Kinetic and thermodynamic study of inter‐ and intramolecular proton transfer in <i>N</i>′‐acetyl formohydrazide tautomers

Tavakol, Hossein

doi:10.1002/qua.22847

Cited by 18 publications

(4 citation statements)

References 58 publications

(56 reference statements)

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“…Hydrazides are known to undergo tautomerism which is rapid in aqueous solutions. 17 Since, both the reactive species are cations, H 2 BrO 3 + and IH 2 2+ , the electrophilic attack of oxidant on nucleophilic nitrogen of hydrazide moiety would be facilitated if the positive charge is transferred to carboxylic oxygen through tautomerism. Therefore, the rapid tautomerism of the hydrazide is considered as the first step of Scheme 1.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, the mechanism of reaction, by considering the IH 2 2+ and H 2 BrO 3 + as the active species of the isoniazid and bromate, respectively, can be represented as in Scheme . Hydrazides are known to undergo tautomerism which is rapid in aqueous solutions . Since, both the reactive species are cations, H 2 BrO 3 + and IH 2 2+ , the electrophilic attack of oxidant on nucleophilic nitrogen of hydrazide moiety would be facilitated if the positive charge is transferred to carboxylic oxygen through tautomerism.…”

Section: Discussionmentioning

confidence: 99%

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Mechanism of Oxidation of the Antituberculosis Drug Isoniazid by Bromate in Aqueous Hydrochloric Acid Medium

Yalgudre

Gokavi

2012

Ind. Eng. Chem. Res.

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The oxidation of isoniazid by bromate was investigated kinetically under pseudo-first-order conditions in acid medium. The reaction was accelerated by the hydrogen ion due to the various protonation equilibria of both the reactants. The mechanism involves diprotonated isoniazid as the active species which forms two complexes with the diprotonated and unprotonated oxidant. The complex formed between the diprotonated oxidant and the protonated −NH2 group of hydrazide moiety of isoniazid decomposes into isonicotinic acid. Formation of another stable ion pair complex decreases the rate of reaction. The UV–vis examination of the solutions support the formation of both protonated isoniazid and the complexes. A probable mechanism on the basis of kinetic results involving formation of an acyl diimide of the isoniazid was proposed.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Mechanism of Oxidation of the Antituberculosis Drug Isoniazid by Bromate in Aqueous Hydrochloric Acid Medium

Yalgudre

Gokavi

2012

Ind. Eng. Chem. Res.

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“…While, because of the highly importance of these synthetic methods, finding the clear details related to their mechanism has high scientific value . Therefore, in the continuation of our previous studies related to the mechanistic studies of chemical phenomena, we wish to report a full theoretical study for all possible mechanisms of this reaction. Surely, the complete reaction pathways and the energies of intermediates and transition states should be reported to provide enough evidences about this mechanism.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of the possible mechanisms for the synthesis of dialkyl thiourea from dithiocarbamate

Ranjbari

Tavakol

2018

Heteroatom Chemistry

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In this study, the different mechanistic ways for the conversion of dithiocarbamate to dialkyl thiourea have been investigated using the high‐accurate DFT calculations. The energy details of all mechanisms were investigated in the gas phase, simple and solvent‐assisted solvation models. Two general mechanisms and several different pathways have been considered to evaluate these mechanisms. The first mechanism (A) involved with the preparation of alkyl isothiocyanate, addition of alkyl amine to it and the final proton transfer. The second mechanism (B) is consisted of the addition of alkyl amine, proton transfer, and elimination of thiol. In the gas phase and solvent‐assisted models, the mechanism A is preferred; while in PCM model, the mechanism B is preferred. In both mechanisms, both solvation models have enhancing effects on the thermodynamics of the reactions and stabilize the product versus the reactant (comparing with the gas phase). In mechanism A, the amine should have at least 1 proton and the dithiocarbamate should also have 1 proton in its structure. Both proton transfer steps of these mechanisms have been facilitated by the proton transfer of amine molecule and both solvation models (PCM and explicit presence of water) increased the barriers and reduced the rate of this mechanism. However, in mechanism B, the PCM solvation model reduces the barriers and accelerates the reaction but the solvent‐assisted model increases the barriers and reduces the reaction's rate. The water molecule could not assist efficiently by making the proton bridge in these cases.

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“…In continuation of our previous researches about tautomerism and to investigate the possibility of diabatic crossing in PESs of organic molecules by theoretical methods, 2‐(pyridin‐2‐yl) furan‐3‐ol (PYFO) was designed. This molecule has three interesting intramolecular motions.…”

Section: Introductionmentioning

confidence: 99%

Tautomerism, dynamic properties and level crossing in 2‐(pyridin‐2‐yl) furan‐3‐ol by density functional theory and natural bond orbital analysis

Tavakol

2011

J of Physical Organic Chem

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Tautomerism, dynamic properties and level crossing in 2-(pyridin-2-yl) furan-3-ol by density functional theory and natural bond orbital analysis Hossein Tavakol a * 2-(Pyridin-2-yl)furan-3-ol (PYFO, T1) and (2E)-2-(pyridin-2(1H)-ylidene)furan-3(2H)-one (PYFO, T2) were considered to study their tautomerism interconversions, relative rotations of rings, OH bond rotations, and possibility of crossing between those energy surfaces using density functional theory methods at the Becke, three-parameter, Lee-Yang-Parr/6-311++G** level of theory. The optimized structures of both tautomers and the transition state of tautomerism are completely planar. A study of tautomerism in PYFO shows that T1 tautomer is about 24.38 kJ/mol more stable than T2. The rate constants of tautomerism interconversion for converting T1 to T2 is 1.98 Â 10 8 M -1 s -1 and for converting T2 to T1 is 3.70 Â 10 12 M -1 s -1 at room temperature that show the possibility of this tautomerism with high rate at ambient temperature. Rotation of OH bond in T1 shows two minimum (at 0 (global minimum) and 180 (local minimum)) and a transition state at 110 (and 265 ) with 47.10 kJ/mol barrier energy. Relative rotation of rings shows global minimum at 0 for both tautomers and local minimum at 154 and 206 for T1 and 180 for T2. The barrier energy for ring rotation of T1 was observed at 90 and 270 with 63.69 kJ/mol height and for T2 was observed at 120 with 170.86 kJ/mol height. Interestingly, the energy levels of ring rotations for T1 and T2 are the same and crossing between them was observed. Therefore, although these two potentials do not have the same symmetries, because of the crossing between their energy level, crossing is not avoided. a Another barrier energy for ring rotation in T1, between 154 and 180 degrees: ΔG # = 1.06 and k = 4.05 Â 10 12 . TAUTOMERISM, DYNAMIC PROPERTIES AND LEVEL CROSSING IN 2-(PYRIDIN-2-YL) FURAN-3-OL

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Kinetic and thermodynamic study of inter‐ and intramolecular proton transfer in N′‐acetyl formohydrazide tautomers

Cited by 18 publications

References 58 publications

Mechanism of Oxidation of the Antituberculosis Drug Isoniazid by Bromate in Aqueous Hydrochloric Acid Medium

Mechanism of Oxidation of the Antituberculosis Drug Isoniazid by Bromate in Aqueous Hydrochloric Acid Medium

Theoretical study of the possible mechanisms for the synthesis of dialkyl thiourea from dithiocarbamate

Tautomerism, dynamic properties and level crossing in 2‐(pyridin‐2‐yl) furan‐3‐ol by density functional theory and natural bond orbital analysis

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