Nucleophilic substitution on nitrogen. Kinetics of reactions of hydroxylamine-O-sulfonate ion
Nucleophilic substitution on nitrogen. Kinetics of reactions of hydroxylamine-O-sulfonate ion
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DOI：
10.1021/ic50129a043
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发表时间：
1973-11
影响因子：
4.6
通讯作者：
J. H. Krueger;P. Blanchet;A. Lee;B. Sudbury
中科院分区：
文献类型：
--
作者：
J. H. Krueger;P. Blanchet;A. Lee;B. Sudbury
在水和 50 wt% 甲醇-水中测量了羟胺-O-磺酸根离子 H2N0S03" 与亲核试剂 (C6H5) 3P 和 (C2HS) 3N 的反应动力学。对于每个反应，观察到 d 型 [H2N0S03-]/df= fc2 [H2N0S03~][Nu] 的速率定律。提出的机理对于每个系统涉及氮原子上的亲核取代，以SO4 2- 作为离去基团，观察到的亲核性顺序是(C6H5)3P>I">(C2H5)3N>Br-、Cl-。一个显着的结果是当氮孤电子对质子化形成分子H3N0S03时H2N0S03的反应性降低。 H2N0S03"反应中观察到的氘同位素效应，与 D20 中的 D2N0S03-相比，(C6H5) 3P 的 are/chAd= 1.5，(C6H5) 3P 的 are/chAd= 1.3。用 CH3 或 C6H5C (0) 取代 H 大大降低了反应性，表明过渡态存在较大的空间影响。
Kinetics of the reactions of hydroxylamine-O-sulfonate ion, H2N0S03", with the nucleophiles,(C6H5) 3P, and (C2HS) 3N have been measured in water and in 50 wt% methanol-water. For each reaction a rate law of the type-d [H2N0S03-]/df= fc2 [H2N0S03~][Nu] was observed. The mechanism proposed for each system involvesnucleophilic substitution on the nitrogen atom, with S04 2-as the leaving group. The order of nucleophilicities observed is (C6H5) 3P> I">(C2H5) 3N> Br-, Cl-. A significant result is the decrease in reactivityof H2N0S03-upon protonation of the nitrogen lone pair to form molecular H3N0S03. Deuterium isotope effects observed for reaction of H2N0S03", compared with D2N0S03-in D20, are/chAd= 1.5 for (C6H5) 3P and 1.3 for. Replacement of H by CH3 or C6H5C (0) greatly decreases reactivity, suggesting a large steric influence in the transition state.