Motional narrowing of the rotational spectrum of trifluoropropyne at 6550 cm(-1) by intramolecular vibrational energy redistribution

We present the basic principles of dynamic rotational spectroscopy for the highly vibrationally excited symmetric top molecule trifluoropropyne (TFP,CF3CCH). Single molecular eigenstate rotational spectra of TFP were recorded in the region of the first overtone of the nu(1) acetylenic stretching mode at 6550 cm(-1) by infrared-pulsed microwave-Fourier transform microwave triple resonance spectroscopy. The average rotational constant (B) of the highly vibrationally mixed quantum states at 6550 cm(-1) is 2909.33 MHz, a value that is 40 MHz larger than the rotational constant expected for the unperturbed C-H stretch overtone (2869.39 MHz). The average rotational constant and rotational line shape of the molecular eigenstate rotational spectra are compared to the distribution of rotational constants expected for the ensemble of normal-mode vibrational states at 6550 cm(-1) that can interact by intramolecular vibrational energy redistribution (IVR). The normal-mode population distribution at 6550 cm(-1) can be described using a Boltzmann distribution with a microcanonical temperature of 1200 K. At this energy the rotational constant distribution in the normal-mode basis set is peaked at about 2910 MHz with a width of about 230 MHz. The distribution is slightly asymmetric with a tail to the high end. The experimentally measured dynamic rotational spectra are centered at the normal-mode distribution peak; however, the spectral width is significantly narrower (40 MHz) than normal-mode ensemble width (230 MHz). This reduction of the width, along with the Lorentzian shape of the eigenstate rotational spectra when compared to the Gaussian shape of the calculated ensemble distribution, illustrates the narrowing of the spectrum due to IVR exchange. The IVR exchange rate was determined to be 120 ps, about ten times faster than the rate at which energy is redistributed from the v=2 level of the acetylenic stretch.     

Synthesis and characterization of some Schiff base transition metal complexes derived from vanillin and L(+)alanine

The cobalt(II), nickel(II), copper(II) and zinc(II)-vanillidene-L(+)alanine complexes were synthesized and characterized by elemental analysis, conductivity measurements, magnetic behavior, infrared, electronic spectral measurements, X-ray powder diffraction and biological studies. The conductance measurements indicate that all the complexes are non-electrolytes. The infrared spectra indicate the coordination of imino nitrogen, phenolic oxygen and carboxylato oxygen atoms. The electronic spectral measurements demonstrate that cobalt(II) and nickel(II)-vanillidene-L(+)alanine complexes are tetrahedral, while copper(II)-vanillidene-L(+)alanine complex has square planar geometry. The cobalt(II) complex is found to be ferromagnetic. The powder XRD studies confirm the crystalline nature of the complexes. The ligand and complexes were less active against PN, PA and BC, whereas copper complex shows moderate activity against AN.     

A biamperometric method for the determination of sulfate

A biamperometric method for the determination of sulfate has been developed. Its application to the determination of sulfate content in rubidium uranium trisulfate is discussed. Sulfate is determined by titration with lead nitrate in aqueous ethanolic medium using ferrocyanide-ferricyanide redox system as biamperometric indicator. Initially, the method has been tested for standard. K₂SO₄ solutions. In case of Rb₂ U(SO₄)₃, since uranium interferes, it is precipitated as ammonium diuranate and excess ammonia is removed prior to the titration. Precision of better than 0.3% was achieved with no significant bias.     

Electric dipole moment of the diatomic tif in its higher vibrational states

The electric dipole moment of ²⁰⁵Tl¹⁹F has been measured in its higher vibrational states up to ν = 7 by studying the Statk effect in the J = O → 1 rotational transitions. The variation of the electric dipole moment with vibrational states is discussed. The electric dipole moment can be written as lμ_νl = 4.1941 (15) + 0.0681(12) (ν + $\text{1}\text{2}$) D.     

Rotational spectrum and molecular constants of the diatomic GaCl in its electronic ground state1ε+

At wavelengths near 1 mm six rotational transitions of GaCl have been observed. The analysis including previous measurements on the rotational transitionJ = 1 ← 0 resulted in extended sets of the Dunham parametersY ₀₁,Y ₁₁,Y ₂₁,Y ₃₁,Y ₀₂,Y ₁₂ andY ₀₃ of the four isotopic species⁶⁹Ga³⁵Cl,⁷¹Ga³⁵Cl,⁶⁹Ga³⁷Cl and⁷¹Ga³⁷Cl. With these microwave data the constantsY ₁₀ ≈ ε_e and —Y ₂₀ ≈ ω _e x _e were determined. The parameters of the Dunham potentiala ₀,a ₁,a ₂,a ₃ andr _e are given. The GaCl was produced by reaction of gaseous CCl₄ with Ga evaporated at 1,500°C.     

Determination of nitrate in thorium,uranium and plutonium solutions

A potentiometric titration method and a conductometric titration method were standardized for the determination of nitrate in thorium, uranium and plutonium solutions in the range of 2–10 mg, and 15–30 mg, respectively, with a precision and accuracy of 2% in both cases. The results were compared with those of other methods like Devarda's alloy reduction method and volumetric titration method. The procedures standardized have been recommended for the determination of nitrate in heavy element solutions used for the preparation of oxide and mixed oxide microspheres by the sol-gel technique.     

Uncatalyzed chemical oscillations in the aqueous acidic bromate oxidation of veratraldehyde

Oscillatory behavior in the uncatalyzed aqueous acidic bromate oxidation of 3,4-dimethoxybenzaldehyde (veratraldehyde) is reported. The generally used H₂SO₄ can be substituted by HNO₃, HClO₄, CCl₃ COOH and H₃PO₄ in this system. The length of the induction period is found to be dependent on the initial concentrations of the reagents and this effect is more prominent in the case of acidity. The precipitate accumulated in the reaction during oscillations has been identified. A plausible mechanism is also suggested. Experiments with allyl alcohol, a bromine scavenger, suggest that elemental bromine formed in the reaction has a role in the mechanism together with or besides bromide inons.

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3,4- () . H₂SO₄ HNO₃, HClO₄, CCl₃ COOH H₃PO₄ . . , , . . , , , , , .

     

Thermal Decomposition Kinetics of Lanthanum Complexes of 1,2-(Diimino-4'-Antipyrinyl)ethane

The kinetics and mechanism of the thermal decomposition of perchlorate, nitrate and iodide complexes of lanthanum with the Schiff base 1,2-(diimino-4'-antipyrinyl)ethane (abbreviated as GA) have been studied by TG and DTG techniques. The kinetic parameters like the activation energy, the pre-exponential factor and the entropy of activation were calculated for the major decomposition stages (Stages I and II) using Coats-Redfern equation. The rate controlling process obey ‘Mampel model’ with random nucleation with one nucleus on each particle. The kinetic parameters indicate that the ligands are loosely bound to metal ion and the activated complex formed in the decomposition reaction is more ordered than the reactants. This revised version was published online in July 2006 with corrections to the Cover Date.     

The reaction of 1-azirines with 2-pyridyl isothiocyanate: Possible approaches to benzodiazepine and benzodiazepine derivatives

The structure of the dimer ( 5 ) from 2-pyridyl isothiocyanate ( 1 ) has been confirmed by ¹³C nmr spectral studies. The cycloaddition of 2-pyridyl isothiocyanate with 1-azirines results in the formation of thiazoles ( 10 ). Thermal decomposition of the vinyl azide ( 14 ) gives the pyrrole ( 15 ) and the pyridazine ( 16 ) instead of 2-(2-pyridyl)-1-azirine ( 12 ).     

Determination of plutonium and uranium in the same aliquot by potentiometric titration

A potentiometric titration method was developed for the determination of plutonium and uranium in the same aliquot in nitric acid medium. Plutonium was first determined by oxidation to Pu/VI/ by fuming with conc. HClO₄. Pu/VI/ formed was reduced to Pu/IV/ with known excess of Fe/II/ and the excess Fe/II/ was titrated with standard K₂Cr₂O₇ to a potentiometric end point. Uranium in the same solution was determined by reduction to U/IV/ with Fe/II/ in conc. H₃PO₄ medium and titrating U/IV/ formed with standard K₂Cr₂O₇ using the potentiometric end point detection technique. For the quantity of plutonium and uranium each in the range of 3–5 mg per aliquot a precision of ±0.2% and ±0.4%, respectively, was obtained.