Selective oxidation of secondary over primary hydroxyl group

561-563Selective oxidation of oligoethylene glycol ether methyl 12(13)–hydroxy-13(12)-[11-hydroxy-3,6,9-trioxa-undecyl-1-oxy]-octadec-9-enoate 3 has been studied using pyridinium chlorochromate (PCC). The reaction has resulted in the formation of methyl 12(13)–oxo-13(12)-[11-hydroxy-3,6,9-trioxa-undecyl-1-oxy]-octadec-9-enoate 5 as an unexpected product wherein only the secondary hydroxyl group has been oxidized while the primary hydroxyl group has remained intact

Synthesis, Characterization, and Evaluation of Surface Properties of Cyclohexanoxycarbonylmethylpyridinium and Cyclohexanoxycarbonylmethylimidazolium Ionic Liquids

New ionic liquids have been synthesized by esterification of cyclohexanol with bromoacetic acid or chloroacetic acid to form cyclohexyl-2-bromoacetate or cyclohexyl-2-chloroacetate. The bromoacetate/chloroacetate on quaternization with heterocyclic bases (pyridine or 2-methylpyridine or 3-methylpyridine or 4-methylpyridine or <i>N</i>-methylimidazole) gave the respective ionic liquids. One of the ionic liquids has been subjected to ion exchange with potassium hexafluorophosphate, potassium trifluoromethanesulfonate, and sodium tetrafluoroborate to get their respective hydrophobic ionic liquids by the exchange of anions. To confirm the exchange of anions, these ionic liquids have been crystallized from acetone and their structures have been established with single crystal X-ray diffraction studies. All the ionic liquids have been found to possess good surface properties and are thermally stable up to a temperature of more than 473.15 K

Self-Assembly and Thermal Stability of Ether-Functionalized Imidazolium Ionic Liquids

A series of short-chain ionic liquids with <i>N</i>-methylimidazolium headgroup have been synthesized and investigated for their self-aggregation behavior in aqueous medium by conductivity, surface tension, and fluorescence techniques. Structure elucidation of these ionic liquids has been done by NMR and mass spectroscopy. Physicochemical parameters such as critical aggregation concentration (cac), surface tension at the cac (γ_cac), adsorption efficiency (p<i>C</i>₂₀), effectiveness of surface tension reduction (Π_cac), saturation adsorption (τ_max), and minimum surface area/molecule (<i>A</i>_min), Gibbs free energy of the aggregation (Δ<i>G</i>°_agg), and Gibbs free energy of adsorption (Δ<i>G</i>°_ads) at the air–water interface of these ionic liquids have been measured. The adsorption and self-aggregation behavior of these short-chain cationics have been found to be better than those of conventional short-chain cationics. Dynamic light scattering (DLS) experiments have provided insights about the size of the aggregates. The thermal stability of these ionic liquids has also been evaluated by using thermal gravimetric analysis (TGA)

Self-Assembly and Biophysical Properties of Gemini 3‑Alkyloxypyridinium Amphiphiles with a Hydroxyl-Substituted Spacer

New gemini pyridinium amphiphiles having alkyl chain lengths of C₁₀, C₁₂, C₁₄ , and C₁₆ and appended with hydroxyl-substituted spacers have been synthesized, characterized, and investigated for their self-assembly as well as adsorption behavior by state-of-the-art techniques such as conductometry, tensiometry, isothermal titration calorimetry (ITC), and spectrofluorometry. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) have provided excellent acumen with respect to the micellar size distribution of investigated dicationics in aqueous media. Furthermore, the interaction of these dicationics with plasmid DNA, at different charge ratios (<i>N</i>/<i>P</i>), has been studied by DLS, agarose gel electrophoresis, and ethidium bromide exclusion measurements. The cytotoxicity of these geminis has been evaluated by using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on BV2 (microglial) and C6 glioma cell lines. It was found that the varying alkyl chain length, fashioned by ether linkage close to the headgroup, and the presence of a polar linker significantly altered the physicochemical properties of these new dicationics as compared to the properties of nonfunctionalized gemini surfactants

Gemini Imidazolium Surfactants: Synthesis and Their Biophysiochemical Study

New gemini imidazolium surfactants <b>9</b>–<b>13</b> have been synthesized by a regioselective epoxy ring-opening reaction under solvent-free conditions. The surface properties of these new gemini surfactants were evaluated by surface tension and conductivity measurements. These surfactants have been found to have low critical micelle concentration (cmc) values as compared to other categories of gemini cationic surfactants and also showed the tendency to form premicellar aggregates in solution at sufficiently low concentration below their cmc values. The thermal degradation of these surfactants was determined by thermograviometry analysis (TGA). These new cationic surfactants have a good DNA binding capability as determined by agarose gel electrophoresis and ethidium bromide exclusion experiments. They have also been found to have low cytotoxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on the C6 glioma cell line

Micellization Behavior of Morpholinium-Based Amide-Functionalized Ionic Liquids in Aqueous Media

Morpholinium-based amide-functionalized ionic liquids (ILs) [C_<i>n</i>AMorph]­[Br], where <i>n</i> = 8, 12, and 16, have been synthesized and characterized for their micellization behavior in aqueous medium using a variety of state of the art techniques. The adsorption and micellization behavior of [C_<i>n</i>AMorph]­[Br] ILs at the air–solution interface and in the bulk, respectively, has been found to be much better compared to that observed for nonfunctionalized homologous ILs and conventional cationic surfactants, as shown by the comparatively higher adsorption efficiency, lower surface tension at the critical micelle concentraiton (γ_cmc), and much lower critical micelle concentration (cmc) for [C<i>_n</i>AMorph]­[Br] ILs. Conductivity measurements have been performed to obtain the cmc, degree of counterion binding (β), and standard free energy of micellization (Δ<i>G</i>_m°). Isothermal titration calorimetry has provided information specifically about the thermodynamics of micellization, whereas steady-state fluorescence has been used to obtain the cmc, micropolarity of the cybotactic region, and aggregation number (<i>N</i>_agg) of the micelles. Both dynamic light scattering and atomic force microscopy have provided insights into the size and shape of the micelles. 2D ¹H–¹H nuclear Overhauser effect spectroscopy experiments have provided insights into the structure of the micelle, where [C₁₆AMorph]­[Br] has shown distinct micellization behavior as compared to [C₈AMorph]­[Br] and [C₁₂AMorph]­[Br] in corroboration with observations made from other techniques