Propargyloxycarbonyl (Poc) amino acid chlorides as efficient coupling reagents for the synthesis of 100% diastereopure peptides and resin bound tetrathiomolybdate as an effective deblocking agent for the Poc group

Synthesis of short peptides using propargyloxycarbonyl amino acid chlorides as effective coupling reagents and polymer supported tetrathiomolybdate as an efficient deblocking agent are reported.     

Ratio of jet cross sections at square root of s = 630 GeV and 1800 GeV

The D0 Collaboration has measured the inclusive jet cross section in barpp collisions at square root of s = 630 GeV. The results for pseudorapidities (eta)<0.5 are combined with our previous results at square root of s = 1800 GeV to form a ratio of cross sections with smaller uncertainties than either individual measurement. Next-to-leading-order QCD predictions show excellent agreement with the measurement at 630 GeV; agreement is also satisfactory for the ratio. Specifically, despite a 10% to 15% difference in the absolute magnitude, the dependence of the ratio on jet transverse momentum is very similar for data and theory.     

Spin probe ESR studies of PEGxLiClO4 polymer electrolyte systems

The technique of Electron Spin Resonance (ESR) is shown to be useful in the study of dynamics of solid polymer electrolytes (SPE). Through the ESR of the nitroxide radical (2,2,6,6-tetramethyl-1-piperidine-1-oxyl; TEMPO) dispersed in the SPE PEG₄₆LiClO₄ temperature dependence of correlation time is found. The glass transition temperature T_g is estimated to be −51 °C from the measurement of T_50G, the temperature at which the extrema separation 2A_ZZ becomes 50G and is found to be close to that measured using DSC (−51.7 °C). T_g for pure PEG-2000, which could not be measured from DSC because of its high crystallinity, is determined to be −72 °C by spin probe ESR. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.     

Study of bonding in some nickel complexes of isonitrosoketones

X-ray K-absorption edge analysis of nickel in some nickel complexes of isonitrosoketones has been carried out using a 400-mm bent crystal spectrometer. The analysis has been used to deduce information regarding the mode of bonding, the magnetic behaviour and the coordination of Ni in the complexes. On the basis of the results obtained, it has been concluded that Ni ions in Ni(HMAO)₂; have square planar structure whereas Ni ions in Ni(HTGA)₂ have tetrahedral structure. On the other hand Ni ions in Ni(EINA)₂; and Ni(INACA)₂, are surrounded by octahedra. Ni ions in Ni(INACA)₂ are in the valence state higher than two and appear to be paramagnetic.     

Mechanism of positive iodine reactions: Kinetics of oxidation of semicarbazide by iodamine-T, iodine monochloride and iodine

Kinetics of oxidation of semicarbazide (SC) by iodamine-T (IAT), iodine monochloride and aqueous iodine has been studied in aqueous perchloric acid medium. The rate laws followed by the oxidation of SC were determined. The rates decreased slightly with increase in ionic strength of the medium in IAT and ICI oxidations, while the reverse trend was observed with I₂. Decrease in dielectric constant of the medium increased the rates with IAT and ICI, while it decreased the rate in I₂ oxidations. Addition of the reduced product,p-toluene-sulphonamide had no effect on the rate with IAT. Addition of I⁻ had slight negative and positive effects on the rates of oxidations with IAT and ICI, respectively, but the negative effect was considerable in I₂ oxidations. Mechanisms consistent with the observed rate laws have been proposed and discussed. Rate determining steps have been identified and their coefficients calculated. These constants were used to predict the rate constants from the deduced rate laws as [SC], [H⁺] and [I⁻] varied. Reasonable agreement between the calculated constants and experimental values provide support for the suggested mechanisms.     

Spectrophotometric studies of 6-methyl pyridine-2-aldoxime-iron (II) complex

6-Methyl pyridine-2-aldoxime produces with iron (II) solution a deep red complex soluble in 50% (by volume) aqueous acetone. The complex is stable at 10–45°C. and its colour intensity does not vary between pH 7·3 and 10·0. The complex obeys Lambert-Beer’s law at 520 mµ in the concentration range of 1·12 to 28·0 p.p.m. of iron.