First principle study of the structure of conjugated amides and thioamides

Velkov, Zhivko; Velkov, Yasen; Balabanova, E. A.; Tadjer, Alia

doi:10.1002/qua.21234

Cited by 8 publications

(5 citation statements)

References 17 publications

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“…For example, spectroscopic investigations using neutron scattering as well as quantum-chemistry calculations of secondary amide derivatives have been used to understand the force field of proteins and poly amino acids . Indeed, compounds such as acetamide, , formamide, thioamide, and their derivatives served as simple models for investigating the nature of secondary amide functions.…”

Section: Introductionmentioning

confidence: 99%

Polymorphism of Paracetamol: A New Understanding of Molecular Flexibility through Local Methyl Dynamics

et al. 2014

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This study focuses on the interplay of molecular flexibility and hydrogen bonding manifested in the monoclinic (form I) and orthorhombic (form II) polymorphs of paracetamol. By means of incoherent inelastic neutron scattering and density functional theory calculations, the relaxation processes related to the methyl side-group reorientation were analyzed in detail. Our computational study demonstrates the importance of considering quantum effects to explain how methyl reorientations and subtle conformational changes of the molecule are intertwined. Indeed, by analyzing the quasi elastic signal of the neutron data, we were able to show a unique and complex motional flexibility in form II, reflected by a coupling between the methyl and the phenyl reorientation. This is associated with a higher energy barrier of the methyl rotation and a lower Gibbs free energy when compared to form I. We put forward the idea that correlating solubility and molecular flexibility, through the relation between pKa and methyl rotation activation energy, might bring new insights to understanding and predicting drug bioavailability.

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Section: Introductionmentioning

confidence: 99%

Polymorphism of Paracetamol: A New Understanding of Molecular Flexibility through Local Methyl Dynamics

et al. 2014

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“…Biochemical and medicinal aspects of amides have been the subject of constant research. − Vibrational spectral investigations as well as quantum chemistry calculations of secondary amide derivatives have been used to understand the force field of proteins and polyamino acids, where compounds such as acetamide, , formamide, thioamide, and their derivatives served as simple models for investigating the nature of secondary amide functions. Also along these lines, in order to understand the dynamics of individual molecular fragments and to model the dynamics of biopolymers, the compounds of the acetanilide family, Figure , have attracted enormous attention.…”

Section: Introductionmentioning

confidence: 99%

Application of Incoherent Inelastic Neutron Scattering in Pharmaceutical Analysis: Relaxation Dynamics in Phenacetin

et al. 2012

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This study centers on the use of inelastic neutron scattering as an alternative tool for physical characterization of solid pharmaceutical drugs. On the basis of such approach, relaxation processes in the pharmaceutical compound phenacetin (p-ethoxyacetanilide, C(10)H(13)NO(2)) were evidenced on heating between 2 and 300 K. By evaluating the mean-square displacement obtained from the elastic fixed window approach, using the neutron backscattering technique, a crossover of the molecular fluctuations between harmonic and nonharmonic dynamical regimes around 75 K was observed. From the temperature dependence of the quasi-elastic line-width, summed over the total Q range explored by the time-of-flight technique, it was possible to attribute the onset of this anharmonicity to methyl group rotations. Finally, using density functional theory-based methods, we were able to calculate the lattice vibrations in the harmonic approximation. The overall spectral profile of the calculated partial contributions to the generalized density of states compares satisfactorily to the experimental spectra in the region of the lattice modes where the intermolecular interactions are expected to play an important role. This study contributes to understanding the relationships between intermolecular hydrogen bonds, intramolecular dynamics, and conformational flexibility in pharmaceuticals on a molecular level, which can help in evaluating phase stability with respect to temperature variations on processing or on storage, and is related to control of polymorphism and pseudopolymorphism.

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“…7,16,22,26 In addition, it was found that the degree of conjugation in thioamides is considerably higher than amides which made it as stronger p-electron attractor. 27 Nevertheless, thiosemicarbazides with thiolated BHT could convert into several radical by donating the proton to reduce DPPH radical. The possible radical formation of synthesized thiosemicarbazides can be drawn as Scheme 5.…”

Section: Antioxidant Evaluation By Dpphmentioning

confidence: 99%

Semicarbazide and thiosemicarbazide containing butylated hydroxytoluene moiety: new potential antioxidant additives for synthetic lubricating oil

et al. 2021

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First principle study of the structure of conjugated amides and thioamides

Cited by 8 publications

References 17 publications

Polymorphism of Paracetamol: A New Understanding of Molecular Flexibility through Local Methyl Dynamics

Polymorphism of Paracetamol: A New Understanding of Molecular Flexibility through Local Methyl Dynamics

Application of Incoherent Inelastic Neutron Scattering in Pharmaceutical Analysis: Relaxation Dynamics in Phenacetin

Semicarbazide and thiosemicarbazide containing butylated hydroxytoluene moiety: new potential antioxidant additives for synthetic lubricating oil

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