Ligand effect in epoxidatidns by hydroperoxides using molybdenum catalyst: epox idation of 3-carene

Epoxidation of (+)-3-carene with pinane hydroperoxide in presence of various transition metal catalysts, has been evaluated as a preparative method for (+)-3α,4α-epoxycarane. Catalysts based on Mo(VI) were found to be most suitable. A distinct ligand effect was noted for this oxidation and a plausible rationale is put forward.     

Thiourea,A convenient reagent for the reductive cleavage of olefin ozonolysis products

A convenient procedure for the preparation of aldehydes, in good to excellent yields, from suitable olefins by ozonolysis in methanol, followed by exposure of the resulting products to thiourea, is described.     

Steric and stereoelectronic effects in the synthesis and photoisomerization of a dinitrone of 2,2,4,4-tetramethylcyclobutanedione

Peroxyacid oxidation of diimine (1) yielded only the $\text{trans}$ isomer of dinitrone (2) which upon photoisomerization gave dioxaziridines (3a) and (3b) and amide (4) as the only isolable isomers; an X-ray crystallographic investigation of (1) shows a considerable geometry distortion.     

A study of\bar np annihilations between 0.5 and 0.8 GeV/c

A study of \(\bar np\) annihilations with \(\bar n\) momentum between 0.5 and 0.8 GeV/c is presented. The search fors-channel resonances in \(\bar np\) annihilations reveal possibly two narrow structures in the odd pions final state. Inclusiveρ ⁰ andf ⁰ cross sections in \(\bar np\) annihilations have been estimated to be 9.0±0.6 mb and 3.4±0.6 mb respectively. Longitudinal and transverse momentum distributions for inclusiveρ ⁰ production have been presented. A study of resonance production in exclusive final state revealsρ ⁰ production to be dominant in the odd pion final states andρ ⁺,ω ⁰ productions are most important for the even pion final states. Theπ ⁺ π ^? effective mass spectra in the backward and the forward directions in the \(\bar np\) c.m. system have been examined for a possible ?-ω interference effect.     

Bulk determination of uranium and thorium in presence of each other by Total Reflection X-ray Fluorescence spectrometry

A study to assess the applicability of Total Reflection X-ray Fluorescence (TXRF) spectrometry as a microanalytical technique for the determination of uranium and thorium as major elements in presence of each other has been made. Effect of dilution of the sample on the analytical results has been investigated. It has been found that dilution of the sample does not affect the analytical results significantly. Also the analytical results of uranium and thorium are similar with different internal standards e.g. cobalt, gallium and yttrium. With a sample size of 10 μL and the concentrations of the analytes in the range of 1–50 μg/mL and total matrix concentration less than 200 μg/mL, the precision and accuracy of the method were found to be better than 3% (1 s) and 4%, respectively. For higher concentration ranges of the analyte (up to about 700 μg/mL), the precision and accuracy values were better than 6% (1 s) and 5%, respectively. The TXRF method has an advantage of using small sample volume of about 10 μL, produces very small radioactive waste and is nondestructive but requires dissolution of the sample.     

Volume shrinkage and abrasive wear properties of crosslinked Poly(ester-urethane-acrylate)/MMA copolymer: Effect of chain length

The current study deals with the preparation of novel crosslink transparent poly(ester-urethane-acrylate)/methyl methacrylate (TPEUMA) copolymers and the effect of hydroxyl terminated aromatic polyester (PEs) was also investigated. The properties of TPEUMA were investigated in terms of double bond concentration, polymerization shrinkage, abrasive wear analysis and chemical resistance. The volume shrinkage decreased due to the significant reduction in the concentration of double bonds. The first two effects reflect in lowering the abrasive wear resistance properties at room temperature, while the larger chain length between crosslink decreases the hardness. Decrease in polymerization shrinkage shows more condensed microstructure which was revealed by the abrasive wear rate of TPEUMAs due to hydrogen bonding near to crosslink point. Increase in the chain length of PEs, decreases the glass transition temperature of TPEUMA copolymer which results in loose microstructure. Worn surface were studied using scanning electron microscope to give insight on the wear mechanism of TPEUMA crosslink. It can be suggested from the present study that this copolymer can be used for a broad range of optical applications.     

Studies in sesquiterpenes—LV: Isolongifolene(part 6): Mechanism of rearrangement of longifolene to isolongifolene-I

The gross mechanism of rearrangement of longifolene to isolongifolene has been elucidated by using site-specifically labelled longifolene-4, 4, 5, 5-d₄ and shown to follow the pathway proposed by Berson et al., which involves an exo, exo Me shift, in preference to the endo, endo Me migration route proposed earlier. An efficient synthesis of longifolene-4, 4, 5, 5-d₄, the key compound in the present investigation, is described.     

Organic reactions in a solid matrix-vi: Silica-gel supported reagents for the isolation of aldehydes and ketones

Semicarbazide-on silica gel and Girard-T-on-silica gel are described and evaluated as convenient reagents for efficient isolation of aldehydes and ketones from mixtures with other usual neutral organic components Semicarbazide-on-silica gel, which can be readily prepared, can effectively replace the classical Girard reagents, for the isolation of aldehydes and ketones in most cases.     

A task-specific ionic liquid [bmim]SCN for the conversion of alkyl halides to alkyl thiocyanates at room temperature

A new “task-specific” ionic liquid (TSIL), 1-n-butyl-3-methylimidazolium thiocyanate ([bmim]SCN), has been prepared and used for the first time as the medium as well as reactant for the synthesis of alkyl thiocyanates from the corresponding alkyl halides by thiocyanate-halide exchange at room temperature. The alkyl thiocyanate products can be easily isolated from the reaction mixture by simple extraction and the ionic liquid 1-n-butyl-3-methylimidazolium halide may be reused for the synthesis of the ionic liquid [bmim]SCN and recycled for further use.