Pub Date : 2018-06-01DOI: 10.3184/146867818X15161889114501
S. Bakhtin, E. Shved, Yuliia Bespal’ko, Yu. Z. Stepanova
The mechanism of action of nucleophilic and non-nucleophilic bases in the system “acetic acid (HOAc) – epichlorohydrin (ECH) – R3X (R = alkyl, X = N, P)” has been studied. The observed orders of the reaction with respect to the components were found. It has been proved that the catalytic activity of the starting bases is determined by their nucleophilicity, rather than basicity. It is shown that the crucial stage of the reaction is the quaternisation of the starting base with the formation of a reactive intermediate, the acetate anion. Monitoring of possible paths of oxirane ring-opening by the initial base and the acetate anion was carried out. The behaviour of the model base, triphenylphosphine, in the quaternisation reaction was studied by UV spectroscopy. The rate constants of quaternisation in the reaction of tribenzylamine and triphenylphosphine with ECH have been estimated. The activation parameters of the stages of oxirane ring-opening by trimethylamine and the acetate anion were calculated using a quantum chemical method. It has been shown that the starting base attacks only the activated oxirane, while the acetate anion is capable of nucleophilic opening of both activated and non-activated ECH rings. A scheme for the catalytic opening of the oxirane ring by the bases in the system “ECH – HOAc – R3X” is proposed, which includes a series of both consecutive and parallel stages leading to the formation of the reaction product.
{"title":"Behaviour Modelling of Organic Bases in the Oxyalkylation Reaction of Proton-Containing Nucleophiles","authors":"S. Bakhtin, E. Shved, Yuliia Bespal’ko, Yu. Z. Stepanova","doi":"10.3184/146867818X15161889114501","DOIUrl":"https://doi.org/10.3184/146867818X15161889114501","url":null,"abstract":"The mechanism of action of nucleophilic and non-nucleophilic bases in the system “acetic acid (HOAc) – epichlorohydrin (ECH) – R3X (R = alkyl, X = N, P)” has been studied. The observed orders of the reaction with respect to the components were found. It has been proved that the catalytic activity of the starting bases is determined by their nucleophilicity, rather than basicity. It is shown that the crucial stage of the reaction is the quaternisation of the starting base with the formation of a reactive intermediate, the acetate anion. Monitoring of possible paths of oxirane ring-opening by the initial base and the acetate anion was carried out. The behaviour of the model base, triphenylphosphine, in the quaternisation reaction was studied by UV spectroscopy. The rate constants of quaternisation in the reaction of tribenzylamine and triphenylphosphine with ECH have been estimated. The activation parameters of the stages of oxirane ring-opening by trimethylamine and the acetate anion were calculated using a quantum chemical method. It has been shown that the starting base attacks only the activated oxirane, while the acetate anion is capable of nucleophilic opening of both activated and non-activated ECH rings. A scheme for the catalytic opening of the oxirane ring by the bases in the system “ECH – HOAc – R3X” is proposed, which includes a series of both consecutive and parallel stages leading to the formation of the reaction product.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"42 1","pages":"121 - 135"},"PeriodicalIF":0.7,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89155813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-01DOI: 10.3184/146867818X15233705894356
Chengyang Li, Hongyi Li, Libo Zhang, Yubo Ma, Tianfu Wang
Five types of 0.006 wt% Rh catalyst supported on the surfaces of Al2O3, ZnO, TiO2(rutile), TiO2(anatase) and CeO2 were prepared by the incipient wetness method and used to catalyse the conversion of dicyclopentadiene (DCPD) to monoformyltricyclodecenes (MFTD). The 0.006 wt% Rh/ZnO catalyst showed the highest performance of the catalysts investigated and a 95.5% MFTD yield with 100% MFTD selectivity could be achieved. This suggested that there may be a key role for the carrier on the catalytic performance in the DCPD hydroformylation. Furthermore, the kinetic profiles for DCPD hydroformylation over the 0.006 wt% Rh/ZnO catalyst have been examined systematically to explore the effect of reaction temperature on the catalytic performance. These data collectively suggested that a specific reaction temperature might enhance DCPD hydroformylation, possibly owing to agglomeration of the active sites at higher reaction temperatures.
{"title":"Hydroformylation of Dicyclopentadiene to Monoformyltricyclodecenes over Supported Ultra-Low Content Rh Catalysts","authors":"Chengyang Li, Hongyi Li, Libo Zhang, Yubo Ma, Tianfu Wang","doi":"10.3184/146867818X15233705894356","DOIUrl":"https://doi.org/10.3184/146867818X15233705894356","url":null,"abstract":"Five types of 0.006 wt% Rh catalyst supported on the surfaces of Al2O3, ZnO, TiO2(rutile), TiO2(anatase) and CeO2 were prepared by the incipient wetness method and used to catalyse the conversion of dicyclopentadiene (DCPD) to monoformyltricyclodecenes (MFTD). The 0.006 wt% Rh/ZnO catalyst showed the highest performance of the catalysts investigated and a 95.5% MFTD yield with 100% MFTD selectivity could be achieved. This suggested that there may be a key role for the carrier on the catalytic performance in the DCPD hydroformylation. Furthermore, the kinetic profiles for DCPD hydroformylation over the 0.006 wt% Rh/ZnO catalyst have been examined systematically to explore the effect of reaction temperature on the catalytic performance. These data collectively suggested that a specific reaction temperature might enhance DCPD hydroformylation, possibly owing to agglomeration of the active sites at higher reaction temperatures.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"47 1","pages":"166 - 172"},"PeriodicalIF":0.7,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87815142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-01DOI: 10.3184/146867818X15233705894365
Z. S. Bereksi, H. Benaïssa
In this work, the sorptive removal assessment of methylene blue by spotted golden thistle stalks was enhanced. Sorption was positively impacted by increasing temperature, initial pH or ionic strength. The sorbent isoelectrical point is 2.6 according to zeta potential measurements. The Elovich and Avrami models best fitted the sorption kinetic data; and an original prediction of equilibrium time is proposed. At 25 °C and for optimal initial pH = 7, the experimental maximal sorption capacity is 75 mg g−1. The Langmuir, Redlich–Peterson, Sips and Tóth models led to good correlations of isothermal data. Desorption percentages are important in both mineral and organic acidic media; the highest levels up to 91% were recorded for 1 × 10−2 M HCl solutions. The pseudo second-order model fitted satisfactorily the desorption kinetics. An innovative concept of regeneration is proposed, which promises significant savings of eluent and operating time. The sorbent regeneration assessment showed constant uptake abilities after five cycles of use.
{"title":"Effects of Some Operating Parameters on Sorption and Desorption Kinetics Related to Spotted Golden Thistle Stalks and Methylene Blue; Isotherm Study at Optimal pH and Sorbent Regeneration","authors":"Z. S. Bereksi, H. Benaïssa","doi":"10.3184/146867818X15233705894365","DOIUrl":"https://doi.org/10.3184/146867818X15233705894365","url":null,"abstract":"In this work, the sorptive removal assessment of methylene blue by spotted golden thistle stalks was enhanced. Sorption was positively impacted by increasing temperature, initial pH or ionic strength. The sorbent isoelectrical point is 2.6 according to zeta potential measurements. The Elovich and Avrami models best fitted the sorption kinetic data; and an original prediction of equilibrium time is proposed. At 25 °C and for optimal initial pH = 7, the experimental maximal sorption capacity is 75 mg g−1. The Langmuir, Redlich–Peterson, Sips and Tóth models led to good correlations of isothermal data. Desorption percentages are important in both mineral and organic acidic media; the highest levels up to 91% were recorded for 1 × 10−2 M HCl solutions. The pseudo second-order model fitted satisfactorily the desorption kinetics. An innovative concept of regeneration is proposed, which promises significant savings of eluent and operating time. The sorbent regeneration assessment showed constant uptake abilities after five cycles of use.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"16 1","pages":"173 - 188"},"PeriodicalIF":0.7,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87006304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-01DOI: 10.3184/146867818X15161889114510
W. Ahmad, I. I. Fagge, Yoke-Leng Sim, Mohammad Niyaz Khan
Pseudo first-order rate constants, k obs , for the alkaline hydrolysis of N-(o-aminophenyl) phthalimide, obtained at constant [CTABr]T (total concentration of cetyltrimethylammonium bromide) and varying concentrations of inert salt MX (MX = sodium formate, sodium acetate, sodium propanoate, sodium butyrate, sodium valerate and sodium hexanoate) follow the relationship: k obs = ( k 0 + θ K X / S [ MX ] ) ( 1 + K X / S [ MX ] ) , where θ and KX/S are empirical constants and S = HO-. The values of KX/S for each aliphatic acid decrease with an increase in [CTABr]T. This relationship gives an empirical constant whose magnitude is the measure of the ability of an ion, X-, to expel another counterion S-, from the cationic micellar surface to the bulk aqueous phase. The values of the empirical constant, KX/S, are used to derive the ion exchange constant, KBrX.
奥林匹克广播服务公司,伪一阶速率常数k的碱性水解N - (o-aminophenyl) phthalimide获得恒定(CTABr) T(总浓度的溴化cetyltrimethylammonium)和不同浓度的惰性盐MX (MX =甲酸钠,醋酸钠,钠propanoate,丁酸钠,钠戊酸酯和己酸酯类钠)遵循的关系:k光突发= X 0 +θk (k / S (MX)) (1 + X k / S (MX)),θ和KX / S和S = HO -实证常量。各脂肪酸的KX/S值随[CTABr]T的增加而降低。这个关系式给出了一个经验常数，其大小是离子X-从阳离子胶束表面驱逐另一个反离子S-到整体水相的能力的度量。经验常数KX/S的值被用来推导离子交换常数KBrX。
{"title":"Kinetics and Mechanism of Alkaline Hydrolysis of N-(o-Aminophenyl)Phthalimide in the Presence and Absence of Cationic Micelles and Sodium Salts of Aliphatic Acids","authors":"W. Ahmad, I. I. Fagge, Yoke-Leng Sim, Mohammad Niyaz Khan","doi":"10.3184/146867818X15161889114510","DOIUrl":"https://doi.org/10.3184/146867818X15161889114510","url":null,"abstract":"Pseudo first-order rate constants, k obs , for the alkaline hydrolysis of N-(o-aminophenyl) phthalimide, obtained at constant [CTABr]T (total concentration of cetyltrimethylammonium bromide) and varying concentrations of inert salt MX (MX = sodium formate, sodium acetate, sodium propanoate, sodium butyrate, sodium valerate and sodium hexanoate) follow the relationship: k obs = ( k 0 + θ K X / S [ MX ] ) ( 1 + K X / S [ MX ] ) , where θ and KX/S are empirical constants and S = HO-. The values of KX/S for each aliphatic acid decrease with an increase in [CTABr]T. This relationship gives an empirical constant whose magnitude is the measure of the ability of an ion, X-, to expel another counterion S-, from the cationic micellar surface to the bulk aqueous phase. The values of the empirical constant, KX/S, are used to derive the ion exchange constant, KBrX.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"7 1","pages":"144 - 156"},"PeriodicalIF":0.7,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80456523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.3184/146867818X15161889114439
Mahdieh Darijani, S. Habibi‐Khorassani, M. Shahraki
A kinetic and mechanistic investigation, using conventional UV-Vis spectrophotometry, of the reaction between dimethyl acetylenedicarboxylate (DMAD) and 1,3-dicarbonyl compounds including acetylacetone (ACAC) and dibenzoylmethane (DBM), has been conducted in a methanol environment with triphenylarsine (TPA) acting as a catalyst. Previously, in a similar reaction, triphenylphosphine (TPP) (instead of TPA) had been employed as a reactant (not a catalyst) for the generation of an ylide (final product). In the present work, of significance is the differential behaviour of TPA which, as a catalyst in the reaction environment, leads to a cyclopropane compound. Of other significance is the different behaviours of the two reactants in the kinetics and mechanism of the reaction. In previous work, TPP acted as a weak nucleophile (a reactant), so the first step of the reaction was recognised as the rate-determining step (RDS). Here, TPA reacts as a stronger nucleophile and a catalyst, resulting in the fourth step of the reaction (step4, k4, a proton transfer process) being recognised as the RDS. The reaction followed second-order kinetics. The proposed mechanism was adapted in accord with the experimental results and the steady-state assumption. The results showed that the reaction rate decreases in the presence of DBM, which participates in the second step (step2), compared to ACAC when it is present as another 1,3-dicarbonyl compound (structural effect). In addition, in previous work, the partial order of the reaction with respect to the 1,3-dicarbonyl compound was zero, while it is one in the present work. As a significant result, not only did a change in the structure of one of the reactants (TPA instead of TPP) create a different product, but also the kinetics and reaction mechanism changed. In addition, the reaction is enthalpy-controlled.
{"title":"Effect of Reactivity on Kinetics and a Mechanistic Investigation of the Reaction between Dimethyl Acetylenedicarboxylate and 1,3-Dicarbonyl Compounds in the Presence of a Catalyst: A Spectrophotometric Approach","authors":"Mahdieh Darijani, S. Habibi‐Khorassani, M. Shahraki","doi":"10.3184/146867818X15161889114439","DOIUrl":"https://doi.org/10.3184/146867818X15161889114439","url":null,"abstract":"A kinetic and mechanistic investigation, using conventional UV-Vis spectrophotometry, of the reaction between dimethyl acetylenedicarboxylate (DMAD) and 1,3-dicarbonyl compounds including acetylacetone (ACAC) and dibenzoylmethane (DBM), has been conducted in a methanol environment with triphenylarsine (TPA) acting as a catalyst. Previously, in a similar reaction, triphenylphosphine (TPP) (instead of TPA) had been employed as a reactant (not a catalyst) for the generation of an ylide (final product). In the present work, of significance is the differential behaviour of TPA which, as a catalyst in the reaction environment, leads to a cyclopropane compound. Of other significance is the different behaviours of the two reactants in the kinetics and mechanism of the reaction. In previous work, TPP acted as a weak nucleophile (a reactant), so the first step of the reaction was recognised as the rate-determining step (RDS). Here, TPA reacts as a stronger nucleophile and a catalyst, resulting in the fourth step of the reaction (step4, k4, a proton transfer process) being recognised as the RDS. The reaction followed second-order kinetics. The proposed mechanism was adapted in accord with the experimental results and the steady-state assumption. The results showed that the reaction rate decreases in the presence of DBM, which participates in the second step (step2), compared to ACAC when it is present as another 1,3-dicarbonyl compound (structural effect). In addition, in previous work, the partial order of the reaction with respect to the 1,3-dicarbonyl compound was zero, while it is one in the present work. As a significant result, not only did a change in the structure of one of the reactants (TPA instead of TPP) create a different product, but also the kinetics and reaction mechanism changed. In addition, the reaction is enthalpy-controlled.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"20 1","pages":"79 - 90"},"PeriodicalIF":0.7,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86848735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.3184/146867818X15066862094897
T. Soldatović, Enisa Selimović
The mole-ratio method was used for determining metal–ligand stoichiometry for the reaction between [ZnCl2(en)] (where en = 1,2-diaminoethane or ethylenediamine) and chloride ion at pH 7.2. The results have shown step-wise formation of 1:1 and 1:2 complexes and indicate additional coordination of chloride ions in the first coordination sphere. The kinetics of ligand substitution reactions of the zinc(II) complex and biologically relevant nucleophiles such as inosine-5′-monophosphate (5′-IMP), guanosine-5′-monophosphate (5′-GMP), L-methionine (L-Met), glutathione (GSH) and DL-aspartic acid (DL-Asp) were investigated at pH 7.2 as a function of nucleophile concentration in the presence of 0.010 M NaCl. The reactions were followed under pseudo first-order conditions by UV-Vis spectrophotometry. The substitution reactions include two steps of consecutive displacement of chlorido ligands and changes in coordination geometry. In the presence of an excess of chloride, the octahedral complex anion [ZnCl4(en)]2- formed. The first step of the substitution reactions could be interpreted as substitution of the axial chlorido ligands in the cis position to bidentate ethylenediamine by the biologically relevant nucleophiles, while the second step could be interpreted as substitution of the equatorial chlorido ligand. The order of reactivity of the investigated nucleophiles for the first reaction step is 5′-IMP > GSH > L-Met > DL-Asp > 5′-GMP, while for the second reaction step the order of reactivity is GSH > L-Met > 5′-IMP > DL-Asp > 5′-GMP.
{"title":"Kinetic Studies of the Reactions between Dichlorido(1,2-Diaminoethane)Zinc(II) and Biologically Relevant Nucleophiles in the Presence of Chloride","authors":"T. Soldatović, Enisa Selimović","doi":"10.3184/146867818X15066862094897","DOIUrl":"https://doi.org/10.3184/146867818X15066862094897","url":null,"abstract":"The mole-ratio method was used for determining metal–ligand stoichiometry for the reaction between [ZnCl2(en)] (where en = 1,2-diaminoethane or ethylenediamine) and chloride ion at pH 7.2. The results have shown step-wise formation of 1:1 and 1:2 complexes and indicate additional coordination of chloride ions in the first coordination sphere. The kinetics of ligand substitution reactions of the zinc(II) complex and biologically relevant nucleophiles such as inosine-5′-monophosphate (5′-IMP), guanosine-5′-monophosphate (5′-GMP), L-methionine (L-Met), glutathione (GSH) and DL-aspartic acid (DL-Asp) were investigated at pH 7.2 as a function of nucleophile concentration in the presence of 0.010 M NaCl. The reactions were followed under pseudo first-order conditions by UV-Vis spectrophotometry. The substitution reactions include two steps of consecutive displacement of chlorido ligands and changes in coordination geometry. In the presence of an excess of chloride, the octahedral complex anion [ZnCl4(en)]2- formed. The first step of the substitution reactions could be interpreted as substitution of the axial chlorido ligands in the cis position to bidentate ethylenediamine by the biologically relevant nucleophiles, while the second step could be interpreted as substitution of the equatorial chlorido ligand. The order of reactivity of the investigated nucleophiles for the first reaction step is 5′-IMP > GSH > L-Met > DL-Asp > 5′-GMP, while for the second reaction step the order of reactivity is GSH > L-Met > 5′-IMP > DL-Asp > 5′-GMP.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"1 1","pages":"53 - 61"},"PeriodicalIF":0.7,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90115301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cerium(III) complexes of two ligands of a diaza-crown ether with different functional groups as side arms were synthesised and characterised. The catalytic ability of the cerium(III) complexes for pUC19 DNA cleavage was investigated and compared using agarose gel electrophoresis. The results indicate that the catalytic activity of the complex CeL2 [L2 = 2,2′- (1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyl) diacetamide] with two carbamoylmethyl groups is significantly higher than the complex CeL1 [L1 = 2,2′- (1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyl) diethanol] with two hydroxyethyl groups under the same conditions. The optimum catalytic concentrations of CeL1 and CeL2 were 7.69 × 10−5 and 3.08 × 10−5 mol L−1 respectively and excessively high concentrations of the complexes can reduce their catalytic efficiency due to the formation of inactive μ-hydroxo dimers. The optimum catalytic acidities of CeL1 and CeL2 were pH 7.0 and 7.5 respectively and excessively high pH of the reaction system can reduce the catalytic efficiency of the complexes due to the formation of cerium(III) hydroxide. DNA cleavage promoted by the two complexes takes place via the same hydrolytic pathway and so the activity difference of the two complexes is attributed to the stability of the complexes, rather than the catalytic mechanism.
{"title":"Nuclease Activity of Diaza-Crown Ether Complexes of Cerium(III) with Different Functional Groups as Side Arms","authors":"Bingying Jiang, Shulan Cai, Jia‐qing Xie, Fa-mei Feng","doi":"10.3184/146867818X15161889114448","DOIUrl":"https://doi.org/10.3184/146867818X15161889114448","url":null,"abstract":"Cerium(III) complexes of two ligands of a diaza-crown ether with different functional groups as side arms were synthesised and characterised. The catalytic ability of the cerium(III) complexes for pUC19 DNA cleavage was investigated and compared using agarose gel electrophoresis. The results indicate that the catalytic activity of the complex CeL2 [L2 = 2,2′- (1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyl) diacetamide] with two carbamoylmethyl groups is significantly higher than the complex CeL1 [L1 = 2,2′- (1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-7,16-diyl) diethanol] with two hydroxyethyl groups under the same conditions. The optimum catalytic concentrations of CeL1 and CeL2 were 7.69 × 10−5 and 3.08 × 10−5 mol L−1 respectively and excessively high concentrations of the complexes can reduce their catalytic efficiency due to the formation of inactive μ-hydroxo dimers. The optimum catalytic acidities of CeL1 and CeL2 were pH 7.0 and 7.5 respectively and excessively high pH of the reaction system can reduce the catalytic efficiency of the complexes due to the formation of cerium(III) hydroxide. DNA cleavage promoted by the two complexes takes place via the same hydrolytic pathway and so the activity difference of the two complexes is attributed to the stability of the complexes, rather than the catalytic mechanism.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"5 1","pages":"91 - 99"},"PeriodicalIF":0.7,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73928970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.3184/146867818X15066862094888
I. I. Fagge, W. Ahmad, Sharifuddin Bin Md Zain, M. Khan
The quantitative correlation of counterion-affinity to aqueous hexadecyltrimethylammonium bromide (HDAB, cationic micelles/nanoparticles) and the counterion-induced HDAB micellar growth, in the presence of different amounts of poly(ethylene glycol hexadecyl ether) (C16E20, nonionic surfactant), was achieved by the use of a semi-empirical kinetic (SEK) method. The values of the ratio of cationic HDAB, as well as mixed HDAB–C16E20, micellar binding constants of X and Br, KX/KBr (= KXBr or RXBr) for X = 4-ClC6H4CO2-, were obtained by the SEK method. The concentration range (0.006–0.015 M) of pure HDAB was found to have no influence on the values of KXBr or RXBr. These observations were also recorded upon addition of a nonionic surfactant, C16E20, in an aqueous solution of HDAB. The mean value of KXBr or RXBr obtained in the presence of pure HDAB (KXBr or RXBr = 50.3) is 2.3 times larger than that in the presence of mixed HDAB–C16E20 (mKXBr or mRXBr = 21.7). From rheometric measurements of aqueous HDA+/4-ClC6H4CO2- with 0.015 M HDAB, single symmetric maxima (at both 25 and 35 °C) were obtained at [4-ClC6H4CO2Na] = 0.03 M. This is evidence for the existence of wormlike micelles/nanoparticles. However, the absence of a maximum in rheometric data for aqueous HDA+/C16E20/4-ClC6H4CO2- with 0.015 M HDAB and 0.006 M C16E20 at various [4-ClC6H4CO2Na] revealed the existence of spherical micelles.
{"title":"Kinetics and Mechanism of Counterionic Salt-Catalysed Piperidinolysis of Anionic Phenyl Salicylate in the Presence of Cationic–Nonionic Mixed Micelles","authors":"I. I. Fagge, W. Ahmad, Sharifuddin Bin Md Zain, M. Khan","doi":"10.3184/146867818X15066862094888","DOIUrl":"https://doi.org/10.3184/146867818X15066862094888","url":null,"abstract":"The quantitative correlation of counterion-affinity to aqueous hexadecyltrimethylammonium bromide (HDAB, cationic micelles/nanoparticles) and the counterion-induced HDAB micellar growth, in the presence of different amounts of poly(ethylene glycol hexadecyl ether) (C16E20, nonionic surfactant), was achieved by the use of a semi-empirical kinetic (SEK) method. The values of the ratio of cationic HDAB, as well as mixed HDAB–C16E20, micellar binding constants of X and Br, KX/KBr (= KXBr or RXBr) for X = 4-ClC6H4CO2-, were obtained by the SEK method. The concentration range (0.006–0.015 M) of pure HDAB was found to have no influence on the values of KXBr or RXBr. These observations were also recorded upon addition of a nonionic surfactant, C16E20, in an aqueous solution of HDAB. The mean value of KXBr or RXBr obtained in the presence of pure HDAB (KXBr or RXBr = 50.3) is 2.3 times larger than that in the presence of mixed HDAB–C16E20 (mKXBr or mRXBr = 21.7). From rheometric measurements of aqueous HDA+/4-ClC6H4CO2- with 0.015 M HDAB, single symmetric maxima (at both 25 and 35 °C) were obtained at [4-ClC6H4CO2Na] = 0.03 M. This is evidence for the existence of wormlike micelles/nanoparticles. However, the absence of a maximum in rheometric data for aqueous HDA+/C16E20/4-ClC6H4CO2- with 0.015 M HDAB and 0.006 M C16E20 at various [4-ClC6H4CO2Na] revealed the existence of spherical micelles.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"121 4 1","pages":"41 - 52"},"PeriodicalIF":0.7,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84084160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.3184/146867818X15066862094914
V. Zhukov, Alan Kong
A skeletal methane kinetic mechanism is developed for conditions relating to the combustion of undiluted methane–oxygen mixtures at high pressures. The new skeletal mechanism is based on the detailed mechanism of oxidation of alkanes by Zhukov (2009). The skeletal model has been created by eliminating unimportant species and reactions from the detailed mechanism. The reduction technique is based on the reaction path and sensitivity analyses. They allow one to determine the reactions and species that play important roles in combustion in rocket combustion chambers. The skeletal mechanism consists of 23 species and 51 reactions. The final and intermediate versions of the skeletal mechanism are compared with the parent detailed mechanism, with other reduced kinetic models and with experimental data on the ignition of methane at high pressures. This comparison shows that the developed skeletal mechanism has a better performance than other kinetic mechanisms in terms of accuracy and required computational power.
{"title":"A Compact Reaction Mechanism of Methane Oxidation at High Pressures","authors":"V. Zhukov, Alan Kong","doi":"10.3184/146867818X15066862094914","DOIUrl":"https://doi.org/10.3184/146867818X15066862094914","url":null,"abstract":"A skeletal methane kinetic mechanism is developed for conditions relating to the combustion of undiluted methane–oxygen mixtures at high pressures. The new skeletal mechanism is based on the detailed mechanism of oxidation of alkanes by Zhukov (2009). The skeletal model has been created by eliminating unimportant species and reactions from the detailed mechanism. The reduction technique is based on the reaction path and sensitivity analyses. They allow one to determine the reactions and species that play important roles in combustion in rocket combustion chambers. The skeletal mechanism consists of 23 species and 51 reactions. The final and intermediate versions of the skeletal mechanism are compared with the parent detailed mechanism, with other reduced kinetic models and with experimental data on the ignition of methane at high pressures. This comparison shows that the developed skeletal mechanism has a better performance than other kinetic mechanisms in terms of accuracy and required computational power.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"22 1","pages":"62 - 78"},"PeriodicalIF":0.7,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87338519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-03-01DOI: 10.3184/146867818X15066862094879
Yuhui Ma, Jing Wang, Yushan Zhang
Enteromorpha prolifera (EP), the main source contributing to the outbreak of ‘green tide’, was used as the raw material to prepare biochars by pyrolysis. The biochars were analysed using N2-adsorption and Fourier transform infrared (FTIR) spectroscopy. The pyrolysis process was investigated by thermogravimetric analysis coupled with FTIR. The adsorption capacities of the biochars were compared in terms of removal efficiencies of methylene blue (MB), oxytetracycline (OTC) and humic acid (HA). The adsorption isotherms of the three organics by the optimum biochar were investigated. The results showed that the Brunauer–Emmett–Teller surface area of the biochar increased from 36 to 643 m2 g−1 with increasing pyrolysis temperature. The surface functional groups contained in EP were damaged during pyrolysis, while–N=O, S=O and C=N groups were formed on the biochar surface. Decomposition of EP resulted in the vigorous release of gaseous products at 240 °C, including CO2, H2O, aldehydes, ethers, aliphatic amines, sulfones and alcohols. CO2 was released due to the decomposition of carbonates above 700 °C and the in situ reduction of CO2 by carbon contained in the biochar was responsible for the high surface area of the biochar prepared at 750 °C (EPC750). EPC750 had the highest adsorption capacities for MB, OTC and HA among the biochars. The adsorption equilibrium data for MB and OTC onto EPC750 followed the Langmuir model with monolayer adsorption capacities of 138.89 and 103.31 mg g−1 respectively. The adsorption data for OTC also exhibited good agreement with the Freundlich model, suggesting the adsorption process was controlled by multiple mechanisms. The adsorption of HA by EPC750 followed the Freundlich model and the maximum adsorption capacity reached 64.27 mg g−1 under the experimental conditions.
{"title":"‘Green Tide’ to Biochar: Preparation and Adsorption Isotherms for Three Typical Organic Pollutants","authors":"Yuhui Ma, Jing Wang, Yushan Zhang","doi":"10.3184/146867818X15066862094879","DOIUrl":"https://doi.org/10.3184/146867818X15066862094879","url":null,"abstract":"Enteromorpha prolifera (EP), the main source contributing to the outbreak of ‘green tide’, was used as the raw material to prepare biochars by pyrolysis. The biochars were analysed using N2-adsorption and Fourier transform infrared (FTIR) spectroscopy. The pyrolysis process was investigated by thermogravimetric analysis coupled with FTIR. The adsorption capacities of the biochars were compared in terms of removal efficiencies of methylene blue (MB), oxytetracycline (OTC) and humic acid (HA). The adsorption isotherms of the three organics by the optimum biochar were investigated. The results showed that the Brunauer–Emmett–Teller surface area of the biochar increased from 36 to 643 m2 g−1 with increasing pyrolysis temperature. The surface functional groups contained in EP were damaged during pyrolysis, while–N=O, S=O and C=N groups were formed on the biochar surface. Decomposition of EP resulted in the vigorous release of gaseous products at 240 °C, including CO2, H2O, aldehydes, ethers, aliphatic amines, sulfones and alcohols. CO2 was released due to the decomposition of carbonates above 700 °C and the in situ reduction of CO2 by carbon contained in the biochar was responsible for the high surface area of the biochar prepared at 750 °C (EPC750). EPC750 had the highest adsorption capacities for MB, OTC and HA among the biochars. The adsorption equilibrium data for MB and OTC onto EPC750 followed the Langmuir model with monolayer adsorption capacities of 138.89 and 103.31 mg g−1 respectively. The adsorption data for OTC also exhibited good agreement with the Freundlich model, suggesting the adsorption process was controlled by multiple mechanisms. The adsorption of HA by EPC750 followed the Freundlich model and the maximum adsorption capacity reached 64.27 mg g−1 under the experimental conditions.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"98 1","pages":"30 - 40"},"PeriodicalIF":0.7,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80994202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：