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Nucleophilic Displacement Reaction of Benzyl Systems

苄基体系的亲核置换反应

基本信息

批准号：
06044264
负责人：
TSUNO Yuho
金额：
--
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Overseas Scientific Survey.
财政年份：
1994
资助国家：
日本
起止时间：
1994 至无数据
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06044264/
关键词：
Nucleophilic Substitution Benzyl Tosylates Duality of S_N1 and S_N2 Menschutkin Reaction ^<18>O-Scrambling Stability of Carbocations Laser Flash Photolysis

项目摘要

Nucleophilic substitution reaction of substituted benzyl arenesulfonates with a series of substituted N,N-dimethyl anilines in acetonitrile have been studied over a range of DMA concentrations. It is found that benzyl tosylates having more electron-releasing substituents than p-OMe-m-Cl have concurrent first-and second-order rates with respect to DNA.The ^<18>O-scrambling within starting sulfonate during the Menschutkin reaction of p-methoxybenzyl-1-^<13>C tosylate-S^<18>O_2 with N,N-dimethylanilines which is typical S_N2 displacement reaction, was determined in MeCN utilizing the split ^<13>C-NMR signals of alkoxy carbon induced by ^<18>O/^<16>O isotopic substitution. It has been shown that the carbocationic intermediates exist in the typical S_N2 reaction in non-solvolyzing solvent MeCN,leading to the conclusion that the S_N1 and S_N2 processes are quite distinct that these results afford no evidence for a singly mechanism intermediate between S_N1 and S_N2 in this reaction.The gas p … More hase basicities of cis 2-aryl-2-butenes have been determined by measuring proton transfer equilibria. It has been shown that the substituent effect on the stability of the conjugate acid ion of the olefin, alpha-ethyl-alpha-methylbenzyl cation, is in complete agreement with that of alpha-cumyl cation, suggesting that alpha, alpha-dialkyl benzyl cations can be characterized by the r value of 1.0 given by the LArSR analysis. This allows us to estimate the torsional angle (rheta) between the benzylic site and the benzene system from the r value of the twisted alpha, alpha-dialkylbenzyl cation and r_<max>=1.0 for the planar alpha, alpha-dialkylbenzyl cation by the equation r/r_<max>=cosrheta, giving rheta=29^o for alpha-t-butyl-alpha-methylbenzyl cation.The decay rate constants of beta-substituted alpha-p-methoxyphenylvinyl cations which are generated by the laser flash photolysis techniques have been determined in acetonitrile involving a small amount of ethanol. The change of rate constants with beta-substituents could be interpreted by the change in stability of vinyl cations and in steric hindrance around cationic center. On the contrary, exalted rate constants observed for beta-cyclobutylidene and beta-cycloheptylidene derivatives cannot be explained simply. Less

研究了取代芳基苯磺酸盐与一系列取代N，N-二甲基苯胺在乙腈中的亲核取代反应。研究发现，与p-OME-m-Cl相比，具有更多电子释放基团的对甲苯磺酸盐相对于DNA具有同时的一级和二级反应速率。在对甲氧基苄基-1-甲苯磺酸酯-S^&lt；18&gt；O_2与N，N-二甲基苯胺的Menschutkin反应中，利用^&lt；13&gt；碳氧碳的裂解核磁共振信号，在MeCN中发现了烷氧碳的^&lt；13&gt；C-核磁共振信号。O/^&lt；16&O同位素替代。结果表明，在非溶剂化的MeCN溶剂中，典型的S_N_2反应中存在碳阳离子中间体，从而得出结论：S_N_1和S_N_2过程是截然不同的，这些结果不能证明在该反应中S_N_1和S_N_2之间存在单一的中间机理。气体p…通过测定质子转移平衡，测定了顺式2-芳基-2-丁烯的更多碱性。结果表明，取代基对烯烃共轭酸阳离子α-乙基-α-甲基苄基阳离子稳定性的影响与对α-异丙基阳离子稳定性的影响完全一致，表明α，α-二烷基苄基阳离子可以用LArSR分析的r值1.0来表征。这使得我们可以根据平面α，α-二烷基苄阳离子扭曲的r值和r_&lt；max&gt；=1.0通过方程r/r_&lt；max&gt；=COSUTRA来估算苄基中心和苯系之间的扭转角(Rheta)，对于α-叔丁基-α-甲基苄基阳离子，Rheta=29^o。反应速率常数随β-取代基的变化可以用乙烯基阳离子稳定性的变化和阳离子中心周围空间位阻的变化来解释。相反，观察到的β-环丁叉和β-环庚叉衍生物的升高的速率常数不能简单地解释。较少