Selective isomerization of 1-alkenes by binary metal carbonyl compounds

An efficient and selective isomerization of 1-alkenes to their corresponding 2-alkenes is achieved by using binary metal carbonyls such as Ru₃(CO)₁₂ as catalysts. Possible mechanisms are discussed. Substituents on the 1-alkene have a significant effect on the isomerization.     

Extraction and coordination behavior of diphenyl hydrogen phosphine oxide towards actinides

Extraction behavior of some selected actinides like U(VI), Th(IV), and Am(III) was investigated with three different H-phosphine oxides, viz. diphenyl hydrogen phosphine oxide (DPhPO), dihexyl hydrogen phosphine oxide (DHePO) and diphenyl phosphite (DPP). The H-phosphine oxides exhibited a dual nature towards the extraction of actinides where the ligand not only extracts the metals by cation exchange but also by coordination with the phosphoryl group at lower and higher acidic concentrations, respectively. Among all ligands employed, DPhPO showed highest extraction with actinides with a substituent dependent trend as follows: DPhPO > DHePO > DPP. This trend emphasizes the importance of substituents around the phosphine oxide towards their extraction of actinides. The coordination behavior of DPhPO was studied by investigating its corresponding complexes with Th(NO₃)₄ and UO₂(NO₃)₂. The metal complexes of these actinides were characterized using FT-IR, ¹H and ³¹P NMR spectroscopic techniques. Density Functional Theory (DFT) calculations were also performed to understand the electronic and geometric structure of the ligand and the corresponding metal complexes.     

Dynamics of a camphoric acid boat at the air–water interface

We report experiments on an agarose gel tablet loaded with camphoric acid (c-boat) spontaneously set into motion by surface tension gradients on the water surface. We observe three distinct modes of c-boat motion: harmonic mode where the c-boat speed oscillates sinusoidally in time, a steady mode where the c-boat maintains constant speed, and an intermittent mode where the c-boat maintains near-zero speed between sudden jumps in speed. Whereas all three modes have been separately reported before in different systems, controlled release of Camphoric Acid (CA) from the agarose gel matrix allowed the observation of all the three modes in the same system. These three modes are a result of a competition between the driving (surface tension gradients) and drag forces acting on the c-boat. Moreover we suggest that there exist two time scales corresponding to spreading of CA and boat motion and the mismatch of these two time scales give rise to the three modes in boat motion. We reproduced all the modes of motion by varying the air–water interfacial tension using Sodium Dodecyl Sulfate (SDS).     

Effect of entrained air on dynamic characteristics of hydraulic servosystem with asymmetric linear motor

Summary A theoretical investigation into the effect of entrained air on dynamic behaviour of hydraulic servosystem is made. The nonlinear system equation developed in dimensionless form is linearised to obtain stiffness, damping ratio and natural frequency in generalised dimensionless form that includes the effects of underlap, leakage, area ratio, per cent air content and the process of change of state of air. A nomogram is developed that helps in quick determination of the dynamic properties directly without any computation. The analysis shows that a decrease in area ratio or an increase in the amount of air entrained into the system reduces both damping ratio and natural frequency. An excessive air entrainment may even lead to instability. The original nonlinear system equation is also solved numerically by fourth order RK-method which shows qualitative agreement with the linear solution. The numerical solution shows that the process of change of state of air also has significant influence on the said dynamic behaviour. A stability chart is prepared relating two most important variables, viz. area ratio and per cent air content, with underlap as a parameter, that facilitates the estimation of allowable air content for a system with given area ratio, or alternatively where the air content in oil is likely to be high; with the help of this graph suitable of underlap and/or area ratio can be selected.

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Sommario Si effettua una ricerca teorica sugli effetti dell'aria catturata sul comportamento dinamico di un servo-sistema idraulico. L'equazione non lineare del sistema, messa in forma adimensionale, viene linearizzata per ottenere la rigidità, il rapporto di smorzamento e la frequenza naturale in una forma adimensionale generalizzata che include gli effetti di restringimento, perdita, rapporto d'area, contenuto percentuale d'aria e il processo di cambiamento di stato dell'aria. Si sviluppa un nomogramma che aiuta a determinare rapidamente le proprietà dinamiche in maniera diretta senza alcun calcolo. L'analisi mostra che una diminuzione del rapporto d'area o un aumento nella quantità d'aria trascinata dentro il sistema riduce sia il rapporto di smorzamento sia la frequenza naturale. Un'eccessiva cattura d'aria può portare a instabilità. L'equazione non lineare viene anche risolta numericamente con un metodo di Runge-Kutta del quart'ordine che mostra un accordo con la soluzione lineare. La soluzione numerica mostra che anche il processo di cambiamento di stato dell'aria ha un'influenza significativa sul suddetto comportamento dinamico. Si prepara un diagramma di stabilità che collega due variabili di grande importanza, cioè il rapporto d'area e il contenuto percentuale d'aria, col restringimento come parametro, che facilita la stima del contenuto d'aria ammissibile per sistemi con un dato rapporto d'area, o alternativamente quando è vero-simile che il contenuto d'aria nell'olio sia elevato; con l'aiuto di questo grafico si possono scegliere valori opportuni di restringimento e/o rapporto d'area.

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Notation V _i initial enclosed volume of fluid - A ₁ piston end cylinder area - A ₂ rod end cylinder area - x nett valve displacement - y output displacement - L cylinder length - d valve sleeve diameter - u _s supply underlap - u _t exhaust underlap - r reference step input - x _p reference port length - P ₁ piston end cylinder pressure - P _s constant supply pressure - p fluid density - c _d orifice discharge coefficient - _oil bulk modulus of oil - K _L laminar leakage coefficient - {ie51-01} reference flow {ie51-02} - t time - M mass of the load - f _b viscous load coefficient - P _at atmospheric pressure - T reference time ({ie51-03}) - percentage of air entrained (by volume) - n polytropic index - X dimensionless nett valve displacement (x/x _p ) - Y dimensionless output displacement (y/x _p ) - Z dimensionless reference step input (r/x _p ) - dimensionless time (t/T) - n dimensionless supply underlap (u _s /x _p ) - v lap ratio (u _t /u _s ) - k area ratio (A ₂/A ₁) - ø dimensionless leakage parameter ({ie51-04}) - P ₁ dimensionless piston end cylinder pressure (P ₁/P _s ) - p _at dimensionless atmospheric pressure (P _at /P _s ) - p dimensionless load pressure (P _L /P _s ) - ₀ dimensionless oil bulk modulus ( _oil/P _s ) - dimensionless cylinder length (L/x _p ) - m dimensionless inertia load parameter (Mx _p /A ₁ P _s T ²) - ₁ dimensionless viscous load parameter (f _b x _p /A ₁ P _s T) - _mix effective bulk modulus of air-oil mixture - compressibility parameter ( _oil/{}_mix)     

Synthesis and characterization of the first metallacyclooctane

Ring closing metathesis (RCM) using Grubbs' 1st generation catalyst with cis-[L(2)Pt(CH(2)CH(2)CH[double bond, length as m-dash]CH(2))(CH(2)CH(2)CH(2)CH[double bond, length as m-dash]CH(2))] yields a platinacyclooctene which can be hydrogenated to the platinacyclooctane, L(2)Pt(CH(2))(7) [L(2) = Ph(2)PCH(2)CH(2)CH(2)PPh(2) (dppp) or Ph(2)PCH(2)CH(2)PPh(2) (dppe)] in high yield.     

An unusual base-controlled equilibrium between monomeric and dimeric nickel(IV)–dimethylglyoxime complexes

Ionic nickel(IV)–dimethylglyoxime complexes have been prepared by oxidation of nickel(II)–dimethylglyoxime in alkaline solutions with ferricyanide. A novel base-controlled equilibrium is demonstrated between the monomeric and dimeric nickel(IV)–dimethylglyoxime complexes in solution. The oxidation state of nickel as +4 is confirmed by titration with hydroxylamine salt. The results obtained from the UV/VIS spectrophotometry, titrimetry, infrared and NMR studies are discussed.     

Accurate determination of interference in pin joints

Suitable pin-to-hole interference can significantly increase the fatigue life of a pin joint. In practical design, the initial stresses due to interference are high and they are proportional to the effective interference. In experimental studies on such joints, difficulties have been experienced in estimating the interference accurately from physical measurements of pin and hole diameters. A simple photoelastic method has been developed to determine the effective interference to a high degree of accuracy. This paper presents the method and reports illustrative data from a successful application thereof.     

An aldol-based build/couple/pair strategy for the synthesis of medium- and large-sized rings: discovery of macrocyclic histone deacetylase inhibitors

An aldol-based build/couple/pair (B/C/P) strategy was applied to generate a collection of stereochemically and skeletally diverse small molecules. In the build phase, a series of asymmetric syn- and anti-aldol reactions were performed to produce four stereoisomers of a Boc-protected γ-amino acid. In addition, both stereoisomers of O-PMB-protected alaninol were generated to provide a chiral amine coupling partner. In the couple step, eight stereoisomeric amides were synthesized by coupling the chiral acid and amine building blocks. The amides were subsequently reduced to generate the corresponding secondary amines. In the pair phase, three different reactions were employed to enable intramolecular ring-forming processes: nucleophilic aromatic substitution (S(N)Ar), Huisgen [3+2] cycloaddition, and ring-closing metathesis (RCM). Despite some stereochemical dependencies, the ring-forming reactions were optimized to proceed with good to excellent yields, providing a variety of skeletons ranging in size from 8- to 14-membered rings. Scaffolds resulting from the RCM pairing reaction were diversified on the solid phase to yield a 14?400-membered library of macrolactams. Screening of this library led to the discovery of a novel class of histone deacetylase inhibitors, which display mixed enzyme inhibition, and led to increased levels of acetylation in a primary mouse neuron culture. The development of stereo-structure/activity relationships was made possible by screening all 16 stereoisomers of the macrolactams produced through the aldol-based B/C/P strategy.