Tautomerism and rotamerism in 2‐methylamino‐, 2‐anilino‐, 2‐acetamido‐, and 2‐benzamido‐pyridines

Pietrzycki, Władysł; Sepiol, Jadwiga; Tomasik, Piotr; Brzózka, Łukasz

doi:10.1002/bscb.19931021105

Cited by 9 publications

(1 citation statement)

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“…DFT vibrational studies of 5-bromo-2-nitropyridine (Sundaraganesan et al 2005), pyridinium complexes (Tayyari et al 2010), and 2-chloro-5-bromopyridine (Hiremath et al 2010; Kishor and Bhoop 2013) were reported. Tautomerization and rotamerization of aminopyridines has been reported (Davoodnia et al 2011; Alkorta and Elguero 2002; Pietrzycki et al 1993). The vibration (IR and Raman) spectra of aminopyridines, methyl-substituted aminopyridines and hydrogen chlorides of aminopyridines had been determined experimentally by Spinner (Spinner 1962).…”

Section: Introductionmentioning

confidence: 97%

Tautomerization, molecular structure, transition state structure, and vibrational spectra of 2-aminopyridines: a combined computational and experimental study

Al‐Otaibi

2015

SpringerPlus

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Background2-amino pyridine derivatives have attracted considerable interest because they are useful precursors for the synthesis of a variety of heterocyclic compounds possessing a medicinal value. In this work we aim to study both structural and electronic as well as high quality vibrational spectra for 2-amino-3-methylpyridine (2A3MP) and 2-amino-4-methylpyridine (2A4MP).ResultsMøller–Plesset perturbation theory (MP2/6-31G(d) and MP2/6-31++G(d,p) methods were used to investigate the structure and vibrational analysis of (2A3MP) and (2A4MP). Tautomerization of 2A4MP was investigated by Density Functional Theory (DFT/B3LYP) method in the gas phase. For the first time, all tautomers including NH → NH conversions as well as those usually omitted, NH → CH and CH → CH, were considered. The canonical structure (2A4MP1) is the most stable tautomer. It is 13.60 kcal/mole more stable than the next (2A4MP2). Transition state structures of pyramidal N inversion and proton transfer were computed at B3LYP/6-311++G(d,p). Barrier to transition state of hydrogen proton transfer is calculated as 44.81 kcal/mol. Transition state activation energy of pyramidal inversion at amino N is found to be 0.41 kcal/mol using the above method. Bond order and natural atomic charges were also calculated at the same level. The raman and FT-IR spectra of (2A3MP) and (2A4MP) were measured (4000–400 cm−1). The optimized molecular geometries, frequencies and vibrational bands intensity were calculated at ab initio (MP2) and DFT(B3LYP) levels of theory with 6-31G(d), 6-31++G(d,p) and 6-311++G(d,p) basis sets. The vibrational frequencies were compared with experimentally measured FT-IR and FT-Raman spectra.ConclusionReconsidering the vibrational analysis of (2A3MP) and (2A4MP) with more accurate FT-IR machine and highly accurate animation programs result in new improved vibrational assignments. Sophisticated quantum mechanics methods enable studying the transition state structure for different chemical systems.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-015-1363-2) contains supplementary material, which is available to authorized users.

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Section: Introductionmentioning

confidence: 97%

Tautomerization, molecular structure, transition state structure, and vibrational spectra of 2-aminopyridines: a combined computational and experimental study

Al‐Otaibi

2015

SpringerPlus

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The molecular origin of the thiamin diphosphate‐induced spectral bands of ThDP‐dependent enzymes

Kovina¹,

Kok²,

Sevostyanova³

et al. 2004

Proteins

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New and previously published data on a variety of ThDP-dependent enzymes such as baker's yeast transketolase, yeast pyruvate decarboxylase and pyruvate dehydrogenase from pigeon breast muscle, bovine heart, bovine kidney, Neisseria meningitidis and E. coli show their spectral sensitivity to ThDP binding. Although ThDP-induced spectral changes are different for different enzymes, their universal origin is suggested as being caused by the intrinsic absorption of the pyrimidine ring of ThDP, bound in different tautomeric forms with different enzymes. Non-enzymatic models with pyrimidine-like compounds indicate that the specific protein environment of the aminopyrimidine ring of ThDP determines its tautomeric form and therefore the changeable features of the inducible effect. A polar environment causes the prevalence of the aminopyrimidine tautomeric form (short wavelength region is affected). For stabilization of the iminopyrimidine tautomeric form (both short- and long-wavelength regions are affected) two factors appear essential: (i) a nonpolar environment and (ii) a conservative carboxyl group of a specific glutamate residue interacting with the N1' atom of the aminopyrimidine ring. The two types of optical effect depend in a different way upon the pH, in full accordance with the hypothesis tested. From these studies it is concluded that the inducible optical rotation results from interaction of the aminopyrimidine ring with its asymmetric environment and is defined by the protonation state of N1' and the 4'-nitrogen.

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Photochemistry of 2-(methylamino)pyridine in a low-temperature argon matrix: Amino–imino tautomerism and rotational isomerism

Akai

Ohno

Aida

2007

Journal of Photochemistry and Photobiology A: Chemistry

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Tautomerism and rotamerism in 2‐methylamino‐, 2‐anilino‐, 2‐acetamido‐, and 2‐benzamido‐pyridines

Cited by 9 publications

References 11 publications

Tautomerization, molecular structure, transition state structure, and vibrational spectra of 2-aminopyridines: a combined computational and experimental study

Tautomerization, molecular structure, transition state structure, and vibrational spectra of 2-aminopyridines: a combined computational and experimental study

The molecular origin of the thiamin diphosphate‐induced spectral bands of ThDP‐dependent enzymes

Photochemistry of 2-(methylamino)pyridine in a low-temperature argon matrix: Amino–imino tautomerism and rotational isomerism

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