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Open Access Article
1 - Using Implicit/Explicit Salvation Models to Theoretical Study Tautomerism in 7H-purine-2, 6-diamine
javad hosseini -
Open Access Article
2 - AB Initio Calculations and IR Studies of Tautometric forms of Uracil and Cytosine and comparing results in different temperatures (25˚C, 37˚C and 40˚C).
M. Monajjemi R. Nikmaram F. Mollaamin Z. Azizi -
Open Access Article
3 - A Theoretical Study on the Aromaticity of 5-methylcytosine tautomers in the gas phase
H. Aghaie K. Zare E. Zahedi S.R. Emamian -
Open Access Article
4 - Ab initio and DFT studies on tautomerism of 5-methyl cytosine in gaseous phase
K. Zare M. Monajjemi E. Zahedi H. Aghaie -
Open Access Article
5 - Thermodynamic Study and Total Energy Calculation for three systems of Enol↔Keto Tautomerism
H. Aghaie M. Monajjemi L. Papei -
Open Access Article
6 - Computational Investigation on Alcohol Nano Sensors in Combination with Carbon Nanotube; A Monte Carlo and Ab Initio Simulation
M. Falahati M. Monajjemi -
Open Access Article
7 - Theoretical investigation of tautomerisation of 3-Amino-1H-1,2,4-Triazol-5(4H)-One by using quantum calculations by DFT method.
بهزاد چهکندیدر این تحقیق بررسی توتومریزاسیون و حالتهای گذار مولکول 3-آمینو-1H-4،2،1- تریآزول-5)4H (- اٌن که حاصل از انتقالات 1و3 پروتون بین اتم های اکسیژن و نیتروژن است با استفاده از محاسبات کوانتومی در سطح محاسباتیDFT-B3LYP/6-311++G(d,p)، در فاز گازی و در محیطی با حضور یک و دو م Moreدر این تحقیق بررسی توتومریزاسیون و حالتهای گذار مولکول 3-آمینو-1H-4،2،1- تریآزول-5)4H (- اٌن که حاصل از انتقالات 1و3 پروتون بین اتم های اکسیژن و نیتروژن است با استفاده از محاسبات کوانتومی در سطح محاسباتیDFT-B3LYP/6-311++G(d,p)، در فاز گازی و در محیطی با حضور یک و دو مولکول آب انجام شده است. بدین منظور ساختار بهینه توتومرهای مختلف مولکول مورد نظر بدست آمدهاند. همچنین با استفاده از محاسبات فرکانس در سطح محاسباتی مشابه، خواص ترمودینامیکی تعادلهای مختلف توتومری از قبیل E∆، H∆، G∆ وKeq بدست آمدهاند. سپس با استفاده از روشهای QST2 و QST3 حالت های گذار تعادلهای توتومری مختلف مولکول3-آمینو-1H-4،2،1- تریآزول-5)4H (- اٌن و مقادیر سینتیکی و ترمودینامیکی آنها محاسبه شدهاند. اثرات تونلزنی نیز بر روی سرعت واکنشهای مربوطه بررسی شدهاند. نتایج نشان میدهند ثابت سرعت واکنشهای توتومری مورد بررسی نسبت به اثرات تونلزنی حساسیت بالایی دارند و سرعت واکنش های توتومری در حدود چهار تا پنج برابر افزایش مییابند. همچنین محاسبات حالت گذارنشان می دهند در غیاب مولکولهای آب سد انرژی مقدار بالایی دارد و سرعت واکنش های توتومری عمدتاً بدون حضور کاتالیزور خیلی آهسته بوده به عبارتی انجامپذیر نیستند. Manuscript profile -
Open Access Article
8 - Investigation of C-O tautomerism in a derivative of Flucytosine: A DFT study
بهزاد چهکندیIn this research investigation of tautomerism and transition states of 6-Hydroxy 5-Flourocytosine from 1,3 proton transfer between oxygen and carbon atoms in the gas phase and in solution and in a micro hydrated environment with 1-3 water molecules was performed by quan MoreIn this research investigation of tautomerism and transition states of 6-Hydroxy 5-Flourocytosine from 1,3 proton transfer between oxygen and carbon atoms in the gas phase and in solution and in a micro hydrated environment with 1-3 water molecules was performed by quantum calculations at the DFT/B3LYP/6-31++G(d,p) level of theory. For this purpose, the optimized geometries of various tautomers of the desired molecule were obtained. Also by using frequency calculations at the same level thermodynamic properties of different tautomeric equilibriums such as ΔE, ΔH, ΔG and Keq were obtained. Then transition states of various tautomeric interconversion of 6-Hydroxy 5-Flourocytosine and it’s kinetic and thermodynamic amounts were calculated by QST2 and QST3 methods. And also the tunneling effects on rates of reaction were investigated. The results show in both gas phase and solution, rate constants of tautomeric reactions have high sensitivity on tunneling effects and rate of tautomeric interconversion increase by about five or more. Also transition state calculations show in absence of water assisted molecules the tautomeric interconversion reacctions have high barrier energy and so are very slow, in other word they can not be done Manuscript profile -
Open Access Article
9 - A tautomerism in 2-amino-7H-purine-6-thiol: Theoretical study using implicit/explicit salvation models
Aeyed Javad Hosseini بیتا محمداصغریA theoretical study at the B3LYP/6-31++G(d,p) level was performed on the tatumerization of 2-amino-7H-purine-6-thiol into 2-amino-9H-purine-6-thiol. Such a tautomerism can take place via three different pathways namely A, B, and C. The energetic results associated with MoreA theoretical study at the B3LYP/6-31++G(d,p) level was performed on the tatumerization of 2-amino-7H-purine-6-thiol into 2-amino-9H-purine-6-thiol. Such a tautomerism can take place via three different pathways namely A, B, and C. The energetic results associated with the gas phase reveal that pathways A, B, and C display a very high activation Gibbs free energy of 47.6, 69.4, and 52.1 kcal/mol, respectively, indicating this process cannot take place in the gas phase. When solvent effects of water are taken into account through a continuum of a uniform dielectric constant, the gas phase activation Gibbs free energies increase to 51.1, 71.9, and 55.4 kcal/mol along pathway A, B, and C, respectively, emphasizing long range solute-solvent interactions do not play a key role in the considered tautomerization. The studied process can easily take place by inclusion of three molecules of water in which a significantly reduced activation Gibbs free energy of 24.8 kcal/mol indicates the predominance of short range solute-solvent interactions over the long range ones. Combination of short range and long range solute-solvent interactions lead to an activation Gibbs free energy of 23.6 kcal/mol for tatumerization of 2-amino-7H-purine-6-thiol into 2-amino-9H-purine-6-thiol. This value clearly points out that employing a polar and protic solvent is able to noticeably reduce the barrier of tatomerization. Manuscript profile -
Open Access Article
10 - Study and comparison of Equilibrium vs. resonance in keto-enol tautomerization in some piroxicam derivatives
abolghasem shameli Ebrahim balali sara hallajian behrooz yousefzadehThe Piroxicam derivatives are nonsteroidal anti-inflammatory drug (NSAID) used to treat pain and help relieve symptoms of arthritis. Which has two or more forms are tautomers, That both form tautomers due to the flexible structure and the possibility of turning around b MoreThe Piroxicam derivatives are nonsteroidal anti-inflammatory drug (NSAID) used to treat pain and help relieve symptoms of arthritis. Which has two or more forms are tautomers, That both form tautomers due to the flexible structure and the possibility of turning around bonding C-C, C-O, C-N and C-S. The hydrogen-bond also play a very important roles in structure compound because Intramolecular and intermolecular hydrogen bond in which the different. In this study, theoretical and computational accuracy using BPV860 / 6-311G ** in the gas phase with software Gaussian 03. Infrared Spectroscopic and Theoretical Studies on the derivetives piroxicam. Relationship between the structure and the stability of these enols was discussed. That enol- keto or imine- enamine forms easily converted into stable forms Manuscript profile -
Open Access Article
11 - A Theoretical Study on Three Tautomeric Forms of Lenalidomide with Density Functional Theory
abolghasem shameli Shima JonideiIn this study, the totemic structure, optical and electron properties, electron absorption spectrum, vibrational frequencies, thermodynamic properties and charge distribution of three amide and imidic acid structures of lenalidomide via quantum chemistry calculations us MoreIn this study, the totemic structure, optical and electron properties, electron absorption spectrum, vibrational frequencies, thermodynamic properties and charge distribution of three amide and imidic acid structures of lenalidomide via quantum chemistry calculations using density functional theory (DFT) Time-dependent (TDDFT) hybridization with B3LYP function and base set 6-311 + G ** were investigated. The computational results show that the amide structure of lenalidomide has good quantum properties that can act as a drug. The energies of the amide and imidic acid structures of lenalidomide indicate that the amide structure with little energy difference is more stable than the imidic acid structure. Calculations of excited states show that the structure of the amide lenalidomide has better adsorption properties. The nonlinear optical properties of the amide structure of lenalidomide are also higher than the imidic acid structure of lenalidomide but the chemical hardness of the amide structure is lower than that of the imidic structure, indicating that the reactivity and charge transfer of the amide structure are higher than the imidic acid structure. Manuscript profile -
Open Access Article
12 - Theoretical study of 2-selenoformyl-3-thioxo-propionaldehyde (STP) in the exited states
ramin rafat alireza nowrooziIn the present study, tatomerism process, hydrogen bond strength and π-electron delocalization of 2-selenoformyl-3-thioxo-propionaldehyde (STP) in the singlet and triplet excites states were investigated. First, all of the H-bonded structures in exited states were op MoreIn the present study, tatomerism process, hydrogen bond strength and π-electron delocalization of 2-selenoformyl-3-thioxo-propionaldehyde (STP) in the singlet and triplet excites states were investigated. First, all of the H-bonded structures in exited states were optimized by CIS and TD-DFT methods. Relative energies indicate that the thiol and enol conformers are the most stable and unstable, respectively: HB Thiol < HB Selenol < HB Enol. Moreover, the electronic energies show that all of the H-bonded structures are more stable in the triplet excited state than the singlet excited state. To justify this order, the affective factors on this stability such as tautomerism, hydrogen bonding and π-electron delocalization were comprehensively investigated. Tautomeric energies express that the thiol tautomer is more stable than the others in terms of thermodynamics. Also, the activation barriers indicate that the thio⇋thiol is more prefer than the other equilibriums, from kinetic point of view. Description of different hydrogen bonds by energetic, geometrical, topological and molecular orbitals emphasize on the presence of a stronger intramolecular hydrogen bond (IMHB) in the enol forms. Furthermore, evaluation of π-electron delocalization (π-ED) represents approximate superiority of enol conformers. The achieved results by HB and π-ED analyzes are in contrast with the mentioned stability order. Ultimately, investigation of above factors indicates that the tautomerism phenomenon plays a dominant role in determining of the structures stability in the excited states. Manuscript profile -
Open Access Article
13 - Investigation into the regioisomeric composition of some fused tetrazoles
Paria Nasehi Omid Baravaye Sanaz Hafezi Birgani Mohsen Nikpour -
Open Access Article
14 - Protonation Constants of Valin in Different Aqueous Solutions of Dimethylsulfoxide
Masumeh Jabbari Ali Shamel Farrokh Ghari -
Open Access Article
15 - Theoretical study on the mechanism of hydromethoxylation catalyzed by palladium(II) complex
S. Ali Beyramabadi Ali Morsali -
Open Access Article
16 - Change of the tautomeric preference for radical cation of pyruvic acid. DFT studies in the gas phase
Ewa Daniela Raczyńska Malgorzta Hallmann Kinga Duczmal -
Open Access Article
17 - Tautomeric equilibria for ionized oxamic acid - inhibitor of LDH
Ewa D. Raczyńska Małgorzata Hallmann Kinga Duczmal -
Open Access Article
18 - Tautomeric behaviors of 5-arylazobarbituric acids in different concentrations
Nader Noroozi Pesyan Jabbar Khalafy Karim Akbari Dilmaghani, Saeed Rastgar, Zahra Malekpoor, Mina Mohammadzadeh