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Static Reaction System (static + reaction_system)
Selected AbstractsThe unimolecular elimination kinetics of benzaldoxime in the gas phaseINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2007Libia L. Julio The kinetics of the gas-phase elimination of benzaldoxime was determined in a static reaction system over the temperature and pressure range 350°C,400°C and 56,140 Torr, respectively. The products obtained were benzonitrile and water. The reaction was found to be homogeneous, unimolecular, and tend to obey a first-order rate law. The observed rate coefficient is represented by the following Arrhenius equation: According to kinetic and thermodynamic parameters, the reaction proceeds through a concerted, semi-polar, four-membered cyclic transition state type of mechanism. © 2007 Wiley Periodicals, Inc. 39: 145,147, 2007 [source] Comparative studies on the pyrolysis of N -arylideneaminoamides: Kinetic and mechanistic studiesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2007Nouria A. Al-Awadi Rates of thermal decomposition of title compounds have been measured using a static reaction system. They undergo a unimolecular first-order elimination to give arylnitrile and the corresponding substituted amides. The decomposition parallels that of N -arylidenamino cyclic amide. The relative elimination rates at 600 K were calculated. The kinetic data reveal that the electronic effects of substituents, such as methyl, phenyl, benzyl, and allyl groups, are associated with the opposing directions in which the lone pair of electrons on the nitrogen atom of the arylidene moiety is being delocalized. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 59,66, 2007 [source] The elimination kinetics and mechanisms of ethyl piperidine-3-carboxylate, ethyl 1-methylpiperidine-3-carboxylate, and ethyl 3-(piperidin-1-yl)propionate in the gas phaseINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2006Angiebelk Monsalve The gas-phase elimination kinetics of the above-mentioned compounds were determined in a static reaction system over the temperature range of 369,450.3°C and pressure range of 29,103.5 Torr. The reactions are homogeneous, unimolecular, and obey a first-order rate law. The rate coefficients are given by the following Arrhenius expressions: ethyl 3-(piperidin-1-yl) propionate, log k1(s,1) = (12.79 ± 0.16) , (199.7 ± 2.0) kJ mol,1 (2.303 RT),1; ethyl 1-methylpiperidine-3-carboxylate, log k1(s,1) = (13.07 ± 0.12),(212.8 ± 1.6) kJ mol,1 (2.303 RT),1; ethyl piperidine-3-carboxylate, log k1(s,1) = (13.12 ± 0.13) , (210.4 ± 1.7) kJ mol,1 (2.303 RT),1; and 3-piperidine carboxylic acid, log k1(s,1) = (14.24 ± 0.17) , (234.4 ± 2.2) kJ mol,1 (2.303 RT),1. The first step of decomposition of these esters is the formation of the corresponding carboxylic acids and ethylene through a concerted six-membered cyclic transition state type of mechanism. The intermediate ,-amino acids decarboxylate as the ,-amino acids but in terms of a semipolar six-membered cyclic transition state mechanism. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 106,114, 2006 [source] The mechanism of neutral amino acid decomposition in the gas phase.INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 8 2001N -dimethylglycine, N -dimethylglycine ethyl ester, The elimination kinetics of N, ethyl 1-piperidineacetate The gas-phase elimination kinetics of the ethyl ester of two ,-amino acid type of molecules have been determined over the temperature range of 360,430°C and pressure range of 26,86 Torr. The reactions, in a static reaction system, are homogeneous and unimolecular and obey a first-order rate law. The rate coefficients are given by the following equations. For N,N-dimethylglycine ethyl ester: log k1(s,1) = (13.01 ± 3.70) , (202.3 ± 0.3)kJ mol,1 (2.303 RT),1 For ethyl 1-piperidineacetate: log k1(s,1) = (12.91 ± 0.31) , (204.4 ± 0.1)kJ mol,1 (2.303 RT),1 The decompositon of these esters leads to the formation of the corresponding ,-amino acid type of compound and ethylene. However, the amino acid intermediate, under the condition of the experiments, undergoes an extremely rapid decarboxylation process. Attempts to pyrolyze pure N,N-dimethylglycine, which is the intermediate of dimethylglycine ethyl ester pyrolysis, was possible at only two temperatures, 300 and 310°C. The products are trimethylamine and CO2. Assuming log A = 13.0 for a five-centered cyclic transition-state type of mechanism in gas-phase reactions, it gives the following expression: log k1(s,1) = (13.0) , (176.6)kJ mol,1 (2.303 RT),1. The mechanism of these ,-amino acids differs from the decarbonylation elimination of 2-substituted halo, hydroxy, alkoxy, phenoxy, and acetoxy carboxylic acids in the gas phase. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33:465,471, 2001 [source] Joint theoretical and experimental study of the gas-phase elimination kinetics of tert -butyl ester of carbamic, N, N -dimethylcarbamic, N -hydroxycarbamic acids and 1-(tert -butoxycarbonyl)-imidazoleJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2007Jose R Mora Abstract The gas-phase elimination kinetics of the title compounds were carried out in a static reaction system and seasoned with allyl bromide. The working temperature and pressure ranges were 200,280,°C and 22,201.5,Torr, respectively. The reactions are homogeneous, unimolecular, and follow a first-order rate law. These substrates produce isobutene and corresponding carbamic acid in the rate-determining step. The unstable carbamic acid intermediate rapidly decarboxylates through a four-membered cyclic transition state (TS) to give the corresponding organic nitrogen compound. The temperature dependence of the rate coefficients is expressed by the following Arrhenius equations: for tert -butyl carbamate logk1 (s,1),=,(13.02,±,0.46),,,(161.6,±,4.7) kJ/mol(2.303,RT),1, for tert -butyl N -hydroxycarbamate logk1 (s,1),=,(12.52,±,0.11),,,(147.8,±,1.1) kJ/mol(2.303,RT),1, and for 1-(tert -butoxycarbonyl)-imidazole logk1 (s,1),= (11.63,±,0.21),(134.9,±,2.0) kJ/mol(2.303,RT),1. Theoretical studies of these elimination were performed at Møller,Plesset MP2/6-31G and DFT B3LYP/6-31G(d), B3LYP/6-31G(d,p) levels of theory. The calculated bond orders, NBO charges, and synchronicity (Sy) indicate that these reactions are concerted, slightly asynchronous, and proceed through a six-membered cyclic TS type. Results for estimated kinetic and thermodynamic parameters are discussed in terms of the proposed reaction mechanism and TS structure. Copyright © 2007 John Wiley & Sons, Ltd. [source] Mechanism and structure,reactivity correlation in the homogeneous, unimolecular elimination kinetics of 2-substituted ethyl methylcarbonates in the gas phaseJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2003Gabriel Chuchani Abstract The gas-phase elimination kinetics of 2-substituted ethyl methylcarbonates were determined in a static reaction system over the temperature range of 323,435°C and pressure range 28.5,242 Torr. The reactions are homogeneous, unimolecular and follow a first-order rate law. The kinetic and thermodynamic parameters are reported. The 2-substituents of the ethyl methylcarbonate (CH3OCOOCH2CH2Z, Z=substituent) give an approximate linear correlation when using the Taft,Topsom method, log(kZ/kH)=,(0.57±0.19),,+(1.34±0.49),R, (r=0.9256; SD=0.16) at 400°C. This result implies the elimination process to be sensitive to steric factors, while the electronic effect is unimportant. However, the resonance factor has the greatest influence for a favorable abstraction of the ,-hydrogen of the C,,H bond by the oxygen carbonyl. Because ,, is significant, a good correlation of the alkyl substituents of carbonates with Hancock's steric parameters was obtained: log(kR/kH) versus ESC for CH3OCOOCH2CH2R at 400°C, R=alkyl, ,=,0.17 (r=0.9993, SD=0.01). An approximate straight line was obtained on plotting these data with the reported Hancock's correlation of 2-alkyl ethylacetates. This result leads to evidence for the ,-hydrogen abstraction by the oxygen carbonyl and not by the alkoxy oxygen at the opposite side of the carbonate. The carbonate decompostion is best described in terms of a concerted six-membered cyclic transition state type of mechanism. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||