Carbon-14 kinetic isotope effects in the debromination of p-methyldibromocinnamic acid

The kinetic isotope effect (KIE) was applied in the study of the mechanism of bromine elimination from p-methyl-erythro-a,b-dibromocinnamic acid, successively labeled at the a and b carbons. The large ¹⁴C KIE for the b-position and small KIE for the a one of side chain of p-methyl-erythro-a,b-dibromocinamic acid proves that elimination of bromine leading to the formation of (E)-p-methylcinnamic acid proceeds via the E1 mechanism.     

FTIR in situ transmission studies on the kinetics of paper degradation via hydrolytic and oxidative reaction paths

This study deals with the quantitative and qualitative interpretation of transmission FTIR spectra of aged model paper samples to prepare the basis for a kinetic model of cellulose degradation involving mixed hydrolytic and oxidative mechanism. The ageing experiments were performed in situ under various conditions (pure water vapour, dried air, 100, 150 °C) to discriminate between hydrolytic and oxidative paths. Our focus was on the spectra between 1500–1900 cm^-1, where the products of paper ageing appear in the form of various carbonyl groups. A procedure of spectra standardization was used to interpret the bands area in terms of the conversion of carbon atoms in cellulose. From the time evolution of the bands the overall kinetic curves were generated. The positions of the carbonyl bands were verified by independent experiments and theoretical calculations (DFT method). A simple model involving a hydrolytic reaction route and first order kinetics was positively tested on the available experimental basis. PACS 81.05.-t; 82.20.Wt; 87.15.Rn     

Mixed Norm and Multidimensional Lorentz Spaces

In the last decade, the problem of characterizing the normability of the weighted Lorentz spaces has been completely solved ([16], [7]). However, the question for multidimensional Lorentz spaces is still open. In this paper, we consider weights of product type, and give necessary and sufficient conditions for the Lorentz spaces, defined with respect to the two-dimensional decreasing rearrangement, to be normable. To this end, it is also useful to study the mixed norm Lorentz spaces. Finally, we prove embeddings between all the classical, multidimensional, and mixed norm Lorentz spaces. Research partially supported by KAW 2000.0048 and STINT KU 2002-4025. Research partially supported by Grants MTM2004-02299, 2005SGR00556 and The Swedish Research Council no. 624-2003-571.     

Lifetimes and side-feeding population of the yrast band levels in 131La

Lifetimes of yrast levels with spins I^π = 23/2^--43/2^- in ¹³¹La populated in the ¹²²Sn(¹⁴N, 5n) reaction at a beam energy of 70MeV are measured by the Doppler Shift Attenuation method. A model of side-feeding population is presented. The model parameters are determined in an experiment based on the lineshape of γ-transitions from two highest spin levels and from the intensity distribution along the yrast band. The properties of the h_11/2 band in ¹³¹La are compared with the theoretical predictions obtained in the framework of the Core-Quasi-Particle Coupling and the self-consistent Total Routhian Surface models.     

Diastereoselective Michael additions to α,β-unsaturated α-sulfinyl phosphonates in the thiolane series

A chiral racemic 2-phosphono-2,3-didehydrothiolane sulfoxide was used as a Michael acceptor in the reactions with several nucleophiles, in particular thiols. In most cases the reactions were fully diastereoselective. The relative configuration of the resulting adducts was determined.     

The 2:1 cocrystal of benzamide and penta­fluoro­benzoic acid

The crystal structure of the title compound, benzamide–2,3,4,5,6‐penta­fluoro­benzoic acid (2/1), 2C₇H₇NO·C₇HF₅O₂, consists of centrosymmetric hexa­meric supermolecules composed of four amide and two carboxylic acid mol­ecules connected via O—H⋯O and N—H⋯O hydrogen bonds. No phen­yl–perfluoro­phenyl π–π stacking inter­actions are observed in this cocrystal.     

Relationships Between the Lipophilicity and Anticonvulsant Activity of N-Benzyl-2-azaspiro[4.4]nonane- and [4.5]decane-1,3-dione Derivatives

JPC – Journal of Planar Chromatography – Modern TLC - The lipophilicity of twenty-one N-benzyl-2-azaspiro[4.4]nonaneand [4.5]decane-1,3-dione derivatives, fifteen of which (1–15)...     

Molecular transient effects in K-band spectroscopy

The time dependence of microwave transient absorption and emission was measured forJ=2←1 of the OCS molecule under on- and off-resonant conditions by the technique of Stark switching. The results are analyzed with the theory of a coherent electromagnetic wave interacting with a two-level quantum system through the electric dipole interaction to obtain the pressure dependence of the relaxation timesT ₂ and in consequence the pressure broadening parameterC _w=26.7±0.9 (μs·mTorr)^?1 has been obtained.