Enhanced Thermocatalytic Activity of Porous Yellow ZnO Nanoflakes: Defect‐ and Morphology‐Induced Perspectives

Herein, we report a simple and effective strategy for the synthesis of yellow ZnO (Y‐ZnO) nanostructures with abundant oxygen vacancies on a large scale, through the sulfidation of ZnO followed by calcination. The developed strategy allows retention of the overall morphology of Y‐ZnO compared with pristine ZnO and the extent of oxygen vacancies can be tuned. The influence of oxygen deficiencies, the extent of defect sites, and the morphology of ZnO on its solution‐phase thermocatalytic activity has been evaluated in the synthesis of 5‐substituted‐1H‐tetrazoles with different nitriles and sodium azide. A reasonable enhancement in the reaction rate was achieved by using Y‐ZnO nanoflakes (Y‐ZnO NFs) as a catalyst in place of pristine ZnO NFs. The reaction was complete within 6 h at 110 °C with Y‐ZnO NFs, whereas it took 14 h at 120 °C with pristine ZnO NFs. The catalyst is easy to recycle without a significant loss in catalytic activity.     

Microwave-assisted synthesis of 3-aminoarylquinolines from 2-nitrobenzaldehyde and indole via SnCl2-mediated reduction and facile indole ring opening

A simple and efficient one-pot two-step synthesis of substituted 3-aminoarylquinolines has been achieved from 2-nitrobenzaldehyde and indoles under microwave irradiation. Firstly 2-nitrobenzaldehydes is reduced to 2-aminobenzaldehyde in situ by commonly used chemo selective reductant SnCl₂ followed by condensation of indole. The acidic nature of the resultant reaction mixture due to SnCl₂ helps in the condensation and facile ring opening of indole leading to the formation of 3-aminoarylquinoline derivatives in good to moderate yields.     

TFA-catalysed tandem double cyclisation: A one-pot,metal-free routes for novel indolo-imidazo[1,2-a]pyridine derivatives

A transition-metal free, one-pot tandem synthetic routes for novel indole and imidazo[1,2-a]pyridine derivative hybrids have been established. An efficient three-component reaction was designed with incorporation of two sequential Groebke–Blackburn–Bienayme (GBB) and cyclization reaction in one-pot under mild acidic condition. The salient feature of this protocol is atom economy, good yield and operational simplicity. A molecular prospective library of 32 compounds was synthesized by utilizing the various substituted aryl aldehydes and 2-aminopyridine.     

Control of pH process using double-control scheme

Control of pH is mostly needed in continuous process industries and is difficult and challenging due to its time-varying and nonlinear nature of the chemical or biological process. Conventional controllers do not incorporate nonlinear dynamics of the entire pH range (both acid and alkali) and do not show good performance. Dynamics based on specific process nonlinearity of two different ranges is used to design double-control scheme in a feedback structure to enhance the performance of pH process. The mathematical model of pH for a weak acid-strong base is used to design IMC based PID double-controller scheme which provides outstanding set-point tracking and disturbances rejection simultaneously to control pH processes.     

Reactions of potassium bis(phosphinimino)methanide with group 11 compounds

Transmetalation of the potassium methanide complex, K{CH(PPh2NSiMe3)2}, with [(Ph3P)2CuI] afforded the corresponding copper complex [{CH(PPh2NSiMe3)2}CuPPh3] (1), whereas the reaction of K{CH(PPh2NSiMe3)2} with [Ph3PAuCl] resulted in the dinuclear gold complex [(Ph3PAu)2{C(PPh2NSiMe3)2}] (2). The solid-state structure of 1 shows the formation of a six-membered metallacycle (N1-P1-C1-P2-N2-Cu) that has a twist boat conformation. In contrast, compound 2 is an alpha,alpha-diaurated species, in which the two gold atoms are coordinated in a linear fashion onto the ligand backbone. Photoluminescence measurements show that the latter compound has a strong violet emission.     

Structural effects on the formation of proton and alkali metal ion adducts of apolar,neutral peptides: electrospray ionization mass spectrometry and Ab initio theoretical studies

Apolar, neutral peptides have been shown to ionize extremely well under the conditions used for electrospray ionization mass spectrometry (ESIMS). Peptides for which the conformations have been independently determined in solution and in crystals have been examined by ESIMS. Studies of peptide helices ranging from 7 to 18 residues reveal that shorter helices yield exclusively singly charged ions, while in larger helices multiply charged species are detectable. Multiple sites for protonation/metallation are introduced in the helix by proline insertion or by changing the chirality in the residue. The preferred site of cation binding to helices may be the C-terminus end, where three free CO groups are available for chelation. Ab initio and DFT calculations at several levels have been carried out for the binding of H+, Li+, Na+, and K+ to CHO-(Gly)3)-OMe. The results reveal that metallation in helices is favoured by chelation to carbonyl groups at the C-terminus, while protonation involved two carbonyl groups and thus favour a 10-membered cyclic hydrogen-bonded structure. In -strands, metallation/protonation occurs at isolated carbonyl groups. Collision induced fragmentation of hydrophobic peptides under ESI conditions reveals that helix fragmentation occurs predominantly from the C-terminus, while in -hairpins cleavage occurs simultaneously at multiple sites.     

Optimum support characteristics for rotor-shaft system with preloaded rolling element bearings

Preloading of rolling element bearings is often used to avoid clearance in the bearings and achieve precise dynamic requirement. Preloading gives rise to an expression of the restoring force, which is a non-linear function of the deformation of the rolling elements. In this paper, frequency-dependent optimum support characteristics have been found out by simultaneously minimizing the unbalance response (UBR) of the rotor and maximizing the stability limit speed (SLS) of a flexible horizontal rotor-shaft system comprising an unsymmetrically placed rotor disc placed on an elastic shaft mounted on preloaded rolling element bearings at the ends supported on viscoelastic polymeric supports. A sensitivity study of the UBR and SLS with respect to the support characteristics has been presented to have an idea about the permissible deviation of the support characteristics from the respective optimum, at any frequency. Thus, the sensitivity study helps the quality control man as well as the manufacturer of such supports to estimate the permissible deviation in the most sensitive frequency zones. The results presented in this work are in terms of non-dimensional parameters of the system and are, therefore, valid for any system under consideration.     

Active transport in the light of thermodynamics of open systems

A brief thermodynamic analysis of transport processes in open systems is presented. It is shown that the concept of an active transport in the usual sense of the existence of a flow against the direction of its conjugate force is operationally unrealistic. The so-called metabolically coupled active transport has been shown to be mathematically falacious. The experimental establishment in favor of the active transport process by the use of metabolic inhibitors has been logically disproven. From this analysis it is naturally concluded that all transport processes in the living organisms can be reduced to passive ones if one recognizes all the possible potential gradients existing in the system. Assuming the existence of active transport process is as erroneous as taking for granted a vital force explaining the life phenomena. It simply indicates our lack of knowledge about the pattern of superposition of a complete set of driving forces or about the nature of a yet unknown physical driving force and the generating mechanism of such a force.     

Studies in nickel(IV) Chemistry. Kinetics of the aquacopper(II)-catalyzed oxidation of phenylhydrazine by tris(dimethylglyoximato)-nickelate(IV) in aqueous medium

The kinetics of electron transfer in the redox system containing phenylhydrazine (S) and tris(dimethylglyoximato)nickelate(IV), in the presence of catalytic amounts of added Cu(II)_aq, have been studied in aqueous medium at an ionic strength of 0.25M in the pH range of 6.01–9.06. The kinetics exhibit pseudo-zero-order disappearance of Ni(IV) when an excess of [S]₀ and small amounts of Cu(II) are present. While the pseudo-zero-order rate constants are almost linearly dependent on [S]₀ at constant [Cu(II)] and pH tending to become non-linearly dependent on higher relative [S]₀, they are linearly dependent on [Cu(II)] in a 20-fold range. The pH-rate profiles with low [S]₀ and [Cu(II)] show a monotonic decrease in rates with increasing pH, the rates tending to attain limiting values at higher relative pH. Results are interpreted in terms of a probable mechanism involving the formation of precursor complexes of phenylhydrazine and Cu(II) species in the medium, followed by the rate-determining breakdown of the precursors with concomitant electron transfer. The hydrolyzed species of Cu(II) reacts more slowly than does the aquacopper(II). Ni(IV) does not appear to have any kinetic role in the redox system and is involved only in rapid product formation steps. The oxidation product of phenylhydrazine is 4-hydroxyazobenzene.