Recent Advances in Transition Metal‐Catalyzed Hydrogenation of Nitriles

Amines are important building blocks possessing various applications in agrochemicals, the fine chemical industry, pharmaceuticals, materials science and biotechnology. The catalytic hydrogenation of nitriles is an important reaction for the one‐step synthesis of diverse amines. However, significant amounts of side product formation during the course of the reaction is a major issue. In recent years, an enormous amount of work has been reported using both homogeneous and heterogeneous transition metal complex catalysts for the selective reduction of nitriles. Transition metal catalysts are the most crucial factor that controls the selectivity in this reaction. Therefore, transition metal catalysts are the central point of this review. We have also briefly discussed the effect of reaction parameters, selectivity to different substrate structures and reaction mechanisms. This review provides an overview of recent developments in transition metal‐catalyzed nitrile reduction along with examples which highlight its vast potential in organic transformations.

     

Regioselectivity in Hydroformylation of Aryl Olefins Using Novel Rhodium Polyether Phosphinite Catalysts

Polyethylene glycol based diphosphinite ligands and their Wilkinson type Rh-polymeric carbonyl complexes were prepared for homogeneous hydroformylation of styrenes. The effect of reaction variables such as temperature, pressure, P/Rh ratio, Substrate/Rh ratio, phosphine and phosphinite ligands on the activity and selectivity performance were discussed in detail. The catalyst showed a high rate of reaction, TON and tunable regioselectivity depending upon reaction conditions as compared to conventional Rh-phosphine based catalysts.     

High-purity synthesis of scrolled mats of multi-walled carbon nanotubes using temperature modulation

Felt-like mats (6-7 μm thick) of multiwalled carbon nanotubes wrapped into scrolls have been synthesized by chemical vapor deposition from a toluene-ferrocene mixture using a temperature ramp from 680 °C to 550 °C in hydrogen-argon atmosphere. Thermogravimetric analysis reveals a very low catalyst content of ca. 1.25 wt% in the as-synthesized sample while, X-ray photo electron and Raman spectroscopies suggest the results matching with that of multiwalled carbon nanotubes. Considering, different time scales of various reactions and the diffusion of different reactants and products a tentative base growth mechanism has been proposed as per the available characterization data in conjunction with possible scrolling effects. Thermal expansion effects could explain a tentative mechanism for rolling action of sheets. Interestingly, electrical conductivity measurements as a function of temperature suggest a semiconducting behavior, despite being governed by different electron transport mechanisms with activation energies of 0.33 and 1.03 meV corresponding to two temperature ranges respectively. Cyclic voltammetry and electrochemical impedance analysis show a reversible redox behavior due to very low catalyst content and an irreversible etching of the Fe catalyst after acid treatment.     

Synthesis of cyclic carbonates from carbon dioxide and epoxides using alkali metal halide supported liquid phase catalyst

Using combination of Mn–Co transition metal species with N-hydroxyphthalimide as a catalyst for one-step oxidation of cyclohexane with molecular oxygen in acetic acid at 353 K can give more than 95% selectivity towards oxygenated products with adipic acid as a major product at a high conversion (ca. 78%). A turnover number of 74 for this partial oxidation are also recorded.     

Torsion problem for elastic cylinder with holes

An integral equation method is given to solve the classical torsion problem in elasticity theory for a multiply connected region. As is well known, the solution depends upon finding the solution of the two-dimensional Laplace's equation which takes the value $\text{1}\text{2}$(x²+y²)+c_i on the boundary, where x,y are the usual Cartesian coordinates, and c_i are unknown constants. The usual approaches are extremely cumbersome. In this paper a new approach is suggested to solve such problems. This method is simple and straightforward and requires the solution of simultaneous linear equations. An example is given which substantiates the theory. The method is very general and can take into account the discontinuity in the displacement component w. The result can therefore be applied to dislocation theory.     

Daily intake of manganese by local population around Kylleng Pyndengsohiong Mawthabah (Domiasiat), Meghalaya in India

Present work is carried out adjacent to world's highest rainfall area Kylleng Pyndengsohiong (KP) Mawthabah (Domiasiat), Meghalaya in India to establish the baseline value of manganese intake through dietary route by the local tribe population in view of proposed uranium mining. The locally available food items collected from villages surrounding the proposed uranium mining site at KP Mawthabah (Domiasiat) were analysed using Energy Dispersive X-Ray Fluorescence (EDXRF) Technique. The manganese concentration in different food categories varies from 2.76-12.50 mg kg^− 1 in cereals, 1.8-4.20 mg kg^− 1 in leafy vegetables, 0.30-13.50 mg kg^− 1 in non leafy vegetables, 0.50-15.30 mg kg^− 1 in roots and tubers, 0.70-1.50 mg kg^− 1 in fruits and 0.12-0.96 mg kg^− 1 in flesh food. The mean dietary intake of Mn was found to be 3.83 ± 0.25 mg d^− 1 compared to Recommended Dietary Allowances (RDAs) of 2-5 mg d^− 1. The daily intake of Manganese by the local tribe population is comparable with the value (3.7 mg d^− 1) recommended by International Commission on Radiological Protection (ICRP) for reference man and lower than the intake value observed for Indian and other Asian population.     

Natural radionuclides in zircon and related radiological impacts in mineral separation plants

The activity concentration of uranium and thorium present in zircon obtained from mineral sand industries are presented. External gamma radiation levels and inhalation of airborne dust are found to be the significant routes of radiation exposure to occupational workers. The annual average dose attributed to zircon processing is estimated to be 2.3 mSv in the plants under study. This paper presents the results of external gamma measurements, estimation of airborne radioactivity in zircon process locations and radon and thoron in the occupational environment of two mineral separation plants in India. Analyses of the solid wastes and liquid effluent generated and resultant environmental impacts are indicated.