Theoretical study of the effect of water clusters on the enol content of acetone as a model for understanding the effect of water on enolization reaction

Structural Chemistry - The enolization of simple carbonyl compounds is a key reaction for many chemical and biochemical processes. Numerous theoretical and experimental studies have been done to...     

One‐pot New Barbituric Acid Derivatives Derived from the Reaction of Barbituric Acids with BrCN and Ketones

Reaction of cyclic β‐dicarbonyl compounds such as pyrimidine‐(1H,3H,5H)‐2,4,6‐trione (BA), 1,3‐dimethyl pyrimidine‐(1H,3H,5H)‐2,4,6‐trione (DMBA) and 2‐thioxo‐pyrimidine‐(1H,3H,5H)‐4,6‐dione (TBA) with cyanogen bromide in acetone and 2‐butanone in the presence of triethylamine afforded a new class of stable heterocyclic spiro[furo[2,3‐d]pyrimidine‐6,5′‐pyrimidine]2,2′,4,4′,6′(3H,3′H,5H)‐pentaones (dimeric forms of barbiturate) at 0 °C and ambient temperature. Structure elucidation was carried out by X‐ray crystallographic, ¹H NMR, ¹³C NMR, two dimensional NMR, FT‐IR spectra, mass spectrometry and elemental analysis. The mechanism of product formation is discussed. The reaction of DMBA with cyanogen bromide in the presence of triethylamine also afforded trimeric form of barbiturate of uracil derivatives in good yield. The reaction of selected acyclic β‐dicarbonyl compounds with cyanogen bromide in the presence of triethylamine in acetone and/or diethyl ether has also been investigated under the same condition. Diethyl malonate and ethyl cyanoacetate brominated and also ethyl acetocetate both brominated and cyanated on active methylene via cyanogen bromide.     

Silver‐Palladium Nanoalloys Modified Carbon Ionic Liquid Electrode with Enhanced Electrocatalytic Activity Towards Formaldehyde Oxidation

Electrocatalysis of the oxidation of formaldehyde on silver‐palladium‐modified carbon ionic liquid electrode (AgPd/CILE) was investigated in 0.1 M NaOH. The electrochemical performance of the AgPd/CILE was compared with those of Pd/CILE and Ag/CILE. Ag plays an important role in the catalytic performance of AgPd nanocatalyst and yields an excellent antifouling effect. Amperometric measurements showed that AgPd/CILE is a promising sensor for the detection of formaldehyde in the range of 10.0 µM–70.0 mM with a sensitivity of 240.6 µA mM^?1 cm^?2 and a detection limit of 2 µM. The method is free from interference of methanol, ethanol and formic acid.     

Chaotic advection induced heat transfer enhancement in a chevron-type plate heat exchanger

The present work examines the role of chaotic mixing as a means of heat transfer enhancement in plate heat exchangers. In order to demonstrate the chaotic behavior, sensitivity to initial conditions and horseshoe maps are visualized. The Nusselt number and the friction factor were computed in the range of reynolds number, 1 < Re < 10. The Nusselt number increases considerably in chaotic models whereas the friction factor increases only marginally.     

Applying inverse DEA and cone constraint to sensitivity analysis of DMUs with undesirable inputs and outputs

In this paper, the inverse data envelopment analysis (DEA) with the preference of cone constraints will be discussed in a way that in the decision-making units, the undesirable inputs and outputs exist simultaneously. Supposing that the efficiency level does not change, if the unit under assessment increases the level of the desirable outputs and decreases the level of the undesirable outputs, how will it affect the amount of the desirable input level and the undesirable input level? To answer this question, the application of the inverse DEA with preference of cone constraints is suggested. The suggested approach, while maintaining the efficiency level, increases the level of its undesirable input and decreases the level of its desirable input by selection of strongly efficient solutions or some weakly efficient solutions of the multiple objective linear programming (MOLP) model. While maintaining the efficiency level, the suggested approach by selection of strongly efficient solution or some of the weakly efficient solutions of the MOLP model can increase the undesirable input level and decrease the desirable input level. Similarly, the suggested approach can be applied if the decision-making unit increases its undesirable input level and decreases the desirable input level so that the undesirable output level decreases and the desirable output level increases while maintaining the efficiency level. As an illustration, two numerical examples are rendered.     

Sensitivity and stability analysis in data envelopment analysis

One of the topics of interest in data envelopment analysis (DEA) is sensitivity and stability and stability analysis of the specific decision making unit (DMU), which is under evaluation. In DEA, efficient DMUs are of primary importance as they define the efficient frontier. In this paper, we develop a new sensitivity analysis approach for the CCR, BCC and Additive models, when variations in the data are considered for a specific efficient DMU and the data for the remaining DMUs are assumed fixed.     

An efficient multistep iteration scheme for systems of nonlinear algebraic equations associated with integral equations

The aim of this research is to present a new iterative procedure in approximating nonlinear system of algebraic equations with applications in integral equations as well as partial differential equations (PDEs). The presented scheme consists of several steps to reach a high rate of convergence and also an improved index of efficiency. The theoretical parts are furnished, and several computational tests mainly arising from practical problems are given to manifest its applicability.