On the reaction of isothiosemicarbazides with heterocumulenes. Part I

Isothiosemicarbazides 2 react with acyl isothiocyanates under addition-cyclization to yield 1,3,4-thiadiazoline-2-imines 3 as well as the isomeric 2-amino-substituted 1,3,4-thiadiazolium-5-acylaminides 3′ . In a similar manner the 2-hydrazino-substituted 1,3-thiazoline 4 adds ethoxycarbonyl isothiocyanate to give the thiosemicarbazide 5 , which undergoes a rearrangement to the 1,3,4-thiadiazoline-2-imine 5′. The [2+2] cycloreversion of 3d involving ethoxycarbonyl iso(thio)cyanate and the thermal induced Dimroth rearrangement of 3′f and h are also discussed.     

Chemometric classification of gunshot residues based on energy dispersive X-ray microanalysis and inductively coupled plasma analysis with mass-spectrometric detection

A gunshot residue sample that was collected from an object or a suspected person is automatically searched for gunshot residue relevant particles. Particle data (such as size, morphology, position on the sample for manual relocation, etc.) as well as the corresponding X-ray spectra and images are stored. According to these data, particles are classified by the analysis-software into different groups: ‘gunshot residue characteristic’, ‘consistent with gunshot residue’ and environmental particles, respectively. Potential gunshot residue particles are manually checked and – if necessary – confirmed by the operating forensic scientist.     

Extraktion von 3d-Metallionen mit zweizähligen Sulfonamiden. I. Liganden mit Schwefel bzw. heterocyclisch gebundenem Stickstoff als zweitem Haftatom

Extraction of 3d-Metal Ions by Bidendate Sulfonamides. I. Ligands with Sulfur or Heterocyclic Nitrogen as a Second Donor Atom The properties of 2-acetylpyridine-p-toluensulfonylhydrazone (APSH - H), arensulfonylthioureas (I), and the esters of arensulfonylmonothiocarbamic acid (II) or arensulfonyldithiocarbamic acid (III) as extractants for the late 3d-metal ions are proved. APSH-H is comparable to the proprietary extractant LIX 34. But, because of the special structure of the corresponding 1,2-chelates, the pH_1/2-values of nickel(II) and cobalt(II) are ≈2 units lower. The pK_s-values, measured in dioxane-water mixtures (75 per cent v/v), increase in the order III < II < I. In aqueous solutions compounds of type III are acids of medium strength. In the case of compounds of type I the substituents of the non-sulfonated nitrogen have a strong influence on the pK_s-values (ΔpK_s = 4.6). Among the late 3d-elements, the ligands II and III extract only copper(II) (pH_1/2 ～2.7 or ～1.6), the ligands I extract zinc(II), cobalt(II), and nickel(II) as well, but not iron(II) and iron(III). The reasons of this unique behaviour are discussed.     

Application of the photoionization detector for the determination of ethanol in aqueous solutions and human breath

A determination of ethanol is described, which is based on a purging system in conjunction with a photoionization detector. With that system a fast and reliable determination of ethanol in aqueous solutions is possible. The system has been used for the analysis of wine. The 3delta-detection limit has been 0.005% ethanol, the relative standard deviation 4.8 to 6.0% and the time constant of the entire analytical system 20 s. The photoionization detector has been also applied to the analysis of artificial and genuine human breath. A comparison with gas-chromatography and non-dispersive IR-detection has been proven the reliability of results.     

ASSESSMENT OF GENOTOXICITY AND MUTAGENICITY OF 1,2-DIOXETANES IN HUMAN CELLS USING A PLASMID SHUTTLE VECTOR

Abstract— 1,2-Dioxetanes are efficient sources of triplet excited carbonyl compounds on thermal decomposition. They cause photochemical and photobiological transformations in the dark. In order to study the genotoxicity and mutagenicity of 1,2-dioxetanes, the replicating shuttle vector pZ189 was damaged with 3,3,4-trimethyl-l,2-dioxetane(TrMD) or 3-hydroxymethyl-3,4,4-trimethyl-l,2-dioxetane (HTMD) in vitro and subsequently transfected into normal human lymphoblasts. We found a dose-dependent increase of genotoxicity (decrease of plasmid survival) and increase of mutation frequency with both dioxetanes. However, TrMD was less mutagenic than HTMD at similar genotoxicity. Sequence analysis of the supF gene revealed more point mutations than deletions. Single base substitutions occurred exclusively at G:C sites: 94.6% of point mutations with TrMD and 100% with HTMD were G:C to T:A and G:C to C:G transversions. These are the typical mutations following 7,8-dihydro-8-oxoguanine (8-oxo-G) formation, the main DNA lesion induced by TrMD and HTMD. Only with TrMD we found 5.4% G:C to A:T transitions, probably reflecting the more pronounced ability of TrMD to form some pyrimidine dimers. Our results indicate that 8-oxo-G is also the most relevant modification in in vivo mutagenesis.     

Thermodynamische Untersuchungen zur Chelatbildung zwischen Aminoterephthalsäure-N,N-diessigsäure und 3 d- bzw. Erdalkalimetallionen. Eine Betrachtung zum Einfluß einer koordinativ inaktiven Carboxylgruppe auf die komplexe Bindung von Metallionen durch Aminopolycarbonsäuren

N-(2-Carboxyphenyl)iminodiacetic acid (H₃A) and N-(2,5-dicarboxyphenyl)iminodiacetic acid (H₄B) are tetradentate ligands and form complexes of the composition MA- and MB^2? with M^II ions. These compounds differ by the additional charge of the second carboxylic group only, which is fixed to the benzene nucleus and which is unable for coordination for steric reasons. Using an anisothermal calorimeter ΔH values for the formation of the complexes MA- and MB^2? in aqueous solution have been measured at an ionic strength 0.1 m KNO₃. From these data, and from the stability constants of the complexes, entropy changes ΔS have been calculated. In all cases investigated (M^m+ = H⁺, Mg²⁺, Ca²⁺, Sr²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) the ΔH values are more negative for the complexes MA^m-3 than for complexes MB^m-4, whereas the ΔS values are greater for complexes MB^m-4. Using a simple model for the molecules of the complexes MB^m-4 and empirically determined dielectric constants of the medium between the central ions and the noncoordinated ionized carboxylic group, the electrostatic attraction between these charges was calculated. Basing on these results the influence of the noncoordinated carboxylic group on the central atom by the mesomeric and inductive effect is discussed.     

Solvation and Ion-Pairing Effects of Choline Acetate Electrolyte in Protic and Aprotic Solvents Studied by NMR Titrations

Choline-based electrolytes have been proposed as environmentally friendly and low-cost alternatives for secondary zinc air batteries. Choline acetate [Ch]⁺[OAc]⁻ in protic (D₂O) and aprotic (DMSO-d₆) solvents has been studied by means of concentration-dependent ¹H NMR, viscosity, and density measurements. The viscosities have been calculated on the basis of the Jones-Dole equation and showed that the dominant contribution originates from short-range ion-solvent interactions. Site-specific association affinities were assigned from NMR chemical shift titrations. In DMSO-d₆, the hydroxyl group of choline was found to have the smallest dissociation constant followed by the methyl group of acetate. The corresponding Gibbs energies at low concentration were found to be in agreement with a solvent-separated ion pair (2SIP) configuration, whereas at concentrations above 300 mM, a solvent-shared ion pair (SIP) configuration was assigned. For [Ch]⁺[OAc]⁻ in D₂O, association effects were found to be weaker, attributed to the high dielectric constant of the solvent. On time scales on the order of 100 ms, NMR linewidth perturbations indicated a change in the local rotational dynamics of the ions, attributed to short-range cation-solvent interactions and not to solvent viscosity. At 184 mM, 40 % of the cations in DMSO-d₆ and 10 % in D₂O were found to exhibit short-range interactions, as indicated by the linewidth perturbations. It was found that at about 300 mM, the ions in DMSO-d₆ exhibit a transition from free to collective translational dynamics on time scales on the order of 400 ms. In DMSO-d₆, both ions were found to be almost equally solvated, whereas in D₂O solvation of acetate was stronger, as indicated by the obtained effective hydrodynamic radii. For [Ch]⁺[OAc]⁻ in DMSO-d₆, the results suggest a solvent-shared ion association with weak H-bonding interactions for concentrations between 0.3–1 M. Overall, the extent of ion association in solvents such as DMSO is not expected to significantly limit charge transport and hinder the performance of choline-based electrolytes.     

Neue Redoxserien auf der Basis von Übergangsmetallkomplexen heterocyclischer Arensulfonylhydrazone

New Redox Series Based on Transition Metal Complexes of Heterocyclic Arenesulfonylhydrazones Heterocyclic bidentate arenesulfonylhydrazones (2-acetylpyridine-p-toluenesulfonylhydrazone ? APSH? H, 2-acetylquinoline-p-toluenesulfonylhydrazone ? ACSH? H) with transition metal ions afford tetrahedral 1,2-complexes M^II(APSH)₂ and M^II(ACSH)₂. In most cases the E-isomers of APSH^? and ACSH^? are coordinated, five-membered chelate rings are formed with the pyridine and hydrazone nitrogen atoms as donor atoms. In the complexes Zn(APSH)₂ and Cu(APSH)₂ probably the Z-isomer of APSH^? is present with the pyridine and the sulfonylamide nitrogen atoms as a donor set, yielding a six-membered chelate ring. These proposals are based on the magnetic moments, the ligand field spectra, and the binding energies (ESCA). Normally the complexes M^II(APSH)₂ and M^II(ACSH)₂ are reduced in two reversible steps. For Fe(APSH)₂ and Fe(ACSH)₂ a third anodic wave, but for Cu(APSH)₂ only one wave is observed. Relations between redox properties and structure of the new complexes are discussed, and the redox series are compared with that of the M(dipy)₃ⁿ⁺-type complexes.     

Improved excitation schemes for multiple-quantum magic-angle spinning for quadrupolar nuclei designed using optimal control theory

We have investigated the use of optimal control theory for the design of improved multiple-quantum excitation schemes for the popular multiple-quantum magic-angle spinning NMR experiment for quadrupolar nuclei with half-integer quadrupolar spin. The advantage of the new low-power experiments, termed OCFASTER, is demonstrated by sensitivity improvements approaching 50% for 87Rb in RbClO4 and RbNO3 as compared to FASTER and standard strong-pulse excitation schemes.