Kinetic and Mechanistic Study of Oxidation of Piperazines by Bromamine-T in Acidic Medium

Oxidations of piperazine, 1-methylpiperazine and 1-ethylpiperazine by bromamine-T (BAT) in buffered acidic medium have been kinetically studied at 303 K. The reaction shows a first-order dependence of the rate each on [BAT]0 and [piperazine]0, and an inverse fractional-order dependence on [H+]. The additions of halide ions and the reduction product of BAT, p-toluenesulfonamide, have no effect on the reaction rate. The variation of ionic strength of the solvent medium has no influence on the rate. Activation parameters have been evaluated from the Arrhenius and Eyring plots. A common mechanism consistent with the kinetic data has been proposed for all piperazines. The protonation constants of substrates have been evaluated. The Hammett linear free-energy relationship has been observed for the reaction with ρ = ?0.5 indicating that the electron-donating groups enhance the reaction rate by stabilizing the transition state. An isokinetic relationship observed shows β = 368 K indicating the dominance of enthalpy factors on the reaction rate.

Synthesis of Novel Non-Nucleoside HIV-1 Reverse Transcriptase Inhibitors-1-(3-Phthalimido-2-oxobutyl)-4-Substituted-phenylpiperazines

We have designed and synthesized a series of new phthalimidopiperazines, biological activity test show that the target compounds(Ic, Ie, ii) can inhibit HIV-I RT with IC50 20.0, 43.8, and 63.7 mu M, respectively.

Synthesis of Some <i>N</i>-[(4-Substituted-1-Piperazinyl)-Oxo(Alkyl and Ethylcarbamoyl)]-3-(2-Thiophenyl)Acrylamides as Non-Steroidal Anti-Allergic and Anti-Inflammatory Agents

An interesting approach for the design of anti-allergies is rationally considered. It was proved that current anti-allergic drugs comprise piperazine and acrylic acid segments. In harmony with these findings, new products 5a-u were synthesized starting from conjugated 2-thiopheneacrylic acid with amino acid esters3a-g followed by coupling of their acid derivatives4a-g with some piperazine segments, with the aim to increase their biological activities and decrease side effects. The anti-allergic and anti-inflammatory activities of the products were evaluated and promising results were obtained.

Crystal Structures, Stability, and Solubility Evaluation of a 2:1 Diosgenin-Piperazine Cocrystal

A cocrystal of diosgenin with piperazine in 2:1 stoichiometry was successfully synthesized.The solid form was prepared by liquid assisted grinding,slurry and crystallization methods.The cocrystal was characterized by powder X-ray diffraction,differential scanning calorimetry,thermogravimetric analysis,Fourier transform infrared spectroscopy,and structure determined by single crystal X-ray diffraction,the hydrogen bonds formed into fish bone structure along the[010]direction and all the molecules packed into 3D layer structure along a axis.After formation of cocrystal,the solubility of diosgenin was improved,and the solubility value in 0.2%SDS solution was approximately 1.5 times as large as that of the parent material.

Poly(ethylene glycol)-supported Piperazine——Synthesis and Application in Knoevenagel Condensation

A soluble, poly（ethylene glycol）-supported piperazine catalyst was prepared. This soluble catalyst efficiently catalyzes the Knoevenagel condensation of various aromatic aldehydes with diethyl malonate or ethyl acetoacetate in a homogeneous phase to afford the desired alkenes in good purity and yield with a facile work-up process. It was found that the polymer reagent could be repeatedly used at least four times without the too much loss of activity. The catalyst has shown a good activity, stability, and recycling capability.

A One-dimensional Cobalt Coordination Polymer Based on Biphenyl-2,3,3',5'-tetracarboxylic Acid and N-donor Ancillary Ligands: Crystal Structure and Magnetic Property

Hydrothermal reactions of biphenyl-2,3,3A,5A-tetracarboxylic acid（H4bptc） with cobalt salt in the presence of 1,4-bis（2-pyridylmethyl）piperazin（bpmp） afforded one novel coordination polymer, namely, [Co（H2bptc）（bpmp）0.5（H2O）]n（1）. Its structure was established by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra and TG analysis. Complex 1 crystallizes in monoclinic, space group P21/c with a = 11.4839（11）, b = 16.6690（16）, c = 11.5559（11） A, V = 2201.8（4） A3, Mr = 539.35, Dc = 1.627 g/cm^3, μ（MoK α） = 0.841 mm-1, F（000） = 1108, Z = 4, the final R = 0.0309 and w R = 0.0705 for 4090 observed reflections（I 2σ（I））. Complex 1 displays a one-dimensional（1D） chain bridged by bpmp. Two carboxylic groups of H4 bptc ligand adopt μ01-η1：η1 and μ1-η1：η coordination modes to bridge adjacent Co（Ⅱ） ions together with bpmp ligand to give alternately arranged left- and right-handed helical chains. In addition, variable-temperature magnetic susceptibility measurements indicate that complex 1 shows weak antiferromagnetic interactions between the adjacent Co（Ⅱ） ions.

Phytochemical,Anti-oxidant and Anthelmintic activities of various leaf extracts of Flacourtia sepiaria Roxb

Objective:The present study was carried out to investigate the phytochemical constituents,in vitro antioxidant potential and anthelmintic activities of Flacourtia sepiaria Roxb leaves.Methods:The dried powdered leaves of Flacourtia sepiaria were extracted using petroleum ether,chloroform,ethyl acetate and methanol by a soxhlet extractor and preliminary phytochemical screening was performed using standard protocols.All the extract was evaluated for their potential antioxidant activities using test such as DPPH,superoxide anion radical,hydroxyl radical,nitric oxide radical scavenging abilities,ferrous chelating ability and total phenolic and flavanoid content.Anthelmintic activity of extract was screened in adult Indian earthworm model.Results:Preliminary screening revealed the presence of bioactive compounds especially phenolics,tannins and terpenoids in all extracts.The phenolic and flavanoid content was highest in methanolic extract and lowest in petroleum ether extract.The paralytic(9.4610.212)and death time(31.43±1.148)of methanolic extract was found to be significant(P<0.05)when compared with paralytic(7.33±0.206)and death lime(18.60±0.229)of standard piperazine citrate at 100 mg/mL concentration.Conclusions:The results of the present study indicate that the leaf extracts of Flacourtia sepiaria exhibited strong antioxidant activity and possess significant anthelmintic activity and thus it is a good source of antioxidant and anthelmintic constituents.

Novel Piperazine-based Gemini and Bola Surfactants

A series of piperazine-based Gemini and Bola surfactants were synthesized. Gemini 1 and 5 have well surface activities. Their critical micelle concentrations （cmc） is 6.47×10^-4 mol/L and 1.17×10^-3mol/L, respectively. Bola surfactants 2 and compound 3, possessing better water solubility, have lower surface activities. Calculation, carried out by MM2 energy minimization, showed that compound with more hydrophobic chains in a spacer of limited length is difficult to be synthesized.

Rapid analysis of piperazine ferulate tablets by optic-fiber sensing technology and the similarity of ultraviolet spectra

A rapid analysis method of piperazine ferulate tablets by optic-fiber sensing technology with UV-vis absorption spectrum was established. Qualitative and quantitative data were obtained and compared by maximum and minimum wavelength, absorbance and contrast spectra. Similarity method was used to identify authenticity of drugs. The difference of contents measured by this method and UV determination method in China Pharmacopoeia showed no statistical significance (P40.05), while the similarity can be used as a parameter to identify the authenticity of drugs.

Modeling the rate of corrosion of carbon steel using activated diethanolamine solutions for CO2 absorption

A mechanistic model is developed to investigate the influence of an activator on the corrosion rate of carbon steel in the absorption processes of carbon dioxide(CO2).Piperazine(PZ)is used as the activator in diethanolamine(DEA)aqueous solutions.The developed model for corrosion takes into consideration the effect of fluid flow,transfer of charge and diffusion of oxidizing agents and operating parameters like temperature,activator concentration,CO2 loading and pH.The study consists of two major models:Vapor–liquid Equilibrium(VLE)model and electrochemical corrosion model.The electrolyte-NRTL equilibrium model was used for determination of concentration of chemical species in the bulk solution.The results of speciation were subsequently used for producing polarization curves and predicting the rate of corrosion occurring at the surface of metal.An increase in concentration of activator,increases the rate of corrosion of carbon steel in mixtures of activated DEA.

Comprehensive evaluation and sensitivity analysis of regeneration energy for acid gas removal plant using single and activated-methyl diethanolamine solvents

The absorption of acid gas using reactive amines is among the most widely used types of capturing technologies.However,the absorption process requires intensive energy expenditure majorly in the solvent regeneration process.This study simultaneously evaluated the regeneration energy of MDEA and PZ/MDEA solvents in terms of heat of absorption,sensible heat,and vaporization heat.Aspen Hysys version 8.8 simulation tool is applied to model the full acid gas removal plant for the chemical absorption process.The new energy balance technique presents around the absorption and desorption columns to bring a new perspective of energy distribution in the capturing of acid gas plants.Sensitivity analysis of regeneration energy and its three contributors is performed at several operation parameters such as absorber and stripper pressures,lean amine circulation rate,solvent concentration,reflux ratio,and CO2 and H2 S concentrations.The results show that the heat of absorption of PZ/MDEA system is higher than that for MDEA system for the same operating conditions.The sensible heat is the main contributor in the required regeneration energy of MDEA solvent system.The simulation results have been validated against data taken from real plant and literature.The product specifications of our simulation corroborate with real plant data in an excellent approach;additionally,the profile temperature of the absorber and the stripper columns are in good agreement with literature.The overall results highlight the direction of the effects of each parameter on the heat of absorption,sensible heat,and vaporization heat.

Phase Transfer Catalyzed Synthesis and Antibacterial Activity of Water-soluble S-Triazolo[3,4-b][1,3,4]thiadiazoles Containing Piperazine Group

6/3-（4-Chlorophenyl）-s-triazolo[3, 4-b][1, 3, 4]thiadiazoles （2,a-e） and （Sa-e） were synthesized respectively by intermolecular cyclization of 5-aryl / 4-chlorophenyl-4-amino-3- mercapto-1, 2, 4-triazoles （la-e） and （4） with 4-chlorobenzoic acid / aryl acids, which were condensed with piperazine under phase transfer catalyst TBAB to yield the corresponding free bases of monopiperazine derivatives and followed to form water-soluble salts （3a-e） and （6a-e） with hydrochloric acid in good yields. The in vitro biological results showed that piperazine group conjugated with the above fused heterocycles played an important role in antibacterial activity. The structures of novel compounds were confirmed by IR, ＇H NMR, MS and elemental analysis.

Experimental studies and artificial neural network modeling of surface tension of aqueous sodium L-prolinate solutions and piperazine blends

The surface tension study is very crucial for the design of CO2 gas absorption contacting equipment. The significance of the surface tension has been increasing due to its consideration in various technological fields. This property influences the mass transfer and hydrodynamics of gas absorption systems, mainly multiphase systems, in which the interface between gas and liquid exists. Therefore, in this study, surface tension of aqueous solutions of sodium L-prolinate(SP) and piperazine(PZ) blends were measured at ten different temperatures from(298.15 to 343.15) K. The SP mass fractions were 0.10, 0.20, and 0.30;while the mass fractions of PZ were 0.02 and 0.05. The experimental results showed that the surface tension increase with increasing the mass fractions of SP and PZ in aqueous blends, and decrease linearly with rising temperature. The experimental data of surface tension were correlated by two empirical correlations as a function of temperature and mass fractions for estimating the predicted data using the optimized correlation coefficients. Moreover, the modeling of surface tension data was carried out using Artificial Neural Network(ANN) approach. The results obtianed from ANN modeling were compared with applied empirical correlation. It was found that the ANN approach outperformed the empirical correlation used in this study. Besides, a quantitative analysis of variation(ANOVA) was performed in order to determine the significance of data. The surface tension of aqueous SP and SP + PZ was also compared with various conventional solvents.

Influence of pretreatment of piperazine ferulate on pharmacokinetic parameters of methotrexate in methotrexate-induced renal injury model rats by HPLC-MS

The present study was designed to investigate the influence of the pretreatment of piperazine ferulate on pharmacokinetic parameters of methotrexate in methotrexate-induced renal injury rats.A simple and efficient high performance liquid chromatography coupled with mass spectrometry(HPLC-MS)method was developed to determine methotrexate in rat plasma.Methotrexate and syringic acid(internal standard)were extracted from rat plasma samples by protein precipitation with acetonitrile.The analysis was performed on a CAPCELL PAK C18column(150 mm×4.6 mm,5μm)with acetonitrile and 5 mmol/l ammonium acetate aqueous(10:90,v/v).The linear range was 5.0×10-2to 100.0μg/ml for methotrexate.Other parameters were all within the acceptance criteria.The validated method was successfully applied the pharmacokinetic study of methotrexate between two methotrexate treated groups(with and without the pretreatment of piperazine ferulate).Compared with the methotrexate treated alone group,the pharmacokinetic parameters in the methotrexate with the pretreatment of piperazine ferulate group showed significantly lower MRT(0-t),MRT(0-∞) and T1/2.Results suggested that methotrexate can be rapidly eliminated,cleared or metabolized in rat blood,which might be related to the pretreatment of piperazine ferulate.The method provided deeper insights into rational clinical use of methotrexate with the pretreatment of piperazine ferulate on cancer patients with renal dysfunction.

The 1:2 Complex of Piperazine with Some Phenols:Hydrogen Bonding Pattern Involved in Transition States in Solution

A novel model for the 1: 2 complex of piperazine with some phenols in solution is established and verified. In CDCl3 solution, one piperazine molecule is tied to two phenol molecules by hydrogen bonds of O-H---N and N-H---O. And the protons of >NH and -OH groups exchange quickly and simultaneously between the atoms of phenol oxygen and piperazine nitrogen.

Effects of hexametazidine on physiological properties of guinea-pig papillary muscles

Effects of hexametazidine [1,4-di（2,3,4-trimethoxybenzyl）piperazine]on the physiological properties of guinea-pig papillary muscles were investigated.Hexametazidine possesses a concentration-dependent negative inotropic effect(IC50=81.8±16.9μmol/L).The effect of hexametazidine（30.8μmol/L）was antago-nized completely by increasing the concentration of Ca2+from 1.8 to 5.4mmol/L.Hexametazidine（30.8μmol/L）increased the threshold concentration of adrenalinefor inducing the automaticity of the muscles from 3.95±1.80 to 6.67±4.84μmol/L（P【0.05）.It prolonged the functional refractory period from 218±14 to 254±20ms（P【0.05）at the concentration of 61.6μmol/L.Hexametazidine（6.2μmol/L）antago-nized the positive inotropic effect of isoprenaline competitively and ofhistamine non-competitively（pA 2 and pD2′ values were 5.45 and 4.13,respectively）.

An Efficient Process for Preparing 4-Methyl-2-phenyl Piperazine Hydrochloride and its Derivatives

An improved method for preparation of 4-methyl-2-phenyl piperazine and its derivatives with higher yield and inexpensive reagents was developed, the products were characterized by 1H-NMR and MS.

Syntheses, Structures and Fluorescent Property of Two Cd(Ⅱ) 3D Coordination Polymers with Mixed Ligands of Azide and Piperazine Derivatives

Two new coordination polymers, [Cd（N3）2（Baep）l/2]n （1） and [Cd2（N3）4（CH3OH）（Bapp）I/.2]n （2） （Baep = 1,4-bis（2-aminoethyl）piperazine, Bapp = 1,4-bis（3-aminopropyl）piperazine） were synthesized. The crystal of 1 is of monoclinic system, space group P21/c with a = 9.341（7）, b = 11.677（9）, c = 8.195（6） A, fl = 93.925（13）, V= 891.8（11） A3, Z= 4, μ（MoKa） = 2.42 mm-1, Mr = 280.58, Dc = 2.090 g/cm3, the final R = 0.0297 and wR = 0.0720. The crystal of 2 is of triclinic system, space group PI with a = 9.121（5）, b = 9.666（5）, c = 10.250（6） A, a = 72.91（2）, β= 77.10（2）, V = 73.95（2）°, V = 820.0（8）°, Z = 2,μ（MoKa） = 2.62 mm-1, Mr= 522.10, Dc = 2.114 g/cm3, the final R = 0.0251 and wR = 0.0632. Single-crystal X-ray diffraction studies reveal that 1 is a 3D structure based on a dinuclear unit {Cd2（N3）a（Baep）}, in which the Baep ligands formed in situ display two different bridging modes. Compound 2 also has a 3D structure based on a tetranuclear cluster {Cda（N3）8（CH3OH）2（Bapp）}, in which the azido anions exhibit four different bridging modes （μ-1,1, μ-1,3, μ-l,l,1 and μ-1,1,3）. The thermal stability and fluorescent property of 1 and 2 have also been investigated.

STUDIES ON THE REGULAR COPOLYMERS OF POLY (1, 4-PHENYLENETEREPHTHALAMIDE)

Two types of the regular copolymer of poly (1, 4-phenyleneterephthalamide) were synthesized by the low temperature solution polycondensation in NMP-CaCl_2 solvent system, using the piperazine or 2,5-dimethylpiperazine as the third components introduced in the main chain of poly (1, 4-phenyleneterephthalamide). The properties of copolymers were characterized by IR, SEM, X-RAY diffraction, polarizing microscopy, TGA and solubilities.Experimental results showed that the copolymers had good solubility and thermal stability, the concentrated sulfuric acid (～98% ) solution of regular PPTA copolymers had liquid crystalline proper-

SYNTHESIS OF 1－（2－AMINOETHYL） PIPERAZINE RESIN AND ITS ADSORBABILITYFOR NOBLE METALLIC IONS

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