Addition of carbon nucleophiles to cyclic N-acyliminium ions in SDS/water

The acid-catalyzed addition of 1,3-dicarbonyl compounds and activated olefins (silyl enol ethers and ethyl vinyl ether) to N-Boc-2-methoxypyrrolidine (1a) and N-Boc-2-methoxypiperidine (1b) in SDS/water medium is described. Good yields of the corresponding 2-substituted N-Boc pyrrolidines were generally observed from 1a while moderate yields prevailed from 1b.     

Effect of iron salt on the color removal of water containing the azo-dye reactive blue 69 using photo-assisted Fe(II)/H2O2 and Fe(III)/H2O2 systems

The effect of chloride, sulfate and nitrate anions on the color removal of water containing the azo-dye reactive blue 69 (RB69) in acidic solution, by using photo-assisted Fenton process with Fe(II)/H₂O₂ and Fe(III)/H₂O₂ systems was investigated. Experiments were conducted in a batch reactor irradiated during 5 h with a domestic 15 W lamp with emission in the visible spectra. Experimental results showed color disappearance in the first 5 min of reaction in the photo-assisted process for all of the different salts, greatly enhancing the reaction rate with respect to the corresponding systems under dark conditions. The exception of the general trend was the Fe₂(SO₄)₃/H₂O₂/UV system, where the decolorization process is slower probably because the oxidative species generated by rupture of Fe(III)–peroxo complexes are less reactive. Total organic matter depletion and mineralization of the effluent were also tested during the experimental runs by means of total organic carbon (TOC) showing that, for most of the photo-assisted experiments high mineralization was reached after 3 h of reaction.     

Isomerism and decoherence

In the present paper we address the problem of optical isomerism embodied in the socalled “Hund’s paradox”, which points to the difficulty to account for chirality by means of quantum mechanics. In particular, we explain the answer to the problem proposed by the theory of decoherence. The purpose of this article is to challenge this answer on the basis of a conceptual analysis of the phenomenon of decoherence, that reveals the limitations of the theory of decoherence to solve the difficulties posed by optical isomerism and, in general, by quantum measurement.     

Hilbert spaces expanded with a unitary operator

We study Hilbert spaces expanded with a unitary operator with a countable spectrum. We show that the theory of such a structure is ω ‐stable and admits quantifier elimination. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Lippia origanoides chemotype differentiation based on essential oil GC‐MS and principal component analysis

Chromatographic (GC/flame ionization detection, GC/MS) and statistical analyses were applied to the study of essential oils and extracts obtained from flowers, leaves, and stems of Lippia origanoides plants, growing wild in different Colombian regions. Retention indices, mass spectra, and standard substances were used in the identification of 139 substances detected in these essential oils and extracts. Principal component analysis allowed L. origanoides classification into three chemotypes, characterized according to their essential oil major components. α‐ and β‐phellandrenes, p‐cymene, and limonene distinguished chemotype A; carvacrol and thymol were the distinctive major components of chemotypes B and C, respectively. Pinocembrin (5,7‐dihydroxyflavanone) was found in L. origanoides chemotype A supercritical fluid (CO₂) extract at a concentration of 0.83±0.03 mg/g of dry plant material, which makes this plant an interesting source of an important bioactive flavanone with diverse potential applications in cosmetic, food, and pharmaceutical products.     

Linear End‐On Coordination Modes of CO2

The second case of linear end‐on and evidence for an unprecedented bridging end‐on coordination mode of CO₂ have been discovered for vanadium aryloxide complexes of the tetradentate ligand system (ONNO)^2? (ONNO=2,4‐Me₂‐2‐(OH) C₆H₂CH₂]₂N(CH₂)₂NMe₂). The reaction of divalent (ONNO)V^II (TMEDA) with CO₂ and under the appropriate reaction conditions affords the trivalent (ONNO)V^III(OH)(η¹‐CO₂) resulting from an intermediate CO₂ deoxygenation pathway followed by H‐atom abstraction from the aromatic solvent, and CO₂ fixation. In contrast, the reduction of trivalent (ONNO)V^IIICl(THF) with K, followed by exposure to CO₂ in ethereal solvent, afforded the dinuclear [(ONNO)V^II]₂ (μ_,η¹‐CO₂).