ACIDITIES OF CARBOXAMIDES, HYDROXAMIC ACIDS, CARBOHYDRAZIDES, BENZENESULFONAMIDES, AND BENZENESULFONOHYDRAZIDES IN DMSO SOLUTION
ACIDITIES OF CARBOXAMIDES, HYDROXAMIC ACIDS, CARBOHYDRAZIDES, BENZENESULFONAMIDES, AND BENZENESULFONOHYDRAZIDES IN DMSO SOLUTION
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DOI：
10.1021/jo00297a063
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发表时间：
1990-05-11
影响因子：
3.6
通讯作者：
WHANG, YE
中科院分区：
文献类型：
--
作者：
BORDWELL, FG;FRIED, HE;WHANG, YE
比较了六个系列的类似氧、氮、碳酸在二甲基亚砜（DMSO）溶液和气相中的酸性，发现元素效应通常使氮酸比碳酸平均酸性高17±5千卡/摩尔，氧酸比氮酸平均酸性高17±5千卡/摩尔。甲酰胺的NH酸度和酮的CH酸度之间的差异要小得多（在DMSO中为1-2 kcal/mol，在气相中为7-8 kcal/mol）。本文报道了一些取代苯甲酰胺、乙酰胺、N-苯乙酰胺、乙酰异羟肟酸、苯甲异羟肟酸、碳酰肼和苯磺酰胺在DMSO中的平衡酸度。乙酰和苯并异羟肟酸被发现是9.8和10.1 pKHA单位更酸性的DMSO，分别比乙酰胺和苯甲酰胺。在每种情况下，N-烷基化的效果比O-烷基化更能降低酸度，这表明在DMSO中，母体是NH酸，而不是OH酸。通过观察到N-烷基异羟肟酸表现出强的同氢键，而母体酸及其O-烷基衍生物没有，提供了NH酸归属的结论性支持证据。异羟肟酸根阴离子在DMSO中的氧化电位接近于O-烷基异羟肟酸根离子的氧化电位，证实它们的共轭酸是NH酸，但在MeOH中它们接近于N-烷基异羟肟酸根离子的氧化电位，表明它们的共轭酸在羟基溶剂中可以作为OH酸。N-烷基和O-烷基异羟肟酸对K ~+、Na ~+和Li ~+离子的螯合能力比母体酸强得多，含氧酸比含氮酸酸性强，含氮酸比类似的碳酸酸性强，但一直缺乏定量数据。然而，最近的气相测量表明，含氧酸，如苯酚或水，比它们的含氮酸对应物苯胺和氨的酸性高12千卡/升或更多。
A comparison of acidities of six series of analogous oxygen, nitrogen, and carbon acids in dimethyl sulfoxide (DMSO) solution and the gas phase has shown that the element effect usually causes nitrogen acids to be more acidic thantheir carbon acid counterparts by an average of 17±5 kcal/mol, and oxygen acids to be more acidic than their nitrogen counterparts by a like amount. A much smaller difference was observed between the NH acidities of carboxamides and the CH acidities of ketones (1-2 kcal/mol in DMSO and 7-8 kcal/mol in the gas phase). Equilibrium acidities in DMSO for a number of substituted benzamides, acetamides, TV-phenylacetamides, acetohydroxamic acids, benzohydroxamic acids, carbohydrazides, and benzenesulfonamides are reported. Acetoand benzohydroxamic acids were found to be 9.8 and 10.1 pKHA units more acidic in DMSO, respectively, than acetamide and benzamide. In each instancethe effect of N-alkylation decreased the acidity more than did O-alkylation, which indicates that the parents are NH, rather than OH, acids in DMSO. Conclusive supporting evidence for the NH acid assignment was provided by the observation that the jV-alkylhydroxamic acids exhibited strong homo-H-bonding, whereas the parent acids and their O-alkyl derivatives did not. Oxidation potentials of hydroxamateanions in DMSO are close to those of O-alkylhydroxamate ions, confirming that their conjugate acids are NH acids, but in MeOH they are close to those of jV-alkylhydroxamate ions showing that their conjugate acids can act as OH acids in hydroxylic solvents. The N-alkyl-and O-alkylhydroxamic acids exhibited much stronger chelating power toward K+, Na+, and Li+ ions than did the parent acids.It has been recognized for many years that oxygen acids are more acidic than nitrogen acids and that nitrogen acids are more acidic than analogous carbon acids, but quan-titative data have been lacking. Recentgas-phase mea-surements1 have shown, however, that oxygen acids, such as phenol or water, are more acidic thantheir nitrogen acid counterparts, aniline and ammonia, by 12 or more kcal/