15 research outputs found
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 (Îł<sub>cac</sub>), adsorption efficiency (p<i>C</i><sub>20</sub>), effectiveness of surface tension reduction (Î <sub>cac</sub>), saturation adsorption (Ď„<sub>max</sub>), and minimum
surface area/molecule (<i>A</i><sub>min</sub>), Gibbs free
energy of the aggregation (Δ<i>G</i>°<sub>agg</sub>), and Gibbs free energy of adsorption (Δ<i>G</i>°<sub>ads</sub>) 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)
Synthesis of β-bromoethoxylates and β-chloroethoxylates from olefinic fatty methyl esters
Self-Assembly and Biophysical Properties of Gemini 3‑Alkyloxypyridinium Amphiphiles with a Hydroxyl-Substituted Spacer
New
gemini pyridinium amphiphiles having alkyl chain lengths of
C<sub>10</sub>, C<sub>12</sub>, C<sub>14</sub> , and C<sub>16</sub> 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<sub><i>n</i></sub>AMorph]Â[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<sub><i>n</i></sub>AMorph]Â[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
(Îł<sub>cmc</sub>), and much lower critical micelle concentration
(cmc) for [C<i><sub>n</sub></i>AMorph]Â[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><sub>m</sub>°). 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><sub>agg</sub>) of the micelles. Both dynamic light scattering
and atomic force microscopy have provided insights into the size and
shape of the micelles. 2D <sup>1</sup>H–<sup>1</sup>H nuclear
Overhauser effect spectroscopy experiments have provided insights
into the structure of the micelle, where [C<sub>16</sub>AMorph]Â[Br]
has shown distinct micellization behavior as compared to [C<sub>8</sub>AMorph]Â[Br] and [C<sub>12</sub>AMorph]Â[Br] in corroboration with
observations made from other techniques