Nucleophilic Displacement Reaction of Benzyl Systems

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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