PKA VALUES FOR SUBSTITUTED ACETOPHENONES - VALUES DETERMINED BY STUDY OF RATES OF HALOGENATION
PKA VALUES FOR SUBSTITUTED ACETOPHENONES - VALUES DETERMINED BY STUDY OF RATES OF HALOGENATION
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DOI：
10.1139/v87-360
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发表时间：
1987-09-01
期刊：
影响因子：
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通讯作者：
KLYM, A
中科院分区：
文献类型：
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作者：
GUTHRIE, JP;COSSAR, J;KLYM, A
测定了七种对位取代苯乙酮在水溶液中的pKa值。测定是基于次氯酸与烯醇化物的扩散控制反应。苯乙酮的测定值如下：取代基，值; H，18.4;p-MeO，19.0;p-F，18.5;p-Cl，18.1;p-Br，18.0;p-NO2，16.7; p-Me 3 N+，17.1。这些pKa值的ρ为-1.95。使用文献值的烯醇含量，我们表明，这个ρ值的大部分反映烯醇化取代基的影响。在相对高的氢氧化物和低的次氯酸盐浓度下，苯乙酮氯化的主要产物是相应的扁桃酸。在类似条件下，苯乙酮溴化得到苯甲酸。
pKavalues in aqueous solution have been determined for sevenp-substituted acetophenones. The determinations are based on the diffusion-controlled reaction of an enolate with hypochlorous acid. The values determined for the acetophenones are as follows: substituent, value; H, 18.4;p-MeO, 19.0;p-F, 18.5;p-Cl, 18.1;p-Br, 18.0;p-NO2, 16.7;p-Me3N+, 17.1. ρ for these pKavalues is −1.95. Using literature values for the enol content we show that most of this ρ value reflects substituent effects upon enolization. With relatively high hydroxide and low hypochlorite concentrations the major products from chlorination of acetophenones are the corresponding mandelic acids. Under similar conditions bromination of acetophenone gives benzoic acid.