A novel method for preparation of vicinal fluoro-iodo compounds using elemental fluorine

Elemental fluorine reacts with iodine at ?75° and the resulting IF is reacted, without any isolation or purification, with olefins thus producing fluoro-iodo compounds in an excellent regio- and stereospecific mode.     

Synthesis of alpha-fluorocarboxylates from the corresponding acids using acetyl hypofluorite.

alpha-Fluorocarboxylic esters and acids were synthesized in good yields. The corresponding esters and acids were converted to their ketene acetals, and these enol derivatives reacted with AcOF made directly from fluorine. This route circumvents the problems associated with nucleophilic fluorinations such as various eliminations and rearrangements. alpha- and beta-branched carboxylic acid derivatives that cannot be directly fluorinated gave by this electrophilic fluorination the corresponding alpha-fluoro derivatives in good yield. Both the fluorination reaction and the preparation of AcOF are fast and suitable for [18]F incorporation into acids and esters needed for working with PET. alpha-Fluoroibuprofen (20) and methyl 2-fluoro-3,3,3-triphenylpropionate (32) are two examples of this general reaction.     

Activation of a CH bond in polypyridine systems by acetyl hypofluorite made from F2

Activation of the relatively inactive polypyridine backbone with strong electrophilic fluorine, originating from acetyl hypofluorite (AcOF) enables attack of the acetoxy moiety at the α position to the heteroatom. Derivatives of bipyridine, phenanthroline and terpyridine systems have been acetoxylated or oxygenated within a few minutes usually in very good yields.     

Polymer‐regulated pattern formation in pseudo‐2D arrays of a fullerene derivative at the solution—Air interface

Self‐assembly of nanoparticles (NPs) into nonclose‐packed (ncp), semi‐two‐dimensional (2D) arrays is of interest in a variety of applications. Of special interest are photochemically active surfactant‐like fullerene derivatives [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM). The study presented here characterizes the morphology and structure of patterns formed by a mixture of PCBM NP and an amphiphilic block‐copolymer tethered at the water–air interface (a surface brush) as a function of the concentration of poly(ethylene oxide) (PEO) dissolved in the liquid subphase. Theoretical modeling of the system shows that the concentration of PEO in the subphase mediates the dimensions of the surface brush and at high PEO concentrations induces a collapse of the brush at the solution–air interface. The state of the surface brush is suggested to tune the semi‐2D patterns observed in the experiments via lateral depletion interactions and, in particular, induce lateral phase separation of the PCBM‐block copolymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

A new efficient route for the formation of quinoxaline N-oxides and N,N'-dioxides using HOF.CH3CN

HOF.CH3CN, a very efficient oxygen-transfer agent made readily from fluorine and aqueous acetonitrile, was reacted with various quinoxaline derivatives to give the corresponding mono N-oxides and especially the N,N'-dioxides in very good yields under mild conditions and short reaction times.     

Efficient synthesis of episulfones and of SO2 with any variation of oxygen isotopes using HOF.CH3CN

[reaction: see text] Episulfones are quite unstable and difficult to make compounds. HOF.CH(3)CN, a powerful oxygen transfer agent operating under very mild conditions, was successfully employed in converting episulfides to episulfones. Unlike other oxidizing agents, no episulfoxides were formed under standard conditions. Reacting H(18)OF.CH(3)CN with either an episulfide or an episulfoxide leads to the corresponding episulfone with all combinations of oxygen isotopes. Decomposition of such episulfones gives any desirable variation of S(18)O(x)()O (x = 16, 18).     

Determination of the coefficient of longitudinal mixing in a undeformed porous medium in the presence of sorption

The article gives and analysis of an expression for the overall coefficient of longitudinal mixing in a porous undeformed medium and obtains analytical expressions for the initial and central moments. The distribution of the concentrations along the filtration channel for a fixed value of the time and the distribution of the concentrations at the outlet of a channel of fixed length are obtained in the form of Hermite polynomials (the forward problem). A method is outlined for determining the coefficient of longitudinal mixing from the experimental distributions and analytical expressions for the moments (the reverse problem). The article gives numerical values of the coefficient of longitudinal mixing found using the method under consideration.Moscow. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 155–161, July–August, 1972.     

Structure of gum arabic in aqueous solution

Gum arabic, a natural polysaccharide derived from exudates of Acacia senegal and Acacia seyal trees, is a commonly used food hydrocolloid. The complex chemical structure of the gum has been widely studied revealing a multifraction material consisting mainly of a highly branched polysaccharide and a protein–polysaccharide complex (GAGP) as a minor component. This work investigates its mesoscopic structure in aqueous solution by small‐angle X‐ray and neutron scattering combined with cryotransmission electrons microscopy. Scattering measurements reveal an intricate shape composed of many spheroidal aggregates assigned to the polysaccharide with a small amount of larger coils. A scattering peak is observed at moderate to high concentrations, the spacing of which exhibits a c^?1/3 power law relation to polymer concentration (c). Upon addition of salt, this peak disappears, indicating its electrostatic nature. The large coils contribute a q^?2 power law at the low scattering vector (q) range. However, at low concentration in which the interaggregate peak is not observed, a q^?1 power law at the low q range indicates the possible existence of a fraction with a locally extended conformation. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3265–3271, 2006