Molecular structure, isomerism, conformational stability and intramolecular hydrogen bonding (IHB) of cis-enol forms of 1-(n-pyridyl)butane-1,3-diones (nPBD) (n = 2, 3, or 4) have been investigated by means of density functional theory (DFT) calculations. Energy differences for all possible nPBD cis-enol forms of isomers with respect to the most stable form of the correspondin...

the nmr spectra of azo dyes, 5-arylazobarbituric (5a-g), 5-arylazo-1,3-dimethylbarbituric(6a-g) and 5-arylazothiobarbituric acids (7a-g) were studied in dmso-d6 in differentconcentrations. an intramolecular hydrogen bond was observed and indicating that thehydrazone forms is mostly predominant. the peak of the hydrazone proton was severelybroadened and its chemical shift appeared at down field ...

molecular structure, isomerism, conformational stability and intramolecular hydrogen bonding (ihb) of cis-enol forms of 1-(n-pyridyl)butane-1,3-diones (npbd) (n = 2, 3, or 4) have been investigated by means of density functional theory (dft) calculations. energy differences for all possible npbd cis-enol forms of isomers with respect to the most stable form of the corresponding isomer have been...

The NMR spectra of azo dyes, 5-arylazobarbituric (5a-g), 5-arylazo-1,3-dimethylbarbituric(6a-g) and 5-arylazothiobarbituric acids (7a-g) were studied in DMSO-d6 in differentconcentrations. An intramolecular hydrogen bond was observed and indicating that thehydrazone forms is mostly predominant. The peak of the hydrazone proton was severelybroadened and its chemical shift appeared at down field ...

A fragment of Histidine rich protein II (HRP II 215-236) was investigated by 14N and 17O electric field gradient, EFG, tensor calculations using DFT. This study is intended to explore the differences between 310-helix and α-helix of HRPII both in the gas phase and in solution. To achieve the aims, the 17O and 14N NQR parameters of a fragment of HRPII (215-236) for both structures are calculated...

a fragment of histidine rich protein ii (hrp ii 215-236) was investigated by 14n and 17o electric field gradient, efg, tensor calculations using dft. this study is intended to explore the differences between 310-helix and α-helix of hrpii both in the gas phase and in solution. to achieve the aims, the 17o and 14n nqr parameters of a fragment of hrpii (215-236) for both structures are calculated...

the influence of cation-π interactions on the strength and nature of intramolecular o...h hydrogen bond has been investigated by quantum chemical calculations in orthohydroxy benzaldehyde (hba) compound. ab initio calculations have been performed at mp2/6-311++g** level of theory. vibrational frequencies and physical properties such as chemical potential and chemical hardness of these compounds...

(1)H NMR chemical shifts have been obtained in the solvents deuterochloroform and dimethyl sulfoxide. The difference in the chemical shifts of an OH or NH group in these two solvents, Δδ = δ(DMSO) - δ(CDCl3), can be converted into the hydrogen bond acidity, A, of the group using the equation A = 0.0065 + 0.133Δδ. The NMR A value, ANMR, can be used as a quantitative assessment of intramolecular ...

The influence of cation-π interactions on the strength and nature of intramolecular O...H hydrogen bond has been investigated by quantum chemical calculations in orthohydroxy benzaldehyde (HBA) compound. Ab initio calculations have been performed at MP2/6-311++G** level of theory. Vibrational frequencies and physical properties such as chemical potential and chemical hardness of these compounds...