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Filipe Belarmino de Lima Gessenildo Pereira Rodrigues Juracy Regis de Lucena Júnior Elizete Ventura Rui Fausto Igor Reva Silmar Andrade do Monte 《International journal of quantum chemistry》2020,120(16):e26263
Multi-reference configuration interaction, MR-CI (including extensivity corrections, named +Q), calculations were performed on the S0–S3 states of cyclohexa-2,4-diene-1-thione (thione 24 ) and cyclohexa-2,5-diene-1-thione (thione 25 ), which are thione isomers of thiophenol. Several types of uncontracted MR-CIS and MR-CISD wavefunctions were employed, comprising MR-CI expansions as large as ~365 × 106 configuration state functions. The nature of the studied excited states was characterized. Vertical excitation energies (ΔE) and oscillator strengths (f) were computed. The most intense transitions (S0 → S2 for 24 and S0 → S3 for 25 ) did not change with the wavefunction, although a variation as large as ~1 eV was obtained for the S3 state of 24 , at the highest (MR-CI+Q) level. On the other hand, ΔE changed at most by ~0.56 eV for 25 as the wavefunction changes, at the same level. The S1 state of both thiones was found to have nπ* character and is in the visible region. For 24 , S2 and S3 are ππ* and nπ* states, respectively, while for 25 the reverse order is obtained. S2 and S3 are in the range ~3.5 to 5.2 eV, again at the highest level. It is the first time that the excited states of the title molecules are studied. The computed results agree with the experimental onset of photoreactions of thiones 24 and 25 found by Reva et al (Phys. Chem. Chem. Phys., 2015 , 17, 4888). 相似文献
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Belarmino AT Froehner S Zanette D Farah JP Bunton CA Romsted LS 《The Journal of organic chemistry》2003,68(3):706-717
Hydrolyses of benzaldehyde acetals, PhCH(OR)(2), are specific hydrogen-ion catalyzed when R = methyl, n-butyl, but with secondary and tertiary alkyl derivatives, R = i-propyl, s-butyl, t-butyl, t-amyl, hydrolyses are general-acid catalyzed. The Br?nsted alpha values for both secondary and tertiary alkyl groups are in the range: alpha = 0.57-0.61. A simple iterative procedure was developed to estimate the individual rate constants for general-acid catalysis by the diacid and monoacid forms of succinic acid buffer. Plots of log k(obs) (at [buffer] = 0 M) against pH are linear for the secondary and tertiary acetals, and plots of log k(H) for the H(3)O(+)-catalyzed reaction, (13)C and (1)H chemical shifts, and (1)J(CH) coupling constants against the Charton steric parameter, nu, for alkoxy groups are linear. The second-order rate constant, k(H), increases about 100-fold on going from R = Me to R = t-amyl, indicating the significant role of steric effects on reactivity. Steric effects upon (13)C NMR chemical shifts and coupling constants indicate that increasing the bulk of the alkoxy moiety increases the electron density at the carbon reaction center, which accelerates hydrolysis. Analysis of the Jencks-More-O'Ferrall free energy diagram for the reaction provides support for concerted proton transfer and C-O bond breaking in the transition state for hydrolyses of benzaldehyde acetals with secondary and tertiary alkyl groups in contrast to specific hydrogen catalysis with R = Me and n-Bu. All our results are consistent with rate-determining acid hydrolysis of benzaldehyde dialkyl acetals to hemiacetal intermediates that breakdown rapidly to benzaldehyde. 相似文献
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Marilia G. Belarmino Cabral Dr. Deise M. Pereira de Oliveira Santos Ahmed Bentaleb Dr. Elizabeth A. Hillard Prof. Dr. Rodrigo Cristiano Prof. Dr. Hugo Gallardo Dr. Fabien Durola Dr. Harald Bock 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(24):8043-8047
The twofold glyoxylic Perkin reaction of perylene‐3,9‐diglyoxylic acid with thiophene‐diacetic acid followed by oxidative photocylization and reaction with α‐branched primary alkylamines yields columnar liquid‐crystalline diimides with two sulfur atoms in the condensed arene system. A broad temperature range of the hexagonal columnar mesophase is induced by racemic doubly branched alkyl chains. The HOMO and LUMO energy levels of these thiophene‐derived diimides qualify them as electron donors with respect to perylene diimides. 相似文献
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José C del Río Ana Gutiérrez María J Martínez Angel T Martínez AT 《Rapid communications in mass spectrometry : RCM》2002,16(1):62-68
A novel series of long-chain unsaturated dicarboxylic acids consisting of a long aliphatic chain attached to the C-3 position of itaconic acid has been identified by gas chromatography/mass spectrometry during in vitro decay of eucalypt wood by the white-rot basidiomycete Ceriporiopsis subvermispora. The major compounds were identified as tetradecyl-, 7-hexadecenyl- and hexadecylitaconic acids by their mass fragmentation patterns. Other members of the same compound series, identified as dodecanyl-, tridecanyl-, tetradecenyl-, pentadecanyl-, octadecenyl- and octadecanylitaconic acids, were present in very minor amounts or traces. Whereas hexadecenylitaconic acid has already been reported in cultures of C. subvermispora, to our knowledge this is the first report of the presence of the other alkylitaconic acids in fungal cultures. These new alkylitaconic-type metabolites may constitute a source for peroxidizable lipids involved in lignin degradation during wood decay by C. subvermispora and other white-rot basidiomycetes. 相似文献
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C.T. dos Santos C. Bormio-Nunes L. Ghivelder A.R. Belarmino 《Journal of magnetism and magnetic materials》2008,320(14):e183-e185
In the present work we study the magnetostriction of Fe91Sn9 and Fe80Sn20 polycrystalline samples produced by arc melting and heat treated at temperatures of 1153 K for 6 h and 1023 K for 24 h, looking for high values of magnetostriction as in Fe–Ga alloys. Magnetostriction, as well as saturation magnetization measurements, was carried out at temperatures close to 203 K in the magnetic field interval 0 to 1.5 T. Results of magnetostriction on sample Fe91Sn9, which has almost pure -phase, show magnitude and behavior similar to pure Fe. The two additional Fe80Sn20 samples have a combination of -phase plus either Fe5Sn3 or Fe3Sn2 and show a peculiar behavior of the magnetostriction. For μ0H<0.3 T the magnetostriction grows from zero to saturation of the -phase. Following, for μ0H>0.3 T, the magnetostriction starts again to grow linearly with the field, but saturation was not observed up to 5 T. This behavior was attributed to the presence of Fe5Sn3 or Fe3Sn2 phases in these samples that are also ferromagnetic as the -phase is. 相似文献
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Dr. Deise M. Pereira de Oliveira Santos Marilia G. Belarmino Cabral Ahmed Bentaleb Prof. Dr. Rodrigo Cristiano Prof. Dr. Hugo Gallardo Dr. Fabien Durola Dr. Harald Bock 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(22):7389-7393
Whereas perylene tetracarboxdiimides derived from amino‐n‐alkanes if at all only show monotropic (thermodynamically unstable) mesogenic self‐assembly, the hexagonal columnar liquid crystalline state can be stabilized over a broad temperature range with doubly branched, doubly racemic alkyl residues. An improved tendency to homeotropic surface orientation is observed, and the orientation of the liquid crystalline domains is maintained upon cycling through the crystalline state at room temperature. 相似文献
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Joaquín Bautista Jordi Pereira Belarmino Adenso-Díaz 《Annals of Operations Research》2008,159(1):233-244
The Car Sequencing Problem (CSP) is a feasibility problem that has attracted the attention of the Constraint Programming community for a number of years now. In this paper, a new version (opt-CSP) that extends the original problem is defined,
converting this into an optimization problem in which the goal is to satisfy the typical hard constraints. This paper presents a solution procedure for opt-CSP using Beam Search. Computational results are presented using public
instances that verify the goodness of the procedure and demonstrate its excellent performance in obtaining feasible solutions
for the majority of instances while satisfying the new constraints. 相似文献