Kinetic and mechanistic studies of the reaction of a range of bases and metal-hydroxo complexes with the phosphonate ester 2,4-dinitrophenyl ethyl methylphosphonate in aqueous solution

The base hydrolysis and spontaneous water hydrolysis of the phosphonate ester 2,4-dinitrophenyl ethyl methylphosphonate (DNPEMP) has been studied in detail and the activation parameters for these processes determined. The catalytic effect of a series of 19 oxygen and nitrogen bases and metal hydroxo complexes has been studied. The Brønsted plot of pK versus logkN has a slope (β) of 0.47, which is fairly typical for phosphate and phosphonate esters. alpha-Effect nucleophiles such as 2-iodosobenzoate, hypochlorite and the hydroperoxide ion (HO-2) exhibit enhanced reactivity, as does fluoride ion and the bifunctional metal complex [Cu(tmen) (OH2)(OH)]+ (tmen = N,N,N',N',-tetramethylethylenediamine). Reactions involving these species appear to take place by a nucleophilic pathway, while the other oxygen and nitrogen bases act as general base catalysts. The solvent deuterium isotope effect for Et3N catalysis, kH2O/kD2O=1.3, is consistent with general base catalysis. The mechanisms of these reactions are discussed in detail.     

希夫碱配合物的研究——Ⅵ.K[Fe(acaccn)(CN)2]·2H2O的合成及晶体结构

制备了K[Fe(acaccn)(CN)₂]·2H₂O.并测定了晶体结构.     

Synthesis and antiallergy activity of [1,3,4]thiadiazolo[3,2-a]-1,2,3-triazolo[4,5-d]pyrimidin-9(3H)-one derivatives. II. 6-Alkyl- and 6-cycloalkylalkyl derivatives.

A series of 6-alkyl- or 6-(cycloalkylalkyl)-[1,3,4]thiadiazolo[3,2- a]-1,2,3-triazolo[4,5-d]pyrimidin-9(3H)-ones 1b--o was synthesized from the corresponding 1,3,4-thiadiazol-5-amines 3b--o and the antiallergic activities of the products were evaluated. Among the compounds 6-(2-cyclohexylethyl)- [1,3,4]thiadiazolo[3,2-a]-1,2,3-triazolo[4,5-d]pyrimidin-9(3H)-one 1h, whose X-ray crystallographic stereostructure is shown, was found to be a promising new antiallergic agent, which has low toxicity and dual activity as a leukotriene D4 receptor antagonist and as an orally active mast cell stabilizer.     

The separation of palladium and platinum by ion flotation

Differences in the ion flotation properties of palladium(II) and platinum(IV) chloro complexes in aqueous solutions are used to achieve separations of these metals. The anionic chloro complex PtCl^2-₆ is floated selectively with cationic surfactants of the type, RNR'₃Br, from solutions of PdCl^2-₄ and various concentrations of hydrochloric acid. The palladium(II) does not float from solutions of ? 3.0 M HCl and the platinum(IV) floated from these solutions can be recovered free of palladium. However, the separation is incomplete as much of the platinum(IV) is also unfloated from these solutions. Quantitative separations are obtained by conversion of the palladium(II) to the cationic ammine, Pd(NH₃)₄²⁺ with aqueous ammonia prior to flotation. The anionic chloro complex of platinum(IV) is unaffected by the presence of ammonia and is floated quantitatively with the surfactant n-hexadecyltri-n-propylammonium bromide from 0.01 M ammonia solutions.     

Radiation degradation of copolymers of methyl methacrylate and 3-oximino-2-butanone methacrylate

Copolymers of methyl methacrylate and 3-oximino-2-butanone methacrylate (OM) were investigated as deep-UV and e-beam resists. Their increased sensitivity relative to PMMA (up to 50 times) was correlated with the radiation chemical yields of the volatile products and main chain scissions. The degradation of these copolymers, activated by the 3-oximino-2-butanone entity, is discussed in terms of energy absorption mechanisms and the subsequent scission reactions.     

Stereoselective diels-alder reactions between 9-alkyl-1,4-dihydronaphthalen-1,4-imines and 2-alkylisoindoles

The Diels-Alder reaction between 9-alkyl-1,4-dihydronaphthalen-1,4-imines ($\text{1}$) and 2-alkylisoindoles ($\text{2}$) occurs in refluxing xylene to give exclusively the exo-endo cyclo-adducts $\text{3}$ ($\text{D}$).     

Schnelle Photometrie komplizierter biochemischer Mehrkomponentensysteme

Zusammenfassung Eine Übersicht über die schnelle photometrische Analyse komplizierter biochemischer Mehrkomponentensysteme wird gegeben. Zunächst werden apparative Probleme und Meßbedingungen behandelt. Anschließend werden die Auswertverfahren für Mehrstoffsysteme in homogener Lösung (multiplikative Farbmischung) und für solche mit inhomogener Verteilung (additive Farbmischung) beschrieben. Als praktische Anwendungsbeispiele dienen die Analyse von Nucleotidsummenspektren und Meerschweinchengehirnreflexionspektren sowie die Bestimmung des Oxigenierungsgrades von Hämoglobin.

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Rapid photometry of complicated biochemical multi-component systems

After discussing general problems concerning apparatus and measuring conditions the analysis of multi-component systems in homogeneous solutions (multiplicative colour mixture) and of those with inhomogeneous distribution (additive colour mixture) is described. Analysis of nucleotides and guinea pig brain and determination of the degree of oxygenation of haemoglobin are presented as examples.

     

Effects of H2O and D2O on polyproline II helical structure

The interaction of solvent with a polypeptide chain is one of the primary factors controlling protein folding and stability. In biologically relevant systems, this solvent is most often water. Experimental estimates of the role of water in peptide folding can be obtained from solvent perturbation experiments. The simplest perturbant for H2O water is its isotopic D2O form. The solvation of peptides known to form PII helices with D2O versus H2O increases their propensity to adopt the PII conformation.     

Observation of an unprecedented Cu Bis-His site: crystal structure of the H129V mutant of nitrite reductase

Copper nitrite reductases contain both an electron-transfer type 1 Cu site and a catalytic type 2 Cu site. We have mutated one of the type 2 copper ligating histidines to observe the effect on catalytic turnover. This mutation has created a unique site where Cu is ligated by 2 His Nepsilon2 atoms alone.     

The synthesis of dicationic extended bis-benzimidazoles

The synthesis of extended dicationic bis-benzimidazoles starting from trans-1,2-bis(4-cyanophenyl)ethene and trans-1,2-bis(4-cyanophenyl)cyclopropane is reported. The target diamidines show significant in vitro activity against B. subtilis.