Triazole pesticides

Triazole pesticides are made by reaction between 1.2.4 triazole and a halo-compound... 

There are 4 most common structures for triazole pesticides... 

An unusual route to triazole pesticide synthesis is by cyclisation of the triazole ring as a synthesis step, by reaction between an °C amine hydrazono derivate and an acid chloride... 

Fc = semi empirical polarity correction factor derived for several classes of compounds (i.e., acetanilides = 0.31 amides = 0.66 halogenated aromatic hydrocarbons = -0.20 non-halogenated aromatic hydrocarbons = -0.27 carbamates = 0.27 dinitroanilines = 0.19 organophosphorous pesticides = 0.01 PAHs = -0.93, triazines = 0.24, triazoles = -0.22 ureas = 0.19). 

On the other hand, triphenyltin acetate and triphenyltin hydroxide were the first commercial products introduced during the early 1960s followed by triphenyltin chloride, tricyclohexyltin hydroxide, bis(trineophenyltin) oxide, and tricyclohexatin-1,2,4-triazole, respectively. Triphenyltin hydroxide was one of the recommended pesticides for rice and necessary for countries like Thailand where rice is a major component of both domestic and export markets (Visoottiviseth, 2001). 

A number of mesoionic 1,2,3,4-oxa- and -thia-triazoles, prepared by standard methods, were assessed for pesticidal and herbicidal activity (79BRP2015878). Pharmacological activity of mesoionic compounds has been reviewed (76AHC(19)l). 

Many detectors have been used to detect pesticides and herbicides in SFC. Among these detectors, the flame ionization detector (FID) is most commonly used for detection of a wide range of pesticides and herbicides, with a detection limit ranging from 1 ppm (for carbonfuran) to 80 ppm (for Karmex, Harmony, Glean, and Oust herbicides). The UV detector has frequently been used for the detection of compounds with chromophores. The detection limit was as low as 10 ppt when solid-phase extraction (SPE) was on-line coupled to SFC. The mass spectrometric detector (MSD) has also been used in many applications as a universal detector. The MSD detection limit reached 10 ppb with on-line SFE (supercritical fluid extraction)-SFC. Selective detection of chlorinated pesticides and herbicides has been achieved by an electron-capture detector (ECD). The limit of detection for triazole fungicide metabolite was reported to be 35 ppb. Other detectors used for detection of pesticides and herbicides include thermoionic, infrared, photometric, and atomic emission detectors. 

Indeed, the promise of IA has led to workable enzyme-linked immunosorbent assays (ELISAs) for a variety of pesticides, including thiolcarbamates, triazoles and triazines, substituted ureas and sulfonylureas, bipyridilium compounds, and other groups of chemicals(2) (Table I). Additionally, radioimmunoassay (RIA) methods exist for chlorinated hydrocarbons, organophosphates, phenoxy adds and other chemical classes. 

Field dosages often span a very broad range, and the typical application rates , shown in Table 8.1, are for general comparison only. Nevertheless, these numbers indicate how field a.i. rates have decreased historically, as more active molecules have been developed examples include the neo-nicotinoid insecticides, triazole fungicides and sulfonylurea herbicides, which are one to two orders of magnitude more active than the early organochlorine, copper and aryloxyalkanoic acid pesticides, respectively. 

Generic pesticides (those that have exceeded their patent life) represent over half of the global crop protection market (US 18 000 million of end-user sales in 1998). The patent expiry of important molecules such as the pyrethroids, triazole fungicides and glyphosate has resulted in substantially reduced prices, and there have been tensions between the major multinational and generic (often national) pesticide companies. Nevertheless, some 70% of the profits from multinational companies come from compounds that have exceeded their normal, 20-year patent life (i.e. approximately 13 years of profitable life Finney, 1988). In response, the major multinational companies have attempted to maintain their market share... 

The last ten years have seen important developments in this respect in the three most important families of pesticides fungicides of the triazole group applied at about 100 g/ha, insecticides of the synthetic pyrethroid type at 20 g/ha and herbicides of the sulfonylurea type at 30 and even as little as 5 g/ha exert an effect which could be achieved with the pesticides of 15-20 years earlier only at rates of a few kilograms per hectare. These modern highly efficient preparations form only a small part of the selection of pesticides available today, but a rapid increase in their share of the total is to be expected as a result of purposeful research work. Another approach toward diminishing environmental contamination by chemicals is the development of new active substances which are less volatile, are degraded more rapidly or are more readily adsorbed by soil particles. 

T riamiphos, 5-amino-3-phenyl-1H-1,2,4-triazol-l -yl-N,N,N, N -tetramethyl-phosphonic diamide, marketed as Wepsyn", has been used primarily in floriculture (roses) and apple orchards for the control of powdery mildew (Koopmans, 1960). In addition to its prophylactic use, it is absorbed by the plants and has a curative effect. According to Magendans and Dekker (1966), triamiphos primarily inhibits the formation of haustoria, but it also reduces spore formation. It also has insecticidal properties, mainly against aphids. Today, triamiphos has been replaced by other pesticides because it is expensive to produce and is very toxic to warmblooded organisms, its acute oral lDjo being 20 mg/kg for rats. 

Baez, M. E., Rodriguez, M., Lastra, O., and Contreras, P., Sohd-phase extraction of organophosphorus, triazine, and triazole-derived pesticides from water samples. A critical study, J. High Resolut. Chromatogr., 20, 591-596, 1997. 

In the past, PCP, lindane and DDT have been used in several instances in Germany to protect wood indoors. In recent years modem biocides such as pyrethroids (e.g. permethrine) or triazoles (e.g. tebuconazole) have been used instead of the classical organic chloro-pesticides to protect wood. 

Basic Compounds. Pesticides such as the 5-triazines and triazoles behave as weak bases in aqueous solutions (72, 73). They readily associate with hydrogen to form protonated species as shown in Equation 2, and the amount of each species in solution is governed by the equilibrium expression in Equation 3 ... 

Some patents refer to the controlled release of certain pesticides [58, 59]. Matolcsi et al. [60] used j8-CyD to prepare inclusion compounds with benzenesul-fonylurea derivatives with herbicidal or plant growth regulator properties [61], obtaining a prolonged controlled release of the active ingredient. Ikeuchi et al. [62] prepared inclusion complexes of triazole derivatives which presented potent insecticidal activities at low concentrations for an extended period. 

CoPc modified carbon paste electrodes were reported by Chicharo et al. to show good catalytic activity towards the measurement of triazolic herbicides sueh as amitrole at low oxidation potential (+0.4 V, Table 7.1) in basic media, a detection limit of 0.04 jig mL was obtained using a injection system . A screen-printed carbon electrode which was impregnated with CoPc electrocatalyst, was employed in conjunction with acetylcholinesterase by Hartley and Hart for the reduction of organophosphate pesticides The detection limits were of the order of 10 and 10 ... 

Liquid chromatography-mass spectrometry The initial attempts to couple LC with MS lacked important attributes for trace analysis sensitivity, robustness, and reliable quantitation. Moreover, the cost of the early LC-MS instruments was prohibitive for most laboratories. The revolutionary introduction of atmospheric pressure ionization (API) techniques, mainly electrospray (ESI) and atmospheric pressure chemical ionization (APCI), resulted in greater applicability of LC-MS and manufacture of more reliable, affordable, and user-friendly instruments. Thus, LC-MS is now becoming an indispensable part of the analytical strategy in many routine laboratories, enabling direct, selective, and sensitive multiclass, multiresidue analysis of more polar, low volatile, and/or thermolabile pesticides, such as carbamates, phenylureas, sulfonylureas, imidazoles, triazoles, imidazolinones, chlorophenoxy acids, and many others. 

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