4-Nitrophenyl benzoate

FIGURE 8. Hammett plots for reactions of 4-nitrophenyl benzoate (PNPB) with Z-substituted acetophenone oximates ( ) and phenoxides (O) in 20 mol% DMSO (A) and 90 mol% DMSO (B) at 25.0 0.1 °C. Reprinted from Tetrahedron Lett., 36, Um, Oh and Kwon, 6903, Copyright (1995), with permission from Elsevier... 

The reactions of 4-nitrophenyl benzoate and O-4-nitrophenyl X-thionobenzoates (25) with a series of pyridines in 20 mol% DMSO were studied at 25 °C (Scheme 8). O-4-Nitrophenyl thionobenzoate (25 X = H) was more reactive than its oxygen... 

Sodium acetate reacts with 4-nitrophenyl benzoates to give mixed anhydrides when the reaction is conducted in a polar aprotic solvent in the presence of a crown ether. The reaction is strongly accelerated by a quaternary nitrogen substituent in the ortho position. Suggest an explanation for this substituent effect. 

Transesterification of 4-nitrophenyl benzoate (6 Y = 4-N02) with a series of Z-substituted phenoxides (7 Z = 4-Me, H, 3-Cl, 4-MeCO, 4-CN) and of a series of eight Y-phenyl benzoates (6) by 4-chlorophenoxide (7 Z = 4-Cl) (Scheme 3) in H2O/DMSO (dimethylsulfoxide) (4 1) at 298 K both exhibited linear Brpnsted plots with slopes, respectively, of /Sjjuc = 0.72 and /Sjg = -0.62, the magnitude of each value indicating a concerted mechanism for both reactions. ... 

The values of k /k. and Kg vary from 6.1 to 5.3 and 25 to 5 M- respectively, with the change from least reactive 3-methylphenyl benzoate to most reactive 4-nitrophenyl benzoate. It is interesting to note that the values of r ain nearly the same for various phenyl benzoates with both 1 and 2, but the values of are 2- to 4-fold smaller in the presence of 2 than the corresponding k values in the presence of 1. Significantly lower values of k, with 2 compared to those with 1 may be attributed to the destabilization of anionic transition by the ionized carboxylic group in 2. 

These are absorbance-time data for the hydrolysis of p-nitrophenyl benzoate in aqueous solution. 

The effect of solvation on the cr-effect has been studied by Curci and Di Furia (1975) for the reactions of t-BuOK and t-BuOOK with p-nitrophenyl diphenylphosphinate [1141 and p-nitrophenyl benzoate [115]. In water the cr-effects (rate ratios for t-BuOO and CF5CH20-) were 6.6 for [ 114] and 5.5... 

Aminolysis of phenyl dithioacetates,8 pyridinolysis of O-ethyl dithiocarbonates,9 reaction of pyrrolidine with O-ethyl 5-aryl dithiocarbonates,10 aminolysis of chlorothionformates,11 pyridinolysis of alkyl aryl thioncarbonates,12 reaction of anionic nucleophiles with nitrophenyl benzoate and its sulfur analogues,36 hydrolysis of methyl benzoate and phenyl acetate containing SMe, SOMe and S02Me substituents,42 solvolysis of phenyl chlorothioformate,79 synthesis of new thiadiazoles,124 examination of a neighbouring sulfonium group in ester hydrolysis,136 hydrolysis of V-type nerve agents,250 and the reactions of peroxymonosulfate ion with phosphorus(V) esters have all been looked at previously in this review. 

The reactions in cationic micellar media between the a-nucleophile salicylhydroxa-mate anion (SHA ) and p-nitrophenyl benzoate (PNPB), tris(3-nitrophenyl) phosphate (TRIS), and bis(2,4-dinitrophenyl) phosphate (BDNPP) were examined kinetically. SHA was incorporated into CTAB micelles and accelerated dephosphorylation of TRIS over the pH range 6.7—11.4. At 1.0 mM SHA in CTAB, the nucleophilicity of SHA followed the order of reactivity, PNPB (C=0, carboxylate ester) > TRIS (phosphate triester) > BDNPP (phosphate diester) monoanionic SHA and dianionic SHA are the reactive species. The critical micelle concentration of CTAB decreased and the fractional ionization constant, a, increased with an increase in the concentration of SHA . ... 

Some of the latest developments in terms of substrates for the Heck reactions are nitrophenyl benzoates [55], acyl benzoates (mixed anhydrides) [236], and substituted benzoic acids [53]. For the last two, the leaving groups are carbon dioxide and carbon monoxide, respectively. A variety of alkenes have been coupled with these substrates. While esters and anhydrides presumably react in a catalytic cycle like that of the classical Heck reaction [237], arenecarboxylic acids, when treated with an equimolar amount of a silver salt as reoxidant, appear to undergo a nonclassical Heck reaction as demonstrated by the coupling with 2-cyclohexenone to give a 3-arylcyclohexenone. 

Also obtained (poor yield) by Fries rearrangement of m-nitrophenyl benzoate with aluminium chloride at 170° for 2 h (11%) [536]. 

The kinetics of the ammoniolysis of p-nitrophenyl benzoate in Pr 0H-H20 mixtures showed that the mechanism was 5 2. The faster rate in solvent mixtures high in water... 

Although the reaction with thiosulfate and with iodide ions may be a mere reduction of the halide, the reaction with sodium benzoate would appear to be a radical dissociation induced by the attack of a negative ion. The fate of the benzoate ion is unknown. Tris-( -nitrophenyl)-methyl benzoate is a stable substance which does not dissociate into radicals.23... 

Recent studies of kinetic acidity involving nitrocarbon acids have included the following benzoate ion-promoted deprotonation of (3- or 4-nitrophenyl)nitromethane and (3,5-dinitrophenyl)nitromethane187 the deprotonation by various bases of a series of... 

Hubbard and Kirsch (1972) have recently proposed that histidine may act as a nucleophile in a-chymotrypsin acylation reactions of esters having a good leaving group (jO-nitrophenol). This suggestion was based on a similarity in p-value for acylation by p-substituted nitrophenyl and dinitrophenyl benzoates and nucleophilic attack on these compounds by imidazole, in contrast with less positive p-values for hydroxide ion catalysis. Hammett p-values for hydrolysis of substituted phenyl esters are given in Table 6 and show little apparent trend. The values for hydroxide ion and alcoholate ions are... 

The solvent affects the chemical equilibria of reactions. Second-order rate constants and equilibrium constants have been determined for the benzoate ion promoted deprotonation reactions of (m-nitrophenyl)nitromethane, (p-nitrophenyl)nitromethane, and (3,5-dinitrophenyl)nitromethane in methanol solution. The pKa values for the arylnitromethanes in methanol are the following pKa = 10.9, 10.5, and 9.86 for m-nitrophenyl)nitromethane, (p-nitrophenyl)nitromethane, and (3,5-dinitrophenyl)nitro-methane, respectively, relative to benzoic acid (pKa = 9.4). A Bronsted B value of... 

A Bac2 mechanism is proposed for die saponification of ethyl benzoate in ethanol-water.37 The reactions of aryl benzoates in absolute ethanol with ethoxide, aryloxides and acetophenone oximates occur via a stepwise mechanism in which the formation of the tetrahedral intermediate is rate determining.38 A stepwise mechanism is also supported for the reactions of /7-nitrophenyl-substituted benzoates with hydroxide and / -chlorophcnoxidc. The evidence comes from breaks in Hammett plots as the acyl... 

A Bronsted fl]t value of 0.5 and occh value of 1.31 have been calculated for deprotonation reactions of (3,5-dinitrophenyl)nitromethane promoted by substituted benzoate ions and of substituted (3-nitro-, 4-nitro- and 3,5-dinitro-)phenyhiitro-methanes promoted by benzoate ion, respectively, in methanol.146 The intrinsic rate constants are (2.0-6.3)x 104 tunes lower than for the same reactions in acetonitrile solution, and this has been attributed to commensurate reduction of strength of the hydrogen bond between the carbon acid and benzoate ion in the imbalanced transition state. The transfer activity coefficient (logMyAN) from methanol to acetonitrile solution have been calculated for (// -nitrophenyl)nitromcthyl anion (3.6) and (m-nitrophenyl)-nitromethane (—1.0). 

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