24573-38-4Relevant academic research and scientific papers
Kinetic study on aminolysis of aryl X-substituted-cinnamates in acetonitrile: Differential medium effect determines reactivity and reaction mechanism
Um, Ik-Hwan,Bae, Ae-Ri,Dust, Julian M.
, p. 13 - 19 (2019/01/10)
A kinetic study on nucleophilic substitution reactions of 2,4-dinitrophenyl X-substituted-cinnamates (1a-1f) and Y-substituted-phenyl cinnamates (2a-2g) with a series of alicyclic secondary amines in MeCN at 25.0 ± 0.1 °C is reported. The Br?nsted-type pl
Kinetic study on alkaline hydrolysis of Y-substituted phenyl X-substituted benzenesulfonates: Effects of changing nucleophile from azide to hydroxide ion on reactivity and transition-state structure
Moon, Ji-Hyun,Kim, Min-Young,Han, So-Yeop,Um, Ik-Hwan
, p. 1563 - 1568 (2015/08/11)
Second-order rate constants (kOH-) for alkaline hydrolysis of 2,4-dinitrophenyl X-substituted benzenesulfonates (1a-1f) and Y-substituted phenyl 4-nitrobezenesulfonates (2a-2g) have been measured spectrophotometrically. Comparison of kOH/
Kinetic study on alkaline hydrolysis of Y-substituted phenyl picolinates: Effects of modification of nonleaving group from benzoyl to picolinyl on reactivity and reaction mechanism
Kim, Myung-Joo,Kim, Min-Young,Um, Ik-Hwan
, p. 1138 - 1142 (2015/07/15)
Second-order rate constants (kOH-) for alkaline hydrolysis of Y-substituted phenyl picolinates (6a-6i) have been measured spectrophotometrically. A linear Bronsted-type plot is obtained with βlg = -0.34, which is typical for reactions reported previously to proceed through a stepwise mechanism with formation of an addition intermediate being the rate-determining step (RDS). However, σYo constants result in a much poorer Hammett correlation than σY- constants. Furthermore, the Yukawa-Tsuno plot exhibits an excellent linear correlation with ρY = 0.82 and r = 0.72, indicating that a negative charge develops partially on the O atom of the leaving group in the RDS. Thus, the reactions have been concluded to proceed through a forced concerted mechanism with a highly unstable intermediate 7. Comparison of the current kinetic data with those reported previously for the corresponding reactions of Y-substituted phenyl benzoates has revealed that modification of the nonleaving group from benzoyl to picolinyl causes not only an increase in reactivity but also a change in the reaction mechanism (i.e., from a stepwise mechanism to a forced concerted pathway).
Study on the transesterification of methyl aryl phosphorothioates in methanol promoted by Cd(II), Mn(II), and a synthetic Pd(II) complex
Edwards, David R.,Neverov, Alexei A.,Brown, R. Stan
scheme or table, p. 1786 - 1797 (2011/04/23)
Methanol solutions containing Cd(II), Mn(II), and a palladacycle, (dimethanol bis(N,N-dimethylbenzylamine-2C,N)palladium(II) (3), are shown to promote the methanolytic transesterification of O-methyl O-4-nitrophenyl phosphorothioate (2b) at 25 °C with impressive rate accelerations of 10 6-1011 over the background methoxide promoted reaction. A detailed mechanistic investigation of the methanolytic cleavage of 2a-d having various leaving group aryl substitutions, and particularly the 4-nitrophenyl derivative (2b), catalyzed by Pd-complex 3 is presented. Plots of k obs versus palladacycle [3] demonstrate strong saturation binding to form 2b:3. Numerical fits of the kinetic data to a universal binding equation provide binding constants, Kb, and first order catalytic rate constants for the methanolysis reaction of the 2b:3 complex (kcat) which, when corrected for buffer effects, give corrected (kcat corr) rate constants. A sigmoidal shaped plot of log(k catcorr) versus sspH (in methanol) for the cleavage of 2b displays a broad sspH independent region from 5.6 ≥ sspH ≥ ~10 with a k minimum = (1.45 ± 0.24) × 10-2 s-1 and a [lyoxide] dependent wing plateauing above a kinetically determined sspKa of 12.71 ± 0.17 to give a k maximum = 7.1 ± 1.7 s-1. Bronsted plots were constructed for reaction of 2a-d at sspH 8.7 and 14.1, corresponding to reaction in the midpoints of the low and high s spH plateaus. The Bronsted coefficients (βLG) are computed as -0.01 ± 0.03 and -0.86 ± 0.004 at low and high sspH, respectively. In the low sspH plateau, and under conditions of saturating 3, a solvent deuterium kinetic isotope effect of kH/kD = 1.17 ± 0.08 is observed; activation parameters (ΔHPd? = 14.0 ± 0.6 kcal/mol and ΔSPd?= -20 ± 2 cal/mol?K) were obtained for the 3-catalyzed cleavage reaction of 2b. Possible mechanisms are discussed for the reactions catalyzed by 3 at low and high sspH. This catalytic system is shown to promote the methanolytic cleavage of O,O-dimethyl phosphorothioate in CD3OD, producing (CD3O)2P=O(S-) with a half time for reaction of 34 min.
Structure and mechanism of PhnP, a phosphodiesterase of the carbon-phosphorus lyase pathway
He, Shu-Mei,Wathier, Matthew,Podzelinska, Kateryna,Wong, Matthew,McSorley, Fern R.,Asfaw, Alemayehu,Hove-Jensen, Bjarne,Jia, Zongchao,Zechel, David L.
experimental part, p. 8603 - 8615 (2012/07/27)
PhnP is a phosphodiesterase that plays an important role within the bacterial carbon-phosphorus lyase (CP-lyase) pathway by recycling a "dead-end" intermediate, 5-phospho-α-d-ribosyl 1,2-cyclic phosphate, that is formed during organophosphonate catabolism
Pitfalls in assessing the α-effect: Reactions of substituted phenyl methanesulfonates with HOO-, OH-, and substituted phenoxides in H2O
Um, Ik-Hwan,Im, Li-Ra,Buncel, Erwin
supporting information; experimental part, p. 8571 - 8577 (2011/03/20)
Toward resolving the current controversy regarding the validity of the α-effect, we have examined the reactions of Y-substituted phenyl methanesulfonates 1a-1l with HOO-, OH-, and Z-substituted phenoxides in the gas phase versus solu
Analysis of linear free-energy relationships combined with activation parameters assigns a concerted mechanism to alkaline hydrolysis of X-substituted phenyl diphenylphosphinates
Um, Ik-Hwan,Han, Jeong-Yoon,Hwang, So-Jeong
supporting information; experimental part, p. 7324 - 7330 (2009/08/07)
A kinetic study is reported for alkaline hydrolysis of X-substituted phenyl diphenylphosphinates (1a-i). The Bronsted-type plot for the reactions of 1a-i is linear over 4.5 pKa units with βlg= -0.49, a typical βlg value for reactions which proceed through a concerted mechanism. The Hammett plots correlated with σo and σ- constants are linear but exhibit many scattered points, while the corresponding Yukawa-Tsuno plot results in excellent linear correlation with ρ= 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 (DN + AN) mechanism is also ruled out on the basis of the small βlg value. As the substituent X in the leaving group changes from H to 4-NO2 and 3,4-(NO2)2, ΔH≠ decreases from 11.3 kcal mol-1 to 9.7 and 8.7 kcal mol-1, respectively, while ΔS≠ 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 1a-i.
Aminolyses of aryl diphenylphosphinates and diphenylphosphinothioates: Effect of modification of electrophilic center from P=O to P=S
Um, Ik-Hwan,Akhtar, Kalsoom,Shin, Young-Hee,Han, Jeong-Yoon
, p. 3823 - 3829 (2008/02/02)
(Chemical Equation Presented) A kinetic study is reported for aminolysis of aryl diphenylphosphinothioates (2a-i). The phosphinothioates 2a-i are less reactive than aryl diphenylphosphinates (1a-i), the oxygen analogues of 2a-i, regardless of the basicity
Alkaline phosphatase mono- and diesterase reactions: Comparative transition state analysis
Zalatan, Jesse G.,Herschlag, Daniel
, p. 1293 - 1303 (2007/10/03)
Enzyme-catalyzed phosphoryl transfer reactions have frequently been suggested to proceed through transition states that are altered from their solution counterparts. Previous work with Escherichia coli alkaline phosphatase (AP), however, suggests that thi
Kinetics and mechanistic study of the reaction of cyclic anhydrides with substituted phenols. Structure-reactivity relationships
Andres, Gabriel O.,De Rossi, Rita H.
, p. 1445 - 1449 (2007/10/03)
(Chemical Equation Presented) The kinetic of the reactions of phthalic and maleic anhydrides with different substituted phenols (Z-PhOH with Z = H, m-CH3, p-CH3, m-Cl, p-Cl, and m-CN) were studied in aqueous solution. Two kinetic processes well separated in time were observed. The fast one is attributed to the formation of the aryl ester in equilibrium with the anhydride and allows the determination of the rate of nucleophilic attack of the phenol on the anhydride (k-A). From the slow kinetic process, the equilibrium constant for this reaction was determined. The Broensted-type plots for the nucleophilic attack of substituted phenols on the anhydrides were linear with slopes βNuc of 0.45 and 0.56 for phthalic and maleic anhydride, respectively. The results are consistent with a mechanism involving rate-determining nucleophilic attack and also with a concerted mechanism. The calculated effective charge on the atoms involved in the reactions and the Broensted β values are consistent with a mechanism involving a concerted or enforced concerted mechanism where a tetrahedral intermediate with significant lifetime is not formed along the reaction coordinate. The latter mechanism is preferred over the stepwise process.
