Analytische Dichtegradienten-Zentrifugation bei Temperaturen zwischen +4?C und +40?C

Zusammenfassung Es wird gezeigt, da\ die bei der analytischen Dichtegradienten-Zentrifugation benötigten Parameter, die von Hearst u. Mitarb. tabelliert wurden, auch für andere Temperaturen als 25C gültig sind. Das ist von gro\er Wichtigkeit, da hochempfindliche Enzyme nur bei Temperaturen um + 4C lÄnger als 24 h nativ bleiben. Man ist deshalb auf eine Zentrifugation bei dieser Temperatur angewiesen. Weil man oft nur sehr wenig Substanz isolieren kann, bleibt nur die Dichtegradienten-Zentrifugation als Methode der Wahl. Ein Vergleich der gemessenen Molekulargewichte bei 6C und 25C zeigt keine Abweichungen, die über die Me\genauigkeit hinausgehen.

---

Analytical density gradient centrifugation at temperatures between +4C and +40 C

It is shown that all the parameters needed for analytical density gradient centrifugation tabulated by Hearst et al. for 25C are valid for other temperatures, too. This will be important in the investigation of highly sensitive enzymes which are only stable at temperatures near +4C over a period of 24 h. Comparison of molecular weights determined at 6C und 25C shows no difference greater than 2%, which will be within the experimental error.

---

---

Das Bundesministerium für Bildung und Wissenschaft hat diese Arbeiten gro\zügig unterstützt.     

OH+ C2H2N←C2H3 + NO→CH3 + NCO反应机理的密度泛函理论研究

应用密度泛函理论研究了反应通道(a)C2H3 NO→CH3 NCO和(b)C2H3 NO→OH C2H2N的反应机理．在B3LYP／6-31G(d)水平上优化了反应物、中间体、过滤态、产物的几何构型，通过频率分析确定了11个中间体和10个过渡态．所有的反应物、中间体、过渡态、产物都在CCSD／6-311 G(d，P)水平上进行了单点能较正．并讨论了反应的异构化过程．计算结果表明10是能量最低的中间体，比反应物的能量低308．479kJ／mol；过渡态1／3，2／5，3／4，4／8比反应物的能量高，其中3／4是能量最高的过渡态，比反应物的能量高91．894kJ／mol．通道(a)和(b)的理论放热值分别为111．059和96．619kJ／mol．     

C3H+与N反应的理论研究

用密度泛函方法在QCISD(T)／6—311 G^**//B3LYP／6—311G^*水平上研究了气相反应C3H^ N的反应机理．得到了不同能量产物的可能的反应通道，获得反应势能面．整个反应为多通道反应，经过多个步骤完成，共找到9个中间体和11个过渡态，产物C3H^ N(P2)为能量较低的产物，通道3：IM5→TS4→IM6→TS5→IM7→TS7→IM8→P2为较为可行的反应通道．     

C77N+异构体的稳定性和电子光谱研究

All of the possible 21 isomers for C77N+, an isoelectronic molecule of C78, were investigated by the INDO methods based on C78(C2V). It indicates from optimization that the most stable isomer is that the nitrogen atom substitutes C(78) located at the C(78)-C(73) bond passed through by the Y shortest axis and the atoms near the Z longest axis are also easy to substitute, whereas the atoms near the X shortest axis are relatively difficult to substitute. At the same time, C78 was compressed a little and ready to perform the further reaction to form C77 NR at the location of substitution. Electronic spectra of C77N+ were calculated by INDO/SCI method and electronic transition was theoretically assigned. The red shift of absorption peaks for electronic spectra of C77N+ took place compared with that of C78(C2V) because of its narrower LUMO HOMO energy gap. There are great differences in characteristic absorptions among C77N+ isomers, which can be considered as evidence of the formation for each isomer.     

Analysenautomat zur simultanen Mikrobestimmung von C,H und N

Zusammenfassung Es wird über ein automatisches Analysengerät zur gleichzeitigen Mikrobestimmung von C, H und N berichtet. Im Gegensatz zu dem bisher bekannten Simultanverfahren (E < 1 mg) werden bei dem beschriebenen Verfahren Einwaagen von 1–10 mg analysiert. Es wird in Helium, dem ozonisierter Sauerstoff zugesetzt wird, verbrannt. Anschließend werden die Reaktionsprodukte mit Helium ausgespült. Wasser wird zunächst ausgefroren, CO₂ und N₂ werden an einer Silicagelsäule bei –60°C adsorbiert und getrennt. Die Messung der 3 Komponenten erfolgt in einer Wärmeleitfähigkeitszelle. Verbrennung und Messung sind voneinander vollkommen unabhängig und daher ohne gegenseitige Beeinflussung.Die Apparatur ist nach dem Baukastenprinzip aufgebaut und kann mit folgenden Teilen als Vollautomat angesehen werden: 1. automatisch gesteuerter Verbrennungsapparat; 2. Meßteil; 3. Integrator; 4. elektronische Mikrowaage; 5. Klein-Computer Combitron S.Mit dieser Apparatur erhält man innerhalb von 17–20 Minuten ausgedruckt das Ergebnis in %-Gehalten von C, H, N. Die Standardabweichung beträgt für N = 0,116%, für C = 0,156%, für H = 0,06%.

---

Analysis automat for the simultaneous microdetermination of C, H and N

Summary A report is given regarding an automatic analysis device for the simultaneous microdetermination of C, H and N. In contrast to the previously used simultaneous procedure (sample = 1 mg), in the procedure described here the samples employed for the analysis weighed 1–10 mg. The combustion is conducted in helium to which ozonized oxygen has been added. The reaction products are subsequently flushed out with helium. Water is frozen out first of all, and CO₂ and N₂ are adsorbed on a silica column at –60° C and separated. The measurement of the three components is carried out in a thermal conductivity cell. The combustion and measurement are entirely independent of each other and therefor are without mutual influence.The apparatus is built up in accord with the principle of standard units and can be viewed as completely automatic if the following parts are employed: 1) Automatically guided combustion apparatus; 2) measuring component; 3) integrator; 4) electronic microbalance; 5) small computer Combitron S. With this set-up there is obtained within 17–20 minutes a printed report of the findings in %-contents of C, H and N. The standard deviation for N = 0.116%, for C = 0.156 %, for H = 0.06 %.

     

Die gleichzeitige Mikrobestimmung von C, H und N in Nitroverbindungen

Ohne Zusammenfassung     

Als neue Methoden zur Bestimmung von C, H und N

Ohne Zusammenfassung     

C75N+位置异构体的电子结构和光谱研究

杂原子的介入可改变纯碳笼的电子结构, 使其在超导、光电子器件及有机铁磁体等方面得到应用, 还可改善其氧化还原性能, 提高反应活性, 因而引起人们的研究兴趣[1～3]. Averdung[1]研究了C59N+与H的反应, 用质谱检测到C59NH和C59NH+2, 并用AM1方法优化其结构; Lamparth[2]以双氮杂富勒烯为前体, 合成了C59N+和C69N+, 测定中间体的 1H NMR谱、 UV谱及产物的FAB质谱, 并用 15N标记法证实了最强的碎片峰是N原子进入母体碳笼骨架所致. Diederich[3]观察到C76氮化物的FAB质谱信号, 但未给出进一步信息. 本文用INDO系列方法对氮杂富勒烯C75N+位置异构体的结构和稳定性进行理论研究, 找出最稳定的异构体, 计算其电子吸收光谱, 为实验室合成分离提供理论依据.     

Stereoselective cascade reactions for construction of polyfunctionalised octahydroquinolines via [2C+2C+1C,1N] cyclisation

A conceptually unifying approach for a highly enantio- and diastereoselective synthesis of polyfunctionalised octrahydroquinolines incorporating three contiguous chiral centres is reported. The synthesis involves diphenylprolinol silyl ether-catalysed Michael addition of 1,3-cyclohexanedione to nitroalkenes followed by potassium carbonate-promoted aza-Henry reaction with N-tosyl aldimines, intramolecular hemiaminalisation and dehydration reaction cascade in a one-pot operation.     

Diode laser spectroscopy of the fundamental bands of 12C14N, 13C14N, 12C15N, 13C15N free radicals in the ground 2 Sigma+ electronic state

Rotationally resolved spectra of the fundamental band of the CN free radical in four isotopic forms have been measured using tunable diode laser absorption spectroscopy. The source of the radical was a microwave discharge in a mixture of isotopically selected methane and nitrogen diluted with argon. The lines were measured to an accuracy of 5 x 10(-4) cm(-1) and fitted to the formula for the vibration rotation spectrum of a diatomic molecule, including quartic distortion constants. The band origins of each of the isotopomers from the five parameter fits were found to be 12C14N: 2042.42115(38) cm(-1), 13C14N: 2000.08479(23) cm(-1), 12C15N: 2011.25594(25) cm(-1), 13C15N: 1968.22093(33) cm(-1) with one standard deviation from the fit given in parenthesis. Some of the lines showed a resolved splitting due to the spin rotation interaction. This was averaged for fitting purposes. The average equilibrium internuclear distance derived from the upsilon = 0 and 1 rotational constants of the four isotopomers is 1.171800(6) A which is in good agreement with the value determined from microwave spectroscopy.     

Crystalline Inclusions Formed in C+N+BF2 Coimplanted on Silicon (111)

In the present work, high-doses (10¹⁷–10¹⁸cm^–2) of carbon, nitrogen, and boron (BF₂⁺) ions were coimplanted on silicon (111) substrates at 21, 25 and 77keV, respectively. Two series of samples have been implanted (series A and B) and subsequently annealed. Series A samples have been implanted at room temperature and treated one minute by rapid thermal annealing (RTA) and 3 hours at 1200°C. Series B samples have been implanted at 600°C and subsequently annealed at 1200°C during 3 hours. The annealing in both series has been carried out in N₂ at atmospheric pressures.The structure of the buried layers has been determined by conventional and high resolution transmission electron microscopy (CTEM and HRTEM). Polycrystalline silicon and new crystalline phases are observed by electron diffraction patterns. The polycrystalline silicon inclusions have been confirmed from analysis of HRTEM images.     

Massenaufgelöste Übergangssignale der Ionen C3H5O+ und C4H7O+

Abundance ratios of C₂H₄ and CO loss (CH₄ and O loss) in the field-free region of a mass spectrometer have been determined by mass resolution of metastable peaks. Using the method ofShannon andMcLafferty the abundance ratios have been applied to characterize the structure of metastable ions. C₃H₅O⁺ ions from 10 compounds and C₄H₇O⁺ ions from 14 compounds have been examined. In the case of C₃H₅O⁺, three types of structurally different isomers are present. C₄H₇O⁺ ions represent a not equilibrating mixture of different. structures in some cases. From examination of 2-pentanone-1,1,1,3,3-d ₅, metastable C₄H₇O⁺ ions from 2-pentanone have been shown to consist of two structurally distinct types of ions which are assumed to be $$\begin{array}{*{20}c} {CH_2 - O^ + } \\ {\begin{array}{*{20}c} | & {||} \\ \end{array} } \\ {CH_2 - C - CH_3 } \\ \end{array}$$ and butyryl ion.     

Synthesis of the C59N+ carbocation. A monomeric azafullerene isoelectronic to C60

A heterofullerene isoelectronic to C60 is reported. The azafullerenium cation C59N+ can be isolated in good yield as a carborane salt via the two-electron oxidation of the C-C bond of (C59N)2 dimer. [C59N][Ag(CB11H6Cl6)2] has been characterized by electronic, IR, Raman, and 13C NMR spectroscopies, MALDI spectrometry, DFT calculations, and X-ray crystallography.     

Simultanbestimmung von C, H und N unter Verwendung eines Analog-Digital-Umsetzers bei W?gung und Detektion

Zusammenfassung Es wird ein Gerät beschrieben zur gleichzeitigen Bestimmung von C, H und N aus einer Probe bei einer Einwaage von 0,2–0,6 mg. Zur Einwaage wird eine direktanzeigende elektromagnetische Waage verwendet. Die Probe wird in einem T-förmigen Quarzrohr mit vier Verbrennungszonen umgesetzt. Wasser wird in einer Kühlfalle festgehalten. CO₂ und N₂ werden gemeinsam bestimmt; anschließend wird nach Absorption des CO₂ über Natronasbest das N₂ einzeln bestimmt. Nach Ausheizen der Kühlfalle wird das Wasser bestimmt. Die Messung erfolgt mit einer Wärmeleitfähigkeitsmeßzelle und digitalem Integrator.Die Anlage ist weitgehend automatisiert. Nettoeinwaage und Impulszahlen werden auf einem Drucker registriert.

---

Summary An apparatus is described for determination of the carbon, hydrogen and nitrogen contents of organic compounds in one sample. The substance is. weighed on a direct-indication electromagnetic balance and is combusted in a T-shaped quartz tube. Carbon dioxide and nitrogen are determined simultaneously; during this time reaction water is retained by a cooling trap. Nitrogen is measured subsequently after absorption of carbon dioxide by soda asbestos. Reaction water is hereafter vaporized and determined. The measurement is performed by a thermal conductivity cell combined with a digital integrator. This unit is extensively automated. Net weight of substance and impulse figures are registered on a printer.

     

Hyperfine coupling constants of the azafullerenes C19N, C59N, C69N, and C75N

The isomers of the nitrogen-substituted fullerenes (azafullerenes) C19N, C59N, C69N, and C75N are examined using all-electron Gaussian atomic orbital basis density functional theory, to determine the doublet radical geometries and hyperfine coupling constants. We find that the inaccuracy of previously calculated hyperfine coupling constants of C59N resulted from a poor treatment of the geometry optimization. We find that UB3LYP minimization of the radical geometry in the 6-31G basis, followed by single-point evaluation of the hyperfine constants in which an expanded basis is used on the atomic sites of interest, forms an efficient compromise between computational cost and accuracy with respect to experimental hyperfine constants. Using this approach, we assign the hyperfine signals observed in experiments on the C69N radical by calculating the hyperfine coupling constants for all five of the isomers and examine the electron spin density distribution. Finally, we present predicted hyperfine coupling constants for the isomers of C19N and C75N for use in the interpretation of future experiments.     

Darstellung und Eigenschaften von N,N-Dialkyl-allylaminoboran-Addukten und N,N-Dimethyl-aminopropylboran

Synthesis and Properties of N,N-Dialkyl-allylaminoboranes and N,N-Dimethylaminopropylborane Complexes of the type H₃B ← NR₂(CH₂CH?CH₂) (R?CH₃ I , C₂H₅ II ) are formed by reaction of Li[BH₄] with dialkylallylammonium salts. By addition of AlCl₃ I can be transformed into the chelate-stabilized N,N-dimethyl-aminopropylborane III . The i.r.-, ¹H, ¹³C-n.m.r. and mass-spectra of I – III are reported and discussed.