ortho-dimethoxy effect in the Chichibabin reaction

A phenomenon, called the o-dimethoxy effect, was detected and consists in the fact that, in the sodium amide with aromatic and heterocyclic compounds with an o-dimethoxy grouping, one of the methoxy groups undergoes demethylation to form the corresponding o-methoxyphenol. The formation of an o-methoxyphenoxide anion in the case of N-heteroaromatic compounds hinders their animation by sodium amide. Compounds with m- and p-dimethoxy groups readily undergo the Chichibabin reaction. It is assumed that the nature of the o-dimethoxy effect is associated with sorption factors that are substantial for heterogeneous reactions such as the Chichibabin reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1105–1111, August, 1971.The authors sincerely thank Professor L. N. Yakhontov and Candidate of Chemical Sciences V. A. Azimov for their assistance in the chromatographic determination of the gases.     

Effect of benzo annelation on the Chichibabin reaction

The kinetics of amination with sodium amide (the Chichibabin reaction) for six azines and five azoles and the kinetics of the piperidinolysis of 2-chloro-substituted azole systems were studied. The following orders of reactivities were established for the Chichibabin reaction: isoquinoline > phenanthridine > benzo[h]quinoline > benzo[f]quinoline > pyridine acridine and 1-methylbenzimidazole > 1-methylnaphth[2,3-d]imidazole > 1-methylperimidine > 1-methylnaphth[1,2-d]imidazole > 3-methylnaphth-[1,2-d]imidazole. The changes in the reactivities are explained by the changes in the hydride labilities of the corresponding complexes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp, 257–261, February, 1979.     

The Chichibabin reaction in the Aminopyridine,azaindole, and azaindoline series

2-Aminopyridine, unlike the 3- and 4-isomers, is animated by sodium amide with the formation of 2,6-diaminopyridine. Among the dimethylaminopyridines, the 3- and 4-isomers are more active in the Chichibabin reaction, while 2-dimethylaminopyridine is converted with great difficulty under the action of sodium amide into 2,6-diaminopyridine with the initial replacement of the dimethylamine residue by an amino group. Azaindoles and azaindolines do not take part in the animation reaction. In 1-phenyl-5-azaindole, under the action of sodium amide, the pyrrole ring opens with the formation of 4-anilino-3-vinylpyridine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1232–1239, September, 1973.     

Wittig-Horner反应的动力学研究

Ｗｉｔｔｉｇ Ｈｏｒｎｅｒ反应是Ｗｉｔｔｉｇ反应的一种改进 ,二者可以互相补充 ,但Ｗｉｔｔｉｇ Ｈｏｒｎｅｒ反应还具有某些独特的优点[1] 。Ｗｉｔｔｉｇ Ｈｏｒｎｅｒ反应用于合成的研究有较多的报道 ,但对于该反应的理论研究却不多见[2 ] 。因此 ,我们合成了α 萘甲基磷酸二丁酯 ,并进行了它同一系列取代苯甲醛反应的动力学研究。在磷酸酯及醇钠恒定过量的条件下 ,测定了几种取代苯甲醛反应的假一级速率常数值。但实际上反应属于三级 ,对磷酸酯、乙醇钠和苯甲醛各为一级。因为当改变各反应组份的浓度时 ,速率发生改变。一般Ｗｉｔｔ…     

Chichibabin pyridinium synthesis

Chichibabin pyridine synthesis involves the reaction of three aldehydes and ammonia to form 2,3,5-trisubstituted pyridines. This study examined the synthesis of tetrasubstituted pyridinium from aldehydes and an amine hydrochloride in the presence/absence of Pr(OTf)₃. Important insights into the reaction mechanisms of Chichibabin pyridinium synthesis were proposed through the investigation of reaction intermediates along with quantitative GC–MS analysis.     

热重法研究煤的燃烧反应及其动力学

我国是个多煤少油的国家,煤炭是我国的主要能源,在我国的一次能源中所占比列高达70%[1].煤炭被广泛用于人类生产与生活的各个方面,且它的利用主要是通过燃烧直接获得能量.然而由于先进技术的欠缺,我国在煤炭的利用中一直存在着燃烧效率不高和环境污染严重等缺点,这与现今能源短缺和环境保护日益受重视的现状不相适应.本文通过研究分析煤的燃烧反应及燃烧反应动力学,为煤炭在利用时燃烧的清洁化与高效化提供科学依据.     

A new variant of the synthesis ofβ,γ′-bipyridyl by means of the Chichibabin reaction

A new method for the synthesis ofβ,γ′-bipyridyl by the Chichibabin reaction has been carried out.     

Study of H/D-exchange reaction kinetics of polypeptides

One of the possible methods for 3D protein structure investigation is the study of gas-phase hydrogen/deuterium (H/D) exchange reaction between protein ions and a D-containing reactant gas, e.g., D₂O or ND₃. A segmented radio frequency quadrupole (RFQ) was used as a molecule-ion reactor to study gasphase H/D-exchange of protonated ions of three different peptides. The ions were produced in an electrospray ion source. The RFQ is a part of ion transport interface of a high resolution orthogonal time-of-fiight mass spectrometer (O-TOF MS). The RFQ was modified for a linear ion trap (LIT) mode of operation to increase a dwell time of target ions inside the RFQ. Phase-sensitive operation of the LIT and the O-TOF MS was controlled by custom developed PC executive program. The reaction mixture of N₂ and ND₃ was injected into the reactor, while keeping its partial pressure in the range of 10⁻³–10⁻² mbar, and corresponding ND3 concentration in the range of 10¹³–10¹⁴ cm⁻³. It was possible to vary the ion dwell time in the reactor between 30 ms and 1 s. H/D-exchange was studied for leucine enkephalin, gramicidin S and apamin. The data analysis based on statistical approach has shown a principal possibility to distinguish different mobile H-atoms of peptides, taking part in H/D-exchange, according to reaction rates.     

Solid-phase reaction kinetics

It is argued that, for the macroscopic parameters of conventional kinetic models to become meaningful, they may be and must be expressed in terms of elementary single-barrier processes. To accomplish this means to associate some (external) extensional measure with a single-barrier elementary act, remaining within the logic of the existing geometrical-probabilistic scheme. A manner of doing this involving the use of Dirichlet fragmentations is suggested.     

六氟化铀与卤化氢气体的反应动力学研究

研究了UF6+HX(HX=HCl, HBr和HI)反应动力学, 结果显示,UF6+HX反应速率随着HCl-HBr-HI次序增加, 在室温下它们的反应速率常数分别为2.32×10^-^6, 6.43×10^-^4, 5.89×10^-^3s^-^1.Pa^-^1。UF6+HCl和UF6+HBr反应的表观活化能分别为11.29和4.18kj/mol。以上反应速率依次增加, 表出活化能依次减小的趋向与HX的键能以HCl-HBr-HI次序减小相符合。     

模拟油品氧化脱硫及反应动力学研究

在H₂O₂/WO₃/ZrO₂氧化体系中对以甲苯为溶剂、二苯并噻吩(DBT)为模型含硫化合物的模拟油品(硫的质量分数为1540×10^-6)进行了氧化脱硫研究,考察了反应温度、反应时间、氧化剂加入量、催化剂用量对DBT转化率的影响。实验结果表明,在反应温度50℃,反应时间90min,氧化剂加入量油/H₂O₂的体积比为20∶1和催化剂用量0.02g/mL的适宜氧化脱硫条件下,96%以上的DBT氧化为容易分离脱除的二苯并噻吩砜(DBTOs);同时研究了DBT氧化反应动力学,得知DBT氧化反应为一级反应,表观活化能E_a为55.37kJ/mol,指前因子A为3.35×10⁷min^-1。     

Study of the kinetics and equilibrium of the benzyl-radical association reaction with molecular oxygen

The forward rate constant, k₁, and the equilibrium constant, K_p, for the association reaction of the benzyl radical with oxygen have been determined. The rate constant k₁ was measured as a function of temperature (between 298 and 398 K) and pressure (at 20 and 760 torr of N₂) by two different techniques, argon-lamp flash photolysis and excimer-laser flash photolysis, both of which employed UV absorption spectroscopy (at 253 nm and 305 nm, respectively) to monitor the benzyl radical concentration. Over the range of conditions studied, we find that the reaction is independent of pressure and is almost independent of temperature, which is in accord with two early studies of the reaction but in apparent disagreement with more recent work. For our results in 760 torr of N₂ and for 298 < T/K < 398, a linear least-squares fitting of the data yield the expression: k₁ = (7.6 ± 2.4) × 10^?13 exp[(190 ± 160) K / T ] cm³ molecule^?1 s^?1. With the flash-photolysis technique, we determined K_p over the temperature range 398–525 K. Experimental values were analyzed alone and combined with theoretically determined entropy values of the benzyl and benzylperoxy radicals to determine the enthalpy of reaction: ΔH = (?91.4 ± 4) kJ mol^?1. Previous work on the benzyl radical enthalpy of formation allows us to calculate ΔH°_{f 298} (Benzylperoxy) = (117 ± 6) kJ mol^?1. In addition, we carried out an RRKM calculation of k₁ using as constraints the thermodynamic information gained by the study of K_p. We find that all the studies of the association reaction are in good agreement once a fall-off effect is taken into account for the most recent work conducted at pressures near 1 torr of helium. © 1994 John Wiley & Sons, Inc.     

Enamines of the 1,2,3,4-tetrahydroiso-quinoline series in the Chichibabin synthesis of pyrrolo[2,1-a]isoquinolines and in reaction with oxalyl chloride

It has been shown that the Chichibabin reaction of enamines of the 1,2,3,4-tetrahydroisoquinoline series and 1,2,3,4-tetrahydrobenzo[f]isoquinoline series with p-bromophenacyl bromide leads to pyrrolo[2,1-a]isoquinoline derivatives. The same heterocyclic system is obtained on interaction of 1-alkyl-3,4-dihydroisoquinolines or their benzo[f]-analogs with oxalyl chloride. The obtained dioxopyrrolines form derivatives of benzo[g]quinoxalino[2,3-b]indolizine on condensation with o-phenylenediamine. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1068–1074, July, 2007.     

Chemometrics study of the kinetics of the Griess reaction

The kinetics of the Griess reaction in which 3‐nitroaniline acts as a nitrosation agent and 1‐naphtylamine as a coupling reagent was studied by chemometrics methods. The kinetic reaction was investigated under pH 1.0 and 25°C by UV‐vis spectrophotometry. The concentrations of nitrite, 3‐nitroaniline and 1‐naphtylamine were such that a second‐order kinetic reaction took place. Data explorations based on principal component analysis and multivariate curve resolution–alternating least squares were performed to obtain information about the reaction. Calculation of band boundaries of the multivariate curve resolution–alternating least squares solutions showed that the rotational ambiguities associated with the calculation of spectra and concentration profiles have been completely removed. The decrease in the ambiguity of the recovered solutions was closely related to the application of the equality constraint. The results of the exploratory data analysis showed that the kinetic reaction proceeds through a two‐step mechanism. Moreover, the two‐steps are second order. Data analysis approaches based on hard modeling and global hard modeling were used to resolve profiles of the reactants, intermediates and products and to evaluate the rate constants. Copyright © 2013 John Wiley & Sons, Ltd.     

Study of kinetics of reaction of titanium raw materials with sulphuric acid

The reaction of ilmenite titanium raw materials with sulphuric acid has been studied in a non-isothermal-non-adiabatic type calorimeter. The influence of different starting conditions, temperature and ilmenite particle-size distribution on the thermo-kinetics of the reaction was investigated. A kinetic model is presented for this heterogeneous system for a specified ilmenite particle-size distribution and starting temperature. On the basis of this model and experimentally determined parameters it it possible to analyse by simulation the autothermic reaction of digestion of different titanium ores with sulphuric acid.     

FRET-based assay of the processing reaction kinetics of stimulus-responsive peptides: influence of amino acid sequence on reaction kinetics

In the field of chemical biology, methods for controlling peptidyl function by a stimulus are attracting increasing attention. Recently, we reported a stimulus-responsive peptide, which can be cleaved after exposure to a stimulus. In this study, we developed a FRET-based assay system to estimate the kinetics of the stimulus-induced processing (peptide bond cleavage) reaction. Based on the FRET system, it was clarified that introduction of a sterically less-hindered or polar residue at the position adjacent to the stimulus-responsive amino acid accelerates the processing reaction.     

Study on reaction kinetics of synthesis of thioether by a visualization technique

In this paper, a novel technique combined light-electronic microscopy and computer imaging trace was used to investigate the synthesis of thioether, which is an intermediate for lansoprazole. The reaction kinetics study by a visualization technique was carried out in a minireactor, and the concentration-grayscale standard curves for thioether were obtained by analyzing the grayscales of digital images for the solutions with 20 different concentrations. Based on the concentration-grayscale standard curves, the reactant concentrations at different times were calculated and the reaction kinetic curve as well as the reaction rate equation were obtained. It was found that the total mass-transfer resistance of sodium imidazole was larger than that of bromopyridine. Liquid-liquid interface of synthesizing thioether was observed and its mass transfer mechanism was discussed.