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The alpha-effect in the SNAr reaction of 1-(4-nitrophenoxy)-2,4-dinitrobenzene with anionic nucleophiles: effects of solvation and polarizability on the alpha-effect
- Title
- The alpha-effect in the SNAr reaction of 1-(4-nitrophenoxy)-2,4-dinitrobenzene with anionic nucleophiles: effects of solvation and polarizability on the alpha-effect
- Authors
- Um, Ik-Hwan; Kim, Min-Young; Cho, Hyo-Jin; Dust, Julian M.; Buncel, Erwin
- Ewha Authors
- 엄익환
- SCOPUS Author ID
- 엄익환
- Issue Date
- 2015
- Journal Title
- CANADIAN JOURNAL OF CHEMISTRY
- ISSN
- 0008-4042
1480-3291
- Citation
- CANADIAN JOURNAL OF CHEMISTRY vol. 93, no. 10, pp. 1109 - 1114
- Keywords
- alpha-effect; SNAr reaction; 1-(phenoxy)-2,4-dinitrobenzene; solvation; polarizability
- Publisher
- CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS
- Indexed
- SCI; SCIE; SCOPUS
- Document Type
- Article
- Abstract
- A kinetic study on SNAr reactions of 1-(4-nitrophenoxy)-2,4-dinitrobenzene (1a) with various anionic nucleophiles in 80 mol% water - 20 mol% DMSO at 25.0 degrees C is reported. The Bronsted-type plot for the reaction of 1a with a series of substituted phenoxides and HOO- results in an excellent linear correlation with beta(nuc) = 1.17. However, OH- exhibits dramatic negative deviation from the Bronsted-type plot, while N-3(-), C6H5S-, and butane-2,3-dione monoximate (Ox(-)) deviate positively from linearity. HOO- is 680-fold more reactive than OH- but does not exhibit the alpha-effect. In contrast, Ox(-) is 166-fold more reactive than isobasic 4-Cl-C6H4O- and exhibits the alpha-effect. Differential solvation effects have been suggested to be responsible for the alpha-effect in this study, i.e., Ox(-) exhibits the alpha-effect, since it is 5.7 kcal/mol less strongly solvated than 4-Cl-C6H4O- in the reaction medium, while HOO- does not show the alpha-effect due to a strong requirement for partial desolvation before nucleophilic attack. The highly enhanced reactivity of polarizable N-3(-) and C6H5S- and extremely decreased reactivity of nonpolarizable OH- are in accord with the hard-soft acid and base principle.
- DOI
- 10.1139/cjc-2015-0073
- Appears in Collections:
- 자연과학대학 > 화학·나노과학전공 > Journal papers
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