Column chromatographic separation of thorium(IV) from ascorbic acid medium using poly-(dibenzo-18-crown-6)

A simple separation method has been developed for thorium(IV) using poly-(dibenzo-18-crown-6) and column chromatography. The separation was carried out from ascorbic acid medium. The adsorption of thorium(IV) was quantitative from 0.001-0.01M ascorbic acid. The elution of thorium(IV) was quantitative with 4.0-8.0M HCl, 3.0-6.0M HClO₄, 4.0-8.0M H₂SO₄ and 1.0-8.0M HBr. The capacity of poly-(dibenzo-18-crown-6) for thorium(IV) was found to be 1.379±0.01 m^.mol/g of crown polymer. Thorium(IV) was separated from a number of cations in binary as well as in multicomponent mixtures. The method was extended to the determination of thorium in monazite sand. It is possible to separate and determine 5 ppm of thorium(IV) by this method. The method is very simple, rapid, selective and has good reproducibility (approximately ±2%).     

Surprises in the design of anion receptors: calorimetry prevents false reasoning

Supplementing bicyclic guanidinium anion receptors with four sec-carboxamido groups leads to enhanced affinity for oxoanions, however, for a different reason than originally planned. Calorimetric analysis reveals that better binding is due to higher association entropies rather than more negative enthalpies. Thus, molecular design following geometric and functional complementarity principles may misguide supramolecular constructions aimed at a unique host-guest binding mode, as required, e.g., by self-assembly or catalysis.     

HPTLC Method for Determination of 20-Hydroxyecdysone in Sida rhombifolia L. and Dietary Supplements

Naturally occurring 20-hydroxyecdysone is an important anabolic ecdysteroid. A simple thin-layer chromatography method to quantitate 20-hydroxyecdysone in methanolic extract of the whole plant material of Sida rhombifolia L. was developed. This method was successfully applied for quantitative evaluation of dietary supplements. The separation was achieved on glass TLC plates coated with silica gel 60F254, using chloroform: methanol (8:2 v/v) as developing solvent. Densitometric evaluation of 20-hydroxyecdysone was performed at 250 nm in reflectance/absorbance mode. The calibration was in the range of 200–1,000 ng spot^?1 and correlation coefficient for the calibration curve was >0.999. In addition, for six different Sida species unique fingerprints were obtained on the HPTLC plate.     

Friedel‐Crafts Benzylation of Arenes over Mixed Oxides

The replacement of liquid acid catalyst by solid acids for the Friedel‐Crafts reaction of aromatic alkylation is a challenging task. Mixed oxide possessing spinel structures were found to catalyze the Friedel‐Craft benzylation of arenes. It was found that the reaction was very fast at 80 °C, hence the reaction was studied with respect to more substrate. The significant point was even at this temperature monobenzylation, with the para isomer predominating, was achieved. Mixed oxides were prepared by co‐precipitation method and were characterized by XRD technique.     

A study of chromatographic properties of liquid crystalline polyacrylates using WCOT columns in gas chromatography

Liquid crystalline polyacrylates (LCPAs) are evaluated as stationary phases for capillary gas chromatography (CGC). Aromatic hydrocarbons as well as polar isomeric compounds are used as test solutes to compare the polarity of the LCPAs with a conventional polysiloxane column and a Carbowax 20M column. The relative polarity of the columns with respect to change in the lateral and terminal substituents is also discussed. Lateral substitution, polarity of the terminal group, together with the solute size, affect the LCPA selectivity.     

Development and validation of a novel high-performance thin-layer chromatography method for the quantitative estimation of neohesperidin from Citrus aurantium peel extract

JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatography method was developed for the estimation of neohesperidin from Citrus aurantium peel....     

Palladium catalyzed atom-efficient cross-coupling reactions of triarylbismuths with aryl iodides and aryl triflates

The atom-efficient cross-coupling of triarylbismuths with aryl iodides or aryl triflates using catalytic Pd(OAc)₂/PPh₃ and K₃PO₄ as base in DMF at 90 °C to afford the corresponding functionalized biaryls in high yields is reported.     

Room‐Temperature Ionic Liquid–Promoted Williamson's Synthesis of Ethers: A Facile Synthesis of Diaryloxymethanes

A simple and efficient method has been developed for the synthesis of phenolic ethers using room‐temperature ionic liquid, not only as solvent but also as promoter. Ionic liquid was recycled and subsequently reused without any loss of the product.