Unusual Rate Enhancement in the Hydroxide-Ion-Catalyzed Cleavage of Acetyl Salicylate Ion (Aspirin Anion) in the Presence of Anionic Micelles

The reaction rate studies on the hydrolytic cleavage of acetyl salicylate ion (AS^-) within the [^-OH] range 0.010-0.025 M reveal AS^- and ^-OH as the reactants. The effects of micelles of sodium dodecyl sulfate (SDS) on observed pseudo-first-order rate constants (k_obs) for the hydrolytic cleavage of AS^- have been studied at different [OH^-]. At a constant [OH^-], the rate constants (k_obs) follow an empirical relationship: k_obs = C + F [SDS]_T where [SDS]_T represents total SDS concentration. The magnitudes of C and F increase with an increase in [OH^-]. These data are explained in terms of the pseudophase model of the micelle.     

Synthesis and Characterization of Novel Monoazo Naphthalimide Disperse Dyes Containing Carboxylic Acid Group with High Heat Fastness Properties

A group of novel monoazo disperse dyes containing carboxylic acid‐1,8‐naphthalimide group has been synthesized. All intermediates and dyes were purified by recrystalization and the column chromatography method. The purified products were characterized by ¹H NMR, ¹³C NMR, FTIR, DSC, UV‐VIS and Elemental Analysis. Spectrophotometric investigations of the synthesized dyes in different solvents were carried out in order to obtain their absorption maxima, molar extinction coefficients and solvatochromic effects. The absorption maxima of the synthesized dyes in acetone varied (513‐549 nm) and the molar extinction coefficient was (17405‐38939 l/mol cm). By changing the media from chloroform to DMF, the solvatochromism effect for all dyes increased. Dispersion of the synthesized dyes was prepared in water containing dispersing agent and applied to polyester fabrics. The dyed fabrics showed that all of the synthesized dyes were suitable for coloring polyester fibers, producing deep red to bluish red with very good fastness properties.     

UV–Spectral Study on the Effects of Inert Salts on the Nonionic Micellar Solubilization of Phenyl Salicylate in the Absence and Presence of a Cationic Surfactant Under Alkaline Aqueous Medium

The values of the fraction of ionizes phenyl salicylate, f_PS-, obtained from initial absorbance measurement of phenyl salicylate at 350 nm, remain unchanged with the increase in [CH₃CO₂Na] from 0.0 to 0.7 M at 0.01 M NaOH (f_PS- ≈ 0.70) and 0.02 M NaOH (f_PS- ≈ 0.93). The values of f_PS- decrease from ～ 1.0 to 0.90 and ～ 1.0 to 0.84 with the increase in respective [CH₃CO₂Na] and [NaBr] from 0.0 to 0.6 M at 0.01 M NaOH, 0.02 M C₁₂E₂₃(=C₁₂H₂₅(OCH₂CH₂)₂₃OH) and 0.01 M CTABr (=C₁₆H₃₃NMe₃Br).     

高能离子的定向发射及其模拟研究

本文用二维粒子模拟方法研究了超强超短脉冲激光与圆形等离子体薄靶相互作用中产生的高能离子.模拟研究结果表明,在圆形等离子体薄靶后表面所产生的高能离子,角分布较小,定向性好,能获得很高的能量,并且等离子体薄靶的形状对高能离子的产生和会聚有一定地影响.     

Effects of nonionic micelles on the rate of alkaline hydrolysis of N-(2'-methoxyphenyl)phthalimide (1): kinetic and rheometric evidence for a transition from spherical to rodlike micelles under the typical reaction conditions

Pseudo-first-order rate constants (k(obs)) for alkaline hydrolysis of N-(2'-methoxyphenyl)phthalimide (1) decrease nonlinearly with increasing total concentration of nonionic surfactant C(m)E(n) (i.e. [C(m)E(n)](T) where m and n represent the respective number of methyl/methylene units in the tail and polyoxyethylene units in the headgroup of a surfactant molecule and m/n=16/20, 12/23 and 18/20) at constant 2% v/v CH(3)CN and 1.0 mM NaOH. The k(obs)vs. [C(m)E(n)](T) data follow the pseudophase micellar (PM) model at ≤ 50 mM C(16)E(20), ≤ 1.4 mM C(12)E(23) and ≤ 2.0 mM C(18)E(20) where rate of hydrolysis of 1 in micellar pseudophase could not be detected. The values of k(obs) fail to follow the PM model at > ～50 mM C(16)E(20), > ～1.4 mM C(12)E(23) and > ～2.0 mM C(18)E(20) which has been attributed to a micellar structural transition from spherical to rodlike which in turn increases C(m)E(n) micellar binding constant (K(S)) of 1 with increasing values of [C(m)E(n)](T). Rheological measurements show the presence of spherical micelles at ≤ 50 mM C(16)E(20), ≤ 1.4 mM C(12)E(23) and ≤ 3.0 mM C(18)E(20). The presence of rodlike micelles is evident from rheological measurements at > ～50 mM C(16)E(20), > ～1.4 mM C(12)E(23) and > ～3.0 mM C(18)E(20).