64993-95-9Relevant academic research and scientific papers
Kinetics and mechanism of alkaline hydrolysis of Y-substituted phenyl phenyl carbonates
Kim, Song-I,Hwang, So-Jeong,Jung, Eun-Mi,Um, Ik-Hwan
experimental part, p. 2015 - 2018 (2010/12/19)
Second-order rate constants (kOH-) have been measured spectrophotometrically for alkaline hydrolysis of Y-substituted phenyl phenyl carbonates (2a-j) and compared with the kOH- values reported previously for the corresponding reactions of Y-substituted phenyl benzoates (1a-j). Carbonates 2a-j are 8 ～ 16 times more reactive than benzoates 1a-j. The Hammett plots correlated with σ- and σo constants exhibit many scattered points, while the Yukawa-Tsuno plot results in excellent linear correlation with ρ = 1.21 and r = 0.33. Thus, the reaction has been concluded to proceed through a concerted mechanism in which expulsion of the leaving group is advanced only a little. However, one cannot exclude a possibility that the current reaction proceeds through a forced concerted mechanism with a highly unstable intermediate.
Do electrostatic interactions with positively charged active site groups tighten the transition state for enzymatic phosphoryl transfer?
Nikolic-Hughes, Ivana,Rees, Douglas C.,Herschlag, Daniel
, p. 11814 - 11819 (2007/10/03)
The effect of electrostatic interactions on the transition-state character for enzymatic phosphoryl transfer has been a subject of much debate. In this work, we investigate the transition state for alkaline phosphatase (AP) using linear free-energy relationships (LFERs). We determined fcat/K M for a series of aryl sulfate ester monoanions to obtain the Bronsted coefficient, βIg, and compared the value to that obtained previously for a series of aryl phosphorothioate ester dianion substrates. Despite the difference in substrate charge, the observed Bronsted coefficients for AP-catalyzed aryl sulfate and aryl phosphorothioate hydrolysis (-0.76 ± 0.14 and -0.77 ± 0.10, respectively) are strikingly similar, with steric effects being responsible for the uncertainties in these values. Aryl sulfates and aryl phosphates react via similar loose transition states in solution. These observations suggest an apparent equivalency of the transition states for phosphorothioate and sulfate hydrolysis reactions at the AP active site and, thus, negligible effects of active site electrostatic interactions on charge distribution in the transition state.
REACTIONS OF IMIDIC ACID DERIVATIVES WITH NUCLEOPHILIC REAGENTS. MECHANISM OF THE ALKALINE HYDROLISIS OF ARYL N-ARYLARENECARBOXIMIDATES
Prudchenko, A. P.,Drizhd, L. P.,Savelova, V. A.
, p. 1715 - 1719 (2007/10/02)
In the kinetics of the alkaline hydrolysis of aryl-N-phenylbenzimidates PhC(OArX) =NPh(I) in a water-dioxane mixture (1:1 by volume) and with a constant ionic strength in 0.2 M sodium perchlorate first order is observed in each of the reagents.The Hammett ρ and Bronsted β parameters with variation of the substituent in the leaving group are 1.6 and -0.35 respectively.The products from the hydrolysis of compounds (I) (X = 2,4-(NO2)2, 2-NO2-4-COCH3) are benzoic acid and substituted diphenylamines and, in the case of the derivatives of (I) benzanilide and the corresponding phenol.In spite of the different qualitative composition of the hydrolysis products the data for all the substituents (including the ortho substituents) satisfy the Hammett and Bronsted equations.The results are explained in terms of an addition-elimination stage mechanism with the formation of a tetrahedral intermediate product in the rate-determining stage.
Dehydrobromination of Some Substituted Phenyl 3-Bromopropionates and Phenyl 3-Bromothiolopropionates. Transmission of Activation Effects through Acyl Bonds
Gilbert, Arthur B.,Peters, Frances B.,Johnson, H. W.
, p. 2724 - 2728 (2007/10/02)
Thirteen aryl 3-bromopropionates and nine aryl 3-bromothiolopropionates were prepared and subjected to dehydrohalogenation with sodium 3,4-dinitrophenoxide in dry tetrahydrofuran at 34.25 deg C.The second-order rate constants for the sulfur esters were approximately 10 times those for the corresponding oxygen esters.Good Hammett plots with ρ's of +0.81+/-0.04 and 0.98+/-0.04 for the oxygen and sulfur series, respectively, were obtained by using ?n.Activation parameters were measured for two oxygen and two sulfur esters; in both bases, low (12-13 kcal/mol) activatio n enthalpies and moderately large negative (19-21 eu) activation entropies were found.At 34.25 deg C, 3'-nitrophenyl 3-bromopropionate dehydrohalogenated 14 times more rapidly than 3'-nitrophenyl 3-chloropropionate; phenyl 3-bromothiolopropionate dehydrohalogenated 11 times more rapidly than the phenyl 3-chlorothiolopropionate.The rate constant ratio for 4'-bromophenyl 3-bromopropionate vs. 4'-bromophenyl 3-bromopropionate-2-d was 1.84; the monodeuterated compound yielded olefinic product with 65percent D.H was abstracted preferentially from 4'-chlorophenyl 3-bromothiolopropionate partially deuterated in the 2-position, but no kinetic results were obtained.No evidence of reversibility was found with 2,4-dinitrophenol-d, and the addition of 2,4-dinitrophenol to kinetic mixtures had essentially no effect on the rate conatants.The results are interpreted to indicate an E2 process near the EL/E1cB borderline with the thiolo ester deviating somewhat more toward an E1cB-I process.
