Kinetic Study on SNAr Reactions of 1‐(Y‐Substituted‐phenoxy)‐2,4‐dinitrobenzenes with Azide Ion: Effect of Changing Nucleophile from Hydroxide to Azide Ion on Reaction Mechanism and Reactivity

Bulletin of the Korean Chemical Society

Young Kim¹  Yeop Han¹  Hwan Um¹  Ok Seo¹  Min‐²  So‐²  Hyeon‐²  Ik‐² 

[1] 750 Korea;Department of Chemistry and Nano Science Ewha Womans University Seoul 120‐

关键词: ;    SNAr reaction;    1‐;    Phenoxy‐;    2,4‐;    dinitrobenzene;    Rate‐;    determining step;    Hammett plot;    Yukawa–;    Tsuno plot;   

DOI  :  10.1002/bkcs.10333

学科分类：化学（综合）

来源: Korean Chemical Society

【 摘 要 】

Second‐order rate constants (kN3−) for SNAr reactions of 1‐(Y‐substituted‐phenoxy)‐2,4‐dinitrobenzenes (2a–2h) within 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 °C have been measured spectrophotometrically. The Brønsted‐type plot is linear with βlg = −0.38. The Hammett plots correlated withandconstants exhibit highly scattered points. In contrast, the Yukawa–Tsuno plot results in an excellent linear correlation with ρY = 1.02 and r = 0.51, indicating that a negative charge develops partially on the O atom of the leaving Y‐substituted‐phenoxy moiety in the transition state. Accordingly, the reactions have been concluded to proceed through a stepwise mechanism, in which expulsion of the leaving group occurs in the rate‐determining step. Comparison of kN3− with the kOH− values reported previously for the corresponding reactions with OH− has revealed thatis only 6‐ to 26‐fold less reactive than OH− toward substrates 2a–2h, although the former is over 11 pKa units less basic than the latter. Solvation and polarizability effects have been suggested to be responsible for the unusual reactivity shown byand OH−. Effects of changing nucleophile from OH− toon reaction mechanism and reactivity are discussed in detail.

【 授权许可】

Unknown