Theoretical prediction of the damping of a railway wheel with sandwich-type dampers

This paper presents a procedure for predicting the damping added to a railway wheel when sandwich-type dampers are installed. Although there are different ways to reduce the noise generated by a railway wheel, most devices are based on the mechanism of increasing wheel damping. This is why modal damping ratios are a clear indicator of the efficiency of the damping device and essential when a vibro-acoustic study of a railway wheel is carried out. Based on a number of output variables extracted from the wheel and damper models, the strategy explained herein provides the final damping ratios of the damped wheel. Several different configurations are designed and experimentally tested. Theoretical and experimental results agree adequately, and it is demonstrated that this procedure is a good tool for qualitative comparison between different solutions in the design stages.     

2,4,6-Tris(4-iodophenoxy)-1,3,5-triazine as a new recyclable “iodoarene” for in situ generation of hypervalent iodine(III) reagent for α-tosyloxylation of enolizable ketones

The synthesis of 2,4,6-tris[(4-iodo)phenoxy)]-1,3,5-triazine 6, as a new recyclable nonpolymeric analogue of iodobenzene is achieved using the reaction of 2,4,6-trichloro-1,3,5-triazine with 4-iodophenol in the presence of KOH. The application of 6 as a recyclable ‘iodoarene’ is demonstrated for α-tosyloxylation of enolizable ketones via in situ generation of hypervalent iodine(III) species using PTSA and MCPBA as the terminal oxidant. The recyclability of the reagent 6 was possible owing to the facile recovery and reuse from the reaction mixture due to its near insolubility in methanol.     

A validated high-performance thin-layer chromatography method for quantification of echioidin from Andrographis echioides plant

JPC – Journal of Planar Chromatography – Modern TLC - A simple, reliable and reproducible high-performance thin-layer chromatography (HPTLC) method was established for determining...     

Un-catalyzed tandem Knoevenagel–Michael reaction for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) in aqueous medium

An environmentally benign un-catalyzed one-pot synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) has been reported via tandem Knoevenagel–Michael reaction of aldehydes with two equivalents of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one in aqueous medium.     

Process development of ABT-450 – A first generation NS3/4A protease inhibitor for HCV

ABT-450 (8), a potent hepatitis C (HCV) NS3/4A protease inhibitor, was approved as part of AbbVie's first generation HCV treatment for the United States in December 2014. A series of process optimizations were developed over six years to support the program starting with recycling of a previous protease inhibitor candidate through route development and final process. This discussion will focus on optimization of the final six steps starting from dipeptide 12 and amino acid 13 and highlights the use of a large scale ring closing metathesis (RCM), reactive crystallizations for isolation of intermediates, and detailed process understanding of the final sulfonamide coupling. The process provides ABT-450 (8) in 72% overall yield for the final 6 steps.     

Understanding stress-induced disorder and breakage in organic crystals: beyond crystal structure anisotropy

Crystal engineering has advanced the strategies for design and synthesis of organic solids with the main focus being on customising the properties of the materials. Research in this area has a significant impact on large-scale manufacturing, as industrial processes may lead to the deterioration of such properties due to stress-induced transformations and breakage. In this work, we investigate the mechanical properties of structurally related labile multicomponent solids of carbamazepine (CBZ), namely the dihydrate (CBZ·2H₂O), a cocrystal of CBZ with 1,4-benzoquinone (2CBZ·BZQ) and the solvates with formamide and 1,4-dioxane (CBZ·FORM and 2CBZ·DIOX, respectively). The effect of factors that are external (e.g. impact stressing) and/or internal (e.g. phase transformations and thermal motion) to the crystals are evaluated. In comparison to the other CBZ multicomponent crystal forms, CBZ·2H₂O crystals tolerate less stress and are more susceptible to breakage. It is shown that this poor resistance to fracture may be a consequence of the packing of CBZ molecules and the orientation of the principal molecular axes in the structure relative to the cleavage plane. It is concluded, however, that the CBZ lattice alone is not accountable for the formation of cracks in the crystals of CBZ·2H₂O. The strength and the temperature-dependence of electrostatic interactions, such as hydrogen bonds between CBZ and coformer, appear to influence the levels of stress to which the crystals are subjected that lead to fracture. Our findings show that the appropriate selection of coformer in multicomponent crystal forms, targetting superior mechanical properties, needs to account for the intrinsic stress generated by molecular vibrations and not solely by crystal anisotropy. Structural defects within the crystal lattice, although highly influenced by the crystallisation conditions and which are especially difficult to control in organic solids, may also affect breakage.

Crystal engineering has advanced the strategies of design and synthesis of organic solids with the main focus being on customising the properties of the materials.     

Investigation of interaction strategies between pyrazolone dyes and poly(acrylamide-co-acrylic acid)

The removal of dyes from waste water before their discharge into aquatic ecosystems is of substantial concern. Amongst functional macromolecules, the combination of polymers with dyes is a research field of enormous potential with regard to high-performance materials. The present study investigates interactions strategies between P(AM-co-AA) polymer with pyrazolone azo dyes in water as green solvent. These interactions were confirmed by FTIR spectroscopy, Ultra-visible spectroscopy, EDAX analysis, and FE-SEM analysis. Polymer P(AM-co-AA) has porous structure in which dyes present in the water get absorb hence it is use to remove pyrazolone dyes from water.

     

Catalyst Control in Switching the Site Selectivity of C−H Olefinations of 1,2-Dihydroquinolines: An Approach to Positional-Selective Functionalization of Quinolines

A unique approach to achieve site-selective C−H olefinations exclusively at the C-3- or C-8-positions in the quinoline framework has been developed by catalyst control. Distal C(3)−H functionalization is achieved by using palladium catalysis, whereas proximal C(8)−H functionalization is obtained by employing ruthenium catalysis. Switching the site selectivity within a single substrate directly indicates two diverse pathways, which are operating under the palladium- and ruthenium-catalyzed reaction conditions.