Syntheses and reactions of terpene β-hydroxyselenides and β-hydroxydiselenides

A convenient method for the synthesis of optically active trans-hydroxyselenides and trans-hydroxydiselenides from the bicyclic terpene group based on the reactions of sodium selenide or sodium diselenide with cis- and trans-(+)-3-carane, trans-(+)-2-carane and (?)-β-pinane epoxides is described. The corresponding cis-hydroxy and cis-methoxydiselenides were obtained in the reaction of sodium diselenide with β-hydroxy- and β-methoxytosylates. The influence of a hydroxy group at the β-position on the diastereomeric ratio of the products of the asymmetric methoxyselenenylation of styrene has been established by composition of the products, crystal structure analyses, and theoretical calculations using a DFT method on the B3LYP level (6-311G(d)).     

Guest Editor's Note: Clifford Algebras and Their Applications

The history and immediate future of the International Conferences on Clifford Algebras and Their Applications. Seven topical sessions in Ixtapa. Dirac operator: cross relations. Polemic guide: signature change, quasigroups, pseudotwistors. Clifford cogebra, coconnection and Dirac operator for Clifford cogebra.     

New Schiff base complexes of ruthenium(III) and their use as catalysts for O-allyl systems isomerization

Seven new ruthenium(III) complexes of the general formula [RuCl(PPh₃)LL′] · xH₂O (LL′ = [ONNO] = symmetrical and unsymmetrical Schiff base derivatives of trans-1,2-diaminocyclohexane and 2-hydroxynaphthaldehyde as well as R-salicylaldehydes, x = 0–3) have been synthesized. The complexes were characterized by physico-chemical and spectroscopic techniques. The catalytic activities of the complexes in the isomerization reaction of selected O-allyl systems, i.e., 1,4-diallyloxybutane and 4-allyloxybutan-1-ol have been studied. Some of the complexes showed high efficiency and E-stereoselectivity in double bond migration of allyl group to 1-propenyl group and high selectivity of isomerization of allyloxyalcohol to cyclic acetal.     

Decompositions of graphs into trees

Let θ be a family of graphs. By a θ-decomposition of a graph G we mean a partition λ of the edge set of G such that every F ? π spans in G a subgraph isomorphic to a graph in θ. In this paper we state the following conjecture: If T₁ and T₂ are two trees having relatively prime sizes then there exists c = c(T₁ T₂) such that every graph G satisfying the condition δ(G) ? c has a {T₁, T₂}-decom-position. We prove this conjecture for some special pairs of trees. In particular, we prove it in the following cases: (i) T₁ and T₂ are stars having relatively prime sizes; (ii) T₁ and T₂ are paths having relatively prime sizes; and. (iii) T₁ = T₂ - {v}, where v is a terminal vertex in T ₂.     

The kinetics of successive addition of oxirane to alkanethiols in the presence of basic catalysts

Rate constants and activation parameters of direct reaction of oxirane with certain alkyl-2-hydroxyethyl sulfides and/or successive oxyethylene adducts in the presence of basic catalyst were studied at temperatures 323–353 K. The reactions were found to be of the first order with respect to oxirane, sulfide, and catalyst concentrations. The kinetics are consistent with a termolecular mechanism.     

Undirected simple connected graphs with minimum number of spanning trees

We show that for positive integers n, m with n(n−1)/2≥m≥n−1, the graph L_n,m having n vertices and m edges that consists of an (n−k)-clique and k−1 vertices of degree 1 has the fewest spanning trees among all connected graphs on n vertices and m edges. This proves Boesch’s conjecture [F.T. Boesch, A. Satyanarayana, C.L. Suffel, Least reliable networks and reliability domination, IEEE Trans. Commun. 38 (1990) 2004-2009].     

The design, synthesis, and application of a chiral coupling reagent derived from strychnine for the enantioselective activation of a carboxylic group

The concept of a chiral coupling reagent for the enantioselective synthesis of peptides with a predictable configuration and enantiomeric purity from racemic substrates is presented. The reagent was prepared by treatment of strychninium tetrafluoroborate with 2-chloro-4,6-dimethoxy-1,3,5-triazine in the presence of sodium bicarbonate yielding N-(4,6-dimethoxy-1,3,5-triazin-2-yl)strychninium tetrafluoroborate in high yield, which is stable at room temperature, and in a broad range of solvents gave enriched Z-Ala-Phe-OMe (dr from 95/5 to 60/40) in high yield with d-configuration on the alanine residue starting from rac-Z-Ala-OH.     

Identification of acrylate copolymers using pyrolysis and gas chromatography

A combination of pyrolysis and gas chromatography were used to investigate thermal degradation products formed from acrylic copolymers containing alkyl acrylate and methacrylate. The method provided an analytical tool for characterizing the chemical composition and structure of the degradation products. Thermal degradation of the synthesized copolymers was analyzed using isothermal (250 °C) pyrolysis–gas chromatography. The degradation process, and the nature and amount of pyrolysis products, provides relevant information about the thermal degradation of acrylic copolymers and the mechanism of pyrolysis. During pyrolysis, the formation of corresponding olefins, alcohols, acrylates and methacrylate was observed.     

Time-resolved spectroscopic measurements of shock-wave induced decomposition in cyclotrimethylene trinitramine (RDX) crystals: anisotropic response

Plate impact experiments on the (210), (100), and (111) planes were performed to examine the role of crystalline anisotropy on the shock-induced decomposition of cyclotrimethylenetrinitramine (RDX) crystals. Time-resolved emission spectroscopy was used to probe the decomposition of single crystals shocked to peak stresses ranging between 7 and 20 GPa. Emission produced by decomposition intermediates was analyzed in terms of induction time to emission, emission intensity, and the emission spectra shapes as a function of stress and time. Utilizing these features, we found that the shock-induced decomposition of RDX crystals exhibits considerable anisotropy. Crystals shocked on the (210) and (100) planes were more sensitive to decomposition than crystals shocked on the (111) plane. The possible sources of the observed anisotropy are discussed with regard to the inelastic deformation mechanisms of shocked RDX. Our results suggest that, despite the anisotropy observed for shock initiation, decomposition pathways for all three orientations are similar.