Nitrogen-containing insecticides

Microbial insecticides are very complex materials in their final formulation, because they are produced by fermentation of a variety of natural products. For growth, the bacteria must be provided with a source of carbon, nitrogen, and mineral salts. Sufficient nutrient is provided to take the strain of choice through its life cycle to complete sporulation with concomitant parasporal body formation. Certain crystalliferous bacilli require sources of preformed vitamins and/or amino acids for growth. Media for growing these bacilli may vary from completely soluble, defined formulations, usable for bench scale work, to rich media containing insoluble constituents for production situations (10,27). Complex natural materials such as cottonseed, soybean, and fish meal are commonly used. In fact, one such commercial production method (25) is based on use of a semisolid medium, a bran, which becomes part of the final product. 

Among phosphorus insecticides containing also nitrogen and sulphur we may mention 00 -diethyl-/S-/ -diethylaminoethyl phosphorothiolate (X). It was prepared (i) from diethyl phos-phorochloridate1 and sodium / -diethylaminoethyl mercaptide, (ii) from sodium diethyl phosphite and / -diethylaminoethyl thiocyanate, (iii) by the isomerization of OO -diethyl-O"-/ -diethylaminoethyl phosphorothionate (XI) obtained from / -diethylaminoethoxide and diethyl phosphorochloridothionate. 

The discovery of the Improved toxicological properties of the aryl- and alkylsulfenyl derivatives of methylcarbamate insecticides stimulated examination of other types of derivatives containing an N-S linkage. In most of the cases where highest insecticidal activity is found, the methylcarbamate nitrogen is attached to a sulfur atom which is attached to another nitrogen atom, as shown in the general structure below. 

The sulfur derivatives of methylcarbamate insecticides which have been described are those containing a sulfenyl (or thio) sulfur attached to the methylcarbamate nitrogen atom. N-Alkylsulfinyl or N-aryIsulfinyl derivatives (general structure... 

An amide is a carbonyl-containing organic molecule in which the carbonyl carbon is bonded to a nitrogen atom. The active ingredient of most mosquito repellents is an amide whose chemical name is 7V,7V-diethyh i-toluamide but is commercially known as DEET, shown in Figure 12.22. This compound is actually not an insecticide. Rather, it causes certain insects, especially mosquitoes, to lose their sense of direction, which effectively protects DEET wearers from being bitten. 

The structures and common names of several other aromatic compounds that have direct use as flavorings, perfumes, therapeutic drugs, or insecticides are shown in Figure 26-2. Many other such compounds that contain nitrogen are shown in Figures 23-1 through 23-3. 

The commercially formulated product contains approximately 65% calcium cyanamide, which is 20% to 24% nitrogen. For most of the twentieth century it has been used as a fertilizer, a cotton defoliant, a herbicide and a soil insecticide. 

Next, pirimicarb, a selective insecticide that kills sap-sucking aphid pests but does not affect the useful predators such as ladybirds (ladybugs) that eat them. It contains a pyrimidine ring—a benzene ring with two nitrogen atoms. 

To separate sulfur-containing organophosphate insecticides, a column temperature of 180° C. and a nitrogen carrier gas flow of 39 ml. per minute were used. The coulometer was operated at maximum sensitivity (512 ohms) at a damping position of 4 and a bias of +100. An iodine-iodine ion cell was used. 

The food supply could be increased due to the use of different hybrid varieties, improved techniques of farming, better seeds, insecticides and herbicides for the eradication of parasites and weeds, but mostly due to the intensive use of natural and synthetic fertilizers. Therefore, the dependence on chemical fertilizers, especially those containing nitrogen, is a hallmark of high-intensity agriculture and since 1960 the worldwide rate of application of nitrogen fertilizers has been increasing (Tilman, 1998). 

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