wiped with Kimwipe between scans. A Ag/Agl reference electrode was made by dipping a silver wire coated with Agl by anodic deposition into a saturated solution of Et4N+I" in DMSO and sealed by a VYCOR membrane.An amount of the neutral compound sufficient to make 5 mL of 3.0 mM solution was weighed into the electrochemical cell and placed on the cell holder. Tetraethylammonium tetrafluoroborate (electrometric grade from Southwestern Analytical Chemicals Inc., dried under vacuum at 70 °C for 48 h, 0.108 mg) was placed in the cell and 5 mL of purified DMSO was added. Pure argon was bubbled through the solution constantly except while recording the scan, at which time the solution was blanketed with argon. About 0.3 equiv of CH3SOCH2K (150-200 mM solution) was added in aliquots and the cyclic voltammogram recorded after each addition. In the case of thiazolium salts, the neutral solution was scanned under argon to ensure that the oxidation of the counterion would not cause interference. Cyclic voltammograms were recorded at a scan rate of 100 mV/s on a Houston 100 X-Y recorder. The ferrocenium/ferrocene redox couple (0.875 mV vs Ag/Agl) was used as a standard. The redox couple of ferrocenium/ferrocene was checked against the reference electrode before and after the measurements.
Abstract. Benzo and dibenzo crown ethers become more water soluble as the number of oxyethylene units increase. Moreover, the solubility in water is larger than expected on the basis of calculations using empirical models, viz., "the fragment model" and "the substituent model". New hydrophobic fragmental constants of the oxyethylene fragment, f(-OCH,CH,-) = -0.17, and of the veratrole fragment, f [C6H4(OCH2-)2] = 0.99, for the system 1-octanol/water have been determined experimentally. Using these values, reliable partition coefficients of macrocyclic polyethers can be calculated. Comparison of the benzo crown ethers with the open-chain model compounds surprisingly did not reveal a macrocyclic effect on the partition coefficient.
determined by accurate mass measurements. Standard workup of an ethereal solution means washing with 5% HC1 (aqueous), water, and 5% KHC03 (aqueous), drying with Na2S04, and evaporation of the solvent in vacuo. Crystal data: P2U a = 12.962(3) A, (b = 6.260 (1) Ac = 15.711 (3) A, ß = 102.20 (2)°, Z = 2; C^H^O, Mr = 386.67, pcalcd = 1.03 g-cm3, pobed = 1.023 (3) g-cm"3 (flotation in aqueous ZnBr2), platelike crystal, 0.35 X 0.25 X 0.06 mm3. Data collection:36 Syntex P21( Cu Ka radiation ( = 1.54178 A), 2752 unique reflections in the 0 < 2 < 158°r ange, 1304 of them observed with I > 1.96 (7), room temperature, no absorption correction (µ = 4.13 cm"* 1). Structure solution: direct methods and weighted Fourier syntheses, refinement by full-matrix least-squares to R = 0.089, Rw = 0.097 using MAGEX 8036 and SHELX programs. Positions and anisotropic thermal parameters of non-H atoms together with positions and isotropic thermal parameters of H atoms refined in two blocks; average thermal parameters
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