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首页> 外文期刊>Journal of Chemical and Engineering Data: the ACS Journal for Data >Excess Thermodynamic Properties of H_2O and D_2O Solutions of Tetramethylurea, an Azeotropic System. Vapor Pressures, Excess Vapor Pressures, and Vapor Pressure Isotope Effects
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Excess Thermodynamic Properties of H_2O and D_2O Solutions of Tetramethylurea, an Azeotropic System. Vapor Pressures, Excess Vapor Pressures, and Vapor Pressure Isotope Effects

机译：共沸体系四甲基脲的H_2O和D_2O溶液的过剩热力学性质蒸气压，过量蒸气压和蒸气压同位素效应

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摘要

Vapor pressures of the tetramethylurea (TMU) + H_2O or + D_2O solutions (1,2,4,8,15,25,50, and 70 molal, 283 <= T/K <= 353) were obtianee from precise differential measurements. The vapor pressures in the lower temperature range show sharp maxima that are 40 to 50% above the Raoult's law value at X_(TMU) = 0.07 (4 molal) which fall with increasing temperature. The vapor pressure isotope effects of the solutions lie significantly below that for pure solvent. Below 50 deg C the difference shows its maximum at 2 to 4 aquamolal, reaching unusually large values at low temperature (40% at 10 deg C). The behavior of the solution is discussed using the cage-model of hydrophobic hydration. In the water-rich r egion, competition between hydrophobic and hydrophilic hydration spheres results in unusually high TMU activity and solution nonideality and in turn accounts for the strong denaturing effect of TMU on natural proteins; this effect is most effective at about 3 m.
机译：精确的差分测量表明，四甲基脲（TMU）+ H_2O或+ D_2O溶液（1、2、4、8、15、25、50和70摩尔，283 <= T / K <= 353）的蒸气压是恒定的。在较低温度范围内的蒸气压显示出急剧的最大值，该最大值在X_（TMU）= 0.07（4摩尔）时比拉乌尔定律值高40％至50％，随着温度的升高而降低。溶液的蒸气压同位素效应明显低于纯溶剂。低于50摄氏度时，差异在2至4个水摩尔摩尔浓度下显示出最大值，在低温下达到异常大的值（10摄氏度时为40％）。使用疏水水合的笼模型讨论了溶液的行为。在富含水的区域中，疏水性和亲水性水化球之间的竞争导致异常高的TMU活性和溶液的非理想性，进而导致TMU对天然蛋白质的强烈变性作用。此效果在约3 m处最有效。

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