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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 30, Number 7
BKCSDE 30(7)
July 20, 2009

Title	Kinetic Studies on the Nucleophilic Substitution Reaction of 4-X-Substituted-2,6-dinitrochlorobenzene with Pyridines in MeOH-MeCN Mixtures
Author	Ryun Youn Sung, Hojune Choi, Jong Pal Lee, Jong Keun Park, Kiyull Yang, In Sun Koo
Keywords	Hydrogen bond, SNAr-Ad.E mechanism, Cross-interaction constants, Isodielectric solvents, Isokinetic solvent mixtures
Abstract	The reaction rates of 4-X-2,6-dinitrochlorobenzenes (X = NO₂, CN, CF₃) with Y-substituted pyridines (Y = 3-OCH₃, H, 3-CH₃, 4-CH₃) in methanol-acetonitrile mixtures were measured by conductometry at 25 oC. It was observed that the rate constant increased in the order of X = 4-NO₂ > 4-CN > 4-CF₃ and the rate constant also increased in the order of Y = 4-CH₃ > 3-CH₃ > H > 3-OCH₃. When the solvent composition was varied, the rate constant increased in order of MeCN > 50% MeOH > MeOH. The electrophilic catalysis by methanol may be ascribed to the formation of hydrogen bonds between alcoholic hydrogen and nitrogen of pyridines in ground state. Based on the transition parameters, ρ_S, ρ_N, β_Y, ρ_XY and solvent effects, the reaction seems to proceed via S_NAr-Ad.E mechanism. We also estimated the isokinetic solvent mixtures (ρ_XY = 0) based on cross-interaction constants, where the substituent effects of the substrate and nucleophile are compensated.
Page	1579 - 1582
Full Text	PDF

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