Search

Endosulfan, one of the most widely used pesticides in various sectors including agriculture, has been reported posing a threat to the ecology as well as to the environment. Contamination of groundwater and surface water sources with various pesticides is well documented, and this problem is prominent, particularly in rural areas. In the present study, efforts are made to remove endosulfan from water using wood charcoal, a local and low cost adsorbent. It gave removal efficiency of more than 90%. Equilibrium time was found to be around 5 h. Wood charcoal showed an uptake capacity of 0.53 mg/g with initial endosulfan concentration in the range of 0.25-5 mg/L and 1.77 mg/g for the range of 2-50 mg/L. Langmuir isotherm gave a better prediction of adsorption capacity than the Freundlich. The Langmuir isotherm fit also gave a better correlation with the experimental data. In the desorption study carried out, 10% solutions of acetone, methanol, acetic acid, saturated EDTA solution, and distilled water were used as eluents. Ten percent methanol solution was found performing well with an adsorbent regeneration of more than 80% after four cycles of adsorption desorption. Desorption was found to follow a zero order equation in the case of 10% solutions of both acetone and methanol. DOI: 10.1061/(ASCE)0733-9372(2008)134:2(102) CE Database subject headings: Adsorption; Desorption; Equilibrium; Abatement and removal; Ecology; Pesticides; Water pollution.

Soils and decayed plant litter contain significant quantities of chlorinated aromatic polymers that have a natural but largely unknown origin. We used cupric oxide ligninolysis coupled with gas chromatography/mass spectrometry to show that Curvularia inaequalis, a widely distributed litter ascomycete, chlorinated the aromatic rings of lignin in wood that it was degrading. In aspen wood decayed for 24 weeks, two chlorolignin fragments, 5-chlorovanillin and 2-chlorosyringaldehyde, were each found at [approximately equal to] 10 [micro]g/g of wood (dry weight). These levels resemble those of similar structures generally found in unpolluted environmental samples. Fractionation of the extractable proteins followed by tandem mass spectrometric analysis showed that the colonized wood contained a previously described C. inaequalis chloroperoxidase that very likely catalyzed lignin chlorination. Chlorolignin produced by this route and humus derived from it are probably significant components of the global chlorine cycle because chloroperoxidase-producing fungi are ubiquitous in decaying lignocellulose and lignin is the earth's most abundant aromatic substance. chloroperoxidase | humus | hypochlorous acid | Pleosporales | soil

Ab initio calculations are used to examine the mechanism of metal chloride-promoted Mukaiyama aldol reaction between trihydrosilyl enol ether and formaldehyde. The results have shown that the formation of a stable pretransition state intermolecular [pi]-[pi] complex between enol silane and the activated formaldehyde is the main driving force for the facile metal chloride-promoted reactions.

The first enantiocontrolled total synthesis of the marine sponge metabolite chlorodysinosin A is described. The structure and absolute configuration are identical to those of dysinosin A except for the presence of a novel 2S,3R-3-chloroleucine residues in the former.

Cross-coupling reactions of biphenyl compounds that were investigated and still-growing number of efficient catalysts with various ligands that were available for the transformations is discussed. It was seen that the Stille coupling was superior to the other methods and enabled the synthesis of the title compounds with diverse connectivity.

The isolation of a bacterium capable of degrading both isomers of the organochloride insecticide endosulfan and its toxic metabolite, endosulfate, is described. The sequence of encodes as enzyme (Ese) is related to the sequence of Esd and the operon not containing ese contains a homologue whose product displayed 62% amino acid identity to the ese-encoded protein.

The cyclization of acetylenic sulfones through the conjugate additions of acyclic or cyclic secondary beta- or gamma-chloroamines is described. The products obtained include variously substituted piperidines, pyrrolizidines, indolizidines and quinolizidines all containing the enamine sulfone moiety.

Stopped-flow and chemical-quench techniques are employed to study the kinetic mechanism of cis-3-chloroacrylic acid dehalogenase (cis-CaaD) which represent the key reaction step in the degradation of the nematocide, 1,3-dichloropropene. The results from the comparison of the unliganded cis-CaaD crystal structure with that of an inactivated cis-CaaD where the prolyl nitrogen of Pro-1 are covalently attached to (R)-2-hydroxypropanoate provides a possible explanation for the isomerization step.

The first total synthesis of chloropeptin II which include the use of an intramolecular Larock indole synthesis for the initial macrocyclization as key element is reported. The intrinsic design of the approach for the single-step acid-catalyzed conversion of chloropeptin II to chloropeptin I also provide a pathway for total synthesis of chloropeptin I.

The B3LYP density functional theory method is used to study the reaction mechanism of cis-3-chloroacrylic acid dehalogenase (cis-CaaD). The results revealed an alternative mechanism for cis-CaaD catalysis and different roles for some active site residues in this mechanism.

Density functional theory based on global and local electrophilicity descriptors are used to study the reliability of local electrophilicity values of the strongest electrophilic sites in generating global intermolecular electrophilicity trends. The values on 15 different organic chlorides show that, for systems having more than one comparatively strong electrophilic site, the local electrophilicity value of the strongest site does not produce a reliable global intermolecular electrophilicity trend.

A study, which illustrates that through judicious choice of metalation-directing functional groups in polysubstituted arenes, it may be possible to design substrates for regiospecific metalation based on steric control, electronic control, or a combination of both in preference to functional group directionalability alone is presented.