Acid-catalysed cyclisation of 2-methyl-2[3-(2,4-dimethoxyphenyl)-5-methoxypent-2-enyl]-cyclopentane-1,3-dione: Structure of a novel product

Acid-catalysed reaction of the title compound (3a) with boiling ethanolic HCl afforded a complex mixture of compounds from which a crystalline keto alcohol was isolated. On the basis of spectral data (UV, IR, NMR and MS), this keto alcohol was assigned the tricyclodecane structure 7a. Acetylation of the keto alcohol followed by hydrogenation gave the dihydro keto acetate 8b which was brominated using dioxane dibromide to give the bromo compound 8c. X-ray crystal structure analysis of the bromo compound confirmed the structure of this compound as well as the parent keto alcohol 7a.     

Heterocyclic steroids—VII : Rearrangement of 1-diethylamino-5-(m-methoxyphenoxy)-pent-2-yne

Thermal rearrangement of diethylamino-5-(m-methoxyphenoxy)-pent-2-yne (3) gives 1-(m-methexyphenoxy)-pent-3,4-diene (14) in about 8% yield. Hydration of the latter yields 1-(m-methoxyphenoxy)-pentan-4-one (6), which has been synthesised by an unambiguous route. A mechanism of formation of the allene (14) from the amine (3) has been suggested.     

Photochemical transformations—I : Reactions of some terpene iodides

Photo-irradiation of longibornyl iodide in n-heptane containing some triethylamine as scavenger for hydrogen iodide, furnished rearranged hydrocarbons (longifolene, longicyclene and longiborn-8-ene). Citronellyl iodide, under similar conditions, led to simple elimination (to furnish 2,6-dimethylocta-2,7-diene) and π-participation (to yield trans-p-menth-8-ene) to almost equal extent. A possible mechanism for these reactions is discussed.     

Spectrophotometric determination of traces of nitrite with rhodamine 6 G

A simple and highly selective spectrophotometric method is described for the determination of nitrite. The method is based on the measurement of decrease in absorbance at 525 nm of rhodamine 6 G in sulphuric acid medium. The decrease in absorbance is instantaneous on addition of nitrite and remains stable for 2 h. Linear calibration graph passing through the origin was obtained in the range 0.01–0.6 g/ml nitrite. The method is free from interference of Cu²⁺, Fe³⁺ and SO ₃ ^2– which normally interfere in other procedures. The method was applied successfully to the determination of nitrite in well and sea water samples and in KNO₃, NaNO₃, table salt, sugar and milk powder samples.     

Third-order derivative spectrophotometric determination of phosphate as ternary complex with molybdate and rhodamine 6G

This paper describes a third-order derivative Spectrophotometric procedure for the determination of traces of phosphate, based on the formation of a ternary ion-association complex by reaction of phosphate with rhodamine 6G in the presence of molybdate. The pink complex is readily formed in 0.08–0.16M H₂SO₄ medium and remained stable for 2 h. The influence of various instrumental parameters and reaction conditions for maximum colour development are discussed. The few interfering ions can be masked by the addition of appropriate reagents. The procedure is simple, rapid and reliable and allows the determination of 1.5 g l^–1 of phosphate. The relative standard deviation for the determination of 0.08 mg l^–1 of phosphate was 1.1%. The method is applicable to the determination of phosphate in river water, sea water, drinking water, milk powder and standard reference materials.     

Liquid-liquid extraction and spectrophotometric determination of cadmium with 1,10-phenanthroline and thymol blue

A simple and highly sensitive extraction spectrophotometric method was developed for the determination of traces of cadmium. The method is based on the preconcentrative extraction of ternary-ion-association complex of cadmium—1,10-phenanthroline-thymol blue into chloroform and subsequent determination by spectrophotometry. The ternary ion associate is stable for 20 h and cadmium content as low as 0.1 g in 90 ml of sample can be determined. The method is precise and has been applied to the determination of cadmium in sea water, solder and high purity zinc and indium materials.     

Effect of water soluble complexing agent on the extraction of Ce(III) and Nd(III) by 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester

Extraction of Ce(III) and Nd(III) by 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHEHPA) in the presence of water soluble complexing agent, glycine, has been studied. An improvement in separation factor between these lanthanides is observed. The extraction data have been analyzed theoretically, taking into account complexation of the metal in the aqueous phase with glycine and chloride ion and plausible complexation in the organic phase.     

Mixed-ligand chelate extraction of trivalent lanthanides with 4,4,4-trifluoro-1-phenyl-1,3-butanedione and neutral oxo-donors

Mixed-ligand chelate extraction of trivalent lanthanides such as Nd(III), Eu(III) and Lu(III) into benzene with mixtures of 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HBFA) and bis-2-ethylhexyl sulphoxide (B2EHSO) or triphenylphosphine oxide (TPhPO) from thiocyanate solutions was investigated. The results demonstrate that these metal ions are extracted as Ln(BFA)(3) with HBFA alone and in the presence of a neutral oxo-donor, B2EHSO or TPhPO(S), as Ln(BFA)(3).S and Ln(BFA)(3).2S. The equilibrium constants of the above species increase monotonically with decreasing ionic radii of these metals ions. The addition of a neutral donor to the metal chelate system not only enhances the extraction efficiency but also improves the selectivity among these trivalent lanthanides. Hence this mixed-ligand system may be useful for the extraction and separation of individual lanthanides and also for the separation of lanthanides as a group from other metal ions.     

Mixed-ligand chelate extraction of trivalent lanthanides and actinides with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 and dihexyl-N,N-diethylcarbamoylmethyl phosphonate

Mixed-ligand chelate extraction of trivalent lanthanides such as La, Eu and Lu and a trivalent actinide, Am into xylene with mixtures of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP) and dihexyl-N,N-diethylcarbamoylmethylphosphonate (CMP) has been studied by tracertechniques. These trivalent metal ions are found to be extracted from 0.01 mol/dm³ chloroacetate buffer solutions as M(PMBP)₃·HPMBP type self adducts with HPMBP alone and in the presence of CMP as M(PMBP)₃·CMP (where M=La, Eu, Lu and Am) into the organic phase. The equilibrium constants of the above species are deduced by non-linear regression analysis. The synergistic constants of trivalent lanthanides do not increase monotonically with atomic number but have a maximum at Eu and that of Am was found to lie between that of La and Eu.     

Preconcentration of rare earth quinolin-8-ol complexes onto activated carbon and determination by first-order derivative x-ray fluorescence spectrometry

A method is described for the determination of traces of rare earths using energy-dispersive x-ray fluorescence spectrometry (EDXRF) after preconcentration of their quinolin-8-ol complexes on activated carbon. Various parameters that influence the adsorptive preconcentration of rare earths on activated carbon, viz., pH, amounts of activated carbon and quinolin-8-ol, time of stirring and aqueous phase volume, were systematically studied. A numerical method based on a simple least-squares procedure using a fifth-order polynomial with 25 consecutive values was developed for smoothing and differentiation of EDXRF data which were previously digitized and averaged. First-order derivative EDXRF in conjunction with adsorptive preconcentration of activated carbon enables down to 10 ng ml^?1 of each rare earth element to be determined.