PROTON AFFINITIES AND AGGREGATION STATES OF LITHIUM ALKOXIDES, PHENOLATES, ENOLATES, BETA-DICARBONYL ENOLATES, CARBOXYLATES, AND AMIDATES IN TETRAHYDROFURAN
PROTON AFFINITIES AND AGGREGATION STATES OF LITHIUM ALKOXIDES, PHENOLATES, ENOLATES, BETA-DICARBONYL ENOLATES, CARBOXYLATES, AND AMIDATES IN TETRAHYDROFURAN
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DOI：
10.1021/ja00019a028
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发表时间：
1991-09-11
影响因子：
15
通讯作者：
MOE, KD
中科院分区：
文献类型：
--
作者：
ARNETT, EM;MOE, KD
标题化合物的质子亲和用它们在25℃的四氢呋喃中与二（三甲基硅基）酰胺锂（LiHMDS）反应时的去质子化热DELTA-H（deep）表示。在37℃条件下，用蒸汽压渗透法测定了浓度为0.10 M时母体酸及其锂盐的聚集数。还研究了苯酚锂在25℃下的电导率。27种不同类型的氧、氮和碳酸的δ - h（深度）s与其在二甲亚砜中公布的pK(a)s相关性相当好（R = 0.95），尽管它们在四氢呋喃中的聚集度从1到7以上不等。在某些情况下，酸的DELTA-H（深度）强烈依赖于测量时LiHMDS与酸的锂盐的浓度比。本报告中VPO确定的聚合数与以前工作人员使用几种技术获得的可用公布值一致。锂盐的聚集数与对应阴离子的碱度（以DELTA-H（deep）表示）没有明显的关系。这一观察结果以及对许多化合物的单体、二聚体、四聚体等之间的平衡的独立证据表明，不同聚集态的相对稳定性之间只有很小的差异。对硝基苯酚锂的电导数据采用Wooster分析，结果表明THF中存在离子三重态、离子对和自由离子之间的平衡。LiHMDS在这种溶剂中的电导率高得惊人，这一性质被用来证明LiHMDS与叔丁基酚酸锂之间的相互作用。
The proton affinities of the title compounds are represented by their heats of deprotonation, DELTA-H(dep), through reactions with lithium bis(trimethylsilyl)amide, LiHMDS, in tetrahydrofuran at 25-degrees-C. Aggregation numbers of the parent acid and of its lithium salt at a concentration of 0.10 M were obtained by vapor-pressure osmometry at 37-degrees-C. Lithium phenolates were also studied by conductivity at 25-degrees-C. DELTA-H(dep)s for 27 oxygen, nitrogen, and carbon acids of varied types correlate fairly well (R = 0.95)with their published pK(a)s in dimethyl sulfoxide although their degrees of aggregation in THF vary from one to over seven. In some cases, the DELTA-H(dep) of an acid is strongly dependent on the concentration ratio of LiHMDS to that of the acid's lithium salt at the time of measurement. Aggregation numbers determined by VPO in this report agree with available published values obtained by previous workers using several techniques. There is no obvious relationship between the aggregation number of the lithium salt and the basicity of the corresponding anion as represented by DELTA-H(dep). This observation along with independent evidence for equilibria betweenmonomers, dimers, tetramers, etc. for a number of compounds indicate that there are only small differences between the relative stabilities of different aggregation states. Conductance data for lithium p-nitrophenolate were treated by Wooster analysis, the results of which suggest equilibria between ion triplets, ion pairs, and free ions in THF. The conductance of LiHMDS in this solvent is surprisingly high, and this property was used to demonstrate an interaction between LiHMDS and lithium omicron-tert-butylphenolate.