scholarly journals Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

2013 ◽  
Vol 9 ◽  
pp. 1620-1629 ◽  
Author(s):  
Andreas Gansäuer ◽  
Meriam Seddiqzai ◽  
Tobias Dahmen ◽  
Rebecca Sure ◽  
Stefan Grimme
Keyword(s):  
Rate Constants ◽  
Activation Barrier ◽  
Computational Study ◽  
Theoretical Data ◽  
Radical Addition ◽  
Radical Center ◽  
Substituted Anilines ◽  
London Dispersion ◽  
Reaction Barriers ◽  
Experimental Values

The intramolecular radical addition to aniline derivatives was investigated by DFT calculations. The computational methods were benchmarked by comparing the calculated values of the rate constant for the 5-exo cyclization of the hexenyl radical with the experimental values. The dispersion-corrected PW6B95-D3 functional provided very good results with deviations for the free activation barrier compared to the experimental values of only about 0.5 kcal mol−1 and was therefore employed in further calculations. Corrections for intramolecular London dispersion and solvation effects in the quantum chemical treatment are essential to obtain consistent and accurate theoretical data. For the investigated radical addition reaction it turned out that the polarity of the molecules is important and that a combination of electrophilic radicals with preferably nucleophilic arenes results in the highest rate constants. This is opposite to the Minisci reaction where the radical acts as nucleophile and the arene as electrophile. The substitution at the N-atom of the aniline is crucial. Methyl substitution leads to slower addition than phenyl substitution. Carbamates as substituents are suitable only when the radical center is not too electrophilic. No correlations between free reaction barriers and energies (ΔG ‡ and ΔG R) are found. Addition reactions leading to indanes or dihydrobenzofurans are too slow to be useful synthetically.

Computational Study on the Kinetics and Mechanisms of Unimolecular Reactions of (Z)-(Z)-N-(λ5-phosphanylidene) Formohydrazonic Formic Anhydride: Intramolecular aza-Wittig Reaction in Competition with Mumm Rearrangement

2020 ◽  
Vol 17 (11) ◽  
pp. 884-889
Author(s):  
Somayeh Mirdoraghi ◽  
Hamed Douroudgari ◽  
Farideh Piri ◽  
Morteza Vahedpour
Keyword(s):  
Rate Constants ◽  
Density Functional ◽  
Wittig Reaction ◽  
Computational Study ◽  
Single Step ◽  
Low Energy ◽  
Coupled Cluster ◽  
Unimolecular Reaction ◽  
Single Step Reaction ◽  
Good Agreement

For (Z)-(Z)-N-(λ5-phosphanylidene) formohydrazonic formic anhydride, Aza-Wittig reaction and Mumm rearrangement are studied using both density functional and coupled cluster theories. For this purpose, two different products starting from one substrate are considered that are competing with each other. The obtained products, P1 and P2, are thermodynamically favorable. The product of the aza-Wittig reaction, P1, is more stable than the product of Mumm rearrangement (P2). For the mentioned products, just one reliable pathway is separately proposed based on unimolecular reaction. Therefore, the rate constants based on RRKM theory in 300-600 K temperature range are calculated. Results show that the P1 generation pathway is a suitable path due to low energy barriers than the path P2. The first path has three steps with three transition states, TS1, TS2, and TS3. The P2 production path is a single-step reaction. In CCSD level, the computed barrier energies are 14.55, 2.196, and 10.67 kcal/mol for Aza-Wittig reaction and 42.41 kcal/mol for Mumm rearrangement in comparison with the corresponding complexes or reactants. For final products, the results of the computational study are in a good agreement with experimental predictions.

Experimental and Theoretical Studies of 2- (naphthalen-1-yl (piperidin-1-yl) methyl)phenol Compound

2020 ◽  
Vol 42 (6) ◽  
pp. 818-818
Author(s):  
Yeliz Ula Yeliz Ula
Keyword(s):  
Molecular Orbital ◽  
Theoretical Data ◽  
Biologically Active ◽  
Oscillator Strengths ◽  
Excitation Energies ◽  
Petasis Reaction ◽  
Vis Spectroscopy ◽  
Phenol Compound ◽  
Lowest Unoccupied Molecular Orbital ◽  
Experimental Values

The 2- (naphthalen-1-yl (piperidin-1-yl) methyl) phenol compound is an alkylaminophenol compound and has been experimentally synthesized by the Petasis reaction. In this study Structural analysis was carried out by FT-IR, NMR, UV-Vis spectroscopy. The high antioxidant value of the compound showed that it could be a potential biologically active drug. Theoretical data support all experimental analysis of the new compound. Comparisons were made by double method. For this purpose, DFT (B3LYP) and HF methods have been used with 6-311G ++ (d, p) set. Also, the compoundand#39;s electronic and structural properties (bond lengths, bond angles and dihedral angles), the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies, electrostatic potential (MEP), vibrational frequencies, Mulliken atomic charges, excitation energies, and oscillator strengths were calculated. As a result; the theoretical and experimental values were found to be compatible.

scholarly journals Computational Study of Methane C–H Activation by Main Group and Mixed Main Group–Transition Metal Complexes

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2794
Author(s):  
Carly C. Carter ◽  
Thomas R. Cundari
Keyword(s):  
Transition Metal Complexes ◽  
Active Site ◽  
Density Functional ◽  
Computational Study ◽  
Divalent Metal ◽  
Main Group ◽  
Free Energies ◽  
Functional Theory ◽  
Activation Barriers ◽  
Experimental Values

In the present density functional theory (DFT) research, nine different molecules, each with different combinations of A (triel) and E (divalent metal) elements, were reacted to effect methane C–H activation. The compounds modeled herein incorporated the triels A = B, Al, or Ga and the divalent metals E = Be, Mg, or Zn. The results show that changes in the divalent metal have a much bigger impact on the thermodynamics and methane activation barriers than changes in the triels. The activating molecules that contained beryllium were most likely to have the potential for activating methane, as their free energies of reaction and free energy barriers were close to reasonable experimental values (i.e., ΔG close to thermoneutral, ΔG‡ ~30 kcal/mol). In contrast, the molecules that contained larger elements such as Zn and Ga had much higher ΔG‡. The addition of various substituents to the A–E complexes did not seem to affect thermodynamics but had some effect on the kinetics when substituted closer to the active site.

scholarly journals Synthesis, characterization and theoretical calculations of Cu(I) complex of trithiocyanuric acid [Cu(ttc)3]

2018 ◽  
Vol 23 (2) ◽  
pp. 241-266 ◽  
Author(s):  
Ximena Verónica Jaramillo-Fierro ◽  
César Zambrano ◽  
Francisco Fernández ◽  
Regino Saenz-Puche ◽  
César Costa ◽  
...  
Keyword(s):  
Computational Study ◽  
Theoretical Calculations ◽  
Photophysical Properties ◽  
Vibrational Frequencies ◽  
Basis Sets ◽  
Vertical Excitation ◽  
Experimental Values ◽  
Homo Lumo ◽  
Perchlorate Hexahydrate ◽  
Good Agreement

A new Cu(I) complex constructed by reaction of trithiocyanuric acid (ttc) and copper (II) perchlorate hexahydrate has been successfully synthesized by a slow sedimentation method in a DMF solvent at room temperature. The molecular structure of the compound was elucidated by MALDI-TOFMS, UV Vis and FTIR spectroscopy, DSC-TGA analysis and magnetic susceptibility measurement. The proposed structure was corroborated by a computational study carried out with the Gaussian09 and AIMAII programs using the RB3LYP hybrid DFT functional with both 6-31G and Alhrich-TZV basis sets. The calculated vibrational frequencies values were compared with experimental FTIR values. Photophysical properties of the synthesized complex were evaluated by UV-Visible spectroscopy and compared with computed vertical excitation obtained from TDDFT. The theoretical vibrational frequencies and the UV Vis spectra are in good agreement with the experimental values. Additionally, the Frontier Molecular Orbitals (HOMO-LUMO) and the Molecular Electrostatic Potential of the complex was calculated using same theoretical approximation. The results showed the interaction between three coordinatedl igand atoms and the Cu(I) ion.

Respirometric evaluation of the biodegradability of confectionary wastewaters

1995 ◽  
Vol 32 (12) ◽  
pp. 11-19 ◽  
Author(s):  
D. Orhon ◽  
G. Yildiz ◽  
E. Ubay Çokgör ◽  
S. Sözen
Keyword(s):  
Mathematical Model ◽  
Curve Fitting ◽  
Rate Constants ◽  
Hydrolysis Rate ◽  
Kinetic Coefficients ◽  
Experimental Values

Confectionary effluents are typical examples of strong wastes of biodegradable nature, quite suitable for respirometric analysis. Three different confectionary effluents have been subjected to a treatability-oriented characterization, mainly by means of respirometric methods, yielding meaningful results on COD fractionation and significant kinetic coefficients. Experimental values have been tested by a multi-component mathematical model using the endogenous decay approach and hydrolysis rate constants corresponding to the slowly biodegradable COD fractions have been evaluated using curve fitting.

Electron-density-based calculations of intermolecular energy: case of urea

1999 ◽  
Vol 55 (5) ◽  
pp. 821-827 ◽  
Author(s):  
Kyrill Yu. Suponitsky ◽  
Vladimir G. Tsirelson ◽  
Dirk Feil
Keyword(s):  
Interaction Energy ◽  
Electron Density ◽  
Theoretical Data ◽  
Multipole Moments ◽  
Intermolecular Interaction Energy ◽  
Hartree Fock ◽  
Intermolecular Energy ◽  
Crystalline Urea ◽  
To Come ◽  
Experimental Values

The intermolecular interaction energy in crystalline urea has been calculated both from diffraction data and from the Hartree–Fock crystalline electron-density distribution, using a modified atom–atom approximation scheme. The electrostatic part of this energy has been calculated from the atomic multipole moments, obtained by adjustment of the multipole model to experimental X-ray and to theoretical Hartree–Fock structure amplitudes. To obtain the induction energy, multipole moments were calculated from structure amplitudes for the crystalline electron density and from those that refer to the electron density of a superposition of isolated molecules. This worked well for the calculation of the interaction energy from Hartree–Fock data (6% difference from the sublimation-energy value), but not for the interaction energy from experimental data, where the moments of the superposition have to come from Hartree–Fock calculations: the two sets of multipole moments are far too different. The uncertainty of the phases of the structure amplitudes, combined with systematic errors in the theoretical data and noise in the experimental values, may account for the discrepancies. The nature of the different contributions to intermolecular interactions for urea is examined.

Photon-Induced L-Shell X-Ray Production Cross Sections for Lanthanides at 59.54 keV

2017 ◽  
Vol 890 ◽  
pp. 223-226 ◽  
Author(s):  
Rıdvan Durak ◽  
Ferdi Akman ◽  
Abdulhalik Karabulut
Keyword(s):  
High Resolution ◽  
Cross Sections ◽  
Production Cross ◽  
Theoretical Data ◽  
Experimental Results ◽  
X Rays ◽  
X Ray ◽  
Reflection Geometry ◽  
Experimental Values ◽  
Annular Source

The Ll, Lα and Lβ X-ray production cross sections for Pr, Nd, Sm, Eu, Gd and Tb elements were determined using a reflection geometry. The excitation was performed with a 241Am radioactive annular source and the L X-rays emitted from targets were counted with a high-resolution Si (Li) detector. The experimental values were compared with other available experimental results and theoretical data. An agreement is observed between the measured and other experimental results or theoretical data.

scholarly journals Hetarylazopyrazolone Dyes Based on Benzothiazole and Benzimidazole Ring Systems: Synthesis, Spectroscopic Investigation, and Computational Study

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Ebru Aktan ◽  
Tahsin Uyar
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Computational Study ◽  
Benzimidazole Ring ◽  
Acid Base ◽  
Functional Theory ◽  
Ring Systems ◽  
Td Dft ◽  
Elemental Analyses ◽  
Experimental Values

In this study, the synthesized coupling component 1-(2-benzothiazolyl)-3-methylpyrazol-5-one reacted with diazotised heterocyclic amines to afford six novel hetarylazopyrazolone dyes. These azo dyes based on benzothiazole and benzimidazole ring systems were characterized by spectral methods and elemental analyses. The solvatochromic behaviors of these dyes in various solvents were evaluated. The ground state geometries of the dyes were optimized using density functional theory (DFT). Solvent, acid-base, and substituent influences on the wavelength of the maximum absorption were examined in detail. Time-dependent density functional theory (TD-DFT) calculations were performed to obtain the absorption spectra of the dyes in various solvents and the results compared with experimental values. Besides, frontier molecular orbitals (FMO) analysis for the dyes is also described from the computational process.

Photo-oxidative Stability and its Correlation with Semi-empirical MO Calculations of Various Tetraazaporphyrin Derivatives in Solution

1997 ◽  
Vol 01 (02) ◽  
pp. 159-167 ◽  
Author(s):  
GüNTER SCHNURPFEIL ◽  
ABDOL KHEZER SOBBI ◽  
WOLFGANG SPILLER ◽  
HOLGER KLIESCH ◽  
DIETER WÖHRLE
Keyword(s):  
Metal Complexes ◽  
Singlet Oxygen ◽  
Oxidative Stability ◽  
Rate Constants ◽  
Energy Levels ◽  
Quantum Yields ◽  
Oxidation Reactions ◽  
Homo And Lumo ◽  
Experimental Values ◽  
Semi Empirical

The photo-oxidative stability of various annelated and substituted tetraazaporphyrin derivatives were investigated in N , N -dimethylformamide by irradiation in the presence of air. First-order rate constants were calculated. In addition, the positions of the HOMO and LUMO energy levels of the compounds were calculated using a commercially available program. A linear correlation between the experimental values of the rate constants and the theoretical values of the HOMO position exists. The method described allows one to predict the photo-oxidative stability by calculating their HOMO levels, which is very important for the use of macrocyclic metal complexes in photo-oxidation reactions in solution. From the calculated triplet energies it is considered that the macrocyclic metal complexes can convert by photoinduced energy transfer triplet oxygen to singlet oxygen. Experimentally, tetraazaporphyrin derivatives show high quantum yields of singlet oxygen formation under irradiation. No correlations of the quantum yields with the position of the HOMOs or with the rate constants of decomposition was observed.

Sign in / Sign up

Export Citation Format

Share Document