The formation of lithium diarylargentates from arylsilver compounds and the corresponding aryllithium compounds

Diarylsilverlithium compounds of the type Ar₂AgLi are formed by treating arylsilver compounds with the corresponding aryllithium compounds. Cryoscopy in benzene shows that the Ar₂AgLi compounds are associated into dimers. NMR spectroscopic data indicate that only one type of aryl group is present in these dimers, and that each aryl group is bridging between one silver and one lithium atom.     

Chemical aspects of penicillin allergy. The direct formation of penicilloyl determinants in penicillin

The aminolysis of two penicillin-like compounds which cannot form penicillenic acid has been studied:

• 1 6-Aminopenicillanic acid (which is highly immunogenic) reacts directly with ε-amino groups at pH 7,4 under CO₂-free conditions; the possible role of its polymerisation in this reaction remains to be studied.
• 2 6-Dinitrophenylamino-penicillanic acid reacts with εamino groups at pH 7,4 as fast as benzylpenicillin and other penicillins. Its immunogenicity in the rabbit is similar to that of benzylpenicillin.

     

Mechanism of rhodium-catalyzed carbene formation from diazo compounds

[reaction: see text] A large and normal nitrogen-15 kinetic isotope effect of 1.035 +/- 0.003 provides direct support for the proposed mechanism for the rhodium-catalyzed carbene formation from diazo compounds, which involves the fast formation of a metal-diazo complex followed by rate-limiting extrusion of N2. The large magnitude of the KIE indicates extensive C-N bond fission in the transition state.     

Organothallium compounds X the formation of polyfluorophenylthallium compounds by desulphination reactions

The acetatobis(polyfluorophenyl)thallium(III) compounds R₂TlO₂CCH₃ (R = C₆F₅, $\text{p}$-HC₆F₄, or $\text{m}$-HC₆F₄) have been prepared by sulphur dioxide elimination reactions from the appropriate lithium polyfluorobenzenesulphinates and thallic trifluoroacetate or acetate under mild conditions. Owing to reduction of the thallic salt by liberated sulphur dioxide, good yields required the stoichiometry 2LiO₂SR: 3TlX₃ (X = O₂CCF₃ or O₂CCH₃). The reactions are considered to proceed via thallium(III) $\text{S}$-sulphinate complexes and a possible mechanism is discussed.     

Rearrangements in the formation of pyrazolines from alkyl hydrazines and unsaturated carbonyl compounds

The isomeric composition of the 2-pyrazolines obtained by the condensation of croton aldehyde and methyl vinyl ketone with C₁–C₄ monoalkyl hydrazines has been studied by the GLC method. It has been shown that in the reaction of croton aldehyde with isopropyl hydrazine, isobutyl hydrazine, and, to a smaller extent, with methyl hydrazine, in addition to the 1-alkyl-5-methyl-2-pyrazolines the 1, 3-isomers are formed. In other cases, only one pyrazoline, corresponding to the structure of the carbonyl compound, is formed. Eight previously-unknown dialkyl-2-pyrazolines are described.     

Carbon-carbon bond formation from ethyl cyanoformate and active methylene compounds

A new methodology which leads to α,β-unsaturated α-amino acids has been developed through a carbon-carbon forming reaction using ethyl cyanoformate and active methylene compounds in the presence of zinc chloride and triethyl amine.     

Aspects of spin-orbit effects in compounds containing heavy elements

This perspective article discusses some widely-known and some less-known consequences of spin-orbit effects in inorganic chemistry, and provides a brief outline of the theoretical methods currently in use, along with a discussion of recent developments and selected applications. This is of critical importance in the interpretation of the electronic delocalization, optical and magnetic properties and Jahn–Teller effects of compounds containing heavy elements.     

Aspects of mechanism and structure in the formation of muonated radicals

Radiolysis effects associated with the implantation of positive muons in liquid samples are reviewed. The major processes to be considered resemble the normal reactions induced by ionising radiation; these are electron ejection and the subsequent chemical reaction of electrons and holes. The thermal or near-thermal reactions are described in terms of a general scheme which includes the various possible routes to the formation of muonium and of muonated organic radicals. The scheme emphasizes the consequences of the extreme dilution of the muon probe, and its outstanding reactivity towards solvents or solutes of even weak basicity, it its role as lightweight proton. The mechanism of radical formation in materials with widely different properties may be predicted from the general scheme. For the few compounds in which the mechanism has been elucidated experimentally this is compared with chemical expectations. Characteristics of the compounds and of their cosolvents which favour or inhibit the different possibilities are discussed in terms of the interplay between reaction mechanism and molecular structure. The balance between competitive processes may be altered by the presence of inert solvent. In protic solvents the balance may also be altered by proton exchange, and indirectly by a modification of reactivities due to hydrogen bonding. Mechanisms involving intermediate muonic cation or radical anion states are established in particular cases. These ionic states may also be the origin of the diamagnetic fraction in certain circumstances.     

Kinetic studies on the formation of N-nitroso compounds

Acetic acid/acetate ion buffer acts catalytically upon the nitrosation of amines under conditions in which the only nitrosating agents are N₂O₃ and NOBr, but inhibits nitrosation by H₂NO ₂ ⁺ . The kinetic characteristics of these phenomena have been analysed quantitatively and compared with similar effects caused by the solventsTHF, DMSO and dioxane. The experimental results show that this behaviour is an effect of the medium.

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Kinetische Untersuchungen zur Bildung von N-Nitroso-Verbindungen, 8. Mitt.: Nachweis eines Medium-Effekts von Essigsäure/Acetat-Puffer auf die Geschwindigkeitskonstante der Nitrosierung

Zusammenfassung Essigsäure/Acetat-Puffer wirkt bei der Nitrosierung von Aminen katalytisch, unter Bedingungen, wo die alleinigen nitrosierenden Agentien N₂O₃ und NOBr sind; andererseits wird die Nitrosierung durch H₂NO ₂ ⁺ unterbunden. Die kinetischen Charakteristika dieses Phänomens wurden quantitativ analysiert und mit ähnlichen Effekten der LösungsmittelTHF, DMSO und Dioxan verglichen. Die experimentellen Ergebnisse zeigen, daß dieses Verhalten auf einen Mediumeffekt zurückzuführen ist.

     

Enthalpies of formation of Ni-Sn compounds

Enthalpies of formation (Δ_fH) of nickel-tin compounds have been measured by direct reaction calorimetry: (approximate value); .Standard states are solid Ni and liquid Sn at the respective working temperatures: 728, 1288, 1389, 1332, 943 and 846 K.The enthalpy of formation of the Ni₃Sn high-temperature form is measured for the first time, while that of Ni₃Sn₂_LT must be considered as approximate because the corresponding calorimetric reaction was incomplete.The chemical and phase compositions of the specimens have been verified by electron probe microanalyses and by high- and room-temperature X-ray diffraction analyses. Unidentified thermal effects have been observed in the Ni₃Sn₂ phases region.     

Thermal investigations of nickel–zinc ferrites formation from malate coordination compounds

Nickel–zinc ferrites have been synthesized via thermal decomposition of polynuclear coordination compounds containing as ligand the anion of malic acid, namely (NH₄)[Fe₂NixZn_1–x(C₄H₄O₅)(OH)₃]·nH₂O (x =0.25, 0.5 and 0.75, n=3 and 5). A comparison between the thermal behaviour of the studied polynuclear coordination compounds is inferred. Fe₂NixZn_1–xO₄ (n=0.25, 0.5 and 0.75) ferrites with mean particle sizes of 65–85 Å and free from other phases are formed after a heating treatment of only one hour at 500°C.     

Electrochemically induced formation of organomercury compounds

A procedure for the alkylation of metallic mercury by (dimethylglyoximato)butylcobalt(III) electrochemically generated in the presence of butyl bromide is proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 309–312, February, 1994.     

原油中有机硫化物成因的硫酸盐热化学还原反应模拟研究

原油中部分有机硫化物来源于硫酸盐热化学还原反应。利用高压釜在高温高压含水条件下对正戊烷 硫酸镁反应体系进行了热模拟实验研究。通过气相色谱仪、微库仑仪、毛细管气相色谱/脉冲火焰光度检测器、红外光谱仪及X射线衍射仪,对气、油、固三相产物进行了分析。结果表明,硫酸盐热化学还原反应在425℃~525℃可以进行,主要生成氧化镁、炭、硫化氢、二氧化碳以及硫醇、硫醚和噻吩类等有机硫化物。根据动力学模型计算出该反应活化能为58.0kJ/mol。     

The formation of Grignard compounds—II

Detailed investigations of CIDNP phenomena during Grignard formation reactions are reported. CIDNP was found in the main product RMgX, as well as in the byproducts R(H) and R(-H) and in one case in the starting halide, i-C₃H₇I. The radical pair$\text{R R}$is shown to be involved in the formation of the polarized products. Furthermore it is proposed that the first step in the reaction sequence is a one electron transfer from magnesium to the organic halide to form the radical anion R-X

which dissociates rapidly to furnish radical R.