Dapson in Heterocyclic Chemistry,Part I: Novel Synthesis of Sulfone Biscompounds for Antimicrobial and Antitumor Activities

This article describes the synthesis of some novel sulfone bis-compounds bearing the biologically active thioether 3–6 ; thioureido 7, 8, 15, 16; triazole 10, 11; thiosemicarbazido 9, 12, 13; and 1,3,4-thiadiazole 14, 17 moieties starting with 4,4′-diisothiocyanato-1,1-diphenylsulfone 2. The structures of newly synthesized compounds were confirmed by elemental analysis, IR, ¹ H-NMR and mass spectral data. Compound 3 was found to be the most active compound against Escherichia coli. Also, compound 15 acted as potent cytotoxic agent.     

Juncenolides H – K,New Briarane Diterpenoids from Junceella juncea

Chemical investigation of the Taiwanese gorgonian coral Junceella juncea resulted in the isolation of four new briarane‐type diterpenoids, juncenolides H, I, J, and K ( 1 – 4 ). Their structures were determined on the basis of spectroscopic analysis, especially 1‐ and 2D‐NMR. The inhibitory effects of compounds 1 – 4 on superoxide‐anion generation and elastase release by human neutrophils were evaluated.     

Synthesis and Antibacterial Assay of Some New Pyrenyl Pyridine Candidates

Russian Journal of General Chemistry - Novel polycyclic compounds, 1-pyrene-based pyridone derivatives, are synthesized by treatment of pyrenyl acetohydtazide with several arylidenemalononitriles...     

Effect of rare earth elements on the structural and optical properties of PMMA for possible uses in polymer optical communications

Rare-earth elements (REEs) as Tm⁺³, Er⁺³, Yb⁺³ and Nd⁺³ have a significant optical photon emission. Therefore, Films of PMMA doped with 5?wt.% of NdCl₃, TmCl₃, ErCl₃ or YbCl₃ were prepared using the casting technique. FTIR of the prepared films has been studied. The optical and dispersion behavior of all doped samples have been investigated. The reflectance (R) and the transmittance (T) were measured in the wavelength range of 200–2500?nm. FTIR of all PMMA reveals that, REEs addition to PMMA samples creates new transmission peaks C=O groups and a decrease in the intensity of the absorption band of C–O groups has been obtained. The results showed the dependency of the refractive index and energy gap on the REE electronic transitions nature. The obtained results suggest strongly the applicability of these PMMA derivatives in improving the performance of the polymer optical fiber (POF).     

Solvolysis of 2‐chloro‐2(3,4‐disubstituted) phenylpropanes: Validity of Hammett–Brown σ+ constants in assessing additive effects of substituents

The objective of this study is to test the suitability of the extended Hammett–Brown equation, log (k_XX/k_HH) = ρ⁺Σσ⁺, in depicting satisfactorily additive effects of electronegative atom‐bearing substituents, which are known to possess diverse and multicomponent influences on the side chain reactions of polysubstituted benzenes. The equation has been used to correlate, for the first time, the additive effect of substituents in the specific rates of solvolysis of 2‐chloro‐2‐phenylpropanes ( 3b–3f ) having 3‐F,4‐Me, 3‐Br,4‐Me, 3‐I,4‐Me, 3‐Me,4‐Me, or 3‐MeO,4‐Me substituents. The rates were determined titrimetrically at 288, 298, and 308 K using 90% aqueous acetone as solvent. Measured additive effects of these substituents on the solvolysis rate and activation parameters of the parent cumyl chloride (2‐chloro‐2‐phenylpropane) are found to be well correlated using the equation given above. Plots of log (k_XX/k_HH) of 3b–3f together with mainly di‐, but also tri‐ and mono‐substituted cumyl chlorides from previous studies against Σσ⁺ give a linear correlation coefficient of 0.990 as a measure of the validity of the equation to depict such systems. The halogen substituents' extent of conformity with additivity reflected in their relative (k_obsd/k_calcd) rate ratios is found to correlate with the steric size of substituents. Plots of rate ratios against Taft's steric factor of each halogen give a linear correlation coefficient of 0.994 for the 3‐halo substituents. The 3,4‐dimethyl substituents' relative rate ratio of 1.03 shows excellent additivity, whereas the 3‐methoxy‐4‐methyl ratio of 1.43 shows the methoxy group to be far less deactivating than predicted. Similar trends were found for the free energy of activation (ΔG? – ΔG₀?) differences, which correlated linearly with a coefficient of 0.983 with Taft's steric factor of halogen atoms. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 514–523, 2012     

The yield condition in the mobilization of yield-stress materials in distensible tubes

In this paper we investigate the yield condition in the mobilization of yield-stress materials in distensible tubes. We discuss the two possibilities for modeling the yield-stress materials prior to yield: solid-like materials and highly-viscous fluids and identify the logical consequences of these two approaches on the yield condition. Our results reveal that these two modeling approaches have far reaching consequences on the yield bottleneck and hence should be critically examined in the light of experimental evidence. As part of this investigation we derive an analytical expression for the pressure field inside a distensible tube with a Newtonian flow using a one-dimensional Navier-Stokes flow model in conjunction with a pressurearea constitutive relation based on elastic tube wall characteristics. This analytical expression has wider applicability than in the identification of the yield condition of yield-stress material.