Base promoted transformation on thiadiazolopyridinium chlorides

1,2,4-Thiadiazolo[2,3-a]pyridinium chlorides undergo a very facile base promoted transformation to give bispyridilimino-1,2,4-thiadiazolidines. The unequivocal structural assignment of these last compounds was achieved by spectroscopic ¹H, 13C and ¹⁵N two dimensional methods.     

Studying Cu2–xSe phase transformation through DSC examination

The thermal effect accompanying the transition of Cu_2–xSe into a superionic conduction state was studied by non-isothermal measurements, at different heating and cooling rates (β=1, 2.5, 5, 10 and 20°C min^–1). During heating the peak temperature (T_p) remains almost stable for all values of β, (136.8±0.4°C for Cu₂Se and 133.0±0.3°C for Cu_1.99Se). A gradual shift of the initiation of the transformation towards lower temperatures is observed, as the heating rate increases. During cooling there is a significant shift in the position of the peak maximum (T_p) towards lower temperatures with the increase of the cooling rate. A small hysteresis is observed, which increases with the increase of the cooling rate, β. The mean value of transformation enthalpy was found to be 30.3±0.8 J g^–1 for Cu₂Se and 28.9±0.9 J g^–1 for Cu_1.99Se. The transformation can be described kinetically by the model f(ǯ)=(1–ǯ)^n(1+kcatX), with activation energy E=175 kJ mol^–1, exponent value n equal to 0.2, logA=20 and log(k_cat)= 0.5.     

A new intramolecular transformation of aromatic nitroso oxides

The possibility of intramolecular interaction of a nitroso oxide group with an aromatic ring is investigated at the UB3LYP/6-311+G(d,p) and G3MP2B3 levels of theory for a wide series of aromatic nitroso oxides. It is found that this reaction leads to the formation of a dioxazole cycle, its subsequent decay resulting in opening of the benzene ring and formation of nitriloxide and carbonyl functional groups. The activation enthalpy of the transformation of phenylnitroso oxide is 75.1 kJ/mol. It is shown that various sub-stituents at ortho-position (with respect to the nitroso oxide fragment) considerably lower the activation barrier of the investigated transformation, particularly in case of o,p-dimethoxyphenylnitroso oxide ΔH ^≠ = 43.7 kJ/mol. It is concluded that in the case of polyaromatic nitroso oxides, for which intramolecular cyclization is more typical (ΔH ^≠ ∼ 50 kJ/mol), a factor favoring the attack on the ortho-carbon atom is the stabilization of the product’s diene group due to its inclusion in the polyaromatic system. It is established that sum of these effects leads to a low activation barrier for the transformation of nitroso oxide that forms during the photooxidizing of 2-azido-1-methoxyphenazine, ΔH ^≠ = 19 kJ/mol. It is proposed that due to the low activation energy of some nitroso oxides, their intramolecular cyclization may be the primary channel of their unimolecular decay.     

Heat of transformation of chains in amorphous sulphur

The heatQ of transformation of the chains in amorphous sulphur was measured calorimetrically. The mean value ¯Q for samples remelted atT _f=443 K increases from 31.5 to 45.9 J g^–1 in the measurement temperature range from 288 to 303 K.For samples remelted in theT _f range from 443 to 573 K, the ¯Q values are from 30.6 to 24.0 J g^–1.The results are discussed on the basis of the theory of nucleation and growth of nuclei.     

Motion of a particle in a ring-shaped potential: An approach via a nonbijective canonical transformation

The problem of a particle in the three-dimensional ring-shaped potential ησ²(2a₀/r ? ηa/r² sin² θ)ε₀ introduced by Hartmann is transformed into the problem of a coupled pair two-dimensional harmonic oscillators with inverse quadratic potentials by using a nonbijective canonical transformation, viz., the Kustaanheimo–Stiefel transformation. The energy E of the levels for the ring-shaped potential is obtained in a straightforward way from the one for the two-dimensional potential — (4Eρ² + η²σ²a ε₀/ρ²).     

Coulombic and ring-shaped potentials treated in a unified way via a nonbijective canonical transformation

This paper is concerned with the three-dimensional potentialV _q =² (2a ₀/r–q a ₀ ²/r ² sin² ) ₀ which comprises as particular cases the ring-shaped potential (q = 1) and the Coulomb potential (q = 0). The Schrödinger equation for the potentialV _q is transformed via a nonbijective canonical transformation, viz., the Kustaanheimo-Stiefel transformation, into a coupled pair of Schrödinger equations for two-dimensional harmonic oscillators with inverse-square potentials. As a consequence, the discrete spectrum for the potentialV _q is obtained in a straightforward way. A special attention is paid to the caseq = 0. In particular, the coupled pair of Schrödinger equations for two-dimensional harmonic oscillators is tackled in the situations where the spectrum for the potentialV ₀ is discrete, continuous, or reduced to the zero point. Finally, some group-theoretical questions about the potentialV _q are mentioned as well as a connection, via the Kustaanheimo-Stiefel and the Levi-Civita transformations, between the quantum-mechanical problems for the potentialV _q and the Sommerfeld and Kratzer potentials.     

Formation and transformation of Amminecarbonatocobalt(III) Complexes

The preparation is described of [CoCO₃(NH₃)₅]ClO₄ · H₂O, trans-[CoCO₃(NH₃)₄(¹⁵NH₃)]ClO₄, and trans-[CoCO₃(NH₃)₄(NH₂CH₃)]ClO₄. The transformation reactions of these complexes, in which a chelate carbonate ligand is formed and one NH₃ is eliminated, were studied in solution and in the solid state. ¹H NMR spectroscopy is used for the identification of the products. It is shown that the transformation reactions are not stereospecific.     

Stereochemistry and transformation of dihydrothebain in the bain synthesis from labelled thebaines

The complete stereochemistry of the Δ⁶-dihydrothebaine → 7-bromodihydrocodeinone dimethyl ketal → codeinone dimethyl ketal → thebaine sequence of transformations has been elucidated by NMR studies of the isotopically labeled compounds prepared using diimide-d₂, methyl hypobromite-[¹⁴C], and methyl hypobromite-d₃. Final elimination of methanol from codeinone dimethyl ketal proceeds in a stereospecific manner: cis under acid catalysis with POC1₃, and trans under alkaline catalysis with EtO^?. As a result of these reactions, variously isotopically labeled thebaines can be prepared.     

Kinetics of the II-III phase transformation of polytetrafluoroethylene at high pressure

The rate of transformation from helical to all-trans-planar polytetrafluoroethylene (PTFE) at high pressures has been determined by monitoring the Raman spectra of PTFE following pressure jumps from the stability field of PTFE II to pressures between 9 and 14 kbar at temperatures between 0 and ?30°C. The transformation kinetics can be described by Avrami's equation for nucleation and growth kinetics with an exponent of 0.5, although observations at lower temperatures suggest that even smaller values of the exponent may be appropriate. At 10 kbar and 0°C, the specific rate constant is 0.51 min^?1/2. The energy and volume of activation are 11 kcal mole^?1 and ?7 cm³ mole^?1, respectively. The values of these parameters suggest that the transformation mechanism involves propagation of helix reversal planes along the several adjacent chains leaving all-trans material in their wakes.     

Phase transformation in spodumene–diopside glass

In situ developments of platelike spodumene–diopside grains were obtained by controlled devitrification of the complex system Li₂O–CaO–MgO–Al₂O₃–SiO₂ glass. The crystallization mechanisms of spodumene–diopside glass were measured by isothermal and non-isothermal processes using classical and differential thermal analysis techniques. The Avrami constant n was 2.0–2.1, indicating two-dimensional crystal growth and platelike grains. The crystalline phases precipitated first were high-quartz_s.s., then transformed to β-spodumene and diopside. The Flexural strength, fracture toughness and thermal shock resistance (in 20°C water) increased from 145 MPa, 1.3 MPa m^1/2, 800°C (pure spodumene) to 197 MPa, 2.9 MPa m^1/2 and 920°C (spodumene–diopside) with low thermal expansion coefficient (from 3∼9·10^–7 to 11.8·10^–7 K^–1). This mean in situ developments of platelike spodumene–diopside grains reinforced the low thermal expansion coefficient glass-ceramics.     

Isotachophoresis for rapid transformation of Escherichia coli

A frequent limitation of electroporation (EP) and chemical transformation (CT) are the need of tedious and time-consuming procedures for inducing transformation competence, the substantial number of cells required, and the low transformation yields typically achieved. Here, we show a new and rapid electrokinetic method for transformation of small number of noncompetent Escherichia coli TOP10 cells (2–3 × 10⁵) at room temperature. Escherichia coli TOP10 cells and plasmid DNA are sequentially injected into a 50 μm ID capillary and focused into 11.5 nL by isotachophoresis (ITP) induced by application of high DC voltage (–16 kV). Through ITP, a large excess of plasmid DNA is brought in contact with the cell surface, with the contact time adjusted by application of a counter-pressure (1.3 psi) opposing the ITP movement. The transformation rate was more than 1000-fold higher compared to EP and CT at survival rates greater than 60%.     

Phase transformation in a nanostructured M300 maraging steel obtained by SPS of mechanically alloyed powders

New complexes of type [Cu(HTBG)₂]Cl₂ (1), [Cu(TBG)₂]·3H₂O (2) and [CuL]·nH₂O (3) L:L¹, n = 2 and (4) L:L², n = 1 (HTBG: 2-tolylbiguanide, L¹ and L²: ligands resulted from 2-tolylbiguanide, ammonia/hydrazine and formaldehyde one pot condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR and UV–Vis data. Redox behaviour was established by cyclic voltammetry. The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against Gram-negative and Gram-positive strains isolated from the hospital environment. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. After water elimination, complexes have a similar thermal behaviour. Processes as water elimination, melting, chloride anion removal as well as oxidative degradation of the organic ligands were observed. The final product of decomposition was copper (II) oxide.     

Connections between perturbation theory and the unitary transformation methods of deriving effective Hamiltonians

The connections between open shell Brillouin–Wigner perturbation theory and the Van Vleck unitary transformation formalisms for generating effective Hamiltonians are explored. An explicit expression is obtained relating the generator ? of the unitary transformation e^i? with the amplitudes to be found from perturbation theory. The “renormalization effects” needed to produce the explicit “orthogonal-Hermitian” form of the effective Hamiltonian in perturbation theory are related directly to the generator of the unitary transformation. The conclusions reached previously by Jørgensen and Brandow regarding the identity of the effective Hamiltonians of the formalisms are explicitly verified for the case that the generator ? satisfied the Kemble condition. The procedure suggests how the powerful techniques of perturbation theory can be used within the unitary transformation framework to guarantee properly renormalized wave functions.     

O-(1-Phenyl-1H-tetrazol-5-yl) Glycosides: Alternative synthesis and transformation into glycosyl fluorides

A number of new glycosyl donors, O-(1-phenyl-1H-tetrazol-5-yl) glycosides, are prepared from the corresponding hemiacetals, commercially available 5-chloro-1-phenyl-1H-tetrazole ( 2 ), and tetrabutylammonium fluoride (Bu₄NF) in either THF or DMF. The mild reaction conditions are compatible with a variety of protecting groups. The glycosyl donors are treated with hydrogen fluoride-pyridine complex (HF·py) to rapidly provide glycosyl fluorides in good-to-excellent yields, apparently by a (single or double) S_N2 mechanism as studied by both ¹H- and ¹⁹F-NMR spectroscopy. Under acidic conditions, glycosyl fluorides equilibrate partially or completely, equilibration requiring a large excess of HF · py.     

The transformation of phenyltin species during sample preparation of biological tissues using multi-isotope spike SSID-GC-ICPMS

A multi-isotope spike species-specific isotope dilution (MI-SSID) calibration strategy in connection with gas chromatography-inductively coupled plasma mass spectrometry was applied to evaluate different extraction procedures for the speciation analysis of phenyltin (PhT) compounds in biological materials: mussel tissue BCR CRM-477 and fish tissue NIES-11. Three different isotope-enriched PhT compounds, ¹¹⁸Sn-enriched monophenyltin (MPhT), ¹²²Sn-enriched diphenyltin (DPhT), and ¹²⁴Sn-enriched triphenyltin (TPhT), were used for the preparation of spikes to follow and correct for six possible interconversion reactions between PhT species that can take place in a sample. The acidity of the extractant, the presence of complexing reagents, and the use of ultrasonic or microwave agitation were found to affect the degradation of PhT compounds. No formation of PhTs through phenylation and negligible degradation of MPhT to inorganic tin were observed under the conditions investigated. The degree of degradation increased with increased acidity of extractant and when ultrasonication or microwave agitation was used. Under relatively mild extraction conditions, the degradation factors for DPhT and TPhT in the two reference materials studied were found, using MI-SSID, to be between 10 and 55% and 2 and 10%, respectively. Using the degradation factors, we calculated corrected concentration values for the organotin species. When microwave extraction at high power output was used, hydrogen radicals were formed that can enhance the degradation of DPhT and TPhT. The hydrogen radicals were trapped using N-tert-butyl-α-phenylnitrone and detected by electron spin resonance spectrometry. The effect of different extraction parameters on the degradation of PhT compounds in biological samples is discussed.     

Microbial transformation of cannabinoids. Part 3: Major metabolites of (3R, 4R)-Δ1-tetrahydrocannabinol

The metabolic transformations of the psychotropic cannabinoid (3R, 4R)-Δ¹-tetrahydrocannabinol (5) (=Δ¹-THC) by cultures of Fusarium Nivale, Gibberella fujikuroi (both Ascomycetes) and Thamnidium elegans (Phycomycetes) were investigated. A number of metaboilites, 1–4 and 6–9 were isolated from the incubations, partly purified and their structures elucidated by combined gas chromatography/mass spectrometry. Four of these metabolites, 1″-hydroxy-Δ¹-THC (4) 2″-hydroxy-β¹-THC (1) 6Δ-hydroxy-ζ¹-THC (8) and 2″,6Δ-dihydroxy-Δ¹-THC (9) so far have not been reported as microbial transformation products of 5 .     

Temperature‐induced solid‐to‐solid transformation in helical homochiral coordination polymers

The reactions of (R)‐ and (S)‐4‐(1‐carboxyethoxy)benzoic acid (H₂CBA) with 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene (1,3‐BMIB) ligands afforded a pair of homochiral coordination polymers (CPs), namely, poly[[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene][μ‐(S)‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)] monohydrate], {[Zn(C₁₀H₈O₅)(C₁₄H₁₄N₄)]·H₂O}_n or {[Zn{(S)‐CBA}(1,3‐BMIB)]·H₂O}_n ( 1‐L ), and poly[[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene][μ‐(R)‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)] monohydrate] ( 1‐D ). Three kinds of helical chains exist in compounds 1‐D and 1‐L , which are constructed from Zn^II atoms, 1,3‐BMIB ligands and/or CBA^2? ligands. When the as‐synthesized crystals of 1‐L and 1‐D were further heated in the mother liquor or air, poly[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene][μ‐(S)‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)], [Zn(C₁₀H₈O₅)(C₁₄H₁₄N₄)]_n or [Zn{(S)‐CBA}(1,3‐BMIB)]_n ( 2‐L ), and poly[[μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene][μ‐(R)‐4‐(1‐carboxylatoethoxy)benzoato]zinc(II)] ( 2‐D ) were obtained, respectively. The single‐crystal structure analysis revealed that 2‐L and 2‐D only contained one type of helical chain formed by Zn^II atoms and 1,3‐BMIB and CBA^2? ligands, which indicated that the helical chains were reconstructed though solid‐to‐solid transformation. This result not only means the realization of helical transformation, but also gives a feasible strategy to build homochiral CPs.     

Changes in the sol-gel transformation behavior of azobenzene moiety-containing methylcellulose irradiated with UV light

Azobenzene moiety-containing methylcellulose (AB-MC) was prepared, the changes of the cloud point of its aqueous solutions as a thermotropic sol-gel transformation behaviour were investigated under irradiation with UV light. AB-MC's with degrees of substitution by the azobenzene moiety DS_AB > 2,5 · 10^-2 were insoluble in water. The azobenzene moiety in the AB-MC was confirmed to be reversibly isomerized from the trans- to the cis-form under irradiation with UV light of wavelengths 390 > λ > 310 nm and from the cis-to the trans-form under irradiation with visible light of λ > 400 nm. The cloud point value of the aqueous solution of AB-MC increased under irradiation with UV light of 390 > λ > 310 nm for the AB-MC's with a DS_AB value in a certain range and the extent of the increase in the cloud point value was higher at higher concentrations of AB-MC.