Kinetic Studies on Interaction of Platinum(II) Complexes with an ‘S’ Containing Ligand in Aqueous Medium

The kinetics of the substitution reactions of [Pt(dach)(H₂O)₂]²⁺ and [Pt(en)(H₂O)₂]²⁺ (where ‘dach’ and ‘en’ are cis-1,2-diaminocyclohexane and ethylenediamine, respectively) with excess N,N′-diethylthiourea have been studied in aqueous solution by UV–Vis spectrophotometry. The effect of different N–N spectator ligands on the reactivity of platinum(II) complexes was investigated by studying the water lability of the reactant complexes. The kinetic study has been substantiated by product isolation, IR, NMR and ESI-MS spectral analysis and DFT calculations. The reactions follow normal square-planar substitution mainly in an associative way. Rate parameters have been evaluated under different conditions. The substitution rates of the complexes studied can be tuned through the nature of the N–N chelates, which is important in the development of new active compounds for cancer therapy.     

Synthesis of Tetrasaccharide Repeating Unit of the K-Antigen from Klebsiella Type-16

Abstract

Starting from L-fucose, D-glucose and lactose, methyl O-[2,3-di-O-benzoyl-4, 6-O-(4-methoxybenzylidene)-β-D-glucopyranosyl]-(1→4)-2,3-di-O-benzoyl-α-L-fucopyranoside and methyl O-(2,3,4,6-tetra-O-benzyl-β-D-galactopyranosyl)-(1→4)-O-(2,3,6-tri-O-benzyl-α-D-glucopyranosyl)-(1→4)-O-(methyl 2,3-di-O-benzoyl-β-D-glucopyranosyluronate)-(1→4)-2,3-di-O-benzoyl-α-L-fucopyranoside were synthesized. Removal of protecting groups gave the tetrasaccharide repeating unit of the antigen from Klebsiella type-16 in the form of its methyl ester methyl glycoside.     

One-pot synthesis of isoquinoline and related compounds via Cu-mediated tandem cross-coupling and cyclization

One-pot synthetic strategy has been developed to access isoquinolines and its analogs via Cu-mediated tandem cross-coupling and cyclization in good yields under mild reaction conditions. A mixture of suitably substituted α-bromoaldehyde, terminal alkyne, and aq NH₃ in CuI/1,10-phenanathroline catalytic system afforded the 3-substituted isoquinoline regio-selectively in good to excellent yields.     

Effect of internal and external conditions on ionization processes in the FAPA ambient desorption/ionization source

Ambient desorption/ionization (ADI) sources coupled to mass spectrometry (MS) offer outstanding analytical features: direct analysis of real samples without sample pretreatment, combined with the selectivity and sensitivity of MS. Since ADI sources typically work in the open atmosphere, ambient conditions can affect the desorption and ionization processes. Here, the effects of internal source parameters and ambient humidity on the ionization processes of the flowing atmospheric pressure afterglow (FAPA) source are investigated. The interaction of reagent ions with a range of analytes is studied in terms of sensitivity and based upon the processes that occur in the ionization reactions. The results show that internal parameters which lead to higher gas temperatures afforded higher sensitivities, although fragmentation is also affected. In the case of humidity, only extremely dry conditions led to higher sensitivities, while fragmentation remained unaffected.     

Three trithiadiazepines and a trithiatriazepine

The structures of 6‐nitro‐1,3λ⁴δ²,5,2,4‐trithiadiazepine [C₂HN₃O₂S₃, ( 1 )], 6,7‐dinitro‐1,3λ⁴δ²,5,2,4‐trithiadiazepine [C₂N₄O₄S₃, ( 2 )], 1,3λ⁴δ²,5,2,4‐trithiadiazepine‐6,7‐dicarbonitrile [C₄N₄S₃, ( 3 )] and 7‐acetyl‐1,3λ⁴δ²,5,2,4,6‐trithiatriazepine [C₃H₃N₃OS₃, ( 4 )] presented here include the most precise determinations of these seven‐membered 10 π‐electron aromatic ring systems published to date. Both ( 2 ) and ( 3 ) are sited around crystallographic twofold axes with half a molecule per asymmetric unit. Comparison with other published derivatives of these rings reveals the effect of substituents on bonding, conformations and intermolecular interactions, including π‐stacking. The deformation density analysis of ( 2 ) is consistent with the expected bonding electron density from other theoretical and experimental studies.     

Comparison of the separation of proteins of wide-ranging molecular weight via trilobal polypropylene capillary-channeled polymer fiber,commercial superficiously porous,and commercial size exclusion columns

Reversed phase and size-exclusion chromatography methods are commonly used for protein separations, although they are based on distinctly different principles. Reversed phase methods yield hydrophobicity-based (loosely-termed) separation of proteins on porous supports, but tend to be limited to proteins with modest molecular weights based on mass transfer limitations. Alternatively, size-exclusion provides complementary benefits in the separation of higher mass proteins based on entropic, not enthalpic, processes, but tend to yield limited peak capacities. In this study, microbore columns packed with a novel trilobal polypropylene capillary-channeled polymer fiber were used in a reversed phase modality for the separation of polypeptides and proteins of molecular weights ranging from 1.4 to 660 kDa. Chromatographic parameters including gradient times, flow rates, and trifluoroacetic acid concentrations in the mobile phase were optimized to maximize resolution and throughput. Following optimization, the performance of the trilobal fiber column was compared to two commercial-sourced columns, a superficially porous C4-derivatized silica and size exclusion, both of which are sold specifically for protein separations and operated according to the manufacturer-specified conditions. In comparison to the commercial columns, the fiber-based column yielded better separation performance across the entirety of the suite, at much lower cost and shorter separation times.     

Irradiation of Fe–Mn@SiO2 with microwave energy enhanced its Fenton-like catalytic activity for the degradation of methylene blue

Research on Chemical Intermediates - The application of microwave energy in the synthesis of catalytic materials has been indicated to induce desirable effects that lead to improved activity....     

Insight into the thermal decomposition of kaolinite intercalated with potassium acetate: an evolved gas analysis

The thermal decomposition process of kaolinite–potassium acetate intercalation complex has been studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS). The results showed that the thermal decomposition of the complex took place in four temperature ranges, namely 50–100, 260–320, 320–550, and 650–780 °C. The maximal mass losses rate for the thermal decomposition of the kaolinite–potassium acetate intercalation complex was observed at 81, 296, 378, 411, 486, and 733 °C, which was attributed to (a) loss of the adsorbed water, (b) thermal decomposition of surface-adsorbed potassium acetate (KAc), (c) the loss of the water coordinated to potassium acetate in the intercalated kaolinite, (d) the thermal decomposition of intercalated KAc in the interlayer of kaolinite and the removal of inner surface hydroxyls, (e) the loss of the inner hydroxyls, and (f) the thermal decomposition of carbonate derived from the decomposition of KAc. The thermal decomposition of intercalated potassium acetate started in the range 320–550 °C accompanied by the release of water, acetone, carbon dioxide, and acetic acid. The identification of pyrolysis fragment ions provided insight into the thermal decomposition mechanism. The results showed that the main decomposition fragment ions of the kaolinite–KAc intercalation complex were water, acetone, carbon dioxide, and acetic acid. TG-FTIR-MS was demonstrated to be a powerful tool for the investigation of kaolinite intercalation complexes. It delivers a detailed insight into the thermal decomposition processes of the kaolinite intercalation complexes characterized by mass loss and the evolved gases.     

Influence of the structural characteristic of pyrolysis products on thermal stability of styrene-butadiene rubber composites reinforced by different particle sized kaolinites

A series of rubber composites were prepared by blending styrene-butadiene rubber (SBR) latex and the different particle sized kaolinites. The thermal stabilities of the rubber composites were characterized using thermogravimetry, digital photography, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Kaolinite SBR composites showed much greater thermal stability when compared with that of the pure SBR. With the increase of kaolinite particle size, the pyrolysis products became much looser; the char layer and crystalline carbon content gradually decreased in the pyrolysis residues. The pyrolysis residues of the SBR composites filled with the different particle sized kaolinites showed some remarkable changes in structural characteristics. The increase of kaolinite particle size was not beneficial to form the compact and stable crystalline carbon in the pyrolysis process, and resulted in a negative influence in improving the thermal stability of kaolinite/SBR composites.