Dimethyl Selenoxide Research Articles

The Ozonolysis of Methylated Selenide Compounds in the Atmosphere: Isotopes, Kinetics, Products, and Mechanisms.

Selenium (Se) is an essential micronutrient with an important atmospheric component in its biogeochemical cycle. In this cycle, phytoplankton form volatile organic Se species, such as dimethyl selenide (CH3SeCH3) and dimethyl diselenide (CH3SeSeCH3), which are emitted into the atmosphere. To predict the atmospheric fate of these methylated Se compounds, we investigated their ozonolysis reaction. We used proton-transfer-reaction time-of-flight mass spectrometry to quantify atmospheric Se and its isotopes, and used this method in kinetic and product studies. The ozonolysis of CH3SeCH3 proceeded with a rate constant of (7.4 ± 2.2) × 10-17 cm3 molec-1 s-1 at 26 ± 1 °C with an activation energy of 50 ± 14 kJ mol-1 forming dimethyl selenoxide (CH3Se(O)CH3). Comparatively, CH3SeSeCH3 reacted with O3 at (2.6 ± 0.9) × 10-17 cm3 molec-1 s-1 at 27 ± 1 °C with an activation energy of 56 ± 5 kJ mol-1 forming methylselinic acid (CH3Se(O)OH). At 20 ppbv of O3, the atmospheric lifetimes of CH3SeCH3 and CH3SeSeCH3 are 7.6 and 22 h, respectively. The Se oxidation products were confirmed by synthesis and can serve as new atmospheric tracers of methylated Se compounds. Overall, we measured Se isotopes in real time and determined the rate constants, activation energies, and oxidation products. These mechanisms can now be used to determine the quantitative atmospheric fate of Se toward O3, and thus its distribution within a changing climate.

The Key Role of Chalcogenurane Intermediates in the Reduction Mechanism of Sulfoxides and Selenoxides by Thiols Explored In Silico.

Sulfoxides and selenoxides oxidize thiols to disulfides while being reduced back to sulfides and selenides. While the reduction mechanism of sulfoxides to sulfides has been thoroughly explored experimentally as well as computationally, less attention has been devoted to the heavier selenoxides. In this work, we explore the reductive mechanism of dimethyl selenoxide, as an archetypal selenoxide and, for the sake of comparison, the reductive mechanism of dimethyl sulfoxide to gain insight into the role of the chalcogen on the reaction substrate. Particular attention is devoted to the key role of sulfurane and selenurane intermediates. Moreover, the capacity of these system to oxidize selenols rather than thiols, leading to the formation of selenyl sulfide bridges, is explored in silico. Notably, this analysis provides molecular insight into the role of selenocysteine in methionine sulfoxide reductase selenoenzyme. The activation strain model of chemical reactivity is employed in the studied reactions as an intuitive tool to bridge the computationally predicted effect of the chalcogen on the chalcogenoxide as well as on the chalcogenol.

Modification of an atmospheric pressure photoionization source for online analysis of exhaled breath coupled with quadrupole time-of-flight mass spectrometry.

Breath analysis is a promising method for metabolomics studies and clinical diagnosis, as it enables the observation of metabolites in a convenient and noninvasive way. In this work, an atmospheric pressure photoionization (APPI) source was modified for online analysis of exhaled breath by coupling with quadrupole time-of-flight mass spectrometry (QTOFMS). Three parameters, namely, the capillary voltage, the sampling flow and the curtain gas flow of the APPI source, were optimized. Five healthy volunteers, three males and two females, were enrolled to test the performance of modified APPI-QTOFMS by analyzing their exhaled breath. A total of 21 compounds were tentatively identified, and four metabolites, namely, dimethyl selenoxide, δ-valerolactam, hydroxymandelic acid and palmitic amide were detected in the exhaled breath for the first time. The result shows that modified APPI-QTOFMS can be used for the online study of exhaled breath. Graphical abstract.

Antiradical activity of dimethyl selenoxide and sodium selenite

Determination of the oxygen radical absorption capacity (ORAC) served to discover antiperoxyradical activity of dimethyl selenoxide (DMSeO). The antiperoxyradical capacity of DMSeO is higher than that of the water-soluble analog of α-tocopherol and trolox and close to the value determined for the butylated hydroxy toluene (BHT). The redox parameters of DMSeO were determined using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The anodic oxidation peaks of DMSeO on the CV and DPV voltammograms in the potential range from −1200 to 1500 mV relative to Ag/Ag+ in CH2Cl2 confirm antioxidant activity of DMSeO towards oxidants and peroxyl radicals. It was established that Na2SeO3 in the acidic medium at pH = 3 shows the antiradical activity towards the stable radical of 2,2′-diphenyl-1-picryl hydrazyl (DPPH) and acts as a two-electron oxidant by trapping two DPPH radicals.

Oxidation mechanisms of dimethyl selenide and selenoxide in the atmosphere initiated by OH radical. A theoretical study

The reaction mechanisms for dimethyl selenide (DMSe) and dimethyl selenoxide (DMSeO) with OH radical are studied by using quantum chemistry calculations. The structures are optimized at MP2 levels, and electronic energies at Gaussian-4 level. Addition complexes are found between reactants as (CH 3) 2Se · OH, (CH 3) 2Se(O) · OH, and (CH 3) 2SeO · HO, which serve as reaction intermediates for further decompositions to CH 3SeOH + CH 3/CH 3SeCH 2 + H 2O, CH 3Se(O)OH + CH 3, and CH 3Se(O)CH 2 + H 2O, respectively. Under the atmospheric conditions, the dominant product channel for DMSe + OH is CH 3SeCH 2 and (CH 3) 2Se · OH, of which the latter is subsequently converted to DMSeO; while the main product for DMSeO + OH is CH 3Se(O)OH. Hydrate formation for DMSeO would not alter the branch ratios because of its small fraction in the atmosphere.

Quantitative and Qualitative Trapping of Volatile Methylated Selenium Species Entrained through Nitric Acid

Quantification and speciation of volatile selenium (Se) fluxes in remote areas has not been feasible previously, due to the absence of a simple and easily transportable trapping technique that preserves speciation. This paper presents a chemo-trapping method with nitric acid (HNO3) for volatile Se species, which preserves speciation of trapped compounds. The recovery and speciation of dimethylselenide (DMSe) and dimethyl diselenide (DMDSe) entrained through both concentrated nitric acid and hydrogen peroxide (H2O2) were compared by HPLC-ICP-MS and HPLC-HG-AFS analyses. It was demonstrated that trap reproducibility was better for nitric acid and a recovery of 65.2 +/- 1.9% for DMSe and 81.3 +/- 3.9% for DMDSe was found in nitric acid traps. HPLC-ES-MS identified dimethyl selenoxide (DMSeO) as the trapped product of DMSe. Methylseleninic acid (MSA) was identified to be the single product of DMDSe trapping. These oxidized derivatives have a high stability and low volatility, which makes nitric acid a highly attractive trapping liquid for volatile Se species and enables reconstruction of the speciation of those species. The presented trapping method is simple, quantifiable, reproducible, and robust and can potentially be applied to qualitatively and quantitatively study Se volatilization in a wide range of natural environments.

Hydrogen bonding and vibrational spectra in kaolinite-dimethylsulfoxide and -dimethylselenoxide intercalates — A solid-state computational study

AbstractThe aims of this study were to obtain accurate structural information on the dimethyl sulfoxide (DMSO) and dimethylselenoxide (DMSeO) kaolinite intercalates, paying close attention to the hydrogen-bond geometries, and to provide a detailed interpretation of the individual vibrational modes of intercalates under study and relate their energies to the formation of the hydrogen bonds. Accurate positions of all the atoms in the structures of kaolinite:dimethylsulfoxide (K:DMSO) and kaolinite:dimethylselenoxide (K:DMSeO) intercalates have been obtained by the total energy minimization in solid state at density functional theory (DFT) level of the theory. The bond distances and angles in the kaolinite 1:1 layer are in good agreement with those reported in the most recent single-crystal refinement of kaolinite. Computed geometries of DMSO and DMSeO agree well with the high-quality diffraction data and independent theoretical ab initio calculations. The organic molecules are fixed in the interlayer space mainly by three moderately strong O-H⋯O hydrogen bonds, of different strengths, with the O⋯O contact distances being within 2.739–2.932 Å (K:DMSO) and 2.681–2.849 Å (K:DMSeO). Substantially weaker C-H⋯O and O-H⋯S(Se) contacts play only a supporting role. The optimized atomic coordinates were used to calculate the individual vibrational modes between 0 and 4000 cm−1. The maximum red shifts of the OH-stretching modes caused by the formation of the O-H⋯O hydrogen bonds were 407 cm−1 (K-DMSO) and 537 cm−1 (K-DMeSO), respectively. The Al-O-H bending modes are spread over the large interval of 100–1200 cm−1, but the dominant contributions are concentrated between 800 and 1200 cm−1. Theoretically calculated energies of the OH- and CH-stretching modes show good agreement with the previously published figures obtained from the infrared and Raman spectra of these intercalates.

Dimethylselenide as a Probe for Reactions of Halogenated Alkoxyl Radicals in Aqueous Solution. Degradation of Dichloro- and Dibromomethane

Using pulse radiolysis and steady-state gamma-radiolysis techniques, it has been established that, in air-saturated aqueous solutions, peroxyl radicals CH 2HalOO (*) (Hal = halogen) derived from CH 2Cl 2 and CH 2Br 2 react with dimethyl selenide (Me 2Se), with k on the order of 7 x 10 (7) M (-1) s (-1), to form HCO 2H, CH 2O, CO 2, and CO as final products. An overall two-electron oxidation process leads directly to dimethyl selenoxide (Me 2SeO), along with oxyl radical CH 2HalO (*). The latter subsequently oxidizes another Me 2Se molecule by a much faster one-electron transfer mechanism, leading to the formation of equal yields of CH 2O and the dimer radical cation (Me 2Se) 2 (*+). In absolute terms, these yields amount to 18% and 28% of the CH 2ClO (*) and CH 2BrO (*) yields, respectively, at 1 mM Me 2Se. In competition, CH 2HalO (*) rearranges into (*)CH(OH)Hal. These C-centered radicals react further via two pathways: (a) Addition of an oxygen molecule leads to the corresponding peroxyl radicals, that is, species prone to decomposition into H (+)/O 2 (*-) and formylhalide, HC(O)Hal, which further degrades mostly to H (+)/Hal (-) and CO. (b) Elimination of HHal yields the formyl radical H-C(*)=O with a rate constant of about 6 x 10 (5) s (-1) for Hal = Cl. In an air-saturated solution, the predominant reaction pathway of the H-C(*)=O radical is addition of oxygen. The formylperoxyl radical HC(O)OO (*) thus formed reacts with Me 2Se via an overall two-electron transfer mechanism, giving additional Me 2SeO and formyloxyl radicals HC(O)O(*). The latter rearrange via a 1,2 H-atom shift into (*)C(O)OH, which reacts with O2 to give CO2 and O2(*)(-). The minor fraction of H-C(*)=O undergoes hydration, with an estimated rate constant of k approximately 2 x 10(5) s(-1). The resulting HC(*)(OH)2 radical, upon reaction with O2, yields HCO 2H and H (+)/O2(*-). Some of the conclusions about the reactions of halogenated alkoxyl radicals are supported by quantum chemical calculations [B3LYP/6-31G(d,p)] taking into account the influence of water as a dielectric continuum [by the self-consistent reaction field polarized continuum model (SCRF=PCM) technique]. Based on detailed product studies, mechanisms are proposed for the free-radical degradation of CH 2Cl 2 and CH 2Br 2 in the presence of oxygen and an electron donor (namely, Me 2Se in this study), and properties of the reactive intermediates are discussed.

Dimethyl selenoxide

The title molecule, C2H6OSe, has a trigonal-pyramidal structure analogous to that of its sulfur analog, dimethyl sulfoxide (DMSO). The Se-O distance in dimethyl selenoxide (DMSeO) is 1.6756 (16) A [versus S-O of 1.531 (5) A in DMSO], consistent with a highly polar bond. In the solid state, the molecules of DMSeO are linked into centrosymmetric dimers formed by two C-H...O hydrogen bonds. These dimers further aggregate into a ladder-like supramolecular network via two additional intermolecular C-H...O interactions. As a result, each O atom of DMSeO acts as an acceptor of three hydrogen bonds.

Selenoxides Are Better Hydrogen-Bond Acceptors than Sulfoxides: a Crystallographic Database and Theoretical Investigation

The relative hydrogen-bond (HB) properties of sulfoxides and selenoxides have been investigated experimentally using data retrieved from the Cambridge Structural database and theoretically through density functional calculations at the B3LYP/6-311++G(3df,3pd)//B3LYP/6-311++G(3df,3pd) level. The HB are significantly shorter (stronger) in selenoxides (d(O···H) = 1.78 (3) A) than in sulfoxides (d(O···H) = 1.85 (2) A). The HB directionalities and linearities observed in the solid state for the two functionalities are very similar. The spatial and molecular surface minima of the electrostatic potential are, respectively, 43.9 and 23.4 kJ/mol more negative in dimethyl selenoxide (DMSeO) in comparison with that in dimethyl sulfoxide (DMSO). The investigation of the S(Se)O bond's electronic structure using the Natural Bond Orbital (NBO) approach shows that negative hyperconjugation of the type nO → σ*S(Se)−C is much more important in DMSO than that in DMSeO. In the HB complexes, the NBO analysis shows competition...

Small organoselenium molecules. 1. Dimethyl selenoxide: structure, complexation, and gas-phase transformation.

For the first time the structural characterization of dimethyl selenoxide coordinated to metal complexes has been performed confirming the Me(2)SeO arrangement assigned by spectroscopic techniques for the molecule in solution and solid state. The structure of Me(2)SeO is trigonal pyramidal with Se-O and Se-C bond lengths of 1.70 and 1.92 A, respectively, and sigma(X-Se-Y) = 301 degrees. As a ligand, dimethyl selenoxide was found to bind to the rhodium centers of various Lewis acidity strengths by using only its oxo functionality in both terminal and bridging fashions. This O-directed coordination preference contrasts with an ambidentate (-S and -O) binding character revealed by dimethyl sulfoxide upon formation of analogous donor-acceptor complexes. The study of dimethyl selenoxide in the gas phase at 135-140 degrees C resulted in a thermal degradation of this molecule. The major decomposition product has been entrapped by a metal complex and identified as dimethyl selenide. The isolation of the coordinated Me(2)Se fragment clearly demonstrates that the Me(2)SeO molecule is less thermally stable than Me(2)SO, which under similar reaction conditions shows no sign of decomposition at temperatures up to 160 degrees C.

Speciation of selenium in plant water extracts by ion exchange chromatography-hydride generation atomic absorption spectrometry

Determination of selenium (Se) speciation in plants is important in studying the bioavailability and toxicity of Se in Se-contaminated soil/sediment. In this study, we used an anion exchange resin (Dowex 1-10X) to separate Se into non-amino acid organic Se, Se-amino acids, selenite (Se [IV]) and selenate (Se [VI]) in a plant ( Stanleya pinnata) extract. The hydride generation atomic absorption spectrometry (HGAAS) was used to determine concentrations of these Se compounds in plant extracts. Results showed that Se compounds can be quantitatively separated by the resin column. Recovery of five spiked standard Se compounds (trimethylselenonium ion (TMSe +), dimethylselenoxide (DMSeO), selenomethionine (Semet), Se [IV] and Se [VI]) in the plant extract ranged from 92.9 to 103%. Water extractable Se accounted for 60.4–72.6% of the total Se in the plant. Among the soluble Se compounds in the plant extract, Se-amino acids were 73–85.5%, Se [VI] ranged from 7.5 to 19.5% and non-amino acid organic Se was less than 7%. Se [IV] in most samples was below the detection limit (1 μg/g). This study showed that considerable amounts of the accumulated Se [VI] in the plant was metabolized to Se-amino acids during growth of the plant.

Effect of moisture and casein on demethylation of trimethylselenonium in soil

Trimethylselenonium ion (TMSe +) is a major urinary selenium (Se) metabolite of animals. The effect of soil moisture and casein on the demethylation of TMSe + were examined in three California soils [Tulare Basin (TL), Losthill (LH) and Five Points (FP) upland areas] treated with 20 μg/g TMSe +. Results showed that soil moisture positively affected the demethylation of TMSe + to volatile dimethylselenide (DMSe). In the non-saline TL and FP soils, the highest demethylation rates were 0.169–0.454, 0.646–2.71, and 3.15–6.01 μg/g per day from a 10, 20, and 100% moisture soil, respectively. During 51 days of the experiment, approximately 75.4–80.2% of added TMSe + was demethylated to volatile DMSe. In contrast, in a saline LH soil, the demethylation rate was <0.2 μg/g per day, and only 7% of the added TMSe + was demethylated to volatile DMSe. Addition of casein stimulated the demethylation of TMSe + in a 10% moisture TL soil. Dissolved DMSe, dimethylselenoxide (DMSeO) and TMSe +, and adsorbed TMSe + were found in the three experimental soils. Concentrations of dissolved and adsorbed TMSe + were much higher in the LH soil than in the TL and FP soils. This study showed that demethylation of TMSe + dominates in the FP and TL soils, and adsorption of TMSe + is a more important process in the LH soil.

Formation of Dimethylselenonium Compounds in Soil

Selenium (Se) methylation/volatilization from Se-contaminated environments has been extensively studied over the last 15 years, but the methylation pathway of Se still remains largely unknown. We developed a sequential purge-and-trap system to collect volatile dimethylselenide (DMSe) and dimethyldiselenide (DMDSe) and to extract dimethylselenonium compounds. These dimethylselenonium compounds included dissolved DMSe and DMDSe, dimethylselenoxide (DMSeO), methylselenomethionine (MSemet), and dimethylselenoniopropionate (DMSeP). We monitored volatile DMSe and DMDSe and soluble dimethylselenonium compounds in a soil spiked with selenomethionine (Semet) at levels ranging from 16 to 80 μg of Se/g. In a moist soil spiked with Semet (80 μg of Se/g), concentrations of volatile DMSe and DMDSe were much higher than those of dissolved DMSe and DMDSe, DMSeO, MSemet, and DMSeP, although all of these compounds followed a similar trend in concentration over the course of the experiment. Concentration of dissolved DMSe and DMDSe, DMSeO, MSemet, and DMSeP increased with soil moisture and Semet concentration. After a 15-day experiment with a moist soil, about 65% of the spiked Semet was transformed to volatile DMSe and DMDSe, 26% was still in soluble forms of Se, and only 9% accumulated in the soil. This study suggests that Semet can undergo a methylation pathway to DMSe (Semet → MSemet → DMSeP → DMSe), and oxidation of dissolved DMSe to DMSeO may occur in soil.

Effect of Soil Moisture on Dimethylselenide Transport and Transformation to Nonvolatile Selenium

Volatilization of dimethylselenide (DMSe) to the atmosphere has been extensively studied, but little is known on its fate in soil environments. This study examined the transport and transformation of DMSe in soil. The transport of DMSe in soil columns was related to the soil moisture content. About 87−96% of the total injected DMSe in air-dried soil was volatilized to the air, whereas in a moist and flooded soil, only 20−88% and 4.3−16.8% were emitted to the air, respectively. After incubation of 40 days, about 13.1−38.8% of the total DMSe was converted to nonvolatile Se in moist soils (35% moisture). This transformation increased with increasing soil moisture content and was also much higher in soil amended with MnO2 in which about 95% of the total DMSe was converted to nonvolatile Se. Oxidized dimethylated Se (ODMSe), which included dimethyl selenoxide (DMSeO) and/or dimethyl selenone (DMSeO2), was the dominant form of nonvolatile Se, accounting for 43.5−53% in the moist soil and 80−90% in the flooded soils. The percentage of other Se species in the experimental soils followed a general descending order: Se[0, −II] > Se[IV] > organic Se > Se[VI]. This study showed that accumulation and transformation of DMSe may be important processes responsible for a low volatilization rate of DMSe in flooded soils and sediments.

Gas-phase reactions of dimethyl selenide with ozone and the hydroxyl and nitrate radicals

Experiments were carried out in a large-volume chamber to investigate the products of the atmospherically important reactions of dimethyl selenide. Dimethyl selenoxide [(CH 3) 2SeO] was observed as the major product of the gas-phase reaction of dimethyl selenide with ozone, with an estimated yield of ∼ 90%. Significant fragmentation via Se-C bond breakage occurred during the reactions of dimethyl selenide with the OH radical and the NO 3 radical as indicated by HCHO formation yields of ∼ 40 and ∼ 60%, respectively. The spectra of the Se-containing products from both the reactions with the OH radical (in the presence of NO x ) and the NO 3 radical are consistent with the formation of nitrate salts, which are postulated to be [CH 3Se(OH) 2] + NO 3 − and [(CH 3) 2SeOH] + NO 3 −, which could arise from the intermediate formation of methaneseleninic acid [CH 3Se(O)OH] and dimethyl selenoxide and their ensuing reactions with HNO 3.

The selenium metabolite selenodiglutathione induces p53 and apoptosis: relevance to the chemopreventive effects of selenium?

Selenodiglutathione (SDG), the initial metabolite of selenite, is shown to be a more powerful inhibitor of cell growth in vitro than selenite itself. This has been established both with mouse erythroleukaemia (MEL) cells and an ovarian cell line (A2780) which is known to contain wild-type p53. Other seleno-compounds, such as selenomethyl selenocysteine (SMS) and dimethyl selenoxide (DMS), which are potent chemopreventive agents and are known to be metabolized to methylated selenium derivatives directly rather than via SDG, are also growth inhibitory to both MEL and A2780 cells, although less so than SDG or selenite. However, cells growth-inhibited by DMS are more viable than cells growth-inhibited to the same extent by SDG or selenite, suggesting that the methylated seleno-compounds may inhibit cell growth in a different manner from that of SDG or selenite. Our studies of the mechanism of growth inhibition by SDG, have established two facts. First, SDG induces p53 protein levels in cells that contain wild-type p53 (A2780 cells), suggesting that SDG induces the DNA damage-recognition pathway. Secondly, SDG induces apoptosis in MEL cells, as judged by flow cytometry and formation of nucleosomal DNA ladders. However, since p53 mutations have been found to be targetted events in all MEL cells examined, our evidence suggests that induction of apoptosis by SDG is not absolutely dependent on the p53 response pathway.

Metabolites of sodium selenite and methylated selenium compounds administered at cancer chemoprevention levels in the rat.

1. The metabolism of orally-administered sodium selenite and five methylated selenium compounds was investigated in the female rat at dosages equivalent to those used in other studies for prevention of mammary cancer. Dimethyl selenide (DMSe) exhaled within 24 h following dosing was measured, along with inorganic and monomethylated (MMSe) forms of selenium plus trimethylselenonium ion (TMSe+) in urine. 2. MMSe was the dominant metabolite of selenite given at low levels (0.1 ppm in the diet), but excretion of DMSe and TMSe+ increased sharply when selenite dosage was increased to the chemopreventive range of 3 ppm dietary Se. When similar chemopreventive levels of mono-, di-, or trimethylated compounds were administered, the total quantity of methylated metabolites was greater than for selenite and the metabolite profile reflected the expected point of entry into the intermediary metabolism pathway; the major metabolites were MMSe from Se-methylselenocysteine, DMSe from selenobetaine methyl ester, and TMSe+ from selenobetaine. However, the profile of metabolites provided clear evidence that the methylated selenium compounds underwent demethylation, as shown by the excretion of inorganic and MMSe. Selenium administered as dimethyl selenoxide was almost completely excreted and about 90% of the dose was recovered as DMSe, indicating that reduction was the major pathway. For TMSe+, about 10% of the dose was excreted as DMSe and 84% as TMSe+. 3. A low, non-toxic level of sodium arsenite (5 ppm As in the diet) that is known to modify differentially the anticarcinogenic activity of selenite and methylated selenium compounds did not modify the excretion of the methylated selenium metabolites. 4. It is concluded that high anticarcinogenic activity is associated with extensive excretion of methylated Se excretory metabolites, but high output of such metabolites per se does not necessarily lead to anticarcinogenic activity. The whole animal has extensive capabilities for interconverting forms of selenium, and retains significant amounts in tissues, complicating the interpretation of Se metabolism and anticarcinogenic action. Further research is needed on the forms of selenium present in tissues.

Infrared band frequency shifts and dipole interactions at surfaces of inorganic and organic clay intercalates

Molecules adsorbed at clay surfaces are often observed to have the frequencies of their infrared (IR) absorption bands altered by the proximity of the surfce. Using a simplified theory of dipole induction, it is shown that dispersion forces give rise to shifts or splitting of requencies which are proportional to the polarizability of the interacting dipoles and to the reciprocal of the cube of the distance between them. Additivity of bond polarizabilities makes this relationship easy to used, and it is able to account for the frequency shifts in the following four systems: hectorite and degraded phlogopite reacted with inorganic cations, dimethyl sulfoxide— and dimethyl selenoxide—kaolinite intercalates, anilinium—vermiculite intercalate, and alkylammonium—vermiculite intercalates. In the last system, the theory explains changes in the NH deformation frequencies of angled and perpendicular CN bonds that have been observed in these intercalates by showing up differences between the NH groups interacting with the clay surface. The theory can be used to determined polarizabilities if interatomic distances and IR band shifts are known. Hence it may be of potential use to comment on charges of interacting groups giving different frequencies shifts, since polarizabilities vary to some extent with charge; this is illustrated using the interaction of NH vibrations with three clays of differing charge. The theory can predict interatomic distances at surfaces from IR band shifts and polarizabilities.

A Convenient Oxidation of Halomethylarenes and Alcohols to Aldehydes with Dimethyl Selenoxide and Potassium Benzeneselenite

A Convenient Oxidation of Halomethylarenes and Alcohols to Aldehydes with Dimethyl Selenoxide and Potassium Benzeneselenite