Synthesis of Functionalized Tetrahydro‐4‐oxoindeno[1,2‐b]pyrroles from Ninhydrin,Acetylenedicarboxylates, and Primary Amines

A one‐pot synthesis of dialkyl 1,3a,4,8b‐tetrahydro‐3a,8b‐dihydroxy‐1‐alkyl‐4‐oxoindeno[1,2‐b]pyrrole‐2,3‐dicarboxylates via three‐component reaction from indan‐1,2,3‐trione hydrate (ninhydrin), primary amines, and dialkyl acetylenedicarboxylates is described.     

Formation of trialkyl quinoline-2,3,4-tricarboxylates by reaction of isatin, dialkyl acetylenedicarboxylates, and sodium O-alkyl carbonodithioates

An efficient one-pot synthesis of quinoline-2,3,4-tricarboxylates is described by reaction of isatin (indoline-2,3-dione) and electron-deficient acetylenic esters in the presence of sodium O-alkyl carbonodithioates, themselves prepared by addition of sodium hydride to a solution of an alcohol in CS₂.     

On the prediction of equilibrium phase behavior of amino acids in aqueous and aqueous-electrolyte solutions using SAFT equation of state

We present an approach based on the statistical associating fluids theory (SAFT) to predict the solubility of amino acids in aqueous and aqueous-electrolyte solutions. This approach can describe the association interactions and their effects on the solubility of amino acids. Using the experimental data of activity coefficients of amino acids in water, the parameters of SAFT model for amino acids are obtained. The solubility of several amino acids in the temperature range of 273.15–373.15 K is predicted. Results obtained from the model are in a good accordance with the experimental data. Also, we examine the effect of pH on the solubility of dl-methionine. Addition of an extra amino acid to the binary solution of amino acid + water makes the system more complex. To check the accuracy of model, we study the ternary solution of dl-serine + dl-alanine + water and dl-valine + dl-alanine + water. Predicted results depict that the proposed model has the ability to describe the ternary solution of amino acids, accurately. Finally, the solubility of amino acids in aqueous-electrolyte solutions is investigated. The long-range interactions caused by the presence of ions affects the solubility of amino acids, leading them to be salted in or out. To treat this kind of interaction, the restrictive primitive mean spherical approximation (RP-MSA) is coupled with the SAFT equation of state. The proposed model can accurately predict the solubility of amino acids in aqueous-electrolyte solutions.     

Comparison of C18 silica and multi‐walled carbon nanotubes as the adsorbents for the solid‐phase extraction of Chlorpyrifos and Phosalone in water samples using HPLC

A comparison between C₁₈ silica and multi‐walled carbon nanotubes (MWCNTs) in the extraction of Chlorpyrifos and Phosalone in environmental water samples was carried out using HPLC. Parameters affecting the extraction were type and volume of elution solvent, pH and flow rate of sample through the adsorbent. The optimum conditions obtained by C₁₈ cartridge for adsorption of these pesticides were 4 mL dichloromethane as elution solvent, sample pH of 5, flow rate of 1 mL/min, and those for MWCNT cartridge were 3 mL dichloromethane, pH of 5 and flow rate of 10 mL/min, respectively. Optimized mobile phase for separation and determination of these compounds by HPLC was methanol/water (80:20 v/v) with pH=5 (adjusted with phosphate buffer). Under optimal chromatographic and SPE conditions, LOD, linear range and precision (RSD n=8) were 3.03×10^?3, 0.01–5.00 μg/mL and 2.7% for Chlorpyrifos and 4.03×10^?4, 0.01–5.00 μg/mL and 2.3% for Phosalone, in C₁₈ cartridge, respectively. These values for MWCNT were 4.02×10^?6, 0.001–0.500 μg/mL and 1.8% for Chlorpyrifos and 1.02×10^?6, 0.001–0.500 μg/mL and 1.5% for Phosalone, respectively.