Facile, one-pot synthesis of phosphinate-substituted bisphenol A and its alkaline-stable diglycidyl ether derivative

A new phosphinate-substituted bisphenol A, 1,1-bis(4-hydroxyphenyl)-1-(6-oxido-6H-dibenz <c,e> <1,2> oxaphosphorin-6-yl)ethane (1), was prepared by a facile, one-pot procedure. In addition, a reaction mechanism for the preparation of (1) was proposed. Based on (1), a diglycidyl ether derivative (2) was prepared and cured by commercially-available curing agents. The structures of (1-2) were confirmed by IR, high-resolution mass, 1-D and 2-D NMR spectra. Properties such as glass transition temperature, coefficient of thermal expansion, thermal decomposition temperature, and flame retardancy of the resulting thermosets were evaluated and compared with those of the thermosets of diglycidyl ether of bisphenol A. The resulting epoxy thermosets show high T_g, low thermal expansion, good thermostability and excellent flame retardancy.     

The Effects of Microenvironment Polarity and Dendritic Branching of Aliphatic Hydrocarbon Dendrons on the Self‐Assembly of 2‐Ureido‐4‐pyrimidinones

Two series of aliphatic hydrocarbon‐based G1–G3 dendritic 2‐ureido‐4‐pyrimidinones (UPy) ( S‐Gn )₂ and ( L‐Gn )₂, differing from one another by the distance between the branching juncture to the urea end, were prepared and characterized. These hydrocarbon dendrons were also appended to a p‐aminonitrobenzene solvatochromic chromophore in order to probe their microenvironment polarity. While positive solvatochromism was observed which indicated the chromophore was solvent accessible, there was no significant difference between the microenvironment polarities on going from the G1 to the G3 dendrons. The self‐assembling behavior and tautomeric preference of the dendritic UPy derviatives were examined by ¹H NMR spectroscopy. The dimerization constants (K_dim*) of the DDAA tautomers were unchanged at 10⁷ M ^?1 in CDCl₃ at both 25 and 50 °C, which were comparable to those of UPy compounds bearing other nonpolar substitutents. Furthermore, the lower limits on the K′_dim* of the DADA tautomeric forms of the ( S‐Gn )₂ and ( L‐Gn )₂ series were determined to be 10⁶ and 10⁵ M ^?1 in CDCl₃, respectively. It was found that a closer proximity of the dendron branching juncture to the UPy unit could lead to a destabilization effect on the dimeric states. Hence, the ( L‐Gn )₂ dimers are more stable than those of ( S‐Gn )₂ in the DDAA form, but the latter are more stable than the former in the tautomeric DADA state. This study showed that both the highly nonpolar microenvironment and the proximity of the dendritic branching juncture to the UPy motif could alter the strength and profile of the hydrogen bond‐mediated self‐assembling process.     

HPTLC Analysis of Thymol in Extracts of Satureja hortensis L. Obtained by Different Techniques

JPC – Journal of Planar Chromatography – Modern TLC - The separation and quantitative analysis of thymol in Satureja hortensis L. extracts is reported. The extracts were obtained by...     

Thermal,mechanical, and morphological properties of novolac‐type phenolic resin blended with fullerenol polyurethane and linear polyurethane

Fullerenol polyurethane (C₆₀‐PU) and linear polyurethane (linear‐PU) modified phenolic resins were prepared in this study. Phenolic resin/C₆₀‐PU and phenolic resin/linear‐PU blends show good miscibility as a result of the intermolecular hydrogen bonding existing between phenolic resin and PU modifiers. DSC and thermogravimetric analysis methods were used to study the thermal properties of phenolic resin blended with different types of PUs. The intermolecular hydrogen bonding that existed between phenolic resin and C₆₀‐PU was investigated by Fourier transform infrared spectroscopy. The morphology and mechanical properties of phenolic resin/C₆₀‐PU and phenolic resin/linear‐PU blends were also investigated. The char yield of the modified phenolic resins decreased with increasing PU modifier content. Significant improvement in the toughness of the modified phenolic resins was observed. The improvements of impact strength were 27.4% for the phenolic resin/linear‐PU system and 54.3% for the phenolic resin/C₆₀‐PU system, respectively, both with 3 phr linear‐PU and C₆₀‐PU content. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2436–2443, 2001     

An efficient and simple model for multiple criteria supplier selection problem

Simply looking for vendors offering the lowest prices is not “efficient sourcing” any more. Selection of suppliers is a multiple criteria decision. We propose a weighted linear program for the multi-criteria supplier selection problem. In addition to mathematical formulation, this paper studies a transformation technique which enables our proposed model to be solved without an optimizer. The model for multi-criteria supplier selection problem can be easily implemented with a spreadsheet package. The model can be widely applied to practical situations and does not require the user with any optimization background.     

Methyl methacrylate in poly(methyl methacrylate)--validation of direct injection gas chromatography

Gas chromatography (GC) was investigated for the determination of residual methyl methacrylate (MMA) in heat-processed poly(methyl methacrylate) (PMMA) denture base material emphasizing recovery and validation. Standard solutions of MMA and emulsion-polymerized PMMA in dichloromethane were analysed, before and after distillation by a room-temperature air stream into a liquid nitrogen trap, and in the presence of PMMA by direct injection. Quantitative NMR analysis using dimethyl sulphoxide as internal calibration standard in deuterated chloroform solutions provided validation. Good concordance was observed between results under all conditions; no problems arose from direct injection of PMMA solution for GC. Good straight line responses in log-log plots were generally observed. For GC and MMA: log-log calibration curve (slope: 0.9552 +/- 0.0051, r2: 0.9992, n = 32) indicated some non-linearity (t = 8.875, p approximately 4 x 10(-10)). Distillation gave slope: 0.9751 +/- 0.0213 (NS versus unity; t = 1.172, p > 0.25). For PMMA solutions, distillation (r2: 0.9301) gave greater scatter than direct injection (r2: 0.9704). For NMR: log-log plot of calculated versus actual MMA (slope: 0.9363 +/- 0.0157, r2: 0.9969, n = 13) again indicated non-linearity (t = 4.0682, p = 0.0019). PMMA solutions gave slope: 0.9477 +/- 0.0328, r2 = 0.9858 (NS versus unity; t = 1.5941, p = 0.13). Determination of MMA in PMMA by GC is recommended.     

A theoretical study on the mechanism, regiochemistry, and stereochemistry of hydrosilylation catalyzed by cationic ruthenium complexes

Density functional calculations have been carried out to understand the anti-addition stereochemistry and Markovnikov regiochemistry of the hydrosilylation of terminal alkynes and the endo-dig product of intramolecular hydrosilylation of homopropargyl alcohols catalyzed by cationic cyclopentadienyl-ruthenium complexes. It has been found that hydride or silyl insertion is concerted with the oxidative addition of the H-Si bond. Hydride insertion is much more favorable than silyl insertion. Such a hydride insertion nicely reproduces the observed regioselectivity, while silyl insertion would predict the opposite result. The hydride insertion leads to the formation of a eta(2)-vinylruthenium intermediate for the reaction of acetylene or a metallacyclopropene intermediate for the reaction of propyne. In the formation of both intermediates, there is a C(alpha)-C(beta) bond rotation so that the transferring hydride becomes anti to the silyl group. This is followed by a facile reductive alpha-silyl migration transition state, which results in the overall anti-addition stereochemistry. The proposed mechanism also rationalizes the observed regio- and stereochemistry of the intramolecular reaction.     

Organic peroxide assisted transition metal hydrosilylation catalysis

Summary The catalytic activity of rhodium complexes for the hydrosilylation of substrates such as alkenes, 1,3-dienes, 1-alkynes, or ketones, is enhanced by the addition of organic oxidizing agents, such ast-butyl hydroperoxide, hydrogen peroxide, orm-chloroperbenzoic acid. Similar enhancement is found for the Group VIA hexacarbonyls in the hydrosilylation of 1,3-dienes.