Ekasith Somsook

Synthesis and Reactivity of Nitrogen Nucleophiles-Induced Cage-Rearrangement Silsesquioxanes

Novel phthalimide and o-sulfobenzimide-functionalized silsesquioxanes were successfully synthesized via nucleophilic substitution reactions from octakis(3-chloropropyl)octasilsesquioxane. Surprisingly, the formation of deca- and dodecasilsesquioxanes cages was discovered during substitution with phthalimide, but only octasilsesquioxane maintained a cage in the o-sulfobenzimide substitution reaction. Moreover, we report the electronic effect of nitrogen nucleophiles to promote cage-rearrangement of inorganic silsesquioxane core for the first time. Structures of products were confirmed by (1)H, (13)C, and (29)Si NMR spectroscopy, ESI-MS analysis, and single-crystal X-ray diffraction.

Bimetallic gold–palladium alloy nanoclusters: an effective catalyst for Ullmann coupling of chloropyridines under ambient conditions

An efficient method for the Ullmann coupling of chloropyridines catalyzed by poly(N-vinylpyrrolidone) (PVP)-stabilized bimetallic Au–Pd alloy nanoclusters (NCs) under ambient conditions is demonstrated. The reaction does not occur with either gold or palladium single-metal clusters alone, nor with a physical mixture of the two metals. The experimental results indicate that the inclusion of Au as a nearest heteroatom is crucial to initiate the coupling and its composition up to 50% is essential to accelerate the reaction. Unlike the conventional transition metal catalysis, 2-chloropyridine was found to be highly reactive as compared to 2-bromopyridine. From the UV-vis and ICP-AES measurements, a significant amount of leached Pd(II) was observed in the coupling with 2-bromopyridine as compared with 2-chloropyridine, indicating that the leaching process might be a crucial factor in diminishing the reactivity.

Enhancing Thai students' learning of chemical kinetics

Chemical kinetics is an extremely important concept for introductory chemistry courses. The literature suggests that instruction in chemical kinetics is often teacher‐dominated at both the secondary school and tertiary levels, and this is the case in Thailand – the educational context for this inquiry. The work reported here seeks to shift students from passive learning to more active, student‐centred learning and involved some 413 first year undergraduate science students in Thailand. Drawing on inquiry‐based learning, the participants were asked to design an experiment investigating the reaction of acids and bases. The research findings suggest that participants were able to explain the changes of the rate of a chemical reaction, and developed good conceptual understanding of chemical kinetics both qualitatively and quantitatively. It also showed this more active teaching approach, which is radically different from normal teaching in Thailand, was an enjoyable experience for the students.

Electrocatalytic oxidation of ascorbic acid using a poly(aniline-co-m-ferrocenylaniline) modified glassy carbon electrode.

A poly(aniline-co-m-ferrocenylaniline) was successfully synthesized on a glassy carbon electrode (GCE) by electrochemical copolymerization using a scan potential range from −0.3 to +0.9 V (vs. Ag/AgCl) in 0.5 M H2SO4 containing 30% acetonitrile (ACN), 0.1 M aniline (Ani) and 0.005 M m-ferrocenyaniline (m-FcAni). The field emission scanning electron microscope (FESEM) and electrochemical methods were used to characterize the poly(Ani-co-m-FcAni) modified electrode. The poly(Ani-co-m-FcAni)/GCE exhibited excellent electrocatalytic oxidation of ascorbic acid (AA) in citrate buffer solution (CBS, pH 5.0). The anodic peak potential of AA was shifted from +0.55 V at the bare GCE to +0.25 V at the poly(Ani-co-m-FcAni)/GCE with higher current responses than those seen on the bare GCE. The scan number at the 10th cycle was selected as the maximum scan cycle in electrochemical polymerization. The limit of detection (LOD) was estimated to be 2.0 μM based on the signal-to-noise ratio (S/N = 3). The amperometric responses demonstrated an excellent selectivity for AA determination over glucose (Glu) and dopamine (DA).

Highly active sustainable ferrocenated iron oxide nanocatalysts for the decolorization of methylene blue

Ferrocenated iron oxide nanoparticles were successfully synthesized in basic conditions. It was unexpected to discover highly active sustainable nanocatalysts for the decolorization of methylene blue in the absence of light and hydrogen peroxide. Cyclopentadienyl radicals may be responsible for the production of active species for the decolorization of methylene blue. The nanocatalysts can be reactivated in sodium chloride solution and reused several times.

Iron oxide/cassava starch-supported Ziegler-Natta catalysts for in situ ethylene polymerization.

Iron oxide nanoparticles were used as supporters for in situ polymerization to produce polymer nanocomposites with well-dispersed fillers in polymer matrix. Iron oxide could be sustained as colloidal solutions by cassava starch to produce a good dispersion of iron oxide in the matrix. New supports based on iron oxide/cassava starch or cassava starch for Ziegler-Natta catalysts were utilized as heterogeneous supporters for partially hydrolyzed triethylaluminum. Then, TiCl4 was immobilized on the supports as catalysts for polymerization of ethylene. High-density polyethylene (HDPE) composites were obtained by the synthesized catalysts. A good dispersion of iron oxide/cassava starch particles was observed in the synthesized polymer matrix promoting to good mechanical properties of HDPE.

Ferrocenated nanocatalysts derived from the decomposition of ferrocenium in basic solution and their aerobic activities for the rapid decolorization of methylene blue and the facile oxidation of phenylboronic acid

A strategic preparation of ferrocenated compounds as aerobic catalysts was successfully carried out for the decolorization of methylene blue and oxidation of phenylboronic acid without light irradiation and excess addition of hydrogen peroxide. Cyclopentadienyl radical formed by the decomposition of ferrocenium under basic conditions plays a major role in the production of reactive oxygen species (ROS) under an aerobic atmosphere.

Hydroconversion of carboxylic acids using mesoporous SBA-15 supported NiMo sulfide catalysts under microwaves

Hydrogenation of octanoic acid was performed in a continuous manner, using microwaves (MW), and a supported metal sulfide catalyst. SBA-15, AlSBA-15 and ZrSBA-15 supported NiMo hydrotreating catalysts were prepared by an incipient wetness impregnation method in order to investigate the role of support acidity. Extrudates of the supported NiMo powders were prepared and sulfided. Octanoic acid in dodecane (10%) was introduced in the continuous flow reactor by means of an HPLC pump and co-fed with hydrogen at a working pressure of 0.5 MPa, while varying the reaction parameters such as temperature and feed flow rate (0.1, 0.25, and 0.5 mL min−1). The power applied to the monomodal cavity varied in the range of 15–150 W and corresponding temperature from 200–350 °C. Catalysts and supports were characterized by small- and wide-angle XRD, N2-physisorption (BET, BJH), HRTEM, ICP-MS, and NH3-TPD. The thermal response under MW showed that the extrudates containing SBA-15 (with or without Al or Zr) exhibited a strong MW response. The comparison of the catalytic activities showed that all SBA-15 supported NiMo catalysts exhibited the same activity range but the selectivity as compared to NiMo/Al2O3 catalysts was different.

Biomass-Based Sulfonic-Functionalized Carbon Solid Acid for Esterification of Acetic Acid

Sulfonic-functionalized carbon material derived from the incomplete carbonization of mungbean vermicelli was reported here as a catalyst for esterification of acetic acid. The catalyst with the highest activity (SBET = 18.1 m2/g and acid site density of 1.53 mmol H+/gcat) was obtained by carbonization at 573 K and sulfonation at 373 K due to a feasible attachment of more SO3H groups to flexible carbon sheets compared to the other synthesized solids. Approximate 64% yield of methyl acetate was achieved over (2:1) molar ratio of methanol to acetic acid with 3 wt% of catalyst. From the economic outlook, this environmentally benign C-SO3H catalyst could be a promising candidate for the esterification of high free fatty acid feedstocks reducing the production cost of biodiesel.

Hydrogel-Templated Solid Base Catalysts for Transesterification of Soybean Oil

A new method for utilization of hydrogel is proposed here for the preparation of solid base catalysts for the transesterification of vegetable oil. When a solution of KF is mixed with a solution of Ca(NO3)2, CaF2 is obtained and inactive as a catalyst in the transesterification of vegetable oils. The catalysts were synthesized by the sequential incorporation of KF and/or Ca(NO3)2 solutions into the hydrogel upon microwave irradiation and then the as-obtained hydrogel was calcined at 800°C for 5 hours to eliminate the template and yield catalysts for the biodiesel productions. The prepared catalysts obtained by the different ways in the incorporation of ions into the hydrogel showed different physical properties and catalytic activities in the transesterification of soybean oil. All catalysts, except the low concentration of Ca(NO3)2, exhibiting the high activity yielding more than 90% FAME after 1 hour at 65°C, using oil to methanol molar ratio of 1:15 and 10 wt% of catalyst amounts.