Odd/even effect in the chain length on the enthalpy of micellization of gemini surfactants in aqueous solution

The micellization properties of cationic symmetric gemini surfactants, [CmH(2m+1)(CH3)2N(CH2)6N(CH3)2CmH(2m+1)]Br2 (designated as CmC6CmBr2, with m = 7, 8, 9, 10, 11, 12, and 16), has been investigated by isothermal titration microcalorimetry. The critical micelle concentration (CMC) and enthalpy of micellization (DeltaHmic) were determined from calorimetric titration curves. The linear decreasing of log CMC with increasing the length of the hydrophobic chain is consistent with an increase in the hydrophobicity of the alkyl chain. Interestingly, with increasing the length of the alkyl chain, the DeltaHmic values of the surfactants with even numbered alkyl chains vary from endothermic to exothermic, whereas the DeltaHmic values of the surfactants with odd numbered alkyl chains are all endothermic and tend to become more endothermic. The pronounced even/odd effect in DeltaHmic is discussed with respect to the "donor-acceptor" interaction.     

Strong adhesion and smooth conductive surface via graft polymerization of aniline on a modified glass fiber surface

The goal of this paper is to prepare surface-conductive glass fibers. The fibers were first hydroxylated, after which they were reacted with 3-bromopropyltrichlorosilane to form a bromopropylsilane monolayer, which was further reacted with aniline to substitute the bromine atoms. The surface-bound aniline molecules were used as active sites for the graft polymerization of polyaniline (PANI). The composition, structure and the morphology of the modified glass fiber surface were examined by X-ray photoelectron spectroscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. The method generated a smooth and homogenous thin layer of PANI on the surface of the glass fiber with a surface conductivity of about 6 S/cm, hence larger than the usual value ( approximately 1 S/cm) of the bulk polyaniline.     

锰（Ⅱ）—邻菲口罗啉配合物极谱吸附波及其应用

在ｐＨ９．５ＮＨ３ＮＨ４Ｃｌ缓冲溶液中，Ｍｎ（Ⅱ）与邻菲口罗啉形成的配合物在－１．３６Ｖ（ｖｓ．ＳＣＥ）处产生一灵敏的吸附波，一阶导数峰电流与Ｍｎ（Ⅱ）浓度在５×１０－８５×１０－６ｍｏｌ／Ｌ范围内呈线性关系，检出限为２×１０－８ｍｏｌ／Ｌ对极谱性质及反应机理进行了研究，用该法测定了大豆和茶叶中的微量锰，结果满意     

Accurate local spin-polarized exchange potential: Reconciliation of generalized Slater and Kohn–Sham methods

Using simple physical arguments, a local spin-polarized exchange potential, V_xσ, is constructed from the single-particle Hartree–Fock (HF ) potentials (generalized Slater method) that reduces to the usual Kohn–Sham (KS ) result in the uniform gas limit. Numerical results for 10 closed subshell atoms demonstrate that the total energy calculated employing this V_xσ is closer to the exact KS results than those of other standard exchange approximations with electron densities and highest occupied orbital eigenvalues that closely approximate the HF results.     

A novel anthracenyl tagged protecting group for "phase-switching" applications in parallel synthesis

A new "phase-switching" protecting group 1 that facilitates the parallel synthesis of carboxylic acids, esters, and carboxamides is described. Its use permits chemistries to be performed in solution, which may be conveniently monitored with conventional analytical techniques, followed by subsequent immobilization onto a solid-phase support to aid compound purification. Carboxylic acids, esters, and carboxamides are then cleaved from the solid support following activation of the "safety-catch" and treatment with the desired nucleophile.     

The Baylis-Hillman condensation of alpha,beta-conjugate cycloketones with aldehydes using diethylaluminum iodide alone as the promoter

The Baylis-Hillman condensation of three types of alpha,beta-conjugate cycloketones with aldehydes was successfully performed by using diethylaluminum iodide as the Lewis acid promoter alone without the direct use of a Lewis base. The reaction proceeded to completion at 0 degree C in CH2Cl2 within 24 h to give modest to good yields (53-72%).     

An efficient preparation of isosteric phosphonate analogues of sphingolipids by opening of oxirane and cyclic sulfamidate intermediates with alpha-lithiated alkylphosphonic esters

D-erythro-(2S,3R,4E)-Sphingosine-1-phosphonate (1), the isosteric phosphonate analogue of naturally occurring sphingosine 1-phosphate (1a), and D-ribo-phytosphingosine 1-phosphonate (2), the isosteric phosphonate analogue of D-ribo-phytosphingosine-1-phosphate (2a), were synthesized starting with methyl 2,3-O-isopropylidene-d-glycerate (4) and D-ribo-phytosphingosine (3), respectively. Oxirane 12 was formed in eight steps from 4, and cyclic sulfamidate 22 was formed in five steps from 3. The phosphonate group was introduced via regioselective ring-opening reactions of oxirane 12 and cyclic sulfamidate 22 with lithium dialkyl methylphosphonate, affording 13 and 23, respectively. The synthesis of 1 was completed by S(N)2 displacement of chloromesylate intermediate 14b with azide ion, followed by conversion of the resulting azido group to a NHBoc group and deprotection. The synthesis of 2 was completed by cleavage of the acetal, N-benzyl, and alkyl phosphonate ester groups.     

Coriatone and corianlactone, two novel sesquiterpenes from Coriaria nepalensis

Both coriatone (1). a novel highly oxygenated picrotoxane-type sesquiterpene, and corianlactone (2). with an unprecedented sesquiterpene basic skeleton, named coriane, were isolated from Coriaria nepalensis Wall. The structures of 1 and 2 were determined by analysis of their two-dimensional NMR data, and the structure of 2 was confirmed by X-ray analysis. Compounds 1 and 2 showed no remarkable inhibitory activity toward K(562) cells. They are cytotoxic with IC(50) > 50 microg/mL (cis-platinim: IC(50) = 0.49 microg/mL).     

Synthesen neuer Phosphono-Analoga von Pantethein-derivaten

Syntheses of New Phosphono Analogues of Pantetheine Derivatives The phosphono analogues 5 and 13 of pantothenate 4′-(dibenzyl phosphate) and pantetheine 4′-(dibenzyl phosphate), respectively, are prepared as intermediates for the synthesis of a coenzyme-A phosphono analogue (Schemes 1 and 2). The synthesis of phosphono analogues 20 and 21 of oxapantetheine, which are structurally similar compounds to the phosphono analogue of pantetheine, is also described (Scheme 3).     

Recovery of thick shear bands in atactic polystyrene

The DSC thermograms of the shear band material cut out by a diamond saw to include some undeformed material revealed two T_g's clearly separated by about 10°C. The first T_g was at the same temperature as the T_g of the undeformed material. The second T_g, which was at a higher temperature than the first T_g, appeared shortly after the shear strain recovery during the heating of the shear band material in the DSC. When the shear strain in the shear band was partially reversed by mechanical means before taking the DSC thermogram, the ΔT between the two T_g's decreased and when the shear strain was mechanically reversed to almost zero, the second T_g disappeared. The stored energy of shear band material was found to be similar to that of the bulk compressed material for large strains. Dimensional recovery during heating of specimens with thick and fine bands was similar, both taking place above T_g.