Structures and Electronic Properties of Ni–Al Alloy Clusters from First-Principles Calculations

Using the density functional theory calculations with the PBE exchange–correlation energy functional, we have studied the low-energy structures and electronic properties of Ni–Al alloy clusters for adsorbing or doping an aluminum atom to Ni_n (n = 13, 19, 23, 26, 29 and 55) clusters. The most stable structures of Ni_nAl are viewed as adding an Al atom at the hollow triangle and rhombus site of the icosahedron (n = 13, 55) and double-icosahedron (n = 19, 23, 26 and 29) structures, respectively. For Ni_n?1Al, it can be seen that an Al atom gradually moves from surface (n = 13, 19, 23 and 26) to the interior site (n = 29, 55) in the most stable structures. The electronic properties of the Ni–Al alloy clusters including binding energies, magnetic properties, charge transfer and density of states have also been studied.     

The Reaction of 2,5-Bis(Dimethyfurfuryl)Furan Dialdehyde with Primary α,ω-Diamines

Abstract

The influence of the H-bond acceptors strength of het-eroatoms present in α,ω-diamines on the reaction course leading to the formation of macrocyclic Schiff bases was studied. For strong acceptors like oxygen and nitrogen atoms the highest yield was obtained. Similar effect was observed for diamines possessing two oxygen atoms, while the presence of three oxygen resulted only in polymerisation reactions.     

Transforming Inert Cycloalkanes into α,ω-Diamines by Designed Enzymatic Cascade Catalysis

Aliphatic α,ω-diamines (DAs) are important monomer precursors that are industrially produced by energy-intensive, multistage chemical reactions that are harmful to the environment. Therefore, the development of sustainable green DA synthetic routes is highly desired. Herein, we report an efficient one-pot in vivo biocatalytic cascade for the transformation of cycloalkanes into DAs with the aid of advanced techniques, including the RetroBioCat tool for biocatalytic route design, enzyme mining for finding appropriate enzymes and microbial consortia construction for efficient pathway assembly. As a result, DAs were successfully produced by the designed microbial consortia-based biocatalytic system. In particular, the highest biosynthesis productivity record of 1,6-hexanediamine was achieved when using either cyclohexanol or cyclohexane as a substrate. Thus, the developed biocatalytic process provides a promising alternative to the dominant industrial process for manufacturing DAs.     

Synthesis,Transport, and Ionophoric Properties of α,ω-Biphosphorylated Azapodands: X. Membrane Transport of Organic Acids by Phosphorylated α,ω-Diazapodands

The membrane transport properties of novel phosphorylated azapodands with respect to mono- and polyfunctional carboxylic acids were studied. The structures of the transported Н-complexes are discussed, the complexing centers in the carriers are considered, and the correlations between the structure and transmembrane transport efficiency of the acid substrates are demonstrated.     

Mono-Protected Diamines. N-tert-Butoxycarbonyl-α,ω-Alkanediamines from α,ω-Alkanediamines

We wish to report a convenient pathway to N-tert-butoxycarbonyl-α,ω-alkanediamines 2a-e [H₂N(CH₂)χNHBOC; χ=2, 3, 4, 5 and 6; (75–90% yields)] by treatment of the corresponding α,ω-alkanediamine with di-tert-butyl dicarbonate in dioxane as the solvent. Only small amounts of the bis-substituted N.N′-tert-butoxycarbonyl-α,ω-alkanediamines 3a-e were formed (2–9%) which were easily removed by an aqueous workup. The α,ω-alkane-aza-diamine 4 was also mono-protected (62% yield of 5) by the same methodology.     

Synthesis of symmetrical acetylenic hydrocarbons and their α,ω-di-derivatives from α,α,α-trichloro- and α,α,α,ω-tetrachloro-alkanes

Summary By the action of sodium in xylene on polychloro hydrocarbons containing -CCl₂-CCl₂- or- CC1=CC1-, groupings the corresponding symmetrical acetylenic hydrocarbons containing 10,14, and 18 carbon atoms in the molecule were obtained. From ,-disubstituted tetrachloroalkanes by the same method 1,10-diethoxy-5-decyne, 1,14-diethoxy-7-tetradecyne, and 1,14-bisdiethylamino-7-tetradecyne were obtained.The spectra were determined in the Optical Laboratory of the Institute of Heteroorganic Compounds of the USSR by N. A. Chumaevskii, who we thank.     

Long-chain α,ω-bisisothiocyanates from a marine sponge

Eighteen long-chain aliphatic α,ω-bisisothiocyanates were isolated from a marine sponge, Pseudaxinyssa sp. from Fiji. Eight compounds are di-, ten are monolefinic. Three additional constituents are α-isothiocyano-ω-formyl compounds.     

Electrochemical oxidation of tetramethyl esters of α,α,ω,ω-alcaneteracarboxylic acids

Cyclization of esters of butane-1,1,4,4- and pentane-1,1,5,5-tetracarboxylic acids during electrolysis in methanol in the presence of Nal produces, with a yield of 95%, the esters of cyclobutane-1,1,2,2- and cyclopentane-1,1,2,2-tetracarboxylic acids. Under similar conditions, esters of the highest ,,,-alkanetetracarboxylic acids undergo iodation and hydroxymethylation due to electrical oxidation of methanol to formaldehyde. During electrolysis in methanol in the presence of NaOAc, the esters of ,,,-alkanetetracarboxylic acids undergo effective hydroxymethylation, followed by cyclization into substituted five- and six-member lactones, or tetrahydrofurans when structurally possible.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2332–2339, October, 1992.     

A facile synthesis of α,α,ω,ω-tetrahalo-α,ω-dicarboxylic esters

The synthesis of some α,α,ω,ω-tetrachloro and tetrabromo-derivatives of the hypolipidemic 3,3,14,14-tetramethylhexadecanedioic acid from α,ω-dihalo-esters, carbon tetrahalides and lithium diisopropyl amide has been described. Interaction of α,ω-dichloro esters with CBr₄ was shown to give the expected α,ω-dibromo-α,ω-dichloro compounds, but treatment of bis(l-methylethyl) 2,15-dibromo-3,3,14,14-tetramethylhexa-decanedioatewith CCl₄ was found to result in halogen exchange yielding the tetrachloro-diester as the major product.     

Some peculiarities of hydrosilylation of α,ω-divinyloligosilanes

The stability of Si-Si bonds in linear and cyclic permethyloligosilanes and in ,-divinyloligosilanes under conditions of hydrosilylation in the presence of the Speier's catalyst was studied. Polycarbosilanes containing silylene fragments in their backbone chains were prepared by the reaction of 1,4-bis(dimethylsilyl)benzene with ,-divinyloligosilanes. It was found that the structure of these polymers is disturbed due to the side reaction involving the cleavage of the Si-Si bond in vinyloligosilanes under the action of H₂PtCl₆.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2547–2549, October, 1996.     

Isolation, Purification, and Properties of α-Amylase from Bacillus subtilis-7A

Cultivation ofBacillus subtilis-7A on waste from alcohol production yielded an active extracellular enzyme -amylase with MW 75 kDa. The enzyme was isolated from the culture medium by 60% saturated ammonium sulfate and purified until homogeneous by gel filtration on Sephadex G-100 and ion-exchange chromatography on DEAE-cellulose. The optimum temperatures for the complex and purified enzyme are 30 and 50°C, respectively. The optimum activity for both preparations occurred at pH 6.5. The substrate specificity of the isolated preparations was studied.     

Synthesis and characterization of α,ω-dichloro-polymethylphenylsilane

The synthesis of a functional polysilane, α,ω-dichloro-polymethylphenylsilane (α,ω-dichloro-PMPS), based on the Wurtz-type reductive coupling, has been considered. A study of some reaction parameters shows that both yield and molecular weight distribution of α,ω-dichloro-PMPS can be greatly influenced by the work-up conditions, reaction time, monomer concentration and temperature during the initiation of the polymerization. By varying the synthesis conditions, different ratios of high and low molecular weight fractions were obtained. Samples of different molecular weight were isolated by fractional precipitation of the crude polymers. The chlorine-end functionalization was confirmed by ²⁹Si NMR spectroscopy and the concentration of end-groups was quantitatively determined by elemental analysis of chlorine.     

Dynamic combinatorial libraries of macrocycles derived from phthalic aldehydes and α,ω-diamines

Dynamic combinatorial chemistry methodology was used to obtain eleven new polyazamacrocycles derived from isophthalic and terephthalic aldehyde and α,ω-diamines. Simple templates, such as alkali metal salts, were found to amplify large macrocycles: 45-membered [3+3]hexaazacrown and 60-membered [4+4]octaazacrown. Parent imine libraries were converted into corresponding secondary libraries of amines using a fast reduction protocol. Methyl carbamate protection of amine group allowed convenient isolation of polyazamacrocycles in very good yields.     

Elimination Reaction of α,ω-Diols by Magnesium

Inrecentyears,someapplicationsofmagnesiuminorganicsynthesisandorganosiliconreactionshavebeenreported""'.Here,wewishtoreportanothernewreaction,theelindnationreactionofsomediolsbymagnesium.Inthepresenceofiodine,l,3-propanediol,l,4-butanediolorl,5-pentanediolreactswithmagnesiumtoproducemagnesiumalkoxides.Whenthemixtureofformedmagnesiumalkoxideinalcoholwasrefluxed,thermaldecompositionoccurswiththeformationofcyclicethersand,respectively,allylalcohol,buten-l-olandpenten-l-ol.Thetotalreactioncorrespo…