Results 1 - 10 of 466
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[en] The nucleophilic substitution reactions of dibutyl chlorophosphate (3) with substituted anilines (XC6H4NH2) and deuterated anilines (XC6H4ND2) are investigated kinetically in acetonitrile at 55.0 .deg. C. The obtained deuterium kinetic isotope effects (DKIEs: kH/kD) are secondary inverse (kH/kD = 0.86-0.97) with the strongly basic anilines while primary normal (kH/kD = 1.04-1.10) with the weakly basic anilines. The DKIEs, steric effects of the two ligands, activation parameters, cross-interaction constants, variation trends of the kH/kD values with X, and mechanism are discussed for the anilinolyses of the nine (R1O)(R2O)P(=O)Cl-type chlorophosphates. A concerted mechanism is proposed with a backside nucleophilic attack transition state for the strongly basic anilines and with a front side attack involving a hydrogen-bonded four-center-type transition state for the weakly basic anilines on the basis of the magnitudes, secondary inverse and primary normal, and variation trends of the kH/kD values with X
[en] A gas chromatographic procedure has been developed for the determination of tributyl phosphate (TBP), dibutyl phosphate (HDBP) and butyl phosphate (H2MBP) in kerosene solutions. The last two compounds were converted into their methyl esters by reaction with a solution of diazomethane in diisopropyl ether prior to analysis. The same procedure was applied to the determination of HBDP and H2MBP produced from gamma irradiation of the 30% TBP-kerosene-3 mol dm-3 HNO3 system. (author)
[en] First phosphorylated glycoconjugates were synthesized in three stages on the basis of isosteviol, D-arabinofuranose, and D-ribofuranose. In the first stage, isosteviol reacted with methyl 5-O-(p-tosyl)-2,3-di-O-benzoyl-D-ribofuranoside and methyl 5-O-(p-tosyl)-2,3-di-O-benzoyl-D-arabinofuranoside to give glycoconjugates in which the diterpenoid fragment is linked through ester bond to the carbohydrate C5 atom. In the second stage, the anomeric methoxy group in the furanoside fragment was replaced by bromine, and the resulting 2,3-di-O-benzoyl-D-ribofuranosyl and 2,3-di-O-benzoyl-D-arabinofuranosyl bromides were treated with dibutyl phosphate to afford the target phosphorylated derivatives.
[en] Di(n-butyl)phthalate (DBP) and benzo(a)pyrene (BaP) are environmental endocrine disruptors that are potentially hazardous to humans. These chemicals affect testicular macrophage immuno-endocrine function and testosterone production. However, the underlying mechanisms for these effects are not fully understood. It is well known that interleukin-1 beta (IL-1β), which is secreted by testicular macrophages, plays a trigger role in regulating Leydig cell steroidogenesis. The purpose of this study was to reveal the effects of co-exposure to DBP and BaP on testicular macrophage subset expression, IL-1β secretion and testosterone production. Adult male Sprague-Dawley rats were randomly divided into seven groups; two groups received DBP plus BaP (DBP + BaP: 50 + 1 or 250 + 5 mg/kg/day) four groups received DBP or BaP alone (DBP: 50 or 250 mg/kg/day; BaP: 1 or 5 mg/kg/day), and one group received vehicle alone (control). After co-exposure for 90 days, the relative expression of macrophage subsets and their functions changed. ED2+ testicular macrophages (reactive with a differentiation-related antigen present on the resident macrophages) were activated and IL-1β secretion was enhanced. DBP and BaP acted additively, as demonstrated by greater IL-1β secretion relative to each compound alone. These observations suggest that exposure to DBP plus BaP exerted greater suppression on testosterone production compared with each compound alone. The altered balance in the subsets of testicular macrophages and the enhanced ability of resident testicular macrophages to secrete IL-1β, resulted in enhanced production of IL-1β as a potent steroidogenesis repressor. This may represent an important mechanism by which DBP and BaP repress steroidogenesis.
[en] Tributyl phosphate(TBP) is used in solvent extraction process for radioactive waste. This compound may be degraded to dibutyl phosphate(DBP-), monobutyl phosphate(MBP2-) and PO43- by radioactive material. Amount of DBP- and MBP2- in TBP must be monitored because they production of these compounds means degradation of which leads to a decrease in the extraction yield. Retention behavior for DBP-, MBP2-, F-, Cl-, NO2-, NO3-, SO42- and PO43- are studied with AS4A-SC(Dionex) analytical column and Na2CO3/NaOH eluent by Ion chromatography. Optimum condition for these anions is 2 mM Na2CO3/1mM NaOH eluent. All anions by this condition is well separated within 15min. Dynamic range is 10 μg/mL -100 μg/mL for DBP and 5μg/mL - 50μg/mL for MBP2- ,respectively. The Detection limit for AS4A-SC are 1 μg/mL for DBP- and 0.5 μg/mL for MBP2- in this system with a 25 μ L sample loop
[en] The extraction of Th(IV), U(VI), Pu(IV), Am(III) and Cm(III) by dibutyl-N, N-diethilcarbamoylphosphonate (DBDECP) from notric, hydrochloric and perchloric acid solutions has been studies as a function of a number of parameters. The effect of size and structure of the extractant molecules has been investigated for lower homologues of carbamoyphosphonate. After evaluating the effect of the diluent, the extraction of inorganic acid HNO3, HCl and HClO4 and the dipendence of the distribution ratios of the actinides from organic extractant concentration and aqueous acid concentration has been studied for the DBDECP-xilene system
[en] The invention relates to the regeneration of the properties of TBP as a solvent for extracting uranium and plutonium. That regeneration method comprises the steps of contacting the TBP solution containing degradation products with an esterifying agent (the degradation products are esterified into triesters) and of recycling the TBP solution containing such triesters. Such a regeneration method leads, in particular, to an improved recovery of plutonium from nuclear fuels
[fr]L'invention concerne la regeneration des caracteristiques du phosphate de tributyle en tant que solvant d'extraction d'uranium et de plutonium. Ce procede de regeneration comprend la mise en contact de la solution de phosphate de tributyle contenant les produits de degradation avec un agent esterifiant, transformant les produits de degradation en triesters, et le recyclage de la solution de phosphate de tributyle contenant les triesters. Cette regeneration permet notamment une meilleure recuperation de plutonium a partir de combustibles nucleaires
[en] Relatively high concentrations of carbonate, oxalate, or nitrate interfere with the direct termination of dibutylphosphoric acid (DBP) by ion chromatography. Carbonate and oxalate are effectively separated from the DBP as insoluble barium salts. A chromatographic method employing reverse-phase resin removes the nitrate interference. Recovery of DBP from carbonate and oxalate solutions exceeds 98% and from nitrate solutions, approximately 88%
[en] The extraction of yttrium from acidic media by a solution of di-n-butyl phosphate (DBP) was studied. The distribution ratio for yttrium was found to decrease with increasing acid concentration and to increase with increasing DBP concentration. The extraction equation proposed is similar to that for D2EHPA. A possible application of the observed extraction behaviour for separating 90Y from 90Sr with the purpose of radiochemical determination of the latter is discussed. (author)