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دسترسی آزاد مقاله
1 - A Theoretical Study on Applying Conformational Analysis of 2-Halo-2-Oxo-1,3,2-Dioxaphosphorinanes
Fatemeh Azarakhshi Nazanin Farhadyar Mehrnoosh KhaleghianThe quantum-chemical calculations on the conformational properties of 2-flouro-2-oxo- 1,3,2-dioxaphosphorinane (1), 2-choloro-2-oxo-1,3,2-dioxaphosphorinane (2) and 2-bromo- 2-oxo-1,3,2-dioxaphosphorinane (3) have been investigated by means of ab initio molecular orbita چکیده کاملThe quantum-chemical calculations on the conformational properties of 2-flouro-2-oxo- 1,3,2-dioxaphosphorinane (1), 2-choloro-2-oxo-1,3,2-dioxaphosphorinane (2) and 2-bromo- 2-oxo-1,3,2-dioxaphosphorinane (3) have been investigated by means of ab initio molecular orbital (HF/6-311+G**) and hybrid density functional theory (B3LYP/6-311+G**) based methods and Natural Bond Orbital (NBO) interpretation in solid state was performed. Geometrical analysis supports clearly the participation of hyperconjugative endo-anomeric (LPO→σ*P-X) effect in the stabilization of axial series of compounds and the participation of exo-anomeric (LPX→σ*P-O) effect in the stabilization of the equatorial phosphinanes in chair conformations. The stereoelectronic effects associated with bonding-anticoding delocalization electron are more significant for the explanation of the conformational behavior of compounds 1-3 than the dipole-dipole interaction effects. پرونده مقاله -
دسترسی آزاد مقاله
2 - conformational properties and the anomeric effect study of phosphinanes
Javad Azizian Mahdieh Entezari Hossein Anaraki Ardakani Shahab ZomorodbakhshAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substitu چکیده کاملAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substituent can be seen by comparing the bond length in 2-chloro and 2- boromo substituented phosphinanes. The effect of anomeric effect have been effected on the bond length in 2-phosphinanes. پرونده مقاله -
دسترسی آزاد مقاله
3 - Theoretical study of conformational properties and the anomeric effect study of the 2- phosphinanes
Javad Azizian Hossein Anaraki Ardakani Shahab ZomorodbakhshAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substitu چکیده کاملAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substituent can be seen by comparing the bond length in 2-chloro and 2-boromo substituented phosphinanes. The effect of anomeric effect have been effected on the bond length in 2- phosphinanes. پرونده مقاله -
دسترسی آزاد مقاله
4 - Solvent effect investigation on the Conformational behaviors of 1-fluoro-N, N-dimethylmethanamine and analogs containing P, As atoms
Raja Ahmadzadeh Nea HasanzadehNBO analysis, hybrid density functional theory (B3LYP/6-311+G**) based methods were used to study the anomeric effects (AE), Stereoelectronic interactions, dipole-dipole interactions on the conformational properties of 1-Fluoro-N, N-dimethylmethanamine (1) and phosphoru چکیده کاملNBO analysis, hybrid density functional theory (B3LYP/6-311+G**) based methods were used to study the anomeric effects (AE), Stereoelectronic interactions, dipole-dipole interactions on the conformational properties of 1-Fluoro-N, N-dimethylmethanamine (1) and phosphorus (2) and arsenic (3) analogues.Moreover, relationships between stability of the anti-conformations of 1-Fluoro-N, N-dimethylmethanamine (1) and the analogs containing P and As (2, 3) compared to the gauche conformations of these compounds in solvents with different dielectric constants were investigated. Results indicated that the anomeric effect depended on the nature of the substitution present in the compounds and decreased when the dielectric constant of the environment, increased. The anomeric effect was confirmed by electron transfers from donor non-bonding orbitals to antibonding orbitals through using bond-length changes. The structures of compounds (1-3) were then investigated employing the theoretical method. The values of Gibbs free energy (ΔG), the anomeric effect (AE), dipole moment, structural parameters, and electron transfers of the stereoisomers in solvents with different dielectric constants were calculated. Results showed that the anti conformers of compounds (1-3) were more stable than the gauche conformers, and this stability trend was explained by changes in dipole moment and in anomeric effect. Furthermore, the change from the N to the P heteroatom increased the stability of the anti form compared to the gauche form. Moreover, the anti conformers were more stable than the gauche conformers when non-polar solvents were used instead of polar ones, but this trend was completely reversed with the change from the P to the As heteroatom. پرونده مقاله -
دسترسی آزاد مقاله
5 - Theoretical study of conformational properties and the anomeric effect study of the 2- phosphinanes
Javad Azizian Mahdieh Entezari Hossein Anaraki Ardakanib Shahab ZomorrodbakhshAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substitu چکیده کاملAb initio HF/6-31G* Methode was employed to calculate the bond length in 2- phosphinanes when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of the anomeric effect depends on the nature of the substituent, the effect of the substituent can be seen by comparing the bond length in 2-chloro and 2-boromo substituented phosphinanes. The effect of anomeric effect have been effected on the bond length in 2- phosphinanes. پرونده مقاله -
دسترسی آزاد مقاله
6 - Spotlight: Catalytic vinylogous anomeric based oxidation (Part I)
Meysam YarieStereoelectronic effects is a bridge between structure and reactivity [1]. Anomeric effect plays an important role in the domain of stereoelectronic interaction and can be used for description of several unusual phenomena. Intramolecular negative hyperconjugation is als چکیده کاملStereoelectronic effects is a bridge between structure and reactivity [1]. Anomeric effect plays an important role in the domain of stereoelectronic interaction and can be used for description of several unusual phenomena. Intramolecular negative hyperconjugation is also known as anomeric effect [2]. In anomeric effect, both donor (lone pairs) and acceptor groups (electronegative elements) coexist in a proper molecule. This coexistence causes the acceptor groups to prefer the axial position in anomeric position (Scheme 1) [1, 3-15]. Meysam Yarie was born in 1987 in Malayer/ Hamedan, Iran. He received his B.Sc. in Applied Chemistry from Malek-Ashtar University of Technology and M.Sc. in Organic Chemistry from Kurdistan University under the supervision of Dr. Kamal Amani. He received his Ph.D. from Bu-Ali Sina University under the supervision of Professor Mohammad Ali Zolfigol. He is currently working towards his Post-Doctoral under the supervision of Professor Mohammad Ali Zolfigol at Bu-Ali Sina University. His research interest is the design, synthesis, characterization and applications of task-specific catalysts, ionic liquids and molten salts in the organic synthesis. پرونده مقاله -
دسترسی آزاد مقاله
7 - Hybrid-DFT study and NBO interpretations of conformational behaviors of 2-methoxy-1,2,4,5-tetrahydro-benzo[d]oxepine, -thiepine and -selenepine
Davood Nori-Shargh Sogand Sarikhani Hooriye Yahyaei Seiedeh Negar Mousavi Nasrin MasnabadiNBO analysis and density functional theory (DFT: B3LYP/6-311+G**) based method were used to study the impacts of the anomeric effects (AE) on the conformational properties of 2-methoxy-1,2,4,5-tetrahydro-benzo[d]oxepine (1), -thiepine (2) and -selenepine (3). The Gibbs چکیده کاملNBO analysis and density functional theory (DFT: B3LYP/6-311+G**) based method were used to study the impacts of the anomeric effects (AE) on the conformational properties of 2-methoxy-1,2,4,5-tetrahydro-benzo[d]oxepine (1), -thiepine (2) and -selenepine (3). The Gibbs free energy difference (Geq–Gax) values (i.e. ΔGeq-ax) at 298.15 K and 1 atm between the axial and equatorial conformations increase from compound 1 to compound 2 but decrease from compound 2 to compound 3. The NBO analysis showed that the AE associated with donor-acceptor (LP→σ*) interactions increases from compound 1 to compound 2 but decreases from compound 2 to compound 3. Also, the calculated dipole moment difference [Δ(μeq - μax)] values between the axial and equatorial conformations increase from compound 1 to compound 2 but increase from compound 2 to compound 3. Based on the results obtained, there is no conflict between the AE and the electrostatic interactions [i.e. Δ(μeq - μax)] on the conformational behaviors of compounds 1-3. پرونده مقاله -
دسترسی آزاد مقاله
8 - Conformational behaviors of trans-2,3-bis(methylthio)-1,4-dioxane, -dithiane and –diselenane. A hybrid-DFT study and NBO interpretations
Davood Nori-Shargh Zahra Mahmoodi Nasrin Masnabadi Hooriye Yahyaei Seiedeh Negar MousaviThe conformational behaviors of 2,3-bis(methylthio)-1,4-dioxane (1), 2,3-bis(methylthio)-1,4-dithiane (2) and 2,3-bis(methylthio)-1,4-diselenane (3) have been analyzed by means ofhybrid-density functional theory (B3LYP/Def2-TZVPP) based method and NBO interpretation.B3L چکیده کاملThe conformational behaviors of 2,3-bis(methylthio)-1,4-dioxane (1), 2,3-bis(methylthio)-1,4-dithiane (2) and 2,3-bis(methylthio)-1,4-diselenane (3) have been analyzed by means ofhybrid-density functional theory (B3LYP/Def2-TZVPP) based method and NBO interpretation.B3LYP/Def2-TZVPP results showed that the axial conformations of compounds 1-3 are morestable than their equatorial conformations. The calculated Gibbs free energy difference (Geq–Gax)values (i.e. ΔGeq-ax) at 298.15 K and 1 atm between the axial and equatorial conformationsdecrease from compound 1 to compound 3. The NBO analysis of donor-acceptor (LP→σ*)interactions showed that the anomeric effects (AE) decrease from compound 1 to compound 3.On the other hand, the calculated dipole moment values between the axial and equatorialconformations [Δ(μeq - μax)] increase from compound 1 to compound 2 but decrease fromcompound 2 to compound 3. However, the variations of the calculated Δ(μeq - μax) values are notin the same trend observed for the corresponding AE and ΔG values. Therefore, the calculatedΔμ values do not seem to be sufficient to account for the axial preferences in compounds 1-3.These findings led to the proposal that the AE, due to donor→acceptor hyperconjugation effect,is more significant for the explanation of the axial conformational preferences of compounds 1-3than the electrostatic effect. پرونده مقاله -
دسترسی آزاد مقاله
9 - Hybrid-DFT study and NBO interpretations of the conformational behavior of 1,2-dihalodisilanes
Davood Nori-Shargh Seiedeh Negar Mousavi Hooriye Yahyaei Somayye Yazdani Bahareh AhmadiHybrid-density functional theory (B3LYP/Def2-TZVPP) based method and NBOinterpretation were used to investigate the conformational behavior of 1,2-dihalodisilanes[halo=F (1), Cl (2), Br (3), I (4)]. The B3LYP/Def2-TZVPP results showed that the anticonformations of compo چکیده کاملHybrid-density functional theory (B3LYP/Def2-TZVPP) based method and NBOinterpretation were used to investigate the conformational behavior of 1,2-dihalodisilanes[halo=F (1), Cl (2), Br (3), I (4)]. The B3LYP/Def2-TZVPP results showed that the anticonformations of compounds 1-4 are more stable than their corresponding gaucheconformations. The stability of the anti conformation compared to the gauche conformationincreases from compound 1 to compound 4. The NBO analysis of donor-acceptor interactionsshowed that the generalized anomeric effect (GAE) is in favor of the gauche conformations ofcompounds 1 and 2. Contrary to compounds 1 and 2, GAE is in favor of the anti conformationsof compounds 3 and 4. The GAE values calculated (i.e. GAEanti-GAEgauche) increase fromcompound 1 to compound 4. On the other hand, the calculated dipole moment values for thegauche conformations increase from compound 1 to compound 3 but decreases from compound3 to compound 4. Based on the results obtained, there is no conflict between the GAE and theelectrostatic model impacts on the conformational preferences in compounds 1-3 but theelectrostatic model can not rationalize the increase of the instability of the gauche conformationof compound 4 compared to its anti conformation on going from compound 3 to compound 4.Consequently, in the conflict between the GAE and the electrostatic model, the former succeededin accounting for the increase of the anti conformation stability from compound 1 to compound4. There is a direct correlation between the calculated GAE, Δ[rSi-Si(G)-rSi-Si(A)] parameters. Thecorrelations between the GAE, bond orders, ΔGAnti-Gauche, ΔG‡(Gauche→Gauche′, C2v),ΔG‡(Anti→Gauche, C2), dipole-dipole interactions, structural parameters and conformationalbehaviors of compounds 1-4 have been investigated. پرونده مقاله
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