Secondary a-deuterium isotope effects in the reaction of 2-phenylethyltrimethylammonium ion by hydroxide ion in aqueous solution and by ethoxide ion in ethanol

Secondary a-deuterium isotope effects in the reaction of 2-phenylethyltrimethylammonium iodide with hydroxide ion in aqueous solution at 97.0° and with ethoxide ion in ethanol at 40.0° have been found to be very small. The results .suggest that the hydrogen compound reacts slightly faster than the deuterium compound. The secondary a-deuterium isotope effect in the reaction of 2-phenylethyl bromide with sodium ethoxide in ethanol is appreciably larger and ammounts to 9 per cent per deuterium atom at 59.8°. The mechanistic implications of these results are discussed

Secondary deuterium isotope effects in some S N1 and E2 reactions

An a-deuterium isotope effect kH/kn of 170/o was found in the E 2 reaction of 2-phenylethyl-l,l-d2 bromide with sodium ethoxide in ethanol. This supports the Streitwieser change-of-hybridization theory and the associated explanation of the absence of such effects in S N2 reactions as being due to the proximity of the incoming group. The magnitude of the ~- and a-deuterium isotope effects in the SNl and E2 reactions of some alkylsulphonium salts were determined and compared with the isotope effects of the corresponding alkyl-halides. An explanation for these differences is given

Removal of Glucocorticosteroids and Anesthetics from Waterwith RO/NF Membranes

This work addresses the removal of glucocorticosteroids (hydrocortisone, HYDRO; and dexamethasone, DEXA) and anesthetics (procaine, PROCA; and lidocaine, LIDO), from water with commercially available reverse osmosis/nanofiltration (RO/NF) membranes. The RO/NF experiments were of long-run type (24 h) in order to accomplish steady-state and to obtain accurate rejection of the selected compounds. The removal of the examined compounds with the RO (XLE, SWC1, LFC–1) and the tight NF (NF90) membranes was higher than 98 %. Relating the solute rejections to membranes\u27 properties has shown that the dominant rejection mechanism of the examined pharmaceuticals by all the membranes was the size exclusion effect. Rejection factors for hydrophilic HYDRO and DEXA compounds confirm that they do not adsorb onto the active layer of the selected membranes. LIDO and PROCA, slightly hydrophobic compounds, had lower rejections after 24 h treatment compared to initial values, and probable they were adsorbed onto polymeric matrix of active layers

Dependence of rates of substitution reactions of pentacyanoaquoiron(II) ion on ionic strength

The second-order rate constants (k) of substitution of water in pentacyanoaquo:iron(II) ion by nitrite, thiocyanate, sulphite or nitrobenzene were determined at various ionic strengths {I) in aqueous solution at 25 oc. The following slopes of the plot of log k versus J'h were obtained : 2.9 (No2-·), 2.5 (SCN-), 4.4 (S0a2-), and zero (nitrosobenzene)

Salting-out assisted liquid–liquid extraction for the determination of ciprofloxacin residues in water samples by high performance liquid chromatography–diode array detector

Abstract Background The occurrence of emerging pollutants like pharmaceuticals and related compounds in the aquatic and terrestrial environments is of increasing concern. Ciprofloxacin is one of the pharmaceuticals which is active against a wide range of bacteria. The main objective of this research is to develop a simple method for the extraction and determination of ciprofloxacin residues in environmental water samples. Results A salting-out assisted liquid–liquid extraction (SALLE) method for the determination of ciprofloxacin in water samples by high-performance liquid chromatography with diode array detector (HPLC–DAD) was developed. The calibration curve was linear over the range of 0.1–100 μg/L with coefficient of determination (r2) of 0.9976. The limits of detection (LOD) and quantification (LOQ) of the method were 0.075 and 0.25 µg/L, respectively. The reproducibility in terms of relative standard deviation (% RSD) was less than 10%. The applicability of the developed method was investigated by analyzing tap water, bottled mineral water and waste water and demonstrated satisfactory recoveries in the ranges of 86.4–120%. Conclusion The method offered a number of features including wide linear range, good recovery, short analysis time, simple operation process and environmental friendly. The developed method can be utilized as an attractive alternative for the determination of ciprofloxacin residues in environmental water matrices