Preparation and Characterization of Protonated Fumaric Acid

Fumaric acid was reacted with the binary superacidic systems HF/SbF₅ and HF/AsF₅. The O,O'-diprotonated [C₄H₆O₄]²⁺([MF₆]^–)₂ (M = As, Sb) and the O-monoprotonated [C₄H₅O₄]⁺[MF₆]^– (M = As, Sb) species are formed depending on the stoichiometric ratio of the Lewis acid to fumaric acid. The colorless salts were characterized by low-temperature vibrational spectroscopy. In case of the hexafluoridoantimonates single-crystal X-ray structure analyses were carried out. The [C₄H₆O₄]²⁺([SbF₆]^–)₂ crystallizes in the monoclinic space group C2/c with four formula units per unit cell and [C₄H₅O₄]⁺[SbF₆]^– crystallizes in the triclinic space group P1 with one formula unit per unit cell. The protonation of fumaric acid does not cause a notable change of the C=C bond length. The experimental data are discussed together with quantum chemical calculations of the cations [C₄H₆O₄ · 4 HF]²⁺ and [C₄H₆O₄ · 2 H₂CO · 2 HF]²⁺.     

Formaldehyde in Super Acids: A Succession of Products from Carbenium through Oxonium Ion to Hydroxymethyl(methylidene)oxonium Salts

An oxonium ion with hydroxymethyl and methylidene substituents is found in the salts 1 -MF₆ (M=As, Sb), which can be isolated from solutions of formaldehyde in superacids HF/MF₅. Their formation was at first surprising, since NMR spectroscopy indicates that protonated monofluoromethanol is present in solution.     

Chlorosulfenylated Carbonic Acid Derivatives

The present article deals first with the synthesis of chlorocarbonylsulfenyl chloride and its imino analogs. The chemical behavior of these bifunctional compounds is illustrated for selected examples. Special attention is given to the syntheses of five-membered heterocycles containing sulfur, oxygen, and/or nitrogen.     

Mid‐IR Spectroscopy and Structural Features of Protonated Carbonic Acid in the Gas Phase

An anti trihydroxycarbenium ion is revealed to be the gas‐phase structure of protonated carbonic acid by IR multiple‐photon dissociation spectroscopy (see picture for calculated structure and comparison of experimental and computed spectra). Deprotonation yields anti‐H₂CO₃ with a nominal gas‐phase basicity of 724 kJ mol^?1.

     

Alkenediazonium Salts: A New Chapter of Classical Organic Chemistry

Whereas the protonation of α-diazo-β-diketones and α-diazo-β-oxo esters with hydrogen chloride and antimony pentachloride yields the corresponding hydroxyalkenediazonium hexachloroantimonates, the “acid-sensitive” α-diazomonocarbonyl compounds can be transformed into resonance-stabilized alkenediazonium salts by an analogous O-alkylation with triethyloxonium hexachloroantimonate. A general route for synthesizing these compounds consists in the transformation of the p-toluenesulfonylhydrazones of α-halogenated aldehydes and ketones with Lewis acids. Alkenediazonium ions which are not resonance stabilized can be isolated at room temperature only if their decomposition at higher temperatures leads, via evolution of nitrogen, to vinyl cations in particularly high energy levels. Facile substitution reactions at the CC double bond with anisole and methanol demonstrate the strongly electrophilic nature of alkenediazonium salts. When electron-donating substituments are attached to C2 of an ethylenediazonium ion, the bond order of the NN triple bond can be reduced to a level comparable with that in diazoacetic ester.     

脲盐的电子结构及其与光谱和能谱的关系

对脲盐的振动和电子光谱及Ｘ光电子能谱进行研究，并用电荷自洽场ＤＶ－Ｘα方法计算其电子结构，确定脲盐正离子ＣＯ（ＮＨ２）２Ｈ＾＋的结构特征，分析其结构变化与光谱和能谱现象的内在联系，并由此提出了形成配合物的反应机理。     

Reaktionen von Ameisensäuremethylester in den supersauren Systemen XF/MF5 (X = H,D; M = As,Sb) und die Kristallstruktur von HC(OH)(OCH3)+AsF6–

Reactions of Formic Acid Methylester in the Super Acidic System XF/MF₅ (X = H, D: M = As, Sb) and the Crystal Structure of HC(OH)(OCH₃)⁺AsF₆^– The reaction of formic acid methyl ester in the superacidic system XF/MF₅ (X = H, D: M = As, Sb) leads to the hydroxy methoxy carbenium hexafluorometallates. The very hydrolysable and thermo labile salts are characterized by vibrational and NMR spectroscopic methods. Under inert conditions they are stable at –20 °C for some weeks. HC(OCH₃)(OH)⁺AsF₆^– crystallizes in the monoclinic space group P2₁/c (No. 14) with a = 5.275(1) Å, b = 11.059(1) Å, c = 12.113(1) Å und β = 96.64(1)° and four formula units per cell.     

Preparation and Characterization of Pure Thiosulfuric Acid

Pure thiosulfuric acid has not been prepared yet, although it is described in most textbooks of inorganic chemistry. Furthermore, no experimental evidence for the structure of thiosulfuric acid is known. Theoretical calculations predict the (SH)(OH) tautomer to be more stable than the (OH)(OH) tautomer. In this work we present the synthesis and spectroscopical characterization of pure thiosulfuric acid. X₂S₂O₃ (X = H, D) was obtained from the reaction of dry Na₂S₂O₃ with anhydrous HF at –60 °C. The experimental vibrational and NMR spectra together with quantum chemical calculations provide evidence for the predicted (SH)(OH) tautomeric structure.     

Eine neue Synthese für Nitrosyl‐Salze mit schwach koordinierenden Anionen am Beispiel von NO[B(CF3)4]

A New Synthesis for Nitrosyl Salts with Weakly Coordinating Anions Exemplified by NO[B(CF₃)₄] A new synthesis for nitrosyl salts of weakly coordinating anions is described, using the corresponding guanidinium salts as starting materials. The guanidinium salt [C(NH₂)₃][B(CF₃)₄] was obtained by a metathesis reaction of K[B(CF₃)₄] with [C(NH₂)₃]Cl. Treatment of the guanidinium salt with liquid NO₂ resulted in analytical pure NO[B(CF₃)₄] in quantitative yield. The guanidinium and nitrosyl tetrakis(trifluormethyl)borates were characterized by vibrational and NMR spectroscopy as well as by DSC measurements.     

The Crystal Structures of Peroxonium Hexafluoroantimonate H3O2SbF6 and Bis(dihydrogenperoxo)hydrogen Hexafluoroantimonate H5O4SbF6

Protonated hydrogen peroxide is produced from the reaction of antimony pentafluoride with bis(trimethylsilyl)peroxide in the presence of hydrogen fluoride. Depending on the stoichiometry of the reaction mixture, the compounds H₃O₂SbF₆ and H₅O₄SbF₆ are formed, which are stable up to room temperature and have been characterized by X-ray crystallography. The structure of the H₃O₂⁺ ion is shown on the right.     

Synthesis,Characterization, and Crystal Structures of Various Energetic Urotropinium Salts with Azide,Nitrate, Dinitramide and Azotetrazolate Counter Ions

Urotropinium nitrate, N‐methylurotropinium azide, dinitramide and azotetrazolate salts have been prepared and fully characterized by analytical and spectoscopic (¹H, ¹³C, ¹⁴N NMR, IR, Raman) methods. The structures of all four compounds have been determined using X‐ray diffraction techniques and represent new examples of the class of high energy density materials (HEDMs).     

Nitrenium Salts in Lewis Acid Catalysis

Molecular compounds featuring nitrogen atoms are typically regarded as Lewis bases and are extensively employed as donor ligands in coordination chemistry or as nucleophiles in organic chemistry. By contrast, electrophilic nitrogen‐containing compounds are much rarer. Nitrenium cations are a new family of nitrogen‐based Lewis acids, the reactivity of which remains largely unexplored. In this work, nitrenium ions are explored as catalysts in five organic transformations. These reactions are the first examples of Lewis acid catalysis employing nitrogen as the site of substrate activation. Moreover, these compounds are readily accessed from commercially available reagents and exhibit remarkable stability toward moisture, allowing for benchtop transformations without the need to pretreat solvents.     

以短链季铵盐/脂肪酸盐为模板合成超微孔二氧化硅

超微孔材料具有1~2 nm的孔径,在分离、催化应用中有望展现出择形催化的能力。 寻找经济、简便的合成超微孔材料的表面活性剂体系是一项有意义的工作。 本研究以短链季铵盐(十烷基三甲基溴化铵,记为C₁₀TAB)和不同链长脂肪酸酸盐混合胶束为模板剂,硅酸钠为硅源,成功制备出高度有序超微孔SiO₂。 通过小角X射线衍射、N₂吸附-脱附、傅里叶变换红外光谱、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等技术手段对产品的结构和性能进行了表征。 结果表明,合成体系中脂肪酸盐碳链长、加入量、晶化温度等对产物孔道有序性有很大影响。 当选择正辛酸钠(SO)为助表面活性剂,当n(C₁₀TAB):n(Na₂SiO₃):n(SO):n(H₂O)=1:1.5:0.3:800,晶化温度为80 ℃时,可以得到高度有序超微孔SiO₂。 煅烧后样品比表面积为1300 m²/g,孔体积0.49 cm³/g,孔径分布在1.90 nm。     

Formation and Fragmentation of Protonated Molecules after Ionization of Amino Acid and Lactic Acid Clusters by Collision with Ions in the Gas Phase

Collisions between O³⁺ ions and neutral clusters of amino acids (alanine, valine and glycine) as well as lactic acid are performed in the gas phase, in order to investigate the effect of ionizing radiation on these biologically relevant molecular systems. All monomers and dimers are found to be predominantly protonated, and ab initio quantum–chemical calculations on model systems indicate that for amino acids, this is due to proton transfer within the clusters after ionization. For lactic acid, which has a lower proton affinity than amino acids, a significant non‐negligible amount of the radical cation monomer is observed. New fragment‐ion channels observed from clusters, as opposed to isolated molecules, are assigned to the statistical dissociation of protonated molecules formed upon ionization of the clusters. These new dissociation channels exhibit strong delayed fragmentation on the microsecond time scale, especially after multiple ionization.     

Transition Metal-Free N-Arylation of Amino Acid Esters with Diaryliodonium Salts

A transition metal-free approach for the N-arylation of amino acid derivatives has been developed. Key to this method is the use of unsymmetric diaryliodonium salts with anisyl ligands, which proved important to obtain high chemoselectivity and yields. The scope includes the transfer of both electron deficient, electron rich and sterically hindered aryl groups with a variety of different functional groups. Furthermore, a cyclic diaryliodonium salt was successfully employed in the arylation. The N-arylated products were obtained with retained enantiomeric excess.     

The Structural Systematics of Protonation of Some Important Nitrogen‐base Ligands. I Some Univalent Anion Salts of Doubly Protonated 2, 2′:6′, 2″‐Terpyridyl

A number of salts of 2,2′:6′,2″ ‐terpyridyl (‘tpy’) with univalent anions (halides : X = Cl, Br, I; oxyanions of increasing basicity: ClO₄, NO₃, ‘tfa’ = trifluoroacetate, ‘tca’ = trichloroacetate), variously solvated, have been structurally characterized by single crystal X‐ray studies. In all cases the tpy moieties are found to be doubly protonated [tpyH₂]²⁺, the hydrogen atoms being associated with the nitrogen atoms of the peripheral rings, these together with the central nitrogen atom being directed towards a common focus, in most cases ‘chelating’ one of the counter‐ion components in diverse ways. Thus the chloride and bromide compounds are isomorphous [(tpyH₂)X]⁺X⁻·H₂O arrays; a second dihydrate phase is also described for the chloride, the two forms having the unchelated anion and water molecules engaged in hydrogen‐bonded networks essentially independent of [(tpyH₂)X]⁺. The iodide is anhydrous, and of a different structural type, the anions, presumably too large for chelation, lying out of plane to either side, and linking different cations into a one‐dimensional polymer; in the perchlorate, the unsolvated aggregate is now discrete [(tpyH₂)X₂], a pair of perchlorate ions disposed to either side of the tpy plane, lying each with one oxygen atom interacting with both of the two protonating hydrogen atoms. In the anhydrous X = NO₃, tfa, tca arrays, the lattices are solvated by the parent acids; one oxygen atom of each anion is chelated by the [tpyH₂]²⁺ as in the chlorides, the other anion, with the acid, forming an independent ‘acid salt’ counterion [XHX]⁻ in each case, retaining the additional protonic hydrogen rather than further protonating the central ring, all being of the form [(tpyH₂)X]X·HX = [(tpyH₂)X][X(HX)].     

聚甲基戊烯膜式氧合器表面碳酸酐酶的固定化及性能研究

聚甲基戊烯(PMP)膜式氧合器表面先用水等离子体改性,以引入羟基官能团;再以溴化氰为偶联剂,将碳酸酐酶(CA)偶联至其表面.改性后用X射线光电子能谱(XPS)、表面接触角及酶活性测定等方法研究PMP表面性能变化.结果表明,等离子体处理后,在PMP表面引入了大量的含氧官能团,与水的表面接触角从103.37°降低至50.01°.再将CA引入PMP表面后,与水的表面接触角进一步降低至39.23°;XPS的C1谱图中出现蛋白质的特征峰;以对硝基苯酚乙酸酯为底物,测得表面接枝CA的活性达到理论单分子层接枝活性的73%.改性后PMP表面物理化学性质的变化证明本文方法确实能成功地将羟基官能团、CA引入其表面.本方法有望应用在膜式氧合器上以提高其清除血液中CO2的能力.