Conversion Of O-phenylenediamine Research Articles

Recyclable Nanocrystalline Copper Based on MoO3/SiO2 as an Efficient Catalyst for Acylation of Amines

Various loadings of copper supported on MoO3/SiO2 (CMS) were prepared by sol-gel method and used for the synthesis of substituted benzimidazole. Further it was characterized by using X‐ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Transmission Electron Microscopy (TEM), and acidity measurement by potentiometric method. XRD results indicated that Cu is present on the support primarily as CuO. The SEM and TEM results showed dispersion of cubic CuO nanoparticles on the surface. These mixed oxides were studied for the acylation of o-phenylene diamine with acetic acid in liquid phase. 10 wt. % CMS gave best results at 110 ºC with 94.81 % conversion of o-phenylene diamine and 100 % selectivity of substituted benzimidazole. Different parameters were studied for optimization of acylation, such as: temperature, acylating agents, solvents, amount of catalyst, and different catalysts. The CMS catalyst could also be recovered and reused at three times without any discernible decrease in its catalytic activity.

β-Cyclodextrin-promoted synthesis of 2-phenylbenzimidazole in water using air as an oxidant

β-Cyclodextrin-promoted conversion of o-phenylenediamine and benzaldehyde to 2-phenylbenzimidazole is described using air as an oxidant. Various factors including reaction temperature, amount of β-cyclodextrin, different feed sequences and different steric hindrances of benzaldehydes were investigated. The observed results are rationalized on the basis of binding modes of inclusion of substrates inside the β-cyclodextrin cavity and find strong support from energy minimization studies and 1H NMR. In this paper β-cyclodextrin blocked the smooth conversion while enhanced the selectivity. This is the first example to use β-cyclodextrin as a catalyst in water to restrain the conversion while improving the selectivity.

Reaction of o-phenylene diamine and carbon disulfide by potassium hydroxide at higher temperature

A semi-continuous reactor was employed to study the reaction of o-phenylene diamine and carbon disulfide in a gas–liquid (KOH solution/organic solvent) two-phase medium to produce potassium salt of 2-mercaptobenzimidazole (C 6H 4(N)(NH)CS −K +, ArS −K +). Gas-phase carbon disulfide of higher temperature is continuously introduced to the reactor for reaction. The main advantage of the present system is that the reaction can be carried out at a relatively higher temperature in the semi-continuous reactor. No quaternary ammonium salt is also required to obtain the desired reaction rate and the conversion. The conversion of o-phenylene diamine is low in the absence of potassium hydroxide. Potassium hydroxide does not directly participate in the reaction with o-phenylene diamine and carbon disulfide to synthesize 2-mercaptobenzimidazole (MBI). It merely reacts with the product 2-mercaptobenzimidazole to form ArSK, and reacts with hydrogen sulfide which is a byproduct from the reaction of synthesizing 2-mercaptobenzimidazole. Nevertheless, the reaction is greatly enhanced in the presence of potassium hydroxide of an appropriate amount. Based on the experimental observation, a simple reaction mechanism is proposed, and a pseudo-first-order rate law is employed to describe the reaction. The effects of the reaction conditions, such as the amount of potassium hydroxide, the agitation speed, the initial concentration of carbon disulfide, the flow rate of gas-phase, the amount of o-phenylene diamine and the temperature on the apparent rate constants ( k app) are investigated in detail.

Synthesis of 2-mercaptobenzimidazole from the reaction of o-phenylene diamine and carbon disulfide in the presence of potassium hydroxide

The reaction of o-phenylene diamine and carbon disulfide to synthesize 2-mercaptobenzimidazole (MBI) enhanced by potassium hydroxide was carried out in a homogeneous solution. No catalysts are required in the reaction. In addition to the reaction of carbon disulfide and hydrogen sulfide to produce S 2− and CS 3 2−, potassium hydroxide is also acted as the enhancer to promote the reaction of synthesizing MBI. A mixture of organic solvent (protic or aprotic solvent) and water is used as the reaction solution in order to obtain a homogeneous phase. The effects of the reaction conditions, including the amount of o-phenylene diamine, amount of carbon disulfide, organic solvents, volume ratio of organic solvent to water, and temperature, on the conversion of o-phenylene diamine were investigated in detail. An appropriate amount of KOH is recommended to produce a high yield of MBI and a high reaction rate in using protic solvent/water as the mixed solution. Nevertheless, the conversion is increased with the increase in the amount of KOH using aprotic solvent. This behavior is different from that of the KOH effect on the conversion of o-phenylene diamine using protic solvent/water as the mixed solution.

Homogeneous catalyzed reaction of carbon disulfide and o-phenylene diamine by tetrabutylammonium hydroxide in the presence of potassium hydroxide

The catalyzed reaction of o-phenylene diamine and carbon disulfide to synthesize 2-mercaptobenzimidazole (MBI) by tetrabutylammonium hydroxide (QOH; Q: (C 4H 9) 4N) was carried out in a homogeneous solution. A mixture of organic solvent (aprotic or protic) and water of an appropriate volume ratio acts as the homogeneous organic solution. The reaction is greatly enhanced either by tetrabutylammonium hydroxide or by tetrabutylammonium bromide in the presence of potassium hydroxide. Effects of the reaction conditions including the concentration of QOH, concentration of KOH, amount of CS 2, organic solvents, volume ratio of organic solvent to water, and temperature on the conversion of o-phenylene diamine are investigated in detail. An explanation is provided for the peculiar phenomena in studying the effects of the concentration of KOH on the conversion of o-phenylene diamine.

Semi-Continuous Gas-Liquid Phase-Transfer Catalyzed Reaction of o-Phenylene Diamine and Carbon Disulfide by Tetrabutylammonium Hydroxide

The phase-transfer catalyzed reaction of o-phenylene diamine and carbon disulfide to synthesize 2-mercaptobenzimidazole (MBI) in a gas phase/liquid-phase solution two-phase medium was carried out in a semi-continuous reactor. Tetrabutylammonium hydroxide (TBAOH or QOH), which is an active compound, was used as the catalyst to promote the reaction rate. The liquid-phase solution contains the mixture of ethanol and water in an appropriate volume ratio. The gas-phase CS2/CH2Cl2 mixture of a higher temperature was continuously introduced to the reactor for reaction. The main advantage of the present system is that the reaction is carried out at a relatively higher temperature in the semi-continuous reactor. The gas-phase CS2/CH2Cl2 mixture first dissolves in the EtOH/H2O liquid-phase solution and reacts with QOH in the liquid-phase solution to produce an active intermediate (HOCS2(superscript -)Q(superscript +)). Then, this active intermediate further reacts with o-phenylene diamine to produce the desired product MBI. Based on the experimental observation, a reaction mechanism is proposed. A kinetic model, which considers the two-step reactions was developed, and a pseudo first order rate law is sufficient to describe the reaction. The effects of the reaction conditions, such as the amount of QOH, the agitation speed, the initial concentration of carbon disulfide, the flow rate of gas phase, the amount of o-phenylene diamine, the volume ratio of EtOH/H2O and the temperature, on the conversion of o-phenylene diamine and the apparent rate constant (k(subscript app) are investigated in detail.

Homogeneous reaction of carbon disulfide ando-phenylene diamine catalyzed by tertiary amines

Synthesis of 2-mercaptobenzimidazole (MBI) was carried out by reacting o-phenylene diamine and carbon disulfide catalyzed by tertiary amine (R3N) in a homogeneous solution. Dichloromethane, chlorobenzene, chloroform, toluene, and benzene were employed as the organic solvent. The advantage of using such organic solvents is that MBI precipitates from the organic solution. Only mechanical separation processes, such as filtration and centrifugation, can be used to obtain the MBI product of high purity. Based on the reaction mechanism, a kinetic model, which included two steps of reactions in the organic phase, was proposed, i.e.: (i) a chemical equilibrium of the reaction of CS2 and R3N to produce an active intermediate (R3N(SINGLEBOND)CS2) was built up within a short period of time and (ii) this active intermediate further reacted with o-phenylene diamine to produce the desired MBI product. A combination of the zeroth order and pseudo-first-order rates law was used to describe the kinetic data. However, the reaction follows pseudo-first-order rate law at higher temperature, and the reaction follows zeroth-order rate law at lower temperature. The effects of the operating conditions on the conversion of o-phenylene diamine were also investigated. © 1996 John Wiley & Sons, Inc.