The reactivity of the A-CH=N-NR-CX-B system. 1,3,4-Oxadiazoles and 2,3,4,5-tetrahydro-1,2,4-triazin-3-ones through the 1–5 and 1–6 cyclization reactions of α-thienylglyoxal monosemicarbazones

The factors influencing the reactivity of α-thienylglyoxal monosemicarbazones when treated with cyclizing reagents (bromine/sodium acetate and hydrobromic acid in acetic acid) were investigated. Depending on the experimental conditions, on the position of the substituent on the semicarbazide residue, and on the cyclizing agent, the substrates 1a-e give the semicarbazone bromides 2a-b, 5 , the 1,3,4-oxadiazoles 3a-c , the 1,2,4-triazine 11 and the 2,3,4,5-tetrahydro-1,2,4-triazine-3-ones 6, 8 and 9 . Compound 6 by thermolysis undergoes ring contraction in the Δ²-1,3,4-oxadiazoline 12 , while treatment with base involves the conversion of 6 into 1,2,4-triazol-5-one 13 . Ir, nmr and mass spectra support the reported structures.     

The use of “actinometer” gases in optical diagnostics of plasma etching mixtures: SF6-O2

The spectroscopic emission intensities from excited F atoms in SF₆-O₂ discharges at 1 torr have been correlated to the densities of atoms in their ground electronic state by measuring the excitation efficiencies of the electrons in the energy range 11 to 17 eV with a method which essentially consists in the analysis of the emission of Ar or N₂, added as actinometer gases to the discharge mixtures. The general applicability of the method has been tested by a direct titration of F atoms with chlorine. The spectroscopic analysis has allowed the determination of useful information on the trends of both the electron densities and their energies as a function of the oxygen percent in the feed.     

NMR stereospecific long-range coupling and preferred conformations in some (E)- and (Z)-α-phenyl-β-[2-(N-methyl)nitropyrrolyl] acrylic acids

NMR data have been used to assign the stereochemistry to some new (E)- and (Z)-α-phenyl-β-[2-(N-methyl)nitropyrrolyl]acrylic acids. The (E)-molecules are biased in the s-cis conformation showing NMR spectroscopic features strictly depending on the conformation.The analysis of the NMR spectra reveals that the (Z)-isomers exist also in the s-cis conformation.     

Derivative-free methods for mixed-integer nonsmooth constrained optimization

Computational Optimization and Applications - In this paper, mixed-integer nonsmooth constrained optimization problems are considered, where objective/constraint functions are available only as the...     

The CuII−CuI−Cu0(Hg) system in the presence of benzotriazole: Part II. A chronocoulometric investigation

Both the oxidation of Cu⁰ at dropping amalgam electrodes immersed in solutions of benzotriazole (BTA) and the reduction of Cu^II at a dropping mercury electrode from BTA solutions have been investigated by the single potential-step chronocoulometric technique. The dependence of the charge Q(t) flowing as a consequence of a given potential jump E_i→E_f upon the initial and final potentials E_i and E_f, as well as upon the time t elapsed from the instant of the potential jump provides direct evidence for the presence of a single adsorbed monolayer of a Cu^I compound on a mercury electrode immersed in a Cu^II solution containing BTA, at applied potentials positive to ≈?0.4 V/SCE. Analogous measurements carried out at dropping amalgam electrodes reveal the presence of a single adsorbed monolayer of a Cu^I compound, or else of an adsorbed multilayer, depending on the potential range investigated. The results of the chronocoulometric measurements are in agreement with those of the polarographic measurements of Part I.     

Zinc(II), cadmium(II) and mercury(II) halide pyrrolidine-2-thione complexes

Summary White crystalline complexes of general formula ML₂X₂, where M = Zn, Cd, Hg; X = Cl, 13r, I and L = pyrrolidine-2-thione, were prepared and studied by i.r. spectroscopy in the 4000-200 cm^–1 range. Evidence for coordination of the ligand to the metal through sulphur was found in each case. The previous assignment of the band present in the ligand at 1110 cm^–1 to the(CS) fundamental is discussed.This work was supported by the National Research Council (C.N.R.) of Italy.     

An infrared spectroscopic investigation on N-methyl-1,3-thiazolidine-2-thione and -2-selone

An infrared investigation cm N-methyl-1,3-thiazolidine-2-thione and -2-selone in the range 4000-200 cm^?1 is reported. The v CS and v CSe vibrations give contributions to the absorptions around 1000 cm^?1 and below 600 cm^?1. The assignments are supported by comparison of their ir spectra with those of S- and Se-methiodides. The π-bond orders of the thio- and seleno-ketonic links in these compounds are higher than those found for 1,3-imidazolidine-2-thione and -2-selone.