Über die Darstellung von Arsendichloridtrifluorid,AsCl2F3

On the Preparation of Arsenic Dichloride Trifluoride, AsCl₂F₃ AsCl₂F₃ is prepared by pyrolysis of [AsCl₄]⁺ [AsF₆]^?. The vibrational spectra of the new low temperature compound are reported and the valence force constants are calculated. The formation of AsCl₂F₃ by ligand exchange reactions is discussed.     

Eine einfache Methode zur Bestimmung von Spurenmengen Kobalt (II)-ionen auf katalytischer Grundlage

Zusammenfassung Es wird eine Methode beschrieben, nach der, gegebenenfalls unter Zuhilfenahme von Testlösungen, Spurenmengen von Co²⁺ in einem Konzentrationsbereich von 10 mg bis zu 0,001 mg herab in 1 ml sich recht genau auf Grund der Katalyse der H₂O₂-Indigocarminreaktion in Gegenwart von Calciumcarbonat als Träger bestimmen lassen. Da das Volumen der Versuchslösung stets 60 ml beträgt (siehe oben), beläuft sich die kleinste noch bestimmbare Co²⁺-Konzentration auf 10^–6 g Co²⁺ in 60 ml was einer Verdünnung von 16·10⁷ entspricht. In bezug auf diese Empfindlichkeit steht die Methode den colorimetrischen bzw. spektrophotometrischen^1,6 und auch den komplexchemischen⁷ Verfahren nicht nach. Sie bietet aber im Vergleich mit diesen insofern gewisse Vorteile, als man die störenden Fremdionen meist nicht zu entfernen braucht, was auf eine beträchtliche Zeitersparnis hinauskommt. Schließlich ist die katalytische Methode, für die mit entsprechenden Abänderungen auch eine Temperatur von 30° C genügen würde, in ihrer Handhabung und Ausführung sehr einfach und bedarf, abgesehen vom Thermostaten, keiner kostspieligen Apparatur.     

Synthesis of Aristotelia-Type Alkaloids. Part XIII. Total syntheses of (+)-makonine, (+)-aristotelinone,and (+)-11,12-didehydroaristoteline

The oxidative transformation of synthetic (+)-aristoteline ((+)- 6 ) into other metabolites which had been isolated from Aristotelia species was investigated. Thus, treatment of (+)- 6 with I₂ as the single oxidant furnished the naturally occurring indole alkaloids (+)-makonine ((+)- 9 ),(+)-aristotelinone ((+)- 11 ), or (+)-11, 12-didehydroaristoteline ((+)- 7 ) in good yields, the selectivity of the oxidation process depending on the chosen reaction conditions.     

Über die Darstellung von Di(i-propyl)thiosulfonium-Salzen

On the Preparation of Di(i-propyl)thiosulfonium Salts [1] The preparation of the mercaptosulfonium salts (i-C₃H₇)₂SSX⁺SbCl₆^? (X = H, D) and of the chlorothiosulfonium salts (i-C₃H₇)₂SSCl⁺MF₆^? (M = As, Sb) and (i-C₃H₇)₂SSSCl⁺SbCl₆^? is reported. They are formed by reaction of chlorinated or protonated (i-C₃H₇)₂S with excess H₂S or SCl₂ and S₂Cl₂. The thiosulfonium compounds are characterized by vibrational and NMR spectroscopic methods.     

Primary reaction dynamics of halorhodopsin,observed by sub-picosecond IR – vibrational spectroscopy

The primary all-trans to 13-cis chromophore isomerization of the light driven chloride pump halorhodopsin has been studied by means of transient absorption spectroscopy in the visible and mid-infrared regime at a time resolution of better than 100 and 220 fs, respectively. The picosecond vibrational dynamics are dominated by two time constants, i.e., 2 and 7.7 ps in accordance with the biphasic decay of the retinal excited electronic state and electronic ground state formation with 1.5 and 6.6 ps. The transient vibrational spectra of the participating electronic states strongly suggest the existence of two distinct S₁ populations as a result of an early branching reaction. It is shown that the 13-cis product is formed with the fast time constant, whereas the all-trans educt state is repopulated via both time constants. Concomitant protein dynamics are indicated by spectral changes on a similar time scale in the amide region.     

The Electronic Structure of Azuleno[1,2,3-cd]phenalene and Azuleno[5,6,7-cd]phenalene,a Comparison

The photoelectron (PE.) spectra of azuleno[l, 2, 3-cd]phenalene ( 1 ) and azuleno- [5,6,7-cd]phenalene( 2 ) have been recorded. The first five bands of both compounds could be assigned to transitions corresponding to removal of electrons from 4a₂, 6b₁, 5b₁, 3a₂ and 4b_l orbitals. This assignment is based mainly on a comparison between the observed ionization potentials and orbital energies calculated in a HMO and a PPP model. The UV./VIS. polarized absorption spectrum of 1 in the region 10000–45000 cm^?1 has been measured by means of the stretched film technique. The measurements were performed in polyethylene sheets at 77°K. Several bands could be assigned to π* ← π transitions calculated by a PPP-CI method. A comparison between the electronic structures of 1 and 2 is made by means of a simple HMO diagram.     

Beiträge zur Chemie des Phosphors. 167 [1, 2]. Konstitutions- und Konfigurationsisomere von Pentaphosphan(7), P5H7

Contributions to the Chemistry of Phosphorus. 167. Constitutional and Configurational Isomers of Pentaphosphane(7), P₅H₇ Phosphane mixtures containing 10—15 P-% of pentaphosphane(7), P₅H₇, are obtained by thermolysis of diphosphane, P₂H₄, or as residue from distillation of crude diphosphane [3]. According to the complete analysis of the ³¹P{¹H}-NMR spectrum on the basis of selective population transfer experiments, P₅H₇ exists as a mixture of three diastereomers of n-P₅H₇ — 1a (erythro, erythro), 1b (erythro, threo), 1c (threo, threo) — and of the constitutional isomer 2-phosphinotetraphosphane 2 (iso-P₅H₇, largest relative isomeric abundance). The correlation between the diastereomers and the observed spin systems results from the preferred gauche orientation of neighboring free electron pairs, the dependence of ¹J(PP) on dihedral angles, and the ³J(PP) long range couplings. From the ³¹P-NMR data of the phosphane molecules P_nH_n+2 with n = 1—5 general relationships for the δ(³¹P) values and the ¹J(PP) coupling constants of chain-type phosphorus hydrides as a function of their structural parameters are derived.     

Untersuchungen zur elektrochemischen Simultanbestimmung von Blei und Zinn

Zusammenfassung Die starke Temperaturabhängigkeit des polarographischen Zinn(II/0)-Signals in Lösungen des vierwertigen Zinns ermöglicht bei –32° C in methanolischer salzsaurer Grundlösung die Bestimmung des Bleis neben hohem Zinnüberschuß. Eine Anwendung des Verfahrens zur wechselstrompolarographischen Bestimmung des Bleis in Rohzinn wird beschrieben.

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Investigations on the simultaneous electrochemical determination of lead and tinII. Polarographic determination of lead in the presence of tin at lower temperatures

Summary The strong temperature dependence of the polarographic tin(II/0) signal in solutions containing tin(IV) renders possible the determination of lead in the presence of a high excess of tin at working temperatures of –32° C in hydrochloric methanol as supporting electrolyte solution. An application of the procedure to the ac-polarographic determination of lead in crude tin is described.

Die vorliegende Arbeit wurde in dankenswerter Weise durch Mittel der Deutschen Forschungsgemeinschaft und des Verbandes der Chemischen Industrie ermöglicht.     

Vibrational structure of endohedral fullerene Sc3N@C78 (D3h'): evidence for a strong coupling between the Sc3N cluster and C78 cage.

The vibrational structure of the endohedral cluster fullerene Sc(3)N@C(78) is studied by FTIR spectroscopy, Raman spectroscopy and DFT-based quantum chemical calculations. Remarkably good agreement between experimental and calculated spectra is achieved and a full assignment of the Sc(3)N-based vibrational modes is given. Significant differences in the vibrational structure of the endohedral cluster fullerene Sc(3)N@C(78) and the empty, charged C(78) (6-): 5 (D(3h)') are rationalized by the strong coupling between the Sc(3)N cluster and the fullerene cage. This coupling has its origin in a significant overlap of the Sc(3)N and C(78) molecular orbitals, and causes atomic-charge and bond-length redistributions compared to the neutral C(78) and the C(78) (6-) anion. An ionic model is not sufficient to describe the electronic, geometric and vibrational structure of the Sc(3)N@C(78) nitride cluster fullerene.