Reaction Mechanism In Organic Chemistry By Parmar Chawla Pdf Download
Paz Warsager
Details: False-color scanning electron microscopy image of a cluster of L-cystine crystals captured on a porous filtration membrane after growth in the presence of a growth inhibitor. The tapered needles result from binding of the inhibitor at the crystal surface, which reduces the crystal growth rate and the crystal size (the cluster is 95 microns across). This suggest that inhibitors might be designed to prevent or limit the formation of L-cystine kidney stones.
Reaction Mechanism In Organic Chemistry By Parmar Chawla Pdf Download
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Details: Bio-inspired crystal engineering of nanoporous zeolites is described by A.I. Lupulescu and J.D. Rimer in their Communication. Molecular analogues of silica proteins in unicellular organisms are effective growth modifiers that exhibit molecular recognition for binding to zeolite surfaces to alter the kinetics of crystallization, tune the architecture of exterior surfaces, and selectively tailor crystal habit with precise 3D control.
Details: Stages of organic-free zeolite crystallization are consistent with the Ostwald step rule where metastable phases nucleate and transform to more thermodynamically stable structures. Constructing kinetic phase diagrams via the judicious selection of synthesis parameters, such as water content, offers a versatile platform for tuning crystal properties and phase purity. See Rimer and co-workers, p 2641.
Details: Zeolite HOU-2 (LTA type) is prepared with the highest silica content (Si/Al = 2.1) reported for Na-LTA zeolites without the use of an organic structure-directing agent. The rational design of Si-rich zeolites has the potential to improve their thermal stability for applications in catalysis, gas storage, and selective separations. See Rimer and co-workers, p 269.
Details: Hematin Crystallization in Water-Deprived Growth Environments. Hematin crystallization is the primary mechanism of heme detoxification in malaria parasites. Here, we show that water-saturated n-octanol serves as a biomimetic medium for crystal growth. This advancement has significant implications for the design of experiments to screen and assess antimalarial drugs. See Vekilov, Rimer and co-workers, p 7790.
Details: This cover is dedicated to the 29 global scientists in the I&EC Research 2018 Class of Influential Researchers. The 2018 Class of Influential Researchers includes both reviews and regular research articles. Collectively, the papers report important new contributions across the broad landscape of research in chemical engineering and applied chemistry. There are many articles focusing on catalysis and reaction kinetics. Applications in view include combustion, diesel exhaust treatment, hydrodeoxygenation and hydrodenitrogenation, electrocatalysis, acid/base catalysis, the oxygen evolution reaction, and oxidative dehydrogenation of ethylene.
Details: This cover highlights a microfluidic platform to elucidate the time-resolved processes controlling crystallization and dissolution of barite. In situ optical microscopy reveals that addition of a common dissolution agent, diethylenetriaminepentaacetic acid (DTPA), alters the morphology of barite crystals grown under flow. In a dissolution environment, increasing the flux of DTPA enhances the rate of barite dissolution. The combined use of microfluidics and optical microscopy provides a robust and broadly-useful platform for capturing crystallization kinetics and morphological transformation under dynamic flow conditions.
Details: The facile reconstruction of zeolite USY surfaces during surfactant-templating was monitored by in situ atomic force microscopy. In this article, the authors show that pre-existing large mesopores in USY are transformed into a narrow distribution of mesopores. Using a combination of techniques, including transmission electron micrographs of ultramicrotomed samples, the authors reveal a homogeneous population of mesopores throughout the entire zeolite crystal.
Details: Crystallization in flow systems is a common occurrence in pipelines, catheters, and commercial processes. this accumulation of mineral scale, such as struvite, poses a problem. Microfluidic devices are an efficient platform to assess crystallization under flow conditions, in which time-resolved measurements allow the quantification of anisotropic growth rates at variable conditions. When coupled with techniques, such as atomic force microscopy, it is then possible to elucidate growth mechanisms and validate predictions made on the basis of macroscopic analysis. More information can be found in the Full Paper by N.J. Irwin, J.D. Rimer, et al. (DOI: 10.1002/chem.201904347).
Details: Nanosized zeolites enable better catalytic performance; however, their synthesis is non-trivial. Here, a simple treatment is presented that enables the growth of nanosized fins on zeolites that act as pseudo-nanoparticles, reducing deactivation rates for methanol-to-hydrocarbon catalysts. See Article by Dai et al.; see Editorial for focus issue; see News & Views by Sastre.
Details: Molten salt synthesis is a versatile method of preparing metal oxide solid solutions with high-index facets and tailored crystal habit. This was demonstrated for (Ni,Mg)O crystals where the selection of the majority component (Mg or Ni0 switches the morphology from octahedral to trapezohedral shapes, respectively. The judicious selection of ions also plays a critical role in (Ni,Mg)O crystallization, with nitrate media promoting the formation of solid solutions and chloride media leading to the formation of segregated oxide phases.
Details: A method of inhibiting the formation of inorganic scale was designed wherein alginate, a bio-derived acidic polysaccharide from brown algae, is explored as an alternative to commercial scale treatments. Our findings reveal that alginate is unique based on its ability to fully suppress both nucleation and crystal growth of barium sulfate (barite) scale, which is an undesirable and ubiquitous phenomenon in industrial systems for wastewater treatment, energy production, and manufacturing. The findings in this study highlight the dual roles and exceptional performance of alginate as a promising and green alternative to current barite scale treatments.
Details: High-index NiO faceting during molten salt synthesis is investigated with density functional theory by J.D. Rimer, M. Maestri, and co-workers in their Research Article on page 25391. Trapezohedral NiO particles observed in experiments are shown to form in LiCl and KCl due to locally ordered alkali chloride structures, which act as capping agents during crystal growth. In the absence of salt, octahedral NiO particles are produced because of their stable hydroxylated surfaces.
Details: Here it is shown that a natural compound, phytate, is a potent inhibitor of barium sulfate (barite) nucleation and crystal growth. Phytate operates by a distinct mode of action leading to roughened barite crystal surfaces where layer advancement is completely suppressed and pyramidal macrosteps emerge on certain facets. These findings identify that phytate is a dual inhibitor of barite nucleation and growth, and is thus a potentially viable environmentally-friendly alternative to current treatments of barite scale.
Details: The cover art illustrates the function of molecular imposters as crystal growth modifiers of ammonium urate, which is a principal component of dolphin kidney stones. Molecules selected with structures similar to urate operate by multiple and sometimes opposing roles of promotion and inhibition of crystal surface nucleation and growth.
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