Theoretical Study of the [4+2] Cycloaddition Reaction of Trifluoroethylene with Five-membered Chalcogens Heterocyclic Compounds

[4+2] cycloaddition reaction has enormous significant in organic chemistry synthesis reactions and yet remains unexplored for the synthesis of fluorine-containing compounds. A density functional theory study of the stereo- and regioselectivity of the [4+2] cycloaddition reaction of trifluoroethylene with furan, thiophene, and selenophene was carried out in the gas phase. The B3LYP functional is used throughout in combination with 6-31G(d) basis set. The analysis of stationary points and the energetic parameters indicates that the reaction mechanism is concerted and confirms that the exo-adducts are thermodynamically and kinetically more favored than endo-adducts. The calculated branching ratio indicates that the exo-adducts have the higher percent yield than endoadducts and the yield of endo-adducts is increased only slightly on proceeding from furan, through thiophene, and onto selenophene. The analysis of the frontier molecular highest occupied molecular orbital (MO) and lowest unoccupied MO orbitals indicates that the exo-adducts are more stable due to their higher energy gab. The reaction energies were compared to the MP2/6-31G(d) and CCSD(T)/6-31G(d) calculations

Adsorption of Cr(Vi) Ion from Aqueous Solutions by Solid Waste of Potato Peels

Pollution of wastewater with heavy metal has always been a serious problem to the environment. Chromium is considered one of the most noxious heavy metals. Adsorption is now reorganized as an alternative technology of defence for chromium removal due to local availability, technical efficiency and cost effectiveness. Potato peel powder can be used as a low cost biosorbent to remove hexavalent chromium from aqueous solutions under various experimental conditions. Different parameters including equilibrium contact time, initial metal ion concentration, potato peel dose, pH and temperature were studied through a number of batch sorption experiments. Both the Langmuir and Freundlich were found to fit the adsorption isotherm of Cr (VI) ion onto potato peel. The Langmuir adsorption capacity was found to be 1.97 mg/g while Freundlich constants including Kf and n were 1.57 and 2.5, respectively. The adsorption kinetic was found to be more fit with the pseudo-first order model. This study showed a high efficiency of potato peel for the biosorption of Cr (VI) ion from aqueous solutions

Homogeneous Photocatalytic Degradation of Acid Alizarin Black Using Hydrogen Peroxide

Photocatalytic degradation of acid alizarin black (AAB) dye (C.I. 21725) in aqueous solution was investigated using UV light in the presence of hydrogen peroxide (H2O2) as a catalyst at different operating conditions. The operating conditions were concentration of catalyst dosage (0.1, 0.2 and 0.3 mL of 30 % H2O2), initial concentration of AAB dye (100, 150 and 200 mg/L) and pH (3.3, 6.84 and 10.8). It was found that the increasing of catalyst concentration enhanced the dye decolourisation. Hydrogen peroxide exerted positive effects on the AAB removal whilst the initial concentration of AAB negatively affected its removal. It was also found that the removal efficiency of AAB increased with the pH value close to neutral (pH 7), while a reversed trend was observed at acidic and basic medium

Multiwalled Carbon Nanotubes for Heterogeneous Nanocatalytic Ozonation

Multiwalled carbon nanotubes functionalized by plasma oxygen (CNTs) have been used as heterogeneous catalysts for the ozonation of methyl orange (MO) dye (CI 13025) in aqueous solutions. It was found that the addition of CNTs significantly enhanced the dye decolorization as compared to ozone alone or when activated carbon was used at the same dose as CNTs. Both the initial ozone concentration and catalyst dosage enhanced the removal of MO. However, ozone gas concentrations higher than 6 g/m3 NTP did not further improve the decolorization rates. The removal efficiency of MO increased with pH in the range 2 to 3, while a reverse trend was observed when the pH increased from 3 to 9. The addition of a radical scavenger resulted in only a limited change in the decolorization rates suggesting that molecular ozone was the main pathway by which MO decolorization occurred in solution. However, under favorable conditions for MO attraction to CNT surface (pH = 3), the decolorization rate has significantly increased. At higher pH than the pKa value of MO (3.47) and the point of zero charge of CNT (3.87), a condition that favors the electrostatic repulsion of MO from CNT, the rates were reduced in the presence of CNT as compared to ozone alone possibly due to loss of part of the supplied ozone in un-useful parallel reactions

Fenton Degradation of Fast Green Dye

The degradation of commercial textile dye named fast green (FG) was investigated by Fenton reagent under different operating conditions in an aqueous solution. The operating conditions were amount of hydrogen peroxide (0.05, 0.1 and 0.15 mL), pH (2-12) and concentration of ferrous ion (10, 20 and 30 mg). The initial rate of degradation was affected by the concentration of Fenton reagents [Fe(II) and H2O2 solution]. The rate of degradation enhanced as the concentration of ferrous ion increased. As the ferrous ion concentration increased from 10 to 30 mg, the removal percent was increased from 73% to 89%, respectively, at 25 min of reaction time. Also, the removal percent of FG increased from 74 % to 81 % as the amount of H2O2 increased from 0.05 to 0.15 mL, respectively, at 25 min of reaction time. It was also found that at pH 3 removal percent reach maximum value with 91.8%.  The kinetic study of FG degradation was also studied in this work and the results indicated that the degradation kinetics of FG followed the first-order kinetic

Estimation and Correlation Analysis of Heavy Metals of Some Well Water in Zakho City, Iraq

This study was carried out to examine the concentrations of major heavy metals in fifteen different well water in Zakho City, Kurdistan Region, Iraq. The studied heavy metals were iron, copper, chromium, aluminum, cadmium, cobalt, nickel, manganese, zinc and lead. The results obtained in the studied area showed that copper, chromium, cobalt, zinc, manganese, aluminum, iron and lead were within the acceptable limits as recommended by WHO for water drinking. However, in all studied areas, cadmium and nickel were mostly founded to exceed the maximum permissible limit set by WHO. It is found that zinc and copper possess a very good positive correlation between each other. The results obtained in this study confirmed the groundwater pollution and hence it is not suitable for consumption without any prior treatment

PHOTOCATALYTIC DEGRADATION OF ACID ALIZARIN BLACK USING POWDER AND NANOPARTICLES OF TITANIUM DIOXIDE

Degradation of Organic pollutants using UV light with a photocatalysts (UV/TiO2

Multi-walled carbon nanotubes for heterogeneous nanocatalytic ozonation

Removing of dye (methyl orange) using ozone with carbon nanotube

Unveiling substituent effects in [3+2] cycloaddition reactions of benzonitrile N-oxide and benzylideneanilines from the molecular electron density theory perspective

The zw- type [3+2] cycloaddition (32CA) reactions of benzonitrile N-oxide with a series of substituted benzylideneanilines have been studied within the Molecular Electron Density Theory (MEDT) at the B3LYP/6-31G(d) computational level. The presence of dimethylamino and methoxy substituents in the aromatic rings of benzylideneaniline makes the reaction more facile relative to the unsubstituted one, while the electron withdrawing nitro substituents relatively induce minimal changes in the energy profile complying with the experimentally observed reaction rates. The presence of non-bonding electron density at the nitrogen atom and the formation of pseudoradical centre at the carbon atom of benzonitrile N-oxide characterise the difference in electronic structure of the TSs relative to the reagents, while the topological analysis of the electron localization function (ELF) and the atoms-in-molecules (AIM) reveal no covalent bond formation at the early TSs. The present MEDT study analyses the experimentally observed substituent effects and complete regioselectivity in the studied 32CA reactions

Theoretical insight into the mechanism and selectivity of the [3+2] cycloaddition reaction of N-methyl-1-phenylmethanimine oxide and bicyclopropylidene from the MEDT perspective

The mechanism and regioselectivity of [3 + 2] cycloaddition (32CA) reactions of N-methyl-1-phenylmethanimine oxide nitrone 1 and bicyclopropylidene 2 are analyzed using molecular electron density theory (MEDT) at the B3LYP/6-311 + + G(d,p) level. A study of the electron localisation function (ELF) predicts the zwitter-ionic nature of the nitrone, allowing its participation in zw-type 32CA reactions with a high energy barrier that must be surmounted by suitable electrophilic-nucleophilic interactions. The global electronic flux from the strong nucleophilic bicyclopropylidene 2 to the electrophilic nitrone 1 is predicted by an analysis of the CDFT indices. In this 32CA reaction, no new covalent bonds are generated at the TSs, and the mechanism is one-step and kinetically controlled with low asynchronicity in bond formation. The Gibbs free energy of this 32CA reaction in the gas phase is −9.88 and −15.01 kcal.mol−1 for exo and endo path, respectively. The increased thermodynamic stability of the cycloadducts 4 favors the endo regiochemical route. The ELF topological examination at the transition states is in agreement with the predictions of bonding evolution theory (BET) for the endo and exo routes, which point to a one-step process including early transition states