The effect of solvent on the α-effect: CO, PO and SO2 centers

Um, Ik‐Hwan; Hong, Jin-Young; Buncel, Erwin

doi:10.1039/b007000i

Cited by 40 publications

(50 citation statements)

References 18 publications

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“…Numerous studies have been performed to enhance the rate of decomposition of toxic organophosphorus compounds 5–12. The use of α‐nucleophiles such as HOO − , o ‐iodosylbenzoate and various oximate anions have been reported to be highly effective to destroy such toxic materials under mild conditions 5–9. Besides, various metal ions have shown significant catalytic effects as Lewis acid catalysts in reactions of various organophosphorus compounds 10–12…”

Section: Introductionmentioning

confidence: 99%

“…[5][6][7][8][9][10][11][12] The use of a-nucleophiles such as HOO À , o-iodosylbenzoate and various oximate anions have been reported to be highly effective to destroy such toxic materials under mild conditions. [5][6][7][8][9] Besides, various metal ions have shown significant catalytic effects as Lewis acid catalysts in reactions of various organophosphorus compounds. [10][11][12] However, mechanistic (experimental and theoretical) studies have been performed much less intensively.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of Linear Free‐Energy Relationships Combined with Activation Parameters Assigns a Concerted Mechanism to Alkaline Hydrolysis of X‐Substituted Phenyl Diphenylphosphinates

Han

Hwang

2008

Chemistry A European J

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A kinetic study is reported for alkaline hydrolysis of X-substituted phenyl diphenylphosphinates (1 a-i). The Brønsted-type plot for the reactions of 1 a-i is linear over 4.5 pK(a) units with beta(lg)=-0.49, a typical beta(lg) value for reactions which proceed through a concerted mechanism. The Hammett plots correlated with sigma(o) and sigma(-) constants are linear but exhibit many scattered points, while the corresponding Yukawa-Tsuno plot results in excellent linear correlation with rho=1.42 and r=0.35. The r value of 0.35 implies that leaving-group departure is partially advanced at the rate-determining step (RDS). A stepwise mechanism, in which departure of the leaving group from an addition intermediate occurs in the RDS, is excluded since the incoming HO(-) ion is much more basic and a poorer nucleofuge than the leaving aryloxide. A dissociative (D(N) + A(N)) mechanism is also ruled out on the basis of the small beta(lg) value. As the substituent X in the leaving group changes from H to 4-NO(2) and 3,4-(NO(2))(2), DeltaH++ decreases from 11.3 kcal mol(-1) to 9.7 and 8.7 kcal mol(-1), respectively, while DeltaS++ varies from -22.6 cal mol(-1) K(-1) to -21.4 and -20.2 cal mol(-1) K(-1), respectively. Analysis of LFERs combined with the activation parameters assigns a concerted mechanism to the current alkaline hydrolysis of 1 a-i.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of Linear Free‐Energy Relationships Combined with Activation Parameters Assigns a Concerted Mechanism to Alkaline Hydrolysis of X‐Substituted Phenyl Diphenylphosphinates

Han

Hwang

2008

Chemistry A European J

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“…[9][10][11][12][13][14] Our study has now been extended to nucleophilic substitution reactions of 2-chloro-4-nitrophenyl X-substitutedbenzo-ates (1a-h) with a series of primary amines including hydrazine to investigate the origin of the -effect. We have also studied the reaction mechanism of the aminolysis of 1a-h through linear free energy relationships such as Brønsted-type, Hammett, and Yukawa-Tsuno plots.…”

Section: Origin Of the -Effect In Reaction Of Aryl Benzoates With Hymentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] Thus, the enhanced nucleophilic reactivity has been termed the -effect by Edward and Pearson in 1962. 1 Numerous studies have been performed to investigate the origin of the -effect.…”

Section: Introductionmentioning

confidence: 99%

“…1 Numerous studies have been performed to investigate the origin of the -effect. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Some important theories suggested as the origin of the -effect are (1) destabilization of the ground state (GS) of the -effect nucleophile due to the electronic repulsion between the adjacent nonbonding electron pairs, (2) stabilization of the transition state (TS), (3) thermodynamic stability of products, and (4) solvent effect. 2 Among them, solvent effect on the -effect has most intensively been studied.…”

Section: Introductionmentioning

confidence: 99%

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Kinetic Study on Nucleophilic Displacement Reactions of 2-Chloro-4-Nitrophenyl X-Substituted-Benzoates with Primary Amines: Reaction Mechanism and Origin of the α-Effect

Um¹,

Kim²,

Kim³

et al. 2014

Bulletin of the Korean Chemical Society

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Second-order rate constants for aminolysis of 2-chloro-4-nitrophenyl X-substituted-benzoates (1a-h) have been measured spectrophotometrically in 80 mol % H 2 O/20 mol % DMSO at 25.0 o C. The Brønsted-type plot for the reactions of 2-chloro-4-nitrophenyl benzoate (1d) with a series of primary amines curves downward, which has been taken as evidence for a stepwise mechanism with a change in rate-determining step (RDS). The Hammett plots for the reactions of 1a-h with hydrazine and glycylglycine are nonlinear while the YukawaTsuno plots exhibit excellent linearity with  X = 1.22-1.35 and r = 0.57-0.59, indicating that the nonlinear Hammett plots are not due to a change in RDS but are caused by stabilization of substrates possessing an electron-donating group (EDG) through resonance interactions between the EDG and C=O bond of the substrates. The -effect exhibited by hydrazine increases as the substituent X changes from a strong EDG to a strong electron-withdrawing group (EWG). It has been concluded that destabilization of hydrazine through the electronic repulsion between the adjacent nonbonding electrons is not solely responsible for the substituent dependent -effect but stabilization of the transition state is also a plausible origin of the -effect.

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Kinetic Study on Nucleophilic Substitution Reactions of Aryl Diphenylphosphinates with Butane‐2,3‐dione Monoximate and Aryloxide Anions: Reaction Mechanism and Origin of the α‐Effect

Han²

2016

Bulletin Korean Chem Soc

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A kinetic study is reported for nucleophilic substitution reactions of X‐substituted‐phenyl diphenylphosphinates (3a–3f) with butane‐2,3‐dione monoximate (Ox−) and a series of Y‐substituted‐phenoxide (Y‐PhO−) ions in 50 mol % H2O/50 mol % DMSO at 25.0 ± 0.1°C. The reactions of 3a–3f with Ox− and 4‐chlorophenoxide (4‐ClPhO−) result in linear Brønsted‐type plots with βlg = −0.70 and −0.64, respectively, a typical βlg value for reactions reported previously to proceed through a concerted mechanism. The Brønsted‐type plots for the reactions of 4‐chloro‐2‐nitrophenyl diphenylphosphinate (3a), 4‐nitrophenyl diphenylphosphinate (3b), and 4‐acetylphenyl diphenylphosphinate (3d) with Y‐PhO− are also linear with βnuc = 0.15–0.35. The current reactions have been concluded to proceed through a concerted mechanism in which the bond formation is much less advanced than the bond rupture in the TS on the basis of the βlg and βnuc values. The α‐effect observed in this study is very small (i.e., the kOxprefix−/kp‐ClPhO− ratio = 16.4 – 43.5) and is independent of the leaving‐group basicity. It has been concluded that the α‐effect shown by Ox− in the current reactions is mainly due to desolvation of Ox− in the reaction medium (ground‐state contribution) rather than stabilization of the transition‐state (TS contribution) on the basis of the kinetic results.

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The effect of solvent on the α-effect: CO, PO and SO2 centers

Cited by 40 publications

References 18 publications

Analysis of Linear Free‐Energy Relationships Combined with Activation Parameters Assigns a Concerted Mechanism to Alkaline Hydrolysis of X‐Substituted Phenyl Diphenylphosphinates

Analysis of Linear Free‐Energy Relationships Combined with Activation Parameters Assigns a Concerted Mechanism to Alkaline Hydrolysis of X‐Substituted Phenyl Diphenylphosphinates

Kinetic Study on Nucleophilic Displacement Reactions of 2-Chloro-4-Nitrophenyl X-Substituted-Benzoates with Primary Amines: Reaction Mechanism and Origin of the α-Effect

Kinetic Study on Nucleophilic Substitution Reactions of Aryl Diphenylphosphinates with Butane‐2,3‐dione Monoximate and Aryloxide Anions: Reaction Mechanism and Origin of the α‐Effect

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