Spectrophotometric titration of phenothiazines using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone

A specific Spectrophotometric titration method is described for the micro-determination of some phenothiazine derivatives in strong orthophosphoric acid medium using the -acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as a mild oxidizing titrant. The wavelengths of maximum absorption of the formed phenothiazonium cation radicals are 500, 515, 530, 533 and 650 nm for trifluoperazine dihydrochloride, promethazine hydrochloride, prochlorperazine dimaleate, chlorpromazine hydrochloride and thiethylperazine dihydrochloride, respectively. Quantitative recoveries are reported for pure drugs and their dosage forms. The method is simple and specific for determining phenothiazine derivatives in presence of their induced degraded oxidation products.     

Charge-Transfer Complexes between Substituted Pyridine N-Oxides and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

Spectrophotometry was used to study charge-transfer complexes between substituted pyridine N-oxides and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Vertical ionization potentials of pyridine N-oxides in the gas phase and in solution were calculated by the CNDO/S3' method. The calculated ionization potentials in chloroform nicely correlate with the experimental charge-transfer wavelengths of the complexes.     

Oxidative transformation of the natural lignan hydroxymatairesinol with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone

The oxidative transformation of the two isomers of the natural lignan hydroxymatairesinol from Norway Spruce (Picea abies) by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), has been studied. Significant differences in the outcome of the reactions were observed when the pure isomers of hydroxymatairesinol were reacted with DDQ under the same conditions. The different stereoelectronic effects in the two isomers as well as their conformational structures seem to determine the site of reaction, which results in different reaction products. Several products were identified by GC-MS and NMR spectroscopy. Oxomatairesinol was obtained in a yield of 25%.     

New Monomer Derived from Monoethanolamine Vinyl Ether and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone,and Redox Resin Thereof

A procedure was developed for synthesis of a new monomer from monoethanolamine vinyl ether and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. The kinetics of its radical polymerization was studied polarographically. The optimal polymerization conditions and properties of the resulting redox resin were studied.     

Preparation of 5,5-dicyano- and 5-cyano-5-ethoxycarbonyl-5,6-dihydro-3,7-diphenyl-4H-1,2-diazepines and their halogenations

5,5-Dicyano- and 5-cyano-5-ethoxycarbonyl-5,6-dihydro-3,7-diphenyl-4H-1,2-diazepines were prepared by the condensation of α-bromoacetophenone azine with malononitrile and ethyl cyanoacetate in the presence of sodium ethoxide, respectively. Halogenations of the dihydrodiazepines gave pyridazines, diazanorcaradienes, 4,4,6,6-tetrachlorodihydrodiazepines, and/or a 4-chloropyrazole whose relative yields strongly depended upon the nature of 5-substituents of the dihydrodiazepines as well as the reaction conditions.     

左旋多巴与2,3-二氯-5,6-二氰-1,4-苯醌的荷移反应研究

研究了左旋多巴和2,3-二氯-5,6-二氰-1,4-苯醌(DDBQ)的反应条件,确定在硼砂溶液中,在60℃反应70 min可获得稳定的络合物,其λmax=346 nm,组成比为1∶1,表观摩尔吸收系数ε=1.1×104L.mol-1.cm-1,应用拟定的方法测定药物制剂测定结果与文献方法一致,回收率在97.25%~102.7%之间,相对标准偏差在0.7%以内。     

Spectroscopic and spectrofluorimetric studies on the interaction of irbesartan with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and iodine

Raman, UV-vis, 1H NMR, FT-IR, mass and fluorescence spectral techniques were employed to investigate the mechanism of interaction of irbesartan (IRB) drug with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and iodine. Interaction of IRB with iodine yields triiodide ion and its formation was confirmed by electronic and Raman spectra. The peaks appeared in Raman spectrum of the isolated product at 143, 113 and 76 cm(-1) are assigned to νas(I-I), νs(I-I) and δ(I3-) respectively, confirmed the presence of I3- ion. The interaction of DDQ with irbesartan was found to proceed through the formation of outer complex and its conversion to the CT complex. Formation constant (K), molar extinction coefficient (?) and thermodynamic properties ΔH#, ΔS# and ΔG# were determined and discussed. Fluorescence quenching studies indicated that the interaction between the IRB and the acceptors are spontaneous and the IRB-DDQ interaction is found to be stronger than that the other system. Solvent variation studies indicated that the binding constant increased with an increase in polarity of the medium.     

2,3-二氯-5,6-二氰基-1,4-苯醌/NaNO2

设计了一种由 2,3-二氯-5,6-二氰基-1,4-苯醌(DDQ)和NaNO2组成的复合催化剂,该催化剂在9,10-二氢蒽氧化脱氢生成蒽的反应中表现出很高的催化活性和选择性. 在120 ℃和1.3 MPa O2下反应 8 h, 9,10-二氢蒽转化率达到99%以上,蒽的选择性为99%. 采用红外光谱和核磁共振方法对催化氧化脱氢的反应历程进行了研究. 结果表明, 9,10-二氢蒽氧气氧化脱氢生成蒽的反应是通过DDQ/DDQH2和NO2/NO两个氧化还原对的电子传递来推动的,以DDQ/NaNO2为催化剂可以有效催化9,10-二氢蒽氧化脱氢生成蒽.     

Synthesis of sulfur-sulfur bond formation from thioamides promoted by 2,3-dichloro-5,6-dicyanobenzoquinone

A mild and efficient synthesis of sulfur-sulfur bond formation from thioformanilides with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) is described. Functionality on the aromatic ring plays a key role in the formation of a sulfur-sulfur bond.     

Separation and determination of rhenium with 5,6-diphenyl-2,3-dihydro(asym)triazine-3-thione

5,6-DiphenyI-2,3-dihydro(asym)triazine-3-thione can be used as a gravimetric reagent for the determination of rhenium (4–50 mg) in the presence of 0.7–1.7 M hydrochloric acid and tin(II) chloride. The composition of the dried complex, which can be weighed directly, is [ReO(C₁₅H₁₀N₃S)₂]₂. The method is simple and rhenium can be determined in the presence of a number of foreign ions.     

Synthesis,Spectroscopic and Computational Studies of Charge-Transfer Complexation Between 4-Aminoaniline and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

A charge-transfer (CT) complex that forms from the reaction of the donor 4-amino aniline (4AA) and the π-acceptor 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) have been studied and characterized experimentally and as well as theoretically at room temperature. The experimental work includes the application of UV–visible spectroscopy to identify the CT band of the CT-complex. The composition of the complex has been investigated using spectrophotometric titration and Job’s method of continuous variation and found to be 1:1. Furthermore, to calculate the formation constant and molar extinction coefficient, we have used the Benesi–Hildebrand equation. Infrared, ¹H NMR, ¹³C NMR and mass spectral studies were used to characterize and confirm the formation of the CT-complex. The experimental studies were supported by quantum chemical simulations using density functional theory. The computational analysis of molecular geometry, Mulliken charges, and molecular electrostatic potential surfaces of reactants and complexes are helpful in assigning the CT route. The C=O bond length of DDQ increased upon complexation with 4AA. We have also observed that a substantial amount of charge has been transferred from 4AA to DDQ in the process of complexation. An excellent consistency has been achieved between experimental and theoretical results.     

Application of soft- and hard-modelling approaches to resolution of kinetics of electron donor-acceptor complex formation of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with imipramine in different solutions

Kinetics of electron donor-acceptor (EDA) complex formation of imipramine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was investigated spectrophotometrically in acetonitrile, 1,2-dichloroethane, and chloroform solutions using soft- and hard-modelling approaches. From the results of exploratory analysis of kinetic data and the spectral changes by soft-modelling approaches, evolving factor analysis (EFA) and orthogonal projection approach (OPA), a consecutive two-steps reaction with two intermediates was proposed for the process in acetonitrile and 1,2-dichloroethane media and one with a single intermediate in chloroform solution. Secondly, by applying, multivariate nonlinear least squares hard-modelling approach on the collected experimental kinetic data matrix, the nonlinear parameters (rate constants) as well as the linear parameters (spectral profiles) were obtained by fitting the collected experimental kinetic data matrix to the proposed model. Small values of standard deviation in the resulting parameters and sum of squares of the residuals (ssq) obtained showed the proper selection of the model. Furthermore, the values of lack of fit and percent of explained variance confirmed the correct identified models. Identification of the model with the aid of soft-modelling approaches followed by application of the hard-modelling approaches decreases significantly the rotational ambiguity associated with the obtained concentration and spectral profiles. Variations in the kinetic constants were in complete agreement with the model proposed and the solvent polarities.     

Molecular and crystal structure of 4,5-dicyano-2,6-diphenylpyrrolo [2,3-d]-pyrimidine and 4,6-diphenyl-7,8-dicyano-2-methyl-3-ethoxycarbonylpyrrolo[1,2-a]-1,4-dihydropyrimidine

M. V. Lomonosov Moscow State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 1, pp. 152–157, January–February, 1994.     

Spectrophotometric determination of mercury(II) with 5,6-diphenyl-2,3-dihydro-asym-triazine-3-thione

A highly selective spectrophotometric method is described for the determination of 0.05–0.55 mg mercury using 5,6-diphenyl-2,3-dihydro-asym-triazine-3-thione (DDTT). The yellow 1:2 complex is extractable into chloroform at pH 10, having a maximum absorbance at 430 nm, ? = 8.1 × 10³M^?1 cm^?1. The only interfering ions are CN^?, Tl(I), and Pd(II). The method was applied to the determination of mercury in organomercury compounds and to the estimation of the solubility product of mercurous sulfate.     

Synthesis of 4-Alkenylated Pyrazolinones by 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-Mediated Oxidative Coupling Reaction

1,3-Diarylpropenes firstly serve as efficient alkenylated reagents for the functionalization of pyrazolinones. In the presence of 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), it undergoes oxidative coupling and final dehydrogenation to give the highly substituted E,E-α,β,γ,δ-dienpyrazolinones in moderate to excellent yields.     

Spectrophotometric,Thermodynamic and Density Functional Studies of Charge Transfer Complex Between Benzhydryl Piperazine and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

The charge transfer complex of benzhydryl piperazine as donor with the π-acceptor 2,3-dichloro-5,6-dicyano-p-benzoquinone has been studied spectrophotometrically in acetonitrile medium at different temperatures. On mixing the donor with acceptor, a reddish brown colored charge transfer complex is formed. Electronic absorption spectra of the complex show charge transfer bands at 587, 546 and 457 nm. The molecular composition of the complex was studied by applying Job’s continuous variation and spectrophotometric titration methods. These results support the formation of the complex in a 1:2 ratio. The Benesi–Hildebrand equation has been applied to compute the formation constant and molecular extinction coefficient. Thermodynamic parameters of the charge transfer complexation reaction (standard entropy, standard enthalpy and standard Gibbs free energy) have been calculated. The results of the spectrophotometric study demonstrated that the charge transfer complex formation is endothermic. The computational studies of the charge transfer complex were performed by using the Gaussian 09 W package of programs. The bond lengths, bond angles, dihedral angles, Mulliken atomic charges, molecular electrostatic potential maps and characterization of the highest occupied molecular orbital and lowest unoccupied molecular orbital surfaces of charge transfer complex were computed.     

Polymers from intermediates obtained from hydrogen cyanide

The recent demonstration of an easy synthesis of diiminosuccinonitrile (DISN) from hydrogen cyanide and cyanogen, the reduction of DISN to diaminomaleonitrile (DAMN), and the use of these compounds to form difunctional heterocycles has made several new polyamide intermediates accessible. The 1- and 2-methyl-1,2,3-triazole-4,5-dicarbonyl chlorides have been polymerized interfacially to form high-melting polyamides of good heat stability. Interfacial polymerization of 1-methylimidazole-4,5-dicarbonyl chloride and trans-2,5-dimethylpiperazine has given a polyamide that is water-soluble. The 2,6- and 2,3-pyrazinedicarbonyl chlorides have been similarly converted to high-melting polyamides. 2,6-Dicyano-3,5-dipiperazinylpyrazine has been prepared from tetracyanopyrazine and piperazine and reacted with toluene diisocyanate to form a strong, stiff polyurea. Polyamides were also made from 2,3-diaminoquinoxaline, 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile, and DAMN.