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Soil
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Soil fumigants are volatile substances applied to soil to combat bacteria, fungi, nematodes, arthropods, and weeds, primarily on fields used to grow potatoes, tomatoes, strawberries, carrots, and peppers. Because of fumigants' use on food crops and the potential for exposure of workers who tend and harvest these crops, the safety of these substances has been a matter of considerable concern. Structural formulas of the most common soil fumigants are shown in Figure 15.7. The most widely accepted soil fumigant has been methyl bromide, H3CBr, but it was phased out of use in most industrialized countries including the United States in 2005 except for some very limited “critical use exemptions.” Metam sodium is the most widely applied fumigant and the third most widely used pesticide in the United States, primarily on potato fields. In soil, it breaks down to methyl isothiocyanate, which is the active agent (shown in Figure 15.7). In 2007, the US Environmental Protection Agency approved limited use of methyl iodide, H3CI. Dimethyl disulfide is a relatively new fumigant that is commonly applied along with chloropicrin.
Methanol Conversions
Published in Saeed Sahebdelfar, Maryam Takht Ravanchi, Ashok Kumar Nadda, 1 Chemistry, 2022
Saeed Sahebdelfar, Maryam Takht Ravanchi, Ashok Kumar Nadda
The chemistry of BASF and Monsanto processes is similar but their kinetics differ due to different rate determining steps. In both systems, two important catalytic cycles exist (Figures 7.7 and 7.8). One encompasses metal carbonyl catalyst and the other iodide promoter. Fig. 7.8 shows the catalytic cycle of acetic acid synthesis on rhodium catalyst. This cycle is a classic example of homogeneous catalytic process. During methanol carbonylaton, methyl iodide is produced from addition of methanol to hydrogen iodide. IR spectroscopic studies showed that the principal species of the rhodium catalyst is [ Rh(CO)2I2]- .
Soil: Earth’s Lifeline
Published in Stanley Manahan, Environmental Chemistry, 2017
Soil fumigants are volatile substances applied to soil to combat bacteria, fungi, nematodes, arthropods, and weeds, primarily on fields used to grow potatoes, tomatoes, strawberries, carrots, and peppers. Because of fumigants’ use on food crops and the potential for exposure of workers who tend and harvest these crops, the safety of these substances has been a matter of considerable concern. Structural formulas of the most common soil fumigants are shown in Figure 15.7. The most widely accepted soil fumigant has been methyl bromide, H3CBr, but it was phased out of use in most industrialized countries including the United States in 2005 except for some very limited “critical use exemptions.” Metam sodium is the most widely applied fumigant and the third most widely used pesticide in the United States, primarily on potato fields. In soil, it breaks down to methyl isothiocyanate, which is the active agent (shown in Figure 15.7). In 2007, the US Environmental Protection Agency approved limited use of methyl iodide, H3CI. Dimethyl disulfide is a relatively new fumigant that is commonly applied along with chloropicrin.
Property and reactivity of polyselenides and polysulfides: a quantum chemistry study
Published in Journal of Sulfur Chemistry, 2023
For the reactions with methyl iodide in methanol, it was demonstrated that phenyl selenolate (C6H5Se−) and selenocyanate (NCSe−) are more nucleophilic than their thiolate counterparts (C6H5S− and NCS−) [12–14]. Furthermore, it was shown that C6H5Se− and C6H5S− are more reactive than NCS− and NCSe− [12]. Our computed data are in agreement with these observations, as is shown in bold and italic in Table 4. In contrast, HS− and CH3S− are slightly more nucleophilic than HSe− and CH3Se− kinetically and thermodynamically. It is interesting to note that, H2Se and CH3SeH are noticeably more likely to deprotonate than their sulfur counterparts in methanol. With deprotonation tendency included, selenols are more nucleophilic than their thiol counterparts.
Organic Telluride Formation from Paint Solvents Under Gamma Irradiation
Published in Nuclear Technology, 2022
Anna-Elina Pasi, Mark R. St.-J. Foreman, Christian Ekberg
Although organic chemistry in a severe accident condition involving tellurium has not been explored, there is evidence of formation of volatile organic species under sump conditions, mainly involving iodine. Previous studies have shown the formation of different organic iodides and their re-volatilization from the sump. Organic iodides have been found to form from organic radicals originating from various paint constituents.15–17 The focus has mainly been on the formation of methyl iodide (CH3I), but other forms of organic iodides have also been shown to form, such as ethyl, isopropyl, and butyl iodide,18 all of which are volatile species and can increase the iodine source term. Another fission product that could have interactions with paint during a nuclear accident is ruthenium. Although ruthenium can be in organometallic compounds, the main interactions with ruthenium and paint in severe accident conditions are either deposition on painted surfaces or possibly oxidation of organic molecules in the sump.19,20
Synthesis, structural and DFT studies on thiosemicarbazone-based dioxomolybdenum(VI) complexes with co-ligands
Published in Journal of Coordination Chemistry, 2022
Berat İlhan-Ceylan, Olcay Bolukbasi, Ayberk Yilmaz, Nahide Gulsah Deniz, Bahri Ülküseven
4-Phenylthiosemicarbazide (1 g, 5.9 mmol) was dissolved in 10 mL of absolute ethanol at 60 °C in a hot water bath. 5-Chloro-2-hydroxybenzophenone (1.1 g, 4.92 mmol) and 2–3 drops of concentrated sulfuric acid were added to the solution and stirred for 6 h. The precipitate obtained was filtered and washed with 5 mL of cold ethanol. The solid substance was dried over diphosphorus pentoxide. The obtained 5-chloro-2-hydroxybenzophenone 4-phenylthiosemicarbazone (0.8 g, 2.1 mmol) was subsequently dissolved in 5 mL of tetrahydrofuran. Methyl iodide (0.14 mL, 2.52 mmol) was added, kept in the dark for 24 h and decanted with diethyl ether, dissolved in ethanol and neutralized with 5% sodium hydrogen carbonate. It was filtered and washed with copious amounts of water and dried over diphosphorus pentoxide [16, 21].