3-Mercaptopropionic acid-nitrile imine adducts. An unprecedented cyclization into 1,3,4-thiadiazol-2(3H)-ones and -2(3H)-thiones

3-Mercaptopropionic acid-nitrile imine acyclic adducts (6a-c) undergo cyclocondensation with 1,1'-carbonyldiimidazole to afford the respective 1,3,4-thiadiazol-2-(3H)-ones (7a-c). Corresponding 1,3,4-thiadiazol-2(3H)-thiones (8a-c) were likewise produced from 6a-cand 1,1'-thiocarbonyldiimidazole, with consequent elimination of the propionate moiety. The constitution of these heterocyclic products follows from analytical and spectral data and is confirmed by single crystal X-ray structure determination for 7b.     

Spectrographic investigation of neodymium malates in aqueous solutions

Conclusions Using high-resolution spectrography the authors have investigated the neodymium chloride-malic acid system in aqueous solution at pH 2.0–8.0.They have determined the composition and calculated the stability constants of the complexes NdMal⁺ and NdMal₂ ^–.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1474–1477, July, 1980.     

Photolysis of xylylbischromones

Photoreorganisation of xylylbischromones occurring through 1,4-biradical is described. In these bischromones, the two chromophores have been found to behave independently.     

Track effects in luminescence of LiF during 1 MeV/amu heavy ion irradiation

Luminescence spectra from pure LiF generated with high-energy heavy ions were studied in dependence on exciting density and irradiation temperature.     

Electrical investigations in the normal and incommensurate phases of [N(CH3)4]2ZnCl4 single crystals

The dielectric permittivity (?) of TMA-ZC single crystals was measured along the mean crystallographic axes a, b and c, in a temperature range from 273 to 340 K. The ?-T relationship exhibited peak values at T_i=296 K and T_c1=279 K for the three axes. These peaks are attributed to the contribution of discommensurations. The d.c. and a.c. electrical conductivity showed anomalous variation at the same transition temperatures, with a remarkable change in the value of the activation energy around the transition temperatures. The j-E characteristic indicates different types of electrical conduction. The mechanism of the phase transition and the electrical process were discussed on the basis of Shottky and Frenkel conduction mechanisms.     

Attempted polymerization of substituted pipecolic acid NCA's: Dimerization and mechanism

Racemic and optically active N-carboxyanhydrides (NCA)s of 2-methyl- and cis-6-methylpipecolic acid, when subjected to polymerization conditions in solution or in bulk whether with “weak” or “strong” base initiators, resisted polymerization under all conditions tried. Instead, the NCA of 2-methylpipecolic acid gave the corresponding cyclic dipeptide and the NCA of cis-6-methylpipecolic acid formed the cyclic dipeptide derived from trans-6-methylpipecolic acid. The mechanism of dimerization of these NCA's was investigated. Evidence was provided for the proposed mechanism in which the active moiety is not a carbamate ion but an amino group. Methyl 2-methylpipecolate underwent an intermolecular S_N2-type reaction upon heating, yielding equimolar quantities of methyl N-methyl-2-methylpipecolate and 2-methylpipecolic acid.     

Normal sulphites of metals

Summary Normal sulphites of metals were prepared by the reaction of metal salts with sodium metabisulphite, in aqueous acid solutions, to prevent the formation of basic sulphites. Visible spectra and magnetic moments show that the transition metal sulphites have distorted octahedral structures. The i.r. spectra showed that the sulphite groups act as O-bonded bridging ligands linking the metal atoms in polymeric chains.