Ensuring complete absence of Ce(IV) and measurement of the stability constant of the fluoride complex of Ce(III)

Literature survey revealed a wide variation in the measured stability constant values of the aqueous fluoride complexes of trivalent cerium. This could be due to inadequate care for full conversion and maintenance of the oxidation state of cerium to trivalent state. In the present work quinhydrone has been used to ensure complete absence of Ce(IV) and the stability constant of CeF(2+) in 1 M NaClO(4) has been measured potentiometrically using a fluoride ion selective electrode. Log beta(1) obtained in this work was 2.936+/-0.024 and fitted well with the general trend of stability constants of the lanthanide (rare earths) fluorides in aqueous solution.     

Liquid-liquid extraction of thorium from malonate solution with liquid anion-exchangers

Thorium is quantitatively extracted with 4% Amberlite LA-1 or LA-2 in xylene, from 0.01M malonic acid medium at pH 3.0 and stripped from the organic phase with 1M hydrochloric acid, then determined spectrophotometrically at 545 nm as its complex with thoron. It is separated from other elements by selective extraction and stripping.     

New application of Pictet-Spengler reaction leading to the synthesis of an unusual seven-membered heterocyclic ring system

A novel strategy for the Pictet-Spengler reaction is reported. Our strategy involves reaction of arylamines, linked to the N-1 of disubstituted imidazoles, with aldehydes in the presence of p-TsOH. The iminium ion generated in situ undergoes C-C bond formation with the C-5 of the imidazoles to furnish triazabenzoazulenes as a novel heterosystem. Our strategy differs from conventional Pictet-Spengler reaction since the latter utilizes only aliphatic amines in which the amine functionality is linked to a C instead of N of the activated aromatic moiety.     

Stability constants of the aqueous mono-fluoride complexes of Pu(III) and Am(III) and their correlation with other metal ions

The stability constants of the aqueous mono-fluoride complexes of Pu(III) and Am(III) have been measured using the distribution method. A correlation of the available stability constants of fluoride complexes of trivalent actinides, up to Cf, with fundamental properties like charge and radii of the metal ion has been discussed. Good correlation within the group and as a part of other metal ions was obtained only for transplutonium elements. The reported stability constant values measured by potentiometry and the value obtained by distribution for Pu³⁺ appear to be much higher than expected from this correlation. However, a better correlation was obtained with transplutonium elements when effective charge instead of formal charge was considered for Pu³⁺ in the BSE function.     

Solvent extraction separation of zirconium from malonate solution with high molecular-weight amines

Zirconium is quantitatively extracted with 4% Amberlite LA-1 or LA-2 in xylene, from 0.01 M malonic acid medium at pH 3.0 and stripped from the organic phase with 2M hydrochloric acid, then determined spectrophotometrically at 665 nm as its complex with Arsenazo III. Zirconium is separated from various other elements by selective extraction and stripping. The method has been applied to the analysis of zircon.     

Synthesis, spectroscopy, thermal studies and supramolecular structures of two new alkali-earth 4-nitrobenzoate complexes containing coordinated imidazole

The reaction of hydrated magnesium or calcium 4-nitrobenzoate (4-nba) generated in situ, with imidazole (Im) results in the formation of the complexes [Mg(H₂O)₂(Im)₂(4-nba)₂] 1 and [Ca(H₂O)₃(Im)(4-nba)₂]·Im 2, which exhibit the same metal:4-nba:Im ratio but different degrees of hydration. Complex 1 crystallizes in the triclinic Pī space group and the Mg atom is located on an inversion centre, while 2 crystallizes in the monoclinic P2₁/c space group and all atoms are located in general positions. In 1 the Im ligands, which are trans to each other, are coordinated to Mg, while 2 contains coordinated as well as free Im. The monodentate 4-nba ligands are disposed trans to each other in 1, while they adopt a cis orientation in 2 resulting in different supramolecular structures. Complex 1 exhibits two types of H-bonding interactions namely O-H···O and N-H···O, while in 2 three varieties of H-bond, viz. O-H···O, N-H···O and O-H···N are observed. The Im ligand ligand functions as a bifurcated H-bond donor in 1 while the O atom of the nitro group functions as a H-bond acceptor. In contrast, the nitro group in 2 is not involved in any H-bonding interactions. The free Im in 2 functions as a bifurcated acceptor and forms an extended chain linking adjacent complex molecules. The chains thus formed are further cross-linked with the aid of H-donor bonds from both the free as well as the coordinated Im. Both 1 and 2 exhibit π-π stacking interactions. Complex 1 is thermally more stable as compared to 2, and both complexes can be dehydrated to the corresponding anhydrous complexes by heating at 140 and 100°C respectively. At elevated temperatures, both the complexes can be pyrolysed to the corresponding oxide. The anhydrous complexes can be rehydrated to obtain the starting hydrated materials.     

Evaluation of thermo-oxidative characteristics of gear oils by different techniques: Effect of antioxidant chemistry

This paper deals with determination of the oxidation stability of gear oils formulated with antioxidants of different chemistries. The oxidation stability has been studied by PDSC, TGA, micro-oxidation, RPVOT and IP 48. The effect of different antioxidants on the thermo-oxidative properties of gear oil is evaluated.     

Neutron activation and radiochemical separation of selenium from environmental and food samples from and around Bombay using ethyl-α-isonitrosoacetoacetate

Neutron activation analysis has been applied for determination of selenium in environmental and food samples. Food and environmental samples from city, industrial and agricultural zones were collected with utmost care. Samples were activated in the flux 1·10¹³ n·cm^–2·s^–1 in the CIRUS reactor of BARC, Bombay, 75-Se was separated from 6.5N HCl solution using ethyl--isonitrosoacetoacetate (HEINA) reagent. The decontamination studies showed the method is very selective. Selenium contents of wheat, rice, vegetables, cereals pulses etc. and of soil, water, and deposits on plants and surface were determined by the procedure developed.     

Allylation of 1-phenyl-1-propyne with N- and O-pronucleophiles using polymer supported triphenylphosphine palladium complex as a heterogeneous and recyclable catalyst

Simple methodology for the allylation of various N- and O-pronucleophiles with 1-phenyl-1-propyne as an allylating agent, using PS-TPP-Pd (polymer supported triphenylphosphine palladium) as a highly active heterogeneous recyclable catalyst has been developed. The protocol is applicable for a wide variety of hindered and functionalized aromatic amines, alcohols, and carboxylic acids. The catalyst exhibited remarkable catalytic activity for five consecutive recycles.