Publisher Summary This chapter discusses molecular refractivity and polarizability. Refractive indices ( n ) of pure substances are more accurately measurable than any other optical properties. The refractive index of a substance varies with its physical state, temperature t , and wave-length λ of the light by which n is observed. The first two of these effects are attributed to the density d . The specific refraction r of a substance multiplied by the molecular weight is referred as molecular refraction. Polarizability of a particle is defined as the dipole moment induced by an electric field of unit intensity. The polarizabilities of monatomic ions and molecules are generally independent of field direction. The principal polarizabilities of molecules can be analyzed in terms of anisotropic bond polarizabilities. Polarizabilities are also responsible for the birefringence, which appears whenever the orientations of anisotropic molecules in an assemblage are derandomized or changed by any disturbing force.

Molecular Refractivity and Polarizability

Publisher Summary This chapter discusses the several possibilities regarding the specification of the energy associated with the anomeric effect, and the experimental data concerning the configurational and conformational equilibria of the anomeric center and the related variations of valence geometry. The free-energy aspect of the anomeric effect as displayed by the equilibria of isomers is the area wherein the very concept was incepted and developed, and which still dominates its investigation. A considerable amount of data has been accumulated during the past two decades on the anomeric effect in terms of structure, energy, reactivity, and other properties. The description and understanding of the nature of stereoelectronic effects is an appropriate field for the application of organic quantum chemistry. Although several molecular orbital (MO) methods successfully describe the stereochemical behavior of pyranose models, their application to the more complex carbohydrates and oligosaccharides is limited at present due to economical reasons. The various rationalizations of the anomeric effect have been offered over the past years; they may be roughly divided into two main groups—namely, the electrostatic and the delocalization rationalization of the anomeric effect. It may be expected that the intramolecular interactions involved in the anomeric effect also influence the other points on the generalized reaction hypersurface.

Anomeric and Exo-Anomeric Effects in Carbohydrate Chemistry

Azadirachtin, a scientific gold mine

Organophosphate pesticides (OPs) are generally regarded as safe for use on crops and animals due to their relatively fast degradation rates. Their degradation varies as a function of microbial composition, pH, temperature, and availability of sunlight. Under laboratory conditions (25°C and pH 7) biodegradation is about one order of magnitude faster than chemical hydrolysis, which in turn is roughly ten times faster than photolysis. Microbial biomass often needs a lengthy adaptation period in which soil bacteria mutate to be able to metabolize OPs. Biodegradation is thus in general an order of magnitude faster in soils that have had repeated applications of OPs compared to control soils which have never had OP applications. Because OPs are relatively soluble, they often enter surface and groundwaters. In the latter OPs are primarily broken down through chemical hydrolysis, which is pH dependent. Hydrolysis half-life of an OP pesticide of 10 days in the laboratory increases to one year if the pH of the water is 6 and the temperature 5°C, suggesting that OPs can persist in the environment for long periods of time. Indeed, OPs are detected in soils years after application. Why this environmental persistence occurs is not clear, but it may be due to sorption of the OPs to soil particles, making them unavailable for microbial metabolism. Example calculations and literature data show that conditions can occur in soil where OPs are preserved and transferred to humans through food. A review of the literature shows that OPs are highly toxic and that human exposure is undesirable. Evidence suggests that OPs are mutagenic and teratogenic and that a large number of modern-day diseases of the nervous and immune system of mammals can be linked to these pesticides. These include BSE (mad cows disease), CJD, Gulf War syndrome, Parkinson’s disease and multiple sclerosis, arguing for a thorough examination of the environmental fate and toxicology of OPs as well as their use.

Environmental fate and toxicology of organophosphate pesticides

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A (1993a) Beauveria bassiana (Balsamo) Vuillemin (Deuteromyces) applied to laboratory colonies of Solenopis invicta Buren (Hymenoptera: Formicidae) in soil. Environ. Entomol. 86, 348-52. Stimac, J. L., Pereira, R M., Alves, S. B. and Wood, L. A (1993b) Mortality in laboratory colonies of Solenopsis invicta (Hymenoptera: Formicidae) treated with Beauveria bassiana (Deuteromycetes). J. Econ. Entomol. 86, 1083-7. St Leger, R J., Butt, T. M., Staples, R C. and Roberts, D. W. (1989) Synthesis of proteins including a cuticle-degrading protease during differentiation of the entomopathogenic fungus Metarhizium anisopliae. Exp. Mycol. 13, 253-62. Storey, G. K. and Gardner, W. A (1987) Vertical movement of commercially formulated Beauveria bassiana conidia through four Georgia soil types. Environ. Entomol. 16, 178-81. Storey, G. K. and Gardner, W. A. (1988) Movement of an aqueous spray of Beauveria bassiana into the profile of four Georgia soils. Environ. Entomol. 17, 135-9. Storey, G. K. 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Formulation of Microbial Biopesticides

The solubility products (Ksp) of 1:1 complexes of glyphosate, [N‐(phosphonomethyl)glycine], with Mg2+, Ca2+, Mn2+, Zn2+, Cu2+ and Fe3+, were determined in buffered (pH 7.0) distilled water, moist Ottawa sand, sandy loam and clay loam soils, each adjusted to 0.02 M with respect to KNO3. The Ksp values decreased in the order of Mg ≍ Ca > Mn > Zn > Cu > Fe, regardless of the medium in which they were determined. The constants measured in Ottawa sand were similar to those in water, but those in the forestry soils depended upon the type of metal ion involved. The values for the Mg, Ca, Mn and Zn complexes were about 2 to 3 times lower in sandy loam soil than those in water, but those in clay loam were about 3 to 10 times lower. The Ksp of the Cu and Fe complexes were similar to those in water regardless of the soil type used. In a bioassay experiment using tomato plants, immersed in the saturated solutions of the complexes or planted in the sand and soils containing saturated solutions of the complexe...

Solubility products of six metal‐glyphosate complexes in water and forestry soils, and their influence on glyphosate toxicity to plants

769. Molecular polarisability: the conformations of some simple carboxylic esters as solutes

Dimilin® WP-25 (diflubenzuron) was applied at a rate of 70 g active ingredient (AI) in 10, 5, and 2.5 L/ha to three spray blocks in a mixed boreal forest near Kaladar, Ontario, Canada. Water, sediment, and aquatic plants were collected from two ponds and a stream at intervals up to 30 days post-treatment for analysis of diflubenzuron (DFB) residues. The duration of detectable residues was different for each substrate, but in all cases was less than two weeks. Zooplankton and benthic invertebrate populations were monitored for up to 110 days post-spray in two ponds in the high volume rate block and in control ponds. Significant mortality occurred in two groups of caged macroinvertebrates (amphipoda and immature corixidae) 1 to 6 days after the ponds were treated with Dimilin. Three taxa of littoral insects (Caenis, Celithemis andCoenagrion) were significantly reduced in abundance in the treated ponds 21 to 34 d post-treatment, but recovered to pre-treatment levels by the end of the season. Of the six remaining groups studied, only one (immature corixidae), may have been slightly affected by treatment. Zooplankton (cladocera and copepoda) populations were reduced 3 days after treatment and remained suppressed for 2–3 months.

Environmental persistence and impact of diflubenzuron in a forest aquatic environment following aerial application

73. Molecular polarisability: the anisotropy of the carbon–oxygen link

A field study was conducted to investigate the persistence of tebufenozide in white spruce foliage. An aqueous suspension concentrate formulation, RH-5992 2F, was sprayed over single trees at three dosage rates, 35, 70 and 140 g of the active ingredient (AI), in 2.0 litre ha -1 , using ground application equipment. Foliage was collected at different intervals of time up to 64 days after treatment and tebufenozide residues were measured by high-performance liquid chromatography. Foliage was also fed to laboratory-reared 4th- and 6th-instar spruce budworm (Choristoneura fumiferana Clemens). The data indicated that tebufenozide residues in foliage declined with time according to first-order kinetics. The average rate-constant and half-life of disappearance (DT 50 ) were 0.0340 and 20.45 days, respectively. Larval mortality declined gradually, corresponding to the residues, but was still appreciable (49 to 70%) when the larvae were fed with foliage collected 64 days after treatment. The amount of foliage consumed by the larvae decreased when foliar residues of tebufenozide increased, thus indicating anti-feedant activity of the chemical. The LD 50 values for both instars were similar and averaged c.25 ng per insect, but the LD 90 values were significantly lower for 4th-instar than for 6th-instar, at 63.6 and 96.1 ng per insect respectively. This implies that, theoretically, at a foliar concentration of 1.0 μg tebufenozide g -1 foliage (fresh wt), the spruce budworm larva needs to consume 65 to 100 mg of foliage in 10 days to cause mortality in about 90% of a population of the insect.

Alam Sundaram

Papers

Solubility products of six metal‐glyphosate complexes in water and forestry soils, and their influence on glyphosate toxicity to plants

769. Molecular polarisability: the conformations of some simple carboxylic esters as solutes

Environmental persistence and impact of diflubenzuron in a forest aquatic environment following aerial application

73. Molecular polarisability: the anisotropy of the carbon–oxygen link

Foliar Persistence and Residual Activity of Tebufenozide Against Spruce Budworm Larvae