An infrared spectroscopic study of the reaction of alcohols and their decomposition products with yttrium oxide

This paper describes an infrared spectroscopic study of the adsorption of methanol, ethanol, acetaldehyde, ethylene, and water on two samples of yttrium oxide, one of which had dehydrating properties and the other, dehydrogenating properties. The occurrence of different surface compounds during the dehydration and dehydrogenation of alcohols is shown. Possible mechanisms for the decomposition of alcohols are discussed.     

A thermodynamic study of the complexation reaction for some amino acids with cerium(III) and yttrium(III)

The thermodynamic parameters for the complexation reaction of leucine, valine, proline and hydroxyproline with cerium(III) and yttrium(III) were determined potentiometrical1y in aqueous solution at 25, 35 °C and μ=0.1. The values for the formation constants have been reported. The values of enthalpy changes (ΔS) and entropy changes (ΔS) are positive for all systems. The chelation effect is believed to be essentially an entropy effect.     

Molecular structure of a series of epoxysulfolanes and products of their reaction with sodium azide

A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Science Center, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 33, No. 1, pp. 145–150, January–February, 1992.     

Synthetic, self-assembly ABCD nanoparticles; a structural paradigm for viable synthetic non-viral vectors

Gene therapy research is still in trouble owing to a paucity of acceptable vector systems to deliver nucleic acids to patients for therapy. Viral vectors are efficient but may be too dangerous. Synthetic non-viral vectors are inherently safer but are currently not efficient enough to be clinically viable. The solution for gene therapy lies with improved synthetic non-viral vectors systems. This review is focused on synthetic cationic liposome/micelle-based non-viral vector systems and is a critical review written to illustrate the increasing importance of chemistry in gene therapy research. This review should be of primary interest to synthetic chemists and biomedical researchers keen to appreciate emerging technologies, but also to biological scientists who remain to be convinced about the relevance of chemistry to biology.     

Synthetic, spectroscopic and structural studies of two novel phosphanyl(organyl)borane compounds

The titanium (II) complex, Cp₂Ti(HBcat)₂, catalyzes the hydroboration of diphenylvinylphosphine by catecholborane and pinacolborane to afford exclusive anti-Markovnikov phosphanyl(organyl)boranes cleanly, rapidly and in good yields. Spectroscopic and X-ray studies of the phosphanyl(organyl)borane products show no evidence of boron-phosphorus interaction, indicating that the compounds preclude formation of Lewis pairs.     

15N NMR studies of amino acids and their reaction products with formaldehyde

Natural abundance ¹⁵N NMR spectroscopy has been used to investigate the effect of pH on the ¹⁵N chemical shifts of lysine and of ε-hydroxymethyllysine. A computer calcualtion which fits the chemical shifts of both α-and ε-nitrogen atoms versus pH has been used to predict the pK_a values. ¹⁵N chemical shifts and some ¹J(¹⁵NH) values of some other amino acids and of their reaction products with formaldehyde are also reported.     

Surface evaluation and electrochemical behavior of cerium conversion coating modified with silane on magnesium alloy

A new cerium conversion coating modified with the hydrolysis silane is designed for AZ31 magnesium alloy, which aims at assessing the surface characterizations and electrochemical behaviors between the cerium conversion coating with and without the silane modified. The effect of the silane addictive is studied by scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The adhesion of the coatings is undertaken according to the American Society for Testing and Materials (ASTM) standard D3359‐08 cross tape test. The electrochemical behavior is evacuated by polarization experiment and electrochemical impedance spectroscopy (EIS) in NaCl electrolyte. The results show that the addition of bis‐[triethoxysilylpropyl] tetrasulfide (BTESPT) to loosen and porous cerium conversion coating leads to the formation of a more compact and homogenous film, higher resistance to water uptake and better adhesion to substrate. Electrochemical measurements show that, compared with the non‐modified cerium conversion coating, the coating modified with the silane exhibits better anticorrosion properties. Copyright © 2014 John Wiley & Sons, Ltd.     

氧翁化合物的结构测定及其与稳定化磷叶立德的反应

氧翁化合物与稳定化磷叶立德反应得到α,β-不饱和羰基化合物Z/E比依赖于氧翁化合物的取代基,讨论了它们的可能机理.     

Reactions of sulfoxonium allylides with nitrile oxides and ring transformations of their reaction products

Reactions of allylides ($\text{1}$) with nitrile oxides ($\text{2}$) afforded furanylglyoxylate oxime ($\text{3}$) and 6H-l,2-oxazine ($\text{4}$). Ring transformations of $\text{3}$ and $\text{4}$ gave $\text{4}$ and pyrrolinone ($\text{6}$), respectively.     

Diffusion-controlled reaction on a sink with two active sites

We have presented an exact solution for the problem of diffusive binding to a spherical macromolecule with two axially symmetric active patches. A highly accurate approximate formula for an effective steric factor has been suggested. This model solution may serve as a benchmark for further studies of diffusive interaction in more realistic models of anisotropic reactivity.     

Impact of reaction products on the Grignard reaction with silanes and ketones

Grignard reactions with alkoxysilanes or carbonyl compounds produce alkoxymagnesium halides as by-products. Kinetic measurements for reactions of silanes and of a ketone were performed with Grignard reagents, enriched in alkoxymagnesium halides and taken in a great excess.The alkoxide-type reaction products complex tightly with Grignard reagents and enhance in this way their nucleophilicity, thus accelerating the reaction. However, alkoxides branched at α-C atom exert an unfavorable steric hindrance to reaction resulting in a decrease in the reaction rate.     

Synthesis, structural characterization, and transmetalation reactions of a tetranuclear magnesium silsesquioxane complex

The reaction of a silsesquioxane trisilanol with methylmagnesium chloride leads to an unprecedented tetranuclear magnesium silsesquioxane complex 1 in high yield. The crystal structure shows an unusually short Mg-Cl bond, indicative of an electron-deficient magnesium atom; 1 has been used as transmetalation agent for the synthesis of metal silsesquioxane complexes. Transmetalation activity was low, but can easily be followed by multinuclear NMR. Crystal data for 1: C(78)H(142)Cl(2)Mg(4)O(26)Si(14).6(C(4)H(8)O), a = 15.744(1) A, b = 26.526(2) A, c = 16.917(1) A, beta = 113.229(2) degrees, monoclinic, P2(1)/n, Z = 2.     

Silylcuprates from allene and their reaction with alpha,beta-unsaturatedd nitriles and imines. Synthesis of silylated oxo compounds leading to cyclopentane and cycloheptane ring formation

The silylcupration of allenes and the subsequent capture of the intermediate cuprate with alpha,beta-unsaturated nitriles is reported. The influence of the substitution of the nitrile, the nature of the silylcopper species, and the temperature on the selectivity of the reaction is studied. An interesting diaddition process was observed (1,2-addition and 1,4-addition), leading to oxo compounds which simultaneously have an allylsilane and a vinylsilane group. The different reactivity of these two units has been employed in the intramolecular allylsilane-terminated cyclization of these adducts, where the vinylsilane moiety remains unchanged. To shed some light on the reaction pathway, the behavior of alpha,beta-unsaturatedd imines was also checked and a new and convenient way for cycloheptane annulation presented. In light of the former results a feasible mechanism is proposed.     

Studies on the reaction of aziridines with nitriles and carbonyls: synthesis of imidazolines and oxazolidines

Reaction of N-tosylaziridines with nitriles and carbonyls to produce imidazolines and oxazolidines has been studied in the presence of a variety of Lewis acids. The reaction is efficient with 1 equiv of BF3.Et2O or Et3OBF4 in CH2Cl2. However, it is catalytic with metal triflates that give the best results for cycloaddition of N-tosylaziridine with nitriles under solvent free conditions. The same reaction with carbonyls proceeds best in CH2Cl2 in the presence of molecular sieves. Among various triflates, Zn(OTf)2 has been found to be the best. The cleavage of the N-Ts bond of the cyclized products has been studied in order to make it more versatile in synthesis. The mechanistic aspect of the reaction has been studied by using chiral aziridines as substrates. These formal [3+2] cycloaddition reactions of aziridines with nitriles and carbonyls proceed in a Ritter fashion.     

New synthetic approach to yttrium hydroxoacetates, structural characterization, and use as a precursor for coated conductors

A novel synthetic approach is given for the preparation of a metal-organic lanthanide sol-gel precursor solution and its application for the production of coated conductors. Besides all other problems concerning the technical process itself, the key to a successful deposition of oxide layers is the choice of the precursor solution and the understanding of the mechanism of deposition. Moreover, the isolation and characterization of the species involved in the reaction is very important. Regarding the complex process occurring during the formation of the surface layer, it is obvious that the best choice should have a compound already containing the final composition of the layer. Two compounds of composition [Y(OAc)3(H2O)2]2 and [Y(OAc)3]2(H2O) were isolated from their precursor solution and characterized by X-ray structural analysis. A short outlook will give an insight into the possible bonding mechanisms of the surface layer. These experiments were made with the mixed metal-oxide system yttrium-stabilized zirconium oxide, which is widely used as a substrate for superconducting oxides. A study of the structure of hydrated yttrium acetates, by single-crystal X-ray diffraction, infrared spectra, and elemental analysis demonstrates that there are two separate structures for hydrated yttrium acetates, which play a role as an intermediate in the building of ceramic oxide layers for coated conductors.     

7-Methylguanine nucleotides and their structural analogues; protolytic equilibria, complexing with magnesium (II) ion and kinetics for alkaline opening of the imidazole ring

First-order rate constants for the alkaline opening of the imidazole ring of several 7-methylguanine nucleotides and their structural analogues were determined. The results obtained suggested that intramolecular interaction between the negatively charged 5'-phosphate group and the positively charged imidazole ring markedly retard the attack of hydroxide ion on the C8 atom of the 7-methylguanine ring. In contrast, hardly any influence on the acidities of the interacting base and phosphate moieties was detectable. No effect on the complexing of the phosphate group with magnesium(II) ion could be detected.     

Chromatographic analysis, isolation and partial characterization of two photocatalysed reaction products of haem and quinone

Quinone was reacted in vitro with free haem under ultraviolet light. Two principal products were detected by liquid chromatography and purified by column chromatography. Mass spectral and Fourier transform infrared analyses showed that both products contained pyrroles and that the first product was probably an ether formed after reaction with the haem vinyl moieties. This product was entirely different from the known N-alkyl intermediates in the haem-catalysed epoxidation reactions of porphyrin dimerization by quinone.     

New approach to the practical synthesis of tri- or tetrasubstituted pyrimidine derivatives: a four-component coupling reaction from a functionalized silane, two types of aromatic nitriles, and acetals

[reaction: see text] A new approach to the synthesis of tri- or tetrasubstituted pyrimidines by a four-component coupling reaction using a functionalized silane, two types of aromatic nitriles, and an acetal is described. The efficient transformation of the pyrimidine framework consisting of an isoxazolyl ring and an ethoxy group to the 1,3,8-triazanaphthalene skeleton also proceeded in nearly quantitative yield.