Singh Ajeet, Chakraborty Shampa, Ganguly Bishwajit
Analytical Science Discipline, Central Salt and Marine Chemicals Research Institute, Bhavnagar, Gujarat 364002, India.
Langmuir. 2007 May 8;23(10):5406-11. doi: 10.1021/la062405o. Epub 2007 Apr 13.
Conformational behaviors of urea and glycinamide have been investigated using the B3LYP functional with the 6-311+G* and 6-311+G** basis sets. Urea monomers have nonplanar minima at all the levels studied, even in the aqueous phase. In the case of glycinamide, the intramolecular hydrogen bond formed from the amide to the amine is important for stabilizing the global minimum. Bond rotations and nitrogen inversion barriers for glycinamide conformations have also been reported. The DFT calculated results suggest that urea conformers interact preferentially with the {111} surface of sodium chloride and such interactions can be responsible for the change in the habit of sodium chloride. Glycinamide conformers have a lower affinity toward the {111} surface of sodium chloride in water. The pyramidality of nitrogens in urea conformers does not influence the relative trends of interaction energies with sodium chloride surfaces. The mode of interactions predicted at the LDA/PWC/DND level for urea and glycinamide with sodium chloride for both slab and cluster models shows that the amide functionality (-CONH2) interacts with both Na(+) and Cl(-) ions on the {100} surface; however, the carbonyl oxygen of these additives predominantly interacts with the sodium ions on the {111} surface.
已使用B3LYP泛函结合6 - 311 + G*和6 - 311 + G**基组研究了尿素和甘氨酰胺的构象行为。在所有研究水平下，尿素单体均具有非平面的极小值，即使在水相中也是如此。对于甘氨酰胺，从酰胺到胺形成的分子内氢键对于稳定全局极小值很重要。还报道了甘氨酰胺构象的键旋转和氮反转势垒。密度泛函理论计算结果表明，尿素构象异构体优先与氯化钠的{111}表面相互作用，这种相互作用可能是氯化钠晶习变化的原因。在水中，甘氨酰胺构象异构体对氯化钠的{111}表面亲和力较低。尿素构象异构体中氮的棱锥形不影响与氯化钠表面相互作用能的相对趋势。对于平板模型和簇模型，在LDA/PWC/DND水平预测的尿素和甘氨酰胺与氯化钠的相互作用模式表明，酰胺官能团(-CONH2)与{100}表面上的Na(+)和Cl(-)离子都相互作用；然而，这些添加剂的羰基氧主要与{111}表面上的钠离子相互作用。
