碱金属-汞和碱金属-铅原子簇的成键本质

Relativistic density-functional calculations on free Hg2, Hg4, Hg8, Pb2 and Pb4 clusters, and those clusters embedded in an alkali (A) atom surrounding are reported. Heavy metal-metal (M-M) distances, binding energies and effective charges have been calculated. The Hg-Hg distance in the weakly bound free clusters is over 330 pm. Upon embedding in an alkali surrounding, the bonding is strengthened; the bond lengths are reduced for square planar Hg4 to below 300 pm. The bonding in the hypothetical tetrahedral alkali-mercury cluster appear to be quite different, where Hg4 will undergo a transition to four Hg1. This explains the strict preference of square over the tetrahedral geometry of Hg4 clusters in amalgams. Pb4 is predicted to be stable in a pure cluster and does not show significantly different bonding feature in the lead-alkali crystal. The effective charges on Hg and Pb are calculated to be -0.4 and -0.6, respectively. The bonding characteristics are also examined by calculation of the M4-An interaction energies. The amalgamation energies lie in the range of 50 to 70 kJ/molHg. The formation energy of alkali-Pb is up to 150 kJ/molPb, much stronger than that of alkali-Hg.     

Cupric sulfate pentahydrate (CuSO4·5H2O): a mild and efficient catalyst for tetrahydropyranylation/depyranylation of alcohols and phenols

Various alcohols and phenols can be smoothly converted to the corresponding THP ethers using 20 mol % CuSO₄·5H₂O under mild reaction conditions at room temperature. Some of the major advantages of this procedure are nonaqueous work-up, very good yields, less expensive catalyst and compatibility with other protecting groups.     

Review of the state of the art of preparative thin-layer chromatography

The state of the art of preparative thin-layer chromatography (PTLC) based on the literature published from 2007 through 2016 is reviewed. Classical capillary flow PTLC, forced flow PTLC, precoated and laboratory prepared plates, instruments, and micropreparative TLC are all covered, including techniques, instruments, and applications. Prospects for future applications and advances in PTLC are suggested.     

Hydrolysis Behaviour of Some Heterocyclic Nitrogen Azomethines

Kinetics of base hydrolysis of some new heterocyclic azomethines derived from aminotriazol and aromatic aldehydes were investigated in the presence of NaOH in 60% (wt/wt) water-ethanol medium. The base hydrolysis of these Schiff bases is strictly first-order with respect to OH^? and Schiff. The rate-determining step is suggested to be the attack of the hydroxide ion on the free base. Effect of the molecular structure of both aldehydes and amines and the nature of organic hydroxylic solvent on the hydrolysis rate was investigated and discussed.     

Organic chemistry of noble gases

The preparation and chemistry of organic derivatives of xenon and other noble gases are reviewed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1849–1857, November, 1993.     

PYRIDINIUM SULFONATE CHLOROCHROMATE (VI), C5H5NSO3H [CrO3Cl] (PSCC): A NEW REAGENT FOR OXIDATION OF ORGANIC SUBSTRATES

A fast, mild, and reasonable oxidizing agent, pyridinium sulfonate chlorochromate (VI), C₅H₅NSO₃H [CrO₃Cl] (PSCC) is synthesized. Its reactions with primary, secondary, benzylic, and allylic alcohols under very mild conditions give the corresponding carbonyl compounds. These are obtained with relatively short reaction times. The oxidant/substrate ratios of 1:1 are employed.     

pH值对有机化合物富集与伏安溶出过程的影响

在碳糊电极上有机化合物的富集能够增加溶出伏安法的灵敏度和选择性。不同的有机化合物的碳糊电极上的富集机理不同,在电极上的伏安溶出条件也不同。使用碳糊电极时,对有机化合物的富集、溶出影响因素是多方面的,其中富集液和溶出液的ｐＨ值对它的影响十分重要文中通过碳糊电极对一些简单有机体例物如氯丙嗪（冬眠灵）、丁基羟基甲醚（ＢＨＡ）、Ｎ,Ｎ－二甲基苯胺（ＤＭＡ）、对苯二酚的富集与伏安溶出进程的研究,从理论和试验     

Towards a Fundamental Understanding of Urea and Thiourea inclusion Compounds

This article reviews some of the fundamental scientific issues associated with solid inclusion compounds, and describes the approaches and strategies that may be used to investigate the structural, dynamic and chemical properties of these systems. Two particular families of solid organic inclusion compounds - the urea and thiourea inclusion compounds - are highlighted. In order to understand the fundamental nature of these solids, it has been necessary to apply a wide range of experimental, computational and theoretical approaches. Each technique provides information on a different aspect of the solid, and the combined information obtained from these complementary approaches allows a comprehensive understanding to be established. Several issues of contemporary interest for urea and thiourea inclusion compounds are described, and the approaches that have been taken towards a fundamental understanding of these systems are explained.     

Photometrisch-potentiometrische Bestimmung der Hydrolysenkonstanten vonN-Bromverbindungen

The equilibrium concentrations of all reaction products emerging from the hydrolysis ofN-bromo compounds in the presence of bromide and thereby also the hydrolysis constants (K ₁) have been calculated from the absorbance at 392.8 nm, thepH-value and the initial concentrations of theN-bromo compound and the bromide. The following compounds have been investigated:N-bromo-succinimide:K ₁=2.2·10^–6, 1,3-dibromo-5,5-dimethylhydantoin:K ₁=1.7·10^–5,N-bromoacetamide:K ₁=1.8·10^–6,N-bromo-monochloroacetamide: 5.2·10^–6,N-bromo-dichloroacetamide:K ₁=8.9·10^–6 andN-bromo-trichloroacetamide:K ₁=1.8·10^–5. The precision of the method, which is mainly suited for weak hydrolizingN-bromocompounds (K ₁<10^–4) are discussed and the overall error of the calculated values was found to be in the range of ±5–12%. The reactivities in aqueous solution of the most frequently usedN-bromo compounds are compared by means of the calculated HOBr equilibrium concentrations. The differences to be expected on the basis of the latters are at concentrations >10^–5 mol/l rather great, while they can be neglected in very dilute solutions (-10^–6 mol/l).

     

Tetraanionic Nitrogen‐Rich Tetrazole‐Based Energetic Salts

1,1,3,3‐Tetra(1H‐tetrazol‐5‐yl)propane‐based energetic salts were synthesized in a simple and straightforward manner. The structures of these new salts were determined by ¹H and ¹³C NMR spectroscopy, IR spectroscopy, MS, and elemental analysis. All of these compounds showed good thermal stabilities above 180 °C, as confirmed by thermogravimetric–differential thermal analysis (TG–DTA) measurements. Moreover, these salts also exhibited high positive enthalpies of formation, high nitrogen content, good thermal stabilities, and moderate detonation properties.