An Efficient Route to Emodic Amine and Analogous <Emphasis Type="Italic">O</Emphasis>-Methyl Protected Derivatives Starting from Emodin

Summary. Emodic amine could be synthesized in a five-step approach in excellent overall yield by following a modified Curtius rearrangement strategy, starting from the naturally occurring emodin. This unique emodin derived 6-amino substituted polyhydroxylated anthraquinone may serve as a promising synthon for a new class of amino functionalized photodynamically active hypericin derivatives. In addition, the partially O-methyl protected 6-amino- and 6-carboxy-anthraquinones could be synthesized in high yields via selective O-methyl ether cleavage from the corresponding tri-O-methyl derivatives.     

Mass spectrometric studies of dithiophosphinato metal complexes

Electron impact induced fragmentation reactions of planar, tetrahedral, octahedral and oligomeric metal dithiophosphinates Me(II)L₂ (L=Et₂PS₂^?; Me(II)=Zn, Cd, Hg, Pb, Co, Mn, Ni, Pd, Pt), Me(III)L₃ (Me(III) = Sb, Bi, In, Rh, Ir) and (Me(I)I)_n (Me(I)/n=Tl/1, Au/2, Cu/4) have been studied. Fragmentation patterns, which are in accordance with metastable peak determinations by linked scans, are reported. In the case of the transition metals the spectra of the complexes show abundant [M]^+· predominantly metal containing ions and, the former being weak and the intensities of the latter being considerably reduced in the case of metal complexes with filled d shells. With planar or tetrahedral transition metal complexes no dependence of fragmentation on the coordination geometry can be observed. The dependence of fragmentation on d configuration, ionization energy of the metal and metal ligand π bonding is discussed. In the case of the oligomeric complexes strong metal-metal interaction is observed even under electron impact.     

Solid-Solute Phase Equilibria in Aqueous Solution. XII. Solubility and Thermal Decomposition of Smithsonite

The solubility constant of ZnCO₃, smithsonite, in aqueous NaClO₄ solutions hasbeen investigated as a function of temperature (288.15 T/K 338.15) atconstant ionic strength I = 1.00 mol-kg^–1. In addition, the solubility of zinccarbonate has been determined at 2.00 and 3.00 mol-kg^–1 NaClO₄ (298.15 K).The solubility measurements have been evaluated by applying the Daviesapproximation, the specific ion-interaction theory, and the Pitzer model, respectively.The thermodynamic interpretation leads to an internally consistent set ofthermodynamic data for ZnCO₃ (298.15 K): solubility constant log*K _p50 ⁰ = 7.25 ± 0.10,standard Gibbs energy of formation _i G (ZnCO₃) = (–777.3±0.6)kJ-mol^–1, standard enthalphy of formation _f H (ZnCO₃)= (–820.2±3.0) kJ-mol^–1,and standard entropy S (ZnCO₃) = (77±10)J-mol^–1 K.^–1. Furthermore, the DSCcurve for the thermal decarbonation of zinc carbonate has been recorded in orderto obtain the enthalpy of formation _fH (ZnCO₃) =(–820.2±2.0) from theheat of decomposition. Finally, our results are also consistent within theexperimental error limits with a recent determination of the standard entropy ofsmithsonite, leading to a recommended set of thermodynamic properties of ZnCO₃:      

Intercomparison on measurements of PCBs in pork fat during the Belgian PCB-crisis

During the Belgian PCB crisis (1999/2000) the quality of the data from the PCB monitoring were studied with a proficiency testing experiment. Pork fat that was spiked at the Institute for Reference Materials and Measurements (EC-JRC-IRMM) was sent out as unknown to all laboratories that participated in the monitoring. In parallel, the material was certified on the basis of the results of several leading PCB laboratories throughout Europe that did not participate in the monitoring. During the first round 15 to 25% deviation was experienced, while in the end of this multistep intercalibration procedure the average deviation for the respective PCBs was 10.9% (PCB 28), 13.1% (PCB 52), 10.1% (PCB 101), 10.7% (PCB 118), 10.7% (PCB 138), 9.1% (PCB 153), 8.1% (PCB 180) and 8.2% for the sum of the 7 PCBs. The concentrations measured for the higher volatile PCB 28 had a tendency to show lower levels, while for PCB 180 this was less pronounced. On the other hand, PCB 153 showed results rather to the higher side. During this exercise the material was also tested for stability by one of the certifying laboratories.     

Dyes of the triphenylmethane type as sensor materials for solvent vapours

Summary The formation of highly coloured trityl ions from substituted phthalides can be utilized for the detection of solvent vapours in the air down to nearly ten ppm. These optochemical sensor materials were optimized with respect to their sensitivity, stability, linearity of the response and exclusion of the humidity influence. For this purpose the 4,4,4-substituents at the aromatic rings of the dyes must yield an appropriate carbenium ion stability. Thus even small amounts of absorbed solvent vapours lead to the reduction of the dye concentration in the sensor layers. The largest sensitivity can be achieved by applying dyes with two — N(CH₃)₂ substituents or, instead of one dimethylamino group, the — OCH₃ group at the aryl rings. Further improvements to reduce the sensor response to moisture were possible by introducing into the phthalides large aromatic ring systems with a hydrophobic behaviour such as indolyl.

---

Farbstoffe vom Triphenylmethan-Typus als Sensormaterial für LösungsmitteldÄmpfe

---

Dedicated to Prof. Dr. Hans Hofmann on the occasion of his 60th birthday     

Beiträge zur Chemie der Pyrrolpigmente, 72. Mitt.

A strategy for the synthesis of bilatrienes-abc bridged between rings A and C has been developed and tested in case of a bibenzylethane bridging fragment. This strategy was then applied to the synthesis of a 2,3-dihydrobilatriene-abc bridged by a (S)-lysine moiety from ring A to ring C (positions 3 and 12) by means of peptide bonds between the two amino groups of lysine and the acetic and propionic acid side chains of the chromophoric unit. The two diastereomers resulting from the two chiral centers of the lysine residue and at position 3 of the chromophore were separated by chromatography.

     

Bis(tetraphenylcyclobutadien)palladium(0)

Tetraphenylcyclobutadienepalladium dichloride reacts with 1,2,3,4-tetraphenyl-1,4-dilithiumbutadiene or with sodium with abstraction of halide to give the sandwich compound bis(tetraphenylcyclobutadiene)palladium(0). The structure of the latter is elucidated by spectroscopic methods and its reactions with Br₂, H₂, K and HNO₃ are described.     

Molecular Structures of Sulfur Cyanide Trifluoride, SF(3)CN, and Sulfinyl Cyanide Fluoride, FS(O)CN

General valence force fields for SF(3)CN and FS(O)CN are derived from vibrational data taken from the literature and from theoretical calculations. Gas phase electron diffraction studies on both molecules yield the following geometric parameters (r(a) distances and angles with 3sigma uncertainties). SF(3)CN: r(S-F(e)) = 155.2(4) r(S-F(a)) = 165.7(3), r(S-C) = 173.6(8), r(C&tbd1;N) = 115.9(4) pm; angle(F(a)SF(e)) = 86.9(3), angle(F(a)SC) = 86.0(4) angle(F(e)SC) = 98.7(8), angle(F(a)SF(a)) = 169.0(6), angle(SCN) = 171(4) degrees. FS(O)CN: r(S-F) = 159.8(3), r(S=O) = 143.2(2), r(S-C) = 178.3(3), r(C&tbd1;N) = 115.0(3) pm; angle(FSO) = 104.9(4), angle(FSC) = 93.9(4), angle(CSO) = 105.3(5), angle(SCN) = 176(4) degrees. These experimental results are compared to ab initio values (HF/3-21G, HF/6-31G, and MP2/6-31G), and the bonding properties in these sulfur (IV) cyanides are discussed.