Alpha-substituted organic peroxides: synthetic strategies for a biologically important class of gem-dihydroperoxide and perketal derivatives

In this paper we review the recent developments in the synthesis of alpha-substituted hydroperoxides. Alpha-substituted hydroperoxides are interesting compounds due to their chemistry and bioactivity and as intermediates for the synthesis of other peroxides, of which cyclic peroxides are of major importance. Although the emphasis of this report will be on the derivatives of gem-dihydroperoxides, perketals, as well as the less studied nitrogen and sulfur derivatives, will also be covered.     

The role of multifunctionalized amine structure and reaction conditions on the transformations of crosslinked copoly(styrene-p-nitrophenylacrylate)

Crosslinked copoly(styrene-p-nitrophenylacrylates), containing 2% (1) or 4% DVB (2) were converted with various diaminoalkanes (1,2-diaminoethane 3a, 1,4-diaminobutane 3b, 1,8-diaminooctane 3c) to amides. The degree of additional crosslinking depended on the chain length of the diaminoalkane, the molar ratio of ester function in 1 or 2 to diaminoalkane, solvent polarity (dimethylformamide, chloroform, toluene), while reaction temperature (50 or 100°C) had only a minor effect. 2 was also converted with various amines bearing additional functional groups (ethanolamine, 3-amino-1-propanol, 4-aminomethylpyridine, 2-(2-aminoethylamino)-ethanol, 2-(2-aminoethoxy)-ethanol, 6-aminocaproic acid, N-propylaminomorpholine, 3-N,N-diethylamino-1-propylamine) to the corresponding amides. The swelling ability of the resins depended on the crosslinking of the starting copoly(styrene-p-nitrophenylacrylate) (1, 2), the structure of the amide, the degree of additional crosslinking, and solvent polarity (chloroform, dimethylformamide, methanol, toluene). The accessibility of nitrogen atoms in the polymer matrix was examined by EtX functionalization of the 3-N,N-diethylamino-1-propylamine derivative (10) and 4-aminomethylpyridine derivative (13), and more than 85% functionalization was found. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1699–1706, 1998     

Interaction energies of ZnO in acrylic polymer lattices

Water‐based acrylic polymers are frequently used as binders in ceramic materials that contain ZnO as a major component. Thin flexible ceramic films used in semiconductor elements are prepared from ceramic powder, polymer binder, dispergant and plasticizer. In the present work, the chemical reaction of acrylic acid, a part of the polymer, and ceramic powder (ZnO) has been studied by semi‐empirical calculations and Fourier transform infrared spectroscopy (FTIR). Systematic evaluation of model structures using varying contents of acrylic acid showed that ZnO adhesion increases as the carboxylate content in the polymer system increases. Interaction energy surfaces provide a quantitative insight into the spatial distribution of ZnO particles in various model structures. These results are also in good agreement with our infrared spectroscopy measurements.     

Halogenation of organic compounds in ionic liquids

1. Download : Download full-size image

The review summarizes, compares and analyzes the data available on halogenation reactions in ionic liquid media.     

Analytical solution for buckling of asymmetrically delaminated Reissner’s elastic columns including transverse shear

The exact analytical solution of buckling in delaminated columns is presented. In order to investigate analytically the influence of axial and shear strains on buckling loads the geometrically exact beam theory is employed with no simplification of the governing equations. The critical forces are then obtained by the linearized stability theory. In the paper, we limit the studies to linear elastic columns with a single delamination, but with arbitrary longitudinal and vertical asymmetry of delamination and arbitrary boundary conditions. The studies of quantitative and qualitative influence of transverse shear are shown in detail and extensive results for buckling loads with respect to delamination length, thickness and longitudinal position are presented.     

Bromination of aromatic molecules with polymer supported reagents

Crosslinked co-poly/styrene-4-vinyl(N-hexylpyridinium bromide) was converted with bromine or chlorine to insoluble polymer supported complexes or respectively, and their reactivity studied in reactions with various aromatic molecules. Reagent was found in all cases to be milder than reagent and regiospecifically transformed alkoxy and amino substituted benzenes ( ) into 4-bromo derivatives, while corresponding reactions with resulted in dibromo derivatives. Several benzoheterocyclic molecules were converted with to substitution or addition products, i.e. 2,3-dibromo-N-methylpyrrole, 3-bromobenzo/b/thiophene, and 2,3-dibromo-2,3-dihydrobenzofuran. In the series of ortho-alkyl disubstituted benzene derivatives, i.e. o-xylene, indane, and tetraline, where the Mills-Nixon effect was established with various electrophilic reagents, bromination reactions with showed higher β-selectivity than the corresponding reactions with bromine. The rate of bromination in various alkyl substituted benzenes with reagent depended on the magnitude of the alkyl group, as well as the para/ortho regioselectivity, amounting to 100% in the case of tert-butylbenzene.     

Proton dipolar spin-lattice relaxation in hexagonal ice

The ultraslow motion of defects in high purity hexagonal H₂O ice has been studied by proton dipolarT _1D measurements in the strong collision limit, using the Jeener technique. The obtained NMR correlation times agree rather well with both the Schottky H₂O diffusion timest _s=r ²/6D and the deuteron correlation times in D₂O ice, suggesting that Schottky rather than interstitial diffusion dominates spin-lattice relaxation in both H₂O and D₂O ice.On leave of absence from University of Ljubljana, Institute J. Stefan.     

Regiospecifity of acetylene photocycloadditions to fluorosubstituted benzenes

Irradiation of a cyclohexane solution of hexafluorobenzene and 1-phenyl-2-alkylsubstituted acetylenes resulted in the formation of bicyclo ( 4.2.0) octatriene derivatives, the quantum yield of (2+2) photoaddition depending on the structure of the acetylene, the con- centration of hexafluorobenzene, and the solvent polarity. Reaction with phenylacetylene resulted in the formation of two isomeric cyclo- octatetraene derivatives. Regiospecific (2+2) photoaddition of 1- phenyl-2-tert-butylacetylene to position C-3 and C-4 in alkoxysubsti- tuted pentafluorobenzene derivatives was observed. (2+2) photoaddition of 1-phenylpropyne-1 to alkoxysubstituted pentafluorobenzenes resulted in 3-phenyl-4-methyl-7-alkoxy-1,2,5,6,8-pentafluorobicyclo (4.2.0) octa- triene derivatives. Replacement of the fluorine atom in hexafluoro- benzene with alkoxy substituents diminished quantum yields of (2+2) photocycloadditions.     

Expert system for solving problems in carbon-13 nuclear magnetic resonance spectroscopy

The expert system CARBON is built around a knowledge base consisting of spectra/structure correlations, tables of data, mathematical formulae and graph-theory procedures and on a data base of 2500 assigned ¹³C-NMR spectra. The built-in knowledge enables the user to obtain suggestions for solutions to problems of different types arising in ¹³C-NMR spectroscopy. Use of the system is facilitated by appropriate command files, large on-line help files, and user-friendly dialogue. The system can be used with spectrometries other than ¹³C-NMR and in other fields concerned with correlations between chemical structures and properties.