Chlorination of drinking water generates disinfection by-products (DBPs) , which have been shown to disrupt spermatogenesis in rodents at high doses, suggesting that DBPs could pose a reproductive risk to men. ... A cohort study /was conducted/ to evaluate semen quality in men with well-characterized exposures to DBPs. ... The results of the present study do not support an association between exposure to DBPs at levels approaching regulatory limits and adverse sperm outcomes, although /there was/ an association between total organohalides and sperm concentration. ... The lone association of total organohalide exposure with sperm concentration may lend support to findings that have suggested that total organohalide is a stronger risk factor for adverse pregnancy outcomes than any of the regulated DBP groups or species and that the toxicity of total organohalides is greater than that of the individual or subclasses of DBPs. ... /Disinfection by-products/
/SIGNS AND SYMPTOMS/ ... Symptoms of exposure may include burning sensation, coughing, wheezing, laryngitis, shortness of breath, headache, nausea, and vomiting. Inhalation may result in spasm, inflammation and edema of the larynx and bronchi, chemical pneumonitis, and pulmonary edema. Material is extremely destructive to tissue of the mucous membranes and upper respiratory tract, eyes, and skin.
/EPIDEMIOLOGY STUDIES/ Chlorination of drinking water generates disinfection by-products (DBPs) , which have been shown to disrupt spermatogenesis in rodents at high doses, suggesting that DBPs could pose a reproductive risk to men. ...This study ...assessed DBP exposure and testicular toxicity, as evidenced by altered semen quality. ... A cohort study /was conducted/ to evaluate semen quality in men with well-characterized exposures to DBPs. Participants were 228 presumed fertile men with different DBP profiles. They completed a telephone interview about demographics, health history, water consumption, and other exposures and provided a semen sample. Semen outcomes included sperm concentration and morphology, as well as DNA integrity and chromatin maturity. Exposures to DBPs were evaluated by incorporating data on water consumption and bathing and showering with concentrations measured in tap water. ... Multivariable linear regression /was used/ to assess the relationship between exposure to DBPs and adverse sperm outcomes. ... The mean (median) sperm concentration and sperm count were 114.2 (90.5) million/mL and 362 (265) million, respectively. The mean (median) of the four trihalomethane species (THM4) exposure was 45.7 (65.3) ug/L, and the mean (median) of the nine haloacetic acid species (HAA9) exposure was 30.7 (44.2) ug/L. These sperm parameters were not associated with exposure to these classes of DBPs. For other sperm outcomes, we found no consistent pattern of increased abnormal semen quality with elevated exposure to trihalomethanes (THMs) or haloacetic acids (HAAs) . The use of alternate methods for assessing exposure to DBPs and site-specific analyses did not change these results. ... Overall, the results of the present study do not support an association between exposure to DBPs at levels approaching regulatory limits and adverse sperm outcomes, although /there was/ an association between total organohalides and sperm concentration that was in line with /the/ hypothesis.... The lone association of total organohalide exposure with sperm concentration may lend support to findings that have suggested that total organohalide is a stronger risk factor for adverse pregnancy outcomes than any of the regulated DBP groups or species ... and that the toxicity of total organohalides is greater than that of the individual or subclasses of DBPs. ... Previous studies have suggested that exposures to THMs via bathing and showering may be more strongly associated with adverse reproductive outcomes than other exposure indicators... /These/ results did not support these findings. /Disinfection by-products/
Fe(0)-Mediated Synthesis of Tri- and Tetra-Substituted Olefins from Carbonyls: An Environmentally Friendly Alternative to Cr(II)
作者:J. R. Falck、Romain Bejot、Deb K. Barma、Anish Bandyopadhyay、Suju Joseph、Charles Mioskowski
DOI:10.1021/jo061445u
日期:2006.10.1
carbonyls by activated polyhalides. In many instances, Fe(0) was equivalent or superior to Cr(II). Notably, Fe(0), but not Cr(II), proved compatible with a wide range of functionality, inter alia, unprotected phenol, aryl nitro, carboxylic acid, and alkyl nitrile. A surprising reversal of stereoselectivity for aldehydes versus ketones was observed using both metals. The resultant α-halo-α,β-unsaturated or α
A novel chiral oxazolidine organocatalyst for the synthesis of an oseltamivir intermediate using a highly enantioselective Diels–Alder reaction of 1,2-dihydropyridine
Enantioselective DielsâAlder reactions of 1,2-dihydropyridines with acroleins using a novel chiral oxazolidine organocatalyst afforded chiral isoquinuclidines that is an efficient synthetic intermediate of oseltamivir, with fairly good chemical yield and excellent enantioselectivity (90%, up to >99% ee).
In Situ Derivatization/Solid-Phase Microextraction for the Determination of Haloacetic Acids in Water
作者:M. N. Sarrión、F. J. Santos、M. T. Galceran
DOI:10.1021/ac000479d
日期:2000.10.1
An in situ derivatization solid-phase microextraction method has been developed for the determination of haloacetic acids (HAAs) in water. The analytical procedure involves derivatization of HAAs to their methyl esters with dimethyl sulfate, headspace sampling using solid-phase microextraction (SPME), and gas chromatography-ion trap mass spectrometry (GC/ITMS) determination. Parameters affecting both derivatization efficiency and headspace SPME procedure, such as the selection of the SPME coating, derivatization−extraction time and temperature, and ionic strength, were optimized. The commercially available Carboxen-poly(dimethylsiloxane) (CAR-PDMS) fiber appears to be the most suitable for the determination of HAAs. Moreover, the formation of HAA methyl esters was dramatically improved (up to 90-fold) by the addition of tetrabutylammonium hydrogen sulfate (4.7 μmol) to the sample as ion-pairing agent in the derivatization step. The precision of the in situ derivatization/HS-SPME/GC/ITMS method evaluated using an internal standard gave relative standard deviations (RSDs) between 6.3 and 11.4%. The method was linear over 2 orders of magnitude, and detection limits were compound-dependent, but ranged from 10 to 450 ng/L. The method was compared with the EPA method 552.2 for the analysis of HAAs in various water samples, and good agreement was obtained. Consequently, in situ derivatization/HS-SPME/GC/ITMS is proposed for the analysis of HAAs in water.
Two effective procedures for the synthesis of trichloromethyl ketones, useful precursors of chiral α-amino and α-hydroxy acids
作者:E.J. Corey、John O. Link、Yang Shao
DOI:10.1016/s0040-4039(00)92656-x
日期:1992.6
Trichloroacetic acid can been converted to trichloromethyl ketones in good yield by two practical new procedures, one involving the catalyzed reaction of trichloroacetic acid with aldehydes at 23 °C followed by oxidation and the other utilizing the coupling of organozinc intermediates with trichloroacetyl chloride
differences of the axial and equatorial conformers were evaluated with respect to the factors normally influencing conformational preference, namely, 1,3-diaxial steric interactions in the axial conformer and hyperconjugation. It was assessed that hyperconjugative interactions, sigma(C-C)/sigma(C-H) and sigma*(C-O), together with a steric effect--the destabilization of the equatorial conformer with increasing