Theoretical studies on the pyrolysis of (Thion)carbonates

2014 ◽  
Vol 13 (06) ◽  
pp. 1450051 ◽  
Author(s):  
Ping Wu ◽  
Jiaxing Li
Keyword(s):  
Theoretical Calculations ◽  
Theoretical Studies ◽  
Nucleophilic Substitutions ◽  
Alkyl Groups ◽  
Thermal Elimination ◽  
Bond Indices ◽  
Wiberg Bond Indices

MP2/6-31G(d) was employed to investigate the theoretical calculations on the pyrolysis of alkyl methyl (thion)carbonates, where alkyl groups referred to ethyl, isopropyl and t-butyl groups. Nine possible pathways were considered for the pyrolysis of alkyl methyl thioncarbonates, while only seven possible pathways were found to pyrolyze alkyl methyl carbonates. Both of them had three pathways to generate the desired alkene products. Not only thermal elimination pathways were calculated, other possible mechanisms, such as rearrangements and nucleophilic substitutions, were also considered. The progress of the reactions was also investigated by the calculation of Wiberg bond indices at MP2/6-31G(d) level.

A theoretical study towards thermolysis process of thionesters and thiolesters

2018 ◽  
Vol 17 (02) ◽  
pp. 1850014 ◽  
Author(s):  
Xun Zhu ◽  
Xiuqin Zhou ◽  
Dongsheng Xiang ◽  
Ping Wu
Keyword(s):  
Theoretical Study ◽  
Theoretical Calculations ◽  
Transition States ◽  
Membered Ring ◽  
Basis Set ◽  
Reaction Progress ◽  
Alkyl Groups ◽  
Thermal Elimination ◽  
Bond Indices ◽  
Wiberg Bond Indices

This paper focuses on the thermal elimination of alkenes from methyl alkyl thionacetates and thiolacetates. Three alkyl groups are calculated: ethyl, isopropyl and tert-butyl. Possible elimination mechanisms are considered, including six- and four-membered ring transition states for alkene elimination, four-membered ring isomerization and a possible five-membered ring decomposition. Theoretical calculations are performed with the MP2 method and the 6-31G* basis set. Wiberg bond indices are also summarized to monitor the reaction progress.

A computational study on the thermal decomposition of di(tri)thiocarbonates

2016 ◽  
Vol 15 (07) ◽  
pp. 1650061 ◽  
Author(s):  
Jingjing Xia ◽  
Ping Wu
Keyword(s):  
Thermal Decomposition ◽  
Computational Study ◽  
Theoretical Calculations ◽  
Reaction Progress ◽  
Bond Indices ◽  
Elimination Reactions ◽  
Wiberg Bond Indices

Alkyl methyl di(tri)thiocarbonates can be thermally decomposed into alkenes. In this paper, theoretical calculations were used to calculate the thermal decomposition procedures. Six compounds, including ethyl, isopropyl and [Formula: see text] dithiocarbonate and trithiocarbonate, were examined. For each decomposition, nine possible paths were considered, including the paths leading to the desired alkene products, as well as rearrangement and elimination reactions. This calculation was performed with the MP2/6-31G(d) method. Wiberg bond indices were also calculated to further reveal the reaction progress.

scholarly journals ELECTRON DENSITY STUDIES ON THE REGIOSELECTIVITY OF DEPROTONATION REACTIONS

2014 ◽  
Vol 70 (a1) ◽  
pp. C287-C287
Author(s):  
Juan Van der Maelen ◽  
Javier Cabeza
Keyword(s):  
Electron Density ◽  
Theoretical Calculations ◽  
Density Ratio ◽  
Atomic Charge ◽  
Heterocyclic Ring ◽  
Bond Critical Point ◽  
Electron Densities ◽  
Total Energy Density ◽  
Topological Parameters ◽  
Alkyl Groups

The C-alkyl groups of cationic triruthenium cluster complexes of the type [Ru3(µ-H)(µ-κ2N1,C2-EtnMemPyHk)(CO)10]+ (EtnMemPyHk represents a generic C-alkyl-N-methyl-pyrazium species) have been deprotonated to give kinetic products that contain unprecedented C-alkylidene derivatives and maintain the original edge-bridged decacarbonyl structure. When the starting complexes contain various C-alkyl groups, the selectivity of these deprotonation reactions is related to the atomic charges of the alkyl H atoms, as suggested by DFT/natural-bond orbital (NBO) calculations. Three additional electronic properties of the C-alkyl C-H bonds have also been found to correlate with the experimental regioselectivity since, in all cases, the deprotonated C-H bond has the smallest electron density at the bond critical point (bcp), the greatest Laplacian of the electron density at the bcp, and the greatest total energy density ratio at the bcp (computed by using the quantum theory of atoms in molecules, QTAIM). The kinetic decacarbonyl products evolve, under appropriate reaction conditions that depend upon the position of the C-alkylidene group in the heterocyclic ring, towards face-capped nonacarbonyl derivatives (thermodynamic products). Theoretical calculations support the proposal that the selectivity of these deprotonation reactions is primarily determined by the atomic charge of the alkyl H atoms: the higher the charge the easier the deprotonation when the starting complexes contain various C-alkyl groups. On the other hand, although QTAIM results have been obtained here only from theoretical electron densities for the above clusters, comparisons with local and integral topological parameters derived from both experimental and theoretical electron densities for the related triruthenium complex [Ru3(μ-H)2(μ3-MeImCH)(CO)9] (Me2Im = 1,3-dimethylimidazol-2-ylidene) may easily be made.

scholarly journals Structural Properties of G,T-Parallel Duplexes

2010 ◽  
Vol 2010 ◽  
pp. 1-11 ◽  
Author(s):  
Anna Aviñó ◽  
Elena Cubero ◽  
Raimundo Gargallo ◽  
Carlos González ◽  
Modesto Orozco ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Structural Properties ◽  
Theoretical Calculations ◽  
Md Simulations ◽  
Theoretical Studies ◽  
Duplex Structure ◽  
Strong Stabilization ◽  
The Stability ◽  
The Impact

The structure of G,T-parallel-stranded duplexes of DNA carrying similar amounts of adenine and guanine residues is studied by means of molecular dynamics (MD) simulations and UV- and CD spectroscopies. In addition the impact of the substitution of adenine by 8-aminoadenine and guanine by 8-aminoguanine is analyzed. The presence of 8-aminoadenine and 8-aminoguanine stabilizes the parallel duplex structure. Binding of these oligonucleotides to their target polypyrimidine sequences to form the corresponding G,T-parallel triplex was not observed. Instead, when unmodified parallel-stranded duplexes were mixed with their polypyrimidine target, an interstrand Watson-Crick duplex was formed. As predicted by theoretical calculations parallel-stranded duplexes carrying 8-aminopurines did not bind to their target. The preference for the parallel-duplex over the Watson-Crick antiparallel duplex is attributed to the strong stabilization of the parallel duplex produced by the 8-aminopurines. Theoretical studies show that the isomorphism of the triads is crucial for the stability of the parallel triplex.

Towards high-level theoretical studies of large biodiesel molecules: an ONIOM/RRKM/Master-equation approach to the isomerization and dissociation kinetics of methyl decanoate radicals

2019 ◽  
Vol 21 (9) ◽  
pp. 5232-5242 ◽  
Author(s):  
Qinghui Meng ◽  
Yicheng Chi ◽  
Lidong Zhang ◽  
Peng Zhang ◽  
Liusi Sheng
Keyword(s):  
Theoretical Calculations ◽  
Theoretical Studies ◽  
Equation Approach ◽  
Dissociation Kinetics ◽  
Master Equation Approach ◽  
High Layer ◽  
High Level ◽  
Kinetics Of ◽  
Oniom Method ◽  
Methyl Decanoate

The isomerization and dissociation reactions of methyl decanoate (MD) radicals were theoretically investigated by using high-level theoretical calculations based on a two-layer ONIOM method, employing the QCISD(T)/CBS method for the high layer and the M06-2X/6-311++G(d,p) method for the low layer.

scholarly journals Numerical simulation of the stress-strain state of complex-reinforced elements

2019 ◽  
Vol 13 (2) ◽  
pp. 110-115
Author(s):  
Olena Krantovska ◽  
Mykola Petrov ◽  
Liubov Ksonshkevych ◽  
Matija Orešković ◽  
Sergii Synii ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Strain State ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Theoretical Studies ◽  
Stress Strain ◽  
Narrow Strip ◽  
Stress Strain State ◽  
Graphical Environment ◽  
Experimental And Theoretical Studies

The article describes a developed technique of a numerical simulation of the stress-strain state of complex-reinforced elements, which allows you to create models of double-span continuous. The performed experimental and theoretical studies allowed us to carry out the testing of the developed design model and to justify the reliability of the proposed numerical simulation methodology. The results of the experimental studies were compared with those of the theoretical studies. The theoretical calculus algorithm was developed by using the finite element method. Theoretical calculations were performed by using the mathematical-graphical environment software system LIRA-SOFT and the mathematical and computer program MATLAB. On the basis of the experimental research, the iso-fields of displacements and stresses in the materials of an eccentrically compressed beam with a small bend of the slab were constructed, which collapse behind the inclined narrow strip of concrete and displacements and stresses in the materials of the eccentrically stretched beam, which is destroyed due to the yield of the upper mounting armature.

Syntheses, theoretical studies, and crystal structures of [Ni(II)SSRRL](PF6)2 and [Ni(II)SRSRL](Cl)(PF6) that contains anagostic interactions

2020 ◽  
pp. 1-10
Author(s):  
Peyton C. Bainbridge ◽  
Rudy L. Luck ◽  
Nick K. Newberry
Keyword(s):  
Theoretical Calculations ◽  
Structural Data ◽  
Theoretical Studies ◽  
Redox Potentials ◽  
X Ray ◽  
H Nmr ◽  
Irreversible Oxidation ◽  
Square Planar ◽  
Reduced Products ◽  
Reversible Reduction

The syntheses of two square planar nickel complexes containing the condensation and subsequently reduced products obtained by reacting [Ni(en)3](BF4)2 and acetone are reported. The complexes 5,5,7,12,12,14-hexamethyl-1(S),4(S),8(R),11(R)-tetraazacyclotetradecane-nickel(II)[PF6]2 and 5,5,7,12,12,14-hexamethyl-1(S),4(R),8(S),11(R)-tetraazacyclotetradecane-nickel(II)[Cl][PF6] labelled as [Ni(II)SSRRL](PF6)2 and [Ni(II)SRSRL](Cl)(PF6), respectively, were found to have slightly different solubilities that allowed for their purification. The complexes were characterized by FTIR, 1H NMR, and UV–vis spectra. Redox potentials, determined by cyclic voltammetry, established that [Ni(II)SSRRL](PF6)2 exhibits a reversible oxidation (E1/2(ox) = 0.85 V) and reduction (E1/2(red) = −1.59 V), whereas [Ni(II)SRSRL](Cl)(PF6) displays an irreversible oxidation (Epa(ox) = 1.37 V) and reversible reduction (E1/2(red) = −1.62 V) relative to the ferrocene couple at 0.0 V. Single crystal X-ray determinations established that one of the compounds, [Ni(II)SSRRL](PF6)2, contained two [Formula: see text] anions, whereas the other compound, [Ni(II)SRSRL](Cl)(PF6), contained one Cl− and one [Formula: see text] anion. In the solid state, compound [Ni(II)SSRRL](PF6)2 was held together by H-bonds between H atoms on the Ni containing dication and F atoms in the [Formula: see text] anion. Compound [Ni(II)SRSRL](Cl)(PF6) crystallized in the form of dimers held together by interactions between H atoms attached to N atoms on adjacent cations binding to two Cl− anions in the middle with these dimers held together by further H-bonding to interstitial [Formula: see text] anions. Complex [Ni(II)SRSRL](Cl)(PF6) was found to contain anagostic interactions on the bases of NMR (downfield shift in C–H protons) and structural data (2.3 < d(H-Ni) < 2.9 Å), as well as theoretical calculations.

Submolecular partitioning of morphine hydrate based on its experimental charge density at 25 K

2005 ◽  
Vol 61 (4) ◽  
pp. 443-448 ◽  
Author(s):  
S. Scheins ◽  
M. Messerschmidt ◽  
P. Luger
Keyword(s):  
Electron Density ◽  
Electron Density Distribution ◽  
Theoretical Calculations ◽  
Topological Analysis ◽  
Theoretical Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resolution Single ◽  
Experimental Electron Density ◽  
Experimental Charge Density

The electron density distribution of morphine hydrate has been determined from high-resolution single-crystal X-ray diffraction measurements at 25 K. A topological analysis was applied and, in order to analyze the submolecular transferability based on an experimental electron density, a partitioning of the molecule into atomic regions was carried out, making use of Bader's zero-flux surfaces to yield atomic volumes and charges. The properties obtained were compared with the theoretical calculations of smaller fragment molecules, from which the complete morphine molecule can be reconstructed, and with theoretical studies of another opiate, Oripavine PEO, reported in the literature.

scholarly journals Structural and theoretical studies of 4-chloro-2-methyl-6-oxo-3,6-dideuteropyrimidin-1-ium chloride (d 6)

2021 ◽  
Vol 77 (4) ◽  
pp. 390-395
Author(s):  
Ray J. Butcher ◽  
Andrew P. Purdy ◽  
Sean A. Fischer ◽  
Daniel Gunlycke
Keyword(s):  
Oxygen Atom ◽  
Title Compound ◽  
Theoretical Calculations ◽  
Chloride Anion ◽  
Monoclinic Space Group ◽  
Theoretical Studies ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Compound C ◽  
Graph Set

The title compound, C5D6ClN2O+·Cl−, crystallizes in the orthorhombic space group, Pbcm, and consists of a 4-chloro-2-methyl-6-oxo-3,6-dihydropyrimidin-1-ium cation and a chloride anion where both moieties lie on a crystallographic mirror. The cation is disordered and was refined as two equivalent forms with occupancies of 0.750 (4)/0.250 (4), while the chloride anion is triply disordered with occupancies of 0.774 (12), 0.12 (2), and 0.11 (2). Unusually, the bond angles around the C=O unit range from 127.2 (6) to 115.2 (3)° and similar angles have been found in other structures containing a 6-oxo-3,6-dihydropyrimidin-1-ium cation, including the monclinic polymorph of the title compound, which crystallizes in the monoclinic space group P21/c [Kawai et al. (1973). Cryst. Struct. Comm. 2, 663–666]. The cations and anions pack into sheets in the ab plane linked by N—H...Cl hydrogen bonds as well as C—H...O and Cl...O interactions. In graph-set notation, these form R 3 3(11) and R 3 2(9) rings. Theoretical calculations seem to indicate that the reason for the unusual angles at the sp 2 C is the electrostatic interaction between the oxygen atom and the adjacent N—H hydrogen.

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