Absolute rate constants for the reactions ofOHradicals withCH3CH2OH, CF2HCH2OHandCF3CH2OH

Summary Pulsed laser photolysis with resonance fluorescence monitoring of OH radicals was applied at T = 300±2 K to obtain the rate constants of k₁= (3.38±0.60)x10^-12, k₂= (2.52±0.44)x10^-13and k₃ = (1.06±0.30)x10^-13cm³molecule^-1s^-1with 2σprecision given for the overall reactions OH + CH₃CH₂OH (1), OH + CF₂HCH₂OH (2) and OH + CF₃CH₂OH (3), respectively. k₂is the first direct kinetic data for the reaction of OH radicals with CF₂HCH₂OH reported in the literature.</o:p>     

Three new vic‐dioxime ligands: Synthesis,characterization, spectroscopy,and redox properties of their mononuclear nickel(II) complexes

Nickel(II) complexes with three new vic‐dioxime reagents, N‐(ethyl‐4‐amino‐1‐piperidine carboxylate)phenylglyoxime (L₁H₂), N‐(ethyl‐4‐amino‐1‐piperidine carboxylate)glyoxime (L₂H₂) and N,N′‐bis(ethyl‐4‐amino‐1‐piperidine carboxylate)glyoxime (L₃H₂), have been prepared. Mononuclear nickel(II) complexes with a metal/ligand ratio of 1:2 were prepared using Ni(II) salt. All these nickel(II) complexes are nonelectrolytes as shown by their molar conductivities (Λ_M) in DMF solution at 10⁻³ M concentration. The ligands are soluble in common solvents such as DMSO, DMF, CHCl₃, and C₂H₅OH. The ligands and their Ni(II) complexes were characterized by elemental analyses, FT‐IR, UV‐visible, ¹H NMR, ¹³C NMR, magnetic susceptibility measurements, cyclic voltammetry, and molar conductivities (Λ_M). The cyclic voltammetric measurements show that [Ni(L₁H)₂] and [Ni(L₂H)₂] complexes exhibit almost similar electrochemical behavior, with two reduction and two oxidation processes based on either metals or oxime moities, while [Ni(L₃H)₂⋅2H₂O] complex displays irreversible, with one reduction and one oxidation processes based on oxime moity. This main difference could be attributed to the highly polarized [Ni(L₃H)₂⋅2H₂O] complex that has four carboxylate groups attached to piperidine on the oxime moieties. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:657–663, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20357     

Acyclic Branched α‐Fluoro Ketones for the Direct Asymmetric Mannich Reaction Leading to the Synthesis of β‐Tetrasubstituted β‐Fluoro Amines

The preparation of acyclic β‐fluoro amines bearing tetrasubstituted fluorine stereocenters is described via a direct Zn/ProPhenol‐catalyzed Mannich reaction. The reaction utilizes branched vinyl or alkynyl α‐fluoro ketones that can be coupled with a range of aryl, heteroaryl, vinyl, or cyclopropyl aldimines in high yield and with excellent diastereo‐ (up to >20:1) and enantioselectivity (up to 99 %). The use of readily cleaved tert‐butoxycarbonyl (Boc) or carboxybenzyl (Cbz) imine protecting groups adds utility to the reaction by allowing for easy access to the free amine products under mild and chemoselective reaction conditions.     

Effect of the Amount of Polysorbate 80 and Oregano Essential Oil on the Emulsion Stability and Characterization Properties of Sodium Alginate Microcapsules

Essential oils have a high volatility that leads to evaporation and loss of their pharmacological effect when exposed to the environment. The objectives of the present work were to prepare microcapsules with oregano essential oil by extrusion using sodium alginate as a shell material and non-ionic surfactant polysorbate 80 as an emulsifier to stabilize the emulsion. The present study was aimed to evaluate the physical parameters of microcapsules and to compare the influence of the amount of emulsifier and the essential oil-to-emulsifier ratio on the capsules’ physical parameters and encapsulation efficiency; to our knowledge, the existing research had not yet revealed whether unstable emulsion affects the encapsulation efficiency of oregano essential oil. This study showed that increasing the emulsifier amount in the formulation significantly influenced encapsulation efficiency and particle size. Moreover, increasing the emulsion stability positively influenced the encapsulation efficiency. The emulsion creaming index depended on the emulsifier amount in the formulation: the highest creaming index (%) was obtained with the highest amount of polysorbate 80. However, the essential oil-to-polysorbate 80 ratio and essential oil amount did not affect the hardness of the microcapsules (p > 0.05). In conclusion, the obtained results could be promising information for production of microcapsules. Despite the fact that microencapsulation of essential oils is a promising and extremely attractive application area for the pharmaceutical industry, further basic research needs to be carried out.