呂 壽東 大韓民国, 慶北大学枝・師範大学, 教授
KOBAYASHI Shinjiro Kyushu Univ., Inst.Fundamental Research of Organic Chemistry Associtate Prof, 有機化学基礎研究センター, 助教授 (20037831)
MISHIMA Masaaki Kyushu Univ., Inst.Fundamental Research of Organic Chemistry Associtate Prof, 有機化学基礎研究センター, 助教授 (20037279)
FUJIO Mizue Kyushu Univ., Inst.Fundamental Research of Organic Chemistry Associtate Prof, 有機化学基礎研究センター, 助教授 (10029887)
YOH Soo-dong Kyungpook Nat'l University, Teacher's College Professor
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
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