve roUs, and tortillas. The total sorbate useful in or on these baked goods ranges from 0.03 wt % for pan breads to 0.5 wt % for tortillas 0.2—0.3 wt % sorbic acid protects chemically leavened yellow and chocolate cakes (127). Emit-pie fillings and icings can be protected with 0.03—0.1 wt % sorbates. 

Clean surfaces are almost always easier to protect chemically from corrosion. Chemical inhibition and inhibitors are often tested on relatively clean surfaces, for a variety of reasons. The effectiveness of almost all commonly used corrosion inhibitors increases as surface cleanliness improves. 

Ring-fluonnated aromatics have found wide applications in pharmaceuticals, crop protection chemicals, polymer intermediates, liquid crystals, etc [10] Routes based on aromatic amines represent one of the major synthetic approaches to these compounds The scope and the techniques have been sufficiently described in reviews [//, I2 and monographs [13, 14, fi] Therefore, only reactions and techniques published after 1971 are discussed... 

Downing et al. (1997) have reported a number of examples, including isomerization of 2,3-dimethyl-2,3-epoxide to methyl-rer/-butyl ketone, which is required for the production of photographic and crop-protection chemicals. 

Crop protection chemicals undergoing field testing to determine dissipation, wildlife exposure and toxicological effects will have undergone extensive laboratory tests to... 

Brief reviews of the paints used to protect chemical plant are given by Ruff (1984) and Hullcoop (1984). 

In 1956 Brown, in a series of patents(68-75), disclosed that clays could be treated with di-, tri-, or tetra-substituted ammonia derivatives. Later, McLaughlin, et al.(76,77), introduced cationic polymers as permanent clay protective chemicals. A series of published results describing laboratory and field applications soon became available(78-81). Structural details of the cationic polymers appeared in patents(82-85). In general the polymers are polyamine derivatives, mostly quaternary in nature. Theng(86,87) has discussed how the multiple cationic centers in these polymers can interact and permanently protect clays. Callaway(88) et al. has noted that cationic polymers may interfere with the performance of crosslinked fracturing fluids. 

Callaway, R.E. "Clay Protection Chemicals A Practical Evaluation and Application Technique for Their Use in Stimulation Fluids", SPE paper 10663, 1982 SPE Formation Damage Control Symposium, Lafayette, March 24-25. 

Although the results presented only reflect agricultural practices of a single year, findings confirm that herbicides are the most widely used type of pesticide, as weeds are the major constraint that limit yield in many crops in conventional crop cultivation systems. According to CropLife (2004), herbicides represent around 50% of all crop protection chemicals used throughout the world, compared with insecticides and fungicides that each account for around 17%. 

Required level of protection Chemical protective clothing/equipment required to work safely. 

EYE PROTECTION Chemical goggles. For splash hazards use goggles and faceshield. 

Commercially the most exploited uses of surface fluorination are fluorinated HDPE fuel tanks for automotive vehicles and to a lesser extent fluorinated HDPE containers for the packaging of solvent-based crop protection chemicals. These products can be fluorinated using either in-line or postfluorination processes.10... 

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