Abstract

The vaporization of lithium pivalate (CH₃)₃CCOOLi (LiPiv) was studied by the Knudsen effusion method with the mass spectral analysis of the gas phase. The saturated vapor consisted of polynuclear molecules (LiPiv)_n, dominated by (LiPiv)₂ and (LiPiv)₄ molecules. The absolute values of the partial pressures of these molecules and their dependence on temperature were calculated. The standard enthalpies of sublimation of the main components of the saturated vapor were determined to be \({{\Delta }_{s}}H_{{298}}^{^\circ }\)(LiPiv)₂ = 174.2 ± 6.6 kJ/mol and \({{\Delta }_{s}}H_{{298}}^{^\circ }\)(LiPiv)₄ = 195.7 ± 4.5 kJ/mol. The enthalpies of dissociation of the dimeric molecules into the monomeric molecules and of the tetrameric molecules into the dimeric molecules were calculated by the second and third laws of thermodynamics; the average values of these enthalpies are \({{\Delta }_{D}}H_{{298}}^{^\circ }\)(LiPiv)₂ = 175.8 ± 13.5 kJ/mol and \({{\Delta }_{D}}H_{{298}}^{^\circ }\)(LiPiv)₄ = 155.2 ± 10.0 kJ/mol. The standard enthalpies of formation of LiPiv in the condensed and gas phase were estimated from the known thermodynamic characteristics of lithium acetate and radicals of acetic and pivalic acids: \({{\Delta }_{f}}H_{{298.15}}^{^\circ }\)(LiPiv_solid) ≤ –804 kJ/mol, \({{\Delta }_{f}}H_{{298.15}}^{^\circ }\)(LiPiv_gas) ≤ –627 kJ/kmol, \({{\Delta }_{f}}H_{{298.15}}^{^\circ }\)((LiPiv)_2(gas)) ≤ –1430 kJ/mol, and \({{\Delta }_{f}}H_{{298.15}}^{^\circ }\)((LiPiv)_4(gas)) ≤ –3017 kJ/mol.

中文翻译：

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根据高温质谱数据分析新戊酸锂的热力学特性

摘要

新戊酸锂 (CH ₃ ) ₃ CCOOLi (LiPiv)的蒸发通过 Knudsen 渗出法和气相质谱分析进行了研究。饱和蒸汽由多核分子(LiPiv) _{n 组成}，主要是(LiPiv) ₂和(LiPiv) ₄分子。计算了这些分子分压的绝对值及其对温度的依赖性。饱和蒸气主要成分的标准升华焓确定为\({{\Delta }_{s}}H_{{298}}^{^\circ }\) (LiPiv) ₂ = 174.2 ± 6.6 kJ/mol 和\({{\Delta }_{s}}H_{{298}}^{^\circ }\) (LiPiv) ₄= 195.7 ± 4.5 kJ/mol。二聚体分子解离为单体分子和四聚体分子解离为二聚体分子的焓由热力学第二和第三定律计算；这些焓的平均值为\({{\Delta }_{D}}H_{{298}}^{^\circ }\) (LiPiv) ₂ = 175.8 ± 13.5 kJ/mol 和\({{\ Delta }_{D}}H_{{298}}^{^\circ }\) (LiPiv) ₄ = 155.2 ± 10.0 kJ/mol。LiPiv 在凝聚态和气相中的标准生成焓是根据已知的醋酸锂和醋酸和新戊酸自由基的热力学特性估算的：\({{\Delta }_{f}}H_{{298.15}}^ {^\circ }\) (LiPiv _solid ) ≤ –804 kJ/mol,\({{\Delta }_{f}}H_{{298.15}}^{^\circ }\) (LiPiv _gas ) ≤ –627 kJ/kmol, \({{\Delta }_{f}}H_ {{298.15}}^{^\circ }\) ((LiPiv) _2(gas) ) ≤ –1430 kJ/mol，和\({{\Delta }_{f}}H_{{298.15}}^{ ^\circ }\) ((LiPiv) _4(gas) ) ≤ –3017 kJ/mol。