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1.
José R. Mora Jesús Lezama Edgar Márquez Luz Escalante Tania Córdova Gabriel Chuchani 《Journal of Physical Organic Chemistry》2011,24(3):229-240
The gas‐phase elimination of kinetics 4‐chlorobutan‐2‐one, 5‐chloropentan‐2‐one, and 4‐chloro‐1‐phenylbutan‐1‐one has been studied using electronic structure methods: B3LYP/6‐31G(d,p), B3LYP/6‐31++G(d,p), MPW91PW91/6‐31G(d,p), MPW91PW91/6‐31++G(d,p), PBEPBE/6‐31G(d,p), PBEPBE /6‐31++G(d,p), and MP2/6‐31++G(d,p). The above‐mentioned substrates produce hydrogen chloride and the corresponding unsaturated ketone. Calculation results of 4‐chlorobutan‐2‐one suggest a non‐synchronous four‐membered cyclic transition state (TS) type of mechanism. However, in the case of 5‐chloropentan‐2‐one and 4‐chloro‐1‐phenylbutan‐1‐one, the carbonyl group assists anchimerically through a polar five‐membered cyclic TS mechanism. The polarization of the C? Cl bond, in the sense of Cδ+…Clδ?, is a rate‐determining step in these elimination reactions. The significant increase in rates in the elimination of 5‐chloropentan‐2‐one and 4‐chloro‐1‐phenylbutan‐1‐one is attributed to neighboring group participation due to the oxygen of the carbonyl group assisting the C? Cl bond polarization in the TS. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
2.
Jose R. Mora Jesus Lezama José M. Albornoz Antonio Hernandez Tania Córdova Gabriel Chuchani 《Journal of Physical Organic Chemistry》2009,22(12):1198-1207
Theoretical study of the elimination kinetics of 2‐phenylethanol, 1‐phenyl‐2‐propanol, and 2‐methyl‐1‐phenyl‐2‐propanol in the gas‐phase has been carried out at the MP2/6‐31G(d,p), B3LYP/6‐31G(d,p), B3LYP/6‐31++G(d,p), MPW1PW91/6‐31G(d,p), MPW1PW91/6‐31++G(d,p), PBEPBE/6‐31G(d,p), and PBEPBE/6‐31++G(d,p) levels of theory. The three substrates undergo two parallel elimination reactions. The first elimination appears to proceed through a six‐membered cyclic transition state to give toluene and the corresponding aldehyde or ketone. The second parallel elimination takes place through a four‐membered cyclic transition state producing water and the corresponding unsaturated aromatic hydrocarbon. Results from MP2/6‐31G(d,p) and MPW1PW91/6‐31++G(d,p) methods were found to be in good agreement with the experimental kinetic and thermodynamic parameters in the formation of toluene and the corresponding carbonyl compound. However, the results for PBEPBE/6‐31G(d,p) were in better agreement with the experimental data for the second parallel reaction yielding water and the corresponding unsaturated aromatic hydrocarbon. The charge distribution differences in the TS related to the substitution by methyl groups in the substrates can account for the observed reaction rate coefficients. The synchronicity parameters imply semi‐polar transition states for these elimination reactions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
3.
Rafael J. Rasse Rosa M. Domínguez Armando Herize Maria Tosta Doris Brusco Gabriel Chuchani 《Journal of Physical Organic Chemistry》2007,20(1):44-48
A homogeneous, molecular, gas‐phase elimination kinetics of 2‐phenyl‐2‐propanol and 3‐methyl‐1‐ buten‐3‐ol catalyzed by hydrogen chloride in the temperature range 325–386 °C and pressure range 34–149 torr are described. The rate coefficients are given by the following Arrhenius equations: for 2‐phenyl‐2‐propanol log k1 (s?1) = (11.01 ± 0.31) ? (109.5 ± 2.8) kJ mol?1 (2.303 RT)?1 and for 3‐methyl‐1‐buten‐3‐ol log k1 (s?1) = (11.50 ± 0.18) ? (116.5 ± 1.4) kJ mol?1 (2.303 RT)?1. Electron delocalization of the CH2?CH and C6H5 appears to be an important effect in the rate enhancement of acid catalyzed tertiary alcohols in the gas phase. A concerted six‐member cyclic transition state type of mechanism appears to be, as described before, a rational interpretation for the dehydration process of these substrates. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
4.
Jerzy Gaca Grażyna Wejnerowska Piotr Cysewski 《Journal of Physical Organic Chemistry》2011,24(11):1045-1050
The present studies show that the currently accepted scheme for the hydrolysis of epichlorohydrin (ECH) needs to be extended by an additional path which makes allowance for the formation and decomposition of glycidol (GL). It was shown experimentally and through UB3LYP/6‐11 + +G(3D,P) calculations that the formation of 3‐chloro‐1,2‐propanediol (MCPD) from ECH should also take into account GL formation as an intermediate product. A modified mechanism for the course of ECH hydrolysis in acidic and neutral medium is proposed. It was shown that ECH hydrolysis in acidic medium in the presence of chloride ions also results in the formation of 1,3‐dichloro‐2‐propanol (DCPD) in addition to GL and MCPD. The possibility of a parallel pathway for water molecule addition to epichlorohydrin was shown which as a consequence led to the parallel appearance of GL and MCPD. It was confirmed by kinetic calculations that the state of equilibrium, reached in the process of ECH chlorination, did not result in GL formation. However, its appearance in the reaction mechanism has been ignored in the literature thus far. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
5.
Libia L. Julio Jesus Lezama Alexis Maldonado José R. Mora Gabriel Chuchani 《Journal of Physical Organic Chemistry》2014,27(5):450-455
The kinetics of the gas‐phase elimination of α‐methyl‐trans‐cinamaldehyde catalyzed by HCl in the temperature range of 399.0–438.7 °C, and the pressure range of 38–165 Torr is a homogeneous, molecular, pseudo first‐order process and undergoing a parallel reaction to produce via (A) α‐methylstyrene and CO gas and via (B) β‐methylstyrene and CO gas. The decomposition of substrate E‐2‐methyl‐2‐pentenal was performed in the temperature range of 370.0–410.0 °C and the pressure range of 44–150 Torr also undergoing a molecular, pseudo first‐order reaction gives E‐2‐pentene and CO gas. These reactions were carried out in a static system seasoned reactions vessels and in the presence of toluene free radical inhibitor. The rate coefficients are given by the following Arrhenius expressions:
- Products formation from α‐methyl‐trans‐cinamaldehyde
- α‐methylstyrene :
- β‐methylstyrene :
- Products formation from E‐2‐methyl‐2‐pentenal
- E‐2‐pentene :
6.
Cristina Pastoriza Juan Manuel Antelo Juan Crugeiras 《Journal of Physical Organic Chemistry》2013,26(7):551-559
Second‐order rate constants (k2) were determined for the addition of ten nitrogenous organic compounds (benzylamine, 2,2,2‐trifluoethylamine chlorhidrate, methylamine chlorhidrate, glycine ethyl ester chlorhidrate, glycine, glycylglycine chlorhidrate, morpholine, pyperidine, pyperazine and dimethylamine) to the N‐chloro‐N‐methyl‐p‐toluenesulfonamide (NCNMPT) in the formation reaction of N‐chloramines in aqueous solution at 25 °C and ionic strength 0.5 M. The series of nucleophiles considered is structurally very varied and covers five pKa units. The kinetic behaviour is similar for all compounds, being the elementary step the transfer of chlorine from the NCNMPT molecule to the nitrogen of the free amino group. These reactions were found first order in both reagents. The values of the rate constants indicate that the more basic amines produce N‐chloramines more readily. Rate constants for the nucleophilic attack are shown to correlate with literature data for some of these nitrogenous organic compounds in their reaction with N‐methyl‐N‐nitroso‐p‐toluenesulfonamide. Both reactions involve that the rate determining step is the attack of nitrogenous compounds upon electrophilic centre (Cl or else NO group). NCNMPT is a particularly interesting substrate, for which has not hitherto been published kinetic information, that allows us to assess the efficiency and the competitiveness of this reaction and compare it with other agents with a Cl+ atom. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
《光谱学快报》2013,46(4-5):521-537
Abstract Proton and carbon‐13 NMR data are presented for 5‐methoxytryptamine, 1; 6‐methoxytryptamine, 2; N,N‐diisopropyl‐5‐methoxytryptamine, 3, (5‐MeO‐DIPT); and N,N‐diisopropyl‐5‐methoxyindole‐3‐glyoxylamide, 4, at 300 MHz (1H) and 75 MHz (13C) in CDCl3 at ambient temperature. Compound 3, considered a potential hallucinogen, had been placed into Schedule I of the Controlled Substances Act, effective April 4, 2003, by the U.S. Drug Enforcement Administration. Compound 4 can serve as a possible precursor to 3. We believe that these are the first proton NMR assignments obtained at medium field (7 tesla) using selective homodecoupling and two‐dimensional homonuclear chemical shift correlation spectra (using one or more of the COSY45, COSY90, and COSYLR experiments) for rigorous aryl proton assignments in this group of compounds. Significant observed differences in the proton and carbon‐13 NMR spectra should allow facile distinction of the 5‐methoxy series, 1 and 3, from the 6‐methoxy series, 2. Energy minimizations to obtain optimized structures for each compound were performed at the Hartree–Fock level with the 6‐31G* basis set, and the resulting geometries are discussed. The presented geometry calculations appear to be the most accurate reported to date for 1 based on the basis set employed, and the first HF/6‐31G* structures for compounds 2, 3, or 4. Appreciable geometry differences in 3 and 4 for the pendant sidechain containing the N[CH(CH3)2]2 moiety are noteworthy. Proximity of the carbonyl oxygens in 4 to H2 and H4 is suggested as a possible contributing factor in the deshielding of these protons in the NMR spectrum. 相似文献
8.
Gas‐phase elimination kinetics of selected aliphatic α,β‐unsaturated aldehydes catalyzed by hydrogen chloride
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Libia L. Julio José R. Mora Alexis Maldonado Gabriel Chuchani 《Journal of Physical Organic Chemistry》2015,28(4):261-265
The gas‐phase elimination of 2‐methyl‐2‐propenal catalyzed by HCl yields propene and CO gas, while E‐2‐pentenal with the same catalyst gives butene and CO gas. The kinetics determinations were carried out in a static system with the reaction vessels deactivated with allyl bromide and the presence of the free radical inhibitor toluene. Temperature and pressure ranges were 350.0–410.0 °C and 34–76 Torr. The elimination reactions are homogeneous and unimolecular, and follow a first‐order rate law. The rate coefficients for the reactions are expressible by the following Arrhenius equations: Data from the kinetic and thermodynamic parameters of these catalyzed elimination reactions implies a mechanism of a concerted five‐membered cyclic transition state structure for the formation of the corresponding olefin and carbon monoxide. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
9.
A combined experimental and density functional study of 1‐(arylsulfonyl)‐2‐R‐4‐chloro‐2‐butenes reactivity towards the allylic chlorine
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Sergey V. Bondarchuk Victor V. Smalius Boris F. Minaev 《Journal of Physical Organic Chemistry》2015,28(6):403-413
Nucleophilic substitution and dehydrochlorination reactions of a number of the ring‐substituted 1‐(arylsulfonyl)‐2‐R‐4‐chloro‐2‐butenes are studied both experimentally and theoretically. The developed synthetic procedures are characterized by a general rapidity, cheapness, and simplicity providing moderate to high yields of 1‐arylsulfonyl 1,3‐butadienes (48–95%), 1‐(arylsulfonyl)‐2‐R‐4‐(N,N‐dialkylamino)‐2‐butenes (31–53%), 1‐(arylsulfonyl)‐2‐R‐2‐buten‐4‐ols (37–61%), and bis[4‐(arylsulfonyl)‐3‐R‐but‐2‐enyl]sulfides (40–70%). The density functional theory B3LYP/6‐311++G(2d,2p) calculations of the intermediate allylic cations in acetone revealed their high stability occurring from a resonance stabilization and hyperconjugation by the SO2Ar group. The reactivity parameters estimated at the bond critical points of the diene/allylic moiety display a high correlation (R2 > 0.97) with the Hammett (σp) constants. 1‐Arylsulfonyl 1,3‐butadienes are characterized by a partly broken π conjugated system, which follows from analysis of the two‐centered delocalization (δ) and localization (λ) index values. The highest occupied molecular orbital energies of 1‐arylsulfonyl 1,3‐butadienes are lower than those of 1,3‐butadiene explaining their low reactivity towards the Diels–Alder condensation. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.
《Journal of Macromolecular Science: Physics》2013,52(3):577-589
Abstract Intercalated polymer/clay nanocomposites were prepared using a polystyrene‐b‐poly(ethylene‐r‐butylene)‐b‐polystyrene (SEBS) cylindrical triblock copolymer. Dynamic rheological measurements, x‐ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetry analysis (TGA) were conducted to investigate the internal structure and physical and phase characteristics of the nanocomposites. The XRD data confirmed that the interlayer distance between the anisotropic silicates increased due to the intercalation of SEBS into the clay interlayers. As the clay loading increased, the onset points of the order–disorder transition (ODT) and order–order transition (OOT) were found to decrease, whereas the thermal decomposition temperatures, monitored by TGA, increased with the clay loading. 相似文献
11.
1,1,1‐Trichloro‐3‐(1‐phenethylamino‐ethylidene)‐pentane‐2,4‐dione is spectroscopically and structurally elucidated by means of linear‐polarized IR spectroscopy (IR‐LD) of oriented solids as a colloidal suspension in nematic liquid crystal. Structural information and IR‐spectroscopic assignment are supported by quantum chemical calculations at MP2 and B3LYP level of theory and 6‐311++G** basis set. The geometry is characterized with an inramolecular hydrogen bond of NH…O?C with length of 2.526 Å and a NHO angle of 140.5(1)°. The NH? C(CH3)C?C? C?O(CH3) fragment is nearly flat with a maximal deviation of total planarity of 10.4°. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
12.
13.
Cristina Pastoriza Juan Manuel Antelo Francisco Andrés Amoedo Mercedes Parajó 《Journal of Physical Organic Chemistry》2015,28(9):602-611
The chlorination reactions of 2‐oxazolidinone with hypochlorous acid (HOCl), tert‐butyl hypochlorite (tBuOCl) and N‐chlorosuccinimide (NCS) were studied at 25 °C, constant ionic strength, and under isolation conditions. The kinetic results obtained in the formation processes of the N‐chloro‐2‐oxazolidinone are summarized in this paper. The kinetics studied showed a first order with respect to the concentration of the each reactant and a complex dependence of the pH on the rate constant. The reactivity order with respect to the chlorinating agent found is k(HOCl) > k(tBuOCl) > k(NCS). Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
14.
Marcelo M. Campos‐Vallette Nancy P. Chandía Ernesto Clavijo David Leal Betty Matsuhiro Igor O. Osorio‐Romn Simonet Torres 《Journal of Raman spectroscopy : JRS》2010,41(7):758-763
The surface‐enhanced Raman scattering (SERS) of sodium alginates and their hetero‐ and homopolymeric fractions obtained from four seaweeds of the Chilean coast was studied. Alginic acid is a copolymer of β‐D ‐mannuronic acid (M) and α‐L guluronic acid (G), linked 1 → 4, forming two homopolymeric fractions (MM and GG) and a heteropolymeric fraction (MG). The SERS spectra were registered on silver colloid with the 632.8 nm line of a He Ne laser. The SERS spectra of sodium alginate and the polyguluronate fraction present various carboxylate bands which are probably due to the coexistence of different molecular conformations. SERS allows to differentiate the hetero‐ and homopolymeric fractions of alginic acid by characteristic bands. In the fingerprint region, all the poly‐D ‐mannuronate samples present a band around 946 cm−1 assigned to C O stretching, and C C H and C O H deformation vibrations, a band at 863 cm−1 assigned to deformation vibration of β‐C1 H group, and one at 799–788 cm−1 due to the contributions of various vibration modes. Poly‐L ‐guluronate spectra show three characteristic bands, at 928–913 cm−1 assigned to symmetric stretching vibration of C O C group, at 890–889 cm−1 due to C C H, skeletal C C, and C O vibrations, and at 797 cm−1 assigned to α C1 H deformation vibration. The heteropolymeric fractions present two characteristic bands in the region with the more important one being an intense band at 730 cm−1 due to ring breathing vibration mode. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
15.
José R. Mora Alexis Maldonado Rosa M. Domínguez Gabriel Chuchani 《Journal of Physical Organic Chemistry》2010,23(9):845-852
The rates of gas‐phase elimination of several β‐substituted diethyl acetals have been determined in a static system and seasoned with allyl bromide. The reactions, inhibited with toluene, are homogeneous, unimolecular, and follow first‐order law kinetics. These elimination processes involve two parallel reactions. The first parallel reaction yields ethanol and the corresponding ethyl vinyl ether. The latter product is an unstable intermediate and further decomposes to ethylene and the corresponding substituted aldehyde. The second parallel reaction gives ethane and the corresponding ethyl ester. The kinetics has been measured over the temperature range of 370–441 °C and pressure range of 23–160 torr. The rate coefficients are given by the following Arrhenius equations: The differences in the rates of ethanol formation may be attributed to electronic transmission of the β‐substituent. The comparative kinetic and thermodynamic parameters of the parallel reactions suggest two different concerted polar four‐membered cyclic transition state types of mechanisms. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
16.
Effects of non‐equidistant grids on momentum conservation is studied for simple test cases of an electrostatic 1D PIC code. The aim is to reduce the errors in energy and momentum conservation. Assuming an exact Poisson solver only numerical errors for the particle mover are analysed. For the standard electric field calculation using a central‐difference scheme, artificial electric fields at the particle position are generated in the case when the particle is situated next to a cell size change. This is sufficient to destroy momentum conservation. A modified electric field calculation scheme is derived to reduce this error. Independent of the calculation scheme additional fake forces in a two‐particle system are found which result in an error in the total kinetic energy of the system. This contribution is shown to be negligible for many particle systems. To test the accuracy of the two electric field calculation schemes numerical tests are done to compare with an equidistant grid set‐up. All tests show an improved momentum conservation and total kinetic energy for the modified calculation scheme of the electric field. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
Vladimir D. Kiselev Dmitry A. Kornilov Helen A. Kashaeva Lyubov N. Potapova Alexander I. Konovalov 《Journal of Physical Organic Chemistry》2014,27(5):401-406
The values of the enthalpy (53.3; 51.3; 20.0 kJ mol?1), entropy (?106; ?122; ?144 J mol?1K?1), and volume of activation (?29.1; ?31.0; ?cm3 mol?1), the reaction volume (?25.0; ?26.6; ?cm3 mol?1) and reaction enthalpy (?155.9; ?158.2; ?150.2 kJ mol?1) have been obtained for the first time for the ene reactions of 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione 1 , with cyclohexene 4 , 1‐hexene 6 , and with 2,3‐dimethyl‐2‐butene 8 , respectively. The ratio of the values of the activation volume to the reaction volume (?V≠corr/ΔVr ? n) in the ene reactions under study, 1 + 4 → 5 and 1 + 6 → 7 , appeared to be the same, namely 1.16. The large negative values of the entropy and the volume of activation of studied reactions 1 + 4 → 5 and 1 + 6 → 7 better correspond to the cyclic structure of the activated complex at the stage determining the reaction rate. The equilibrium constants of these ene reactions can be estimated as exceeding 1018 L mol?1, and these reactions can be considered irreversible. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
18.
M. Kurt S. Okur S. Demic J. Karpagam N. Sundaraganesan 《Journal of Raman spectroscopy : JRS》2011,42(8):1682-1689
We have synthesized 4‐[N‐phenyl‐N‐(3‐methylphenyl)‐amino]‐benzoic acid (4‐[PBA]) and investigated its molecular vibrations by infrared and Raman spectroscopies as well as by calculations based on the density functional theory (DFT) approach. The Fourier transform (FT) Raman, dispersive Raman and FT‐IR spectra of 4‐[PBA] were recorded in the solid phase. We analyzed the optimized geometric structure and energies of 4‐[PBA] in the ground state. Stability of the molecule arising from hyperconjugative interactions and charge delocalization was studied using natural bond orbital analysis. The results show that change in electron density in the σ* and π* antibonding orbitals and E2 energies confirm the occurrence of intramolecular charge transfer within the molecule. Theoretical calculations were performed at the DFT level using the Gaussian 09 program. Selected experimental bands were assigned and characterized on the basis of the scaled theoretical wavenumbers by their total energy distribution. The good agreement between the experimental and theoretical spectra allowed positive assignment of the observed vibrational absorption bands. Finally, the calculation results were applied to simulate the Raman and IR spectra of the title compound, which show agreement with the observed spectra. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
19.
The amphiphilic triblock copolymer, poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) (PEO‐b‐PPO‐b‐PEO) was incorporated into novolac resin to prepare thermosetting blends. The morphology of the thermosetting blends was investigated by means of atomic force microscopy (AFM) and small‐angle x‐ray scattering (SAXS) and the nanostructures were obtained. It was identified that the reaction‐induced phase separation occurred in the blends of phenolic thermosets with the model poly(propylene oxide) (PPO), whereas poly(ethylene oxide) (PEO) was miscible with novolac resin after and before the curing reaction. In terms of miscibility and phase behavior of the subchains of the triblock copolymer with novolac resin, it was demonstrated that the formation of nanostructures in the thermosets followed a mechanism of reaction‐induced microphase separation. 相似文献