Reactions of 2,4-dinitrophenyl phosphate

Some examples of rate and binding constants for these micelle-assisted reactions are in Table 6. There are very large differences in k j /k y/ for these reactions, but the rate effects on decarboxylation are large and depend upon the charge on the head group. Reaction of 2,4-dinitrophenyl phosphate is often written as generating intermediate metaphosphate ion, but this species is so short-lived that reaction follows an enforced association mechanism (Buchwald and Knowles, 1982). 

Dephosphorylation reactions of 2,4-dinitrophenyl phosphate with benzohydroxamate and deferoxamine (DFO) (130) occur by attack at phosphorus, but because they involve attacks by monoanions on dianions, they are only modestly accelerated by these a-nucleophiles. This is in contrast to their extraordinary reactivity towards the di- and triesters of 2,4-dinitrophenyl phosphate (described in the section titled Phosphate and Phosphonate Diester and Triesters ). 

Bunton CA, Diaz S, HeUyer JM, Ihara Y, lonescu LG. Micellar effects on the reactions of 2,4-dinitrophenyl phosphate and ethyl p-nitrophenyl phosphate with amines. J Org Chem. 1975 40 2313-2317. 

Doubts have recently been expressed regarding the validity of the metaphosphate pathway for hydrolysis of the monoanion of 2,4-dinitrophenyl phosphate (111) 70,71,72) since the basicity of the 2,4-dinitrophenolate group is insufficient to produce a zwitterion corresponding to 106 or even a proton transfer via intermediates of type 103 or 105 (pKa values in water 4.07 for 2,4-dinitrophenol, 1.0 and 4.6 for 2,4-dinitrophenyl phosphate). Instead, hydrolysis and phosphorylation reactions of the anion 111 are formulated via oxyphosphorane intermediates according to 114. 

Reactions of 2,4-dinitrochloro-benzene and -naphthalene are speeded by DDDAOH and the corresponding chloride -I- NaOH (Cipiciani et at., 1984). The rate/surfactant concentration profiles and the rate constants are very similar to those for reactions in solutions of the corresponding C16 single chain surfactants which form normal micelles. The spontaneous hydrolysis of 2,4-dinitrophenyl phosphate dianion is also speeded by DDDAC1 and rates reach plateau values in very dilute surfactant (Savelli and Si, 1985). 

Fig. 3. Bronsted plot for the reactions of substituted pyridines with the dianion of 2.4-dinitrophenyl phosphate. The line, which is taken from the corresponding plot for the monoanions, is included...

Linear free-energy relationships (LFER) with monoanionic phosphorylated pyr-idines indicate a loose transition state in which metaphosphate is not an intermediate.16 The hydrolysis of the monoanion of 2,4-dinitrophenyl phosphate is thought to be concerted,39 but the possibility of a metaphosphate intermediate has not been ruled out with esters having less activated leaving groups. A stereochemical study of the hydrolysis of phenyl phosphate monoanion indicates that the reaction proceeds with inversion.21 This result implies either a concerted mechanism, or a discrete metaphosphate intermediate in a pre-associative mechanism. 

Buchwald, Friedman and Knowles succeeded in preparing 2,4-dinitrophenyl phosphate in which the three free oxygen atoms on phosphate were labeled stereospecifically with different isotopes of oxygen. Solvolysis of this compound in methanol and analysis of the methyl phosphate product showed that the reaction had proceeded with inversion of configuration at phosphorus (79). This remarkable experiment supports a concerted bimolecular displacement mechanism, with no metaphosphate intermediate, for the solvolysis of 2,4-dinitrophenyl phosphate in methanol. However, it does not rigorously exclude a stepwise mechanism in which a metaphosphate intermediate with a very short lifetime is formed and reacts with methanol faster than it rotates, and it does not provide direct evidence for a bimolecular, concerted reaction with solvent water. 

Ramirez and Marecek have investigated the solvolyses of 2,4-dinitrophenyl phosphate in aprotic and protic solvents and described reaction conditions that are consistent with the involvement of free metaphosphate anion 45, 46). In particular, the dianion of the reactive phosphate monoester is capable of transferring its phosphoryl group to /err-butanol whereas the monoanion of the same ester is essentially unreactive in the same reaction. Since rert-butanol is unreac-tive as a nucleophile for steric reasons, the phosphorylation of this alcohol is considered to be a diagnostic test for the involvement of the highly reactive metaphosphate anion. 

Figure 1. Br0nsted-type plots for the reactions of substituted quinuclidines with the dianions of 2,4-dinitrophenyl phosphate complexed with calcium (upper line), 2,4-dinitrophenyl phosphate (middle line), and p-nitrophenyl phosphate (lower line) at 39 °C, ionic strength 1.0 (KCl) ( ) and ionic strength 1.5 (KCl) (o) (Reproduced from reference 12. Copyright 1986 American Chemical Society.)...

Ramirez, le Noble and coworkers (Ramirez et al., 1986) measured the volume of activation for the hydrolysis of 2,4-dinitrophenyl phosphate and found that the reaction is accelerated by pressure. The expectation for a dissociative process is that there will be a reduction in rate caused by an increase in pressure since the rate-determining step is expansive. In comparison, a reaction that proceeds by nucleophilic addition involves shrinkage and should be aided by pressure. Thus the experiment supports a concerted mechanism. 

It has to be pointed out that, with a few exceptions, the acceleration by polyelectrolytes was associated with decreases and Table IV gives the thermodynamic parameters for the aquation reactions of Co(NH3)5Br induced by Ag". Similar decreases in and AS were found for various reactions the Hg -induced aquation of Co(NH3)5Br , the SpjAr reaction of dinitrochlorobenzoic acid with OH [51], the hydrolysis of 2,4-dinitrophenyl phosphates [reaction (E)] [33], the outer-sphere electron-transfers between Co-complexes [Co(NH3)5N3, Co(NH3)5Br , Co(en)2Cl2 ] and Ru(NH3)6 or [8, 20] [en ethylenediamine], the polyvinyl-imidazole-accelerated solvolysis of p-nitrophenylacetate [52], the coupling reactions of dinitrofluorobenzene with aminoacids [53], dipeptides [53] and aniline [54], the lignin sulfonic acid-accelerated hydrolysis of methyl acetate [55], and the hydrolysis of nitrophenyl esters [37]. The opposite tendency (acceleration caused by increases... 

Dephosphorylation reactions of mono-, di-, and triesters of 2,4-dinitrophenyl phosphate (100) with deferoxamine (DFO) and... 

A kinetic isotope effect 160/180 of 2% in the spontaneous hydrolysis of the 2,4-dinitrophenyl phosphate dianion, whose ester oxygen is labeled, suggests a P/O bond cleavage in the transition state of the reaction, and thus also constitutes compelling evidence for formation of the metaphosphate 66,67). The hydrolysis behavior of some phosphoro-thioates (110) is entirely analogous 68). 

Yet another situation is observed in the 2,4-dinitrophenyl phosphate dianion. A significant effect of amines on the rate of decomposition is admittedly observed however, typical 2nd order kinetics, lower enthalpy of activation compared with spontaneous hydrolysis, and strongly negative AS values (see Table 3) indicate an Sn2(P) reaction. Surprisingly, the reaction rate remains unaffected by the basicity of the amine, even when its pKa value changes by 8 units. 

J Steffans et al., 1973, 1975. The reference reaction is the attack of the anion of a carboxylic acid of pK, 3.91 on methyl 2,4-dinitrophenyl phosphate at 39° (Kirby and Younas, 1970). The intramolecular reaction is corrected for the better leaving group using y LO=1.26 (Khan et al., 1970), and to 39° using the activation energy measured for the intermolecular reaction with acetate (Kirby and Younas, 1970). 

K. Yoshida, Y. Kurono, Y. Mori, K. Ikeda, Esterase-Like Activity of Human Serum Albumin. V. Reaction with 2,4-Dinitrophenyl Diethyl Phosphate , Chem. Pharm. Bull. 1985, 33, 4995-5001. 

The kinetics of the hydrolysis of di(2,4-dinitrophenyl) phosphate (DDNPP) were studied in basic solutions buffered with Bis-Tris propane (BTP) in the presence of La3+, Sm3+, Tb3+, and Er3+. Two equivalents of the 2,4-dinitrophenolate ion were liberated for each equivalent of DDNPP and the reaction showed first-order kinetics. Potentiometric titrations showed the formation of dinuclear complexes such as [Ln2(BTP)2(OH) ](6 " i, with values of n varying as a function of pH for all studied metals. Hence the catalytic effect depends on the formation of dinuclear lanthanide ion complexes with several hydroxo ligands.97... 

A detailed study of the specific rates of solvolysis of N,N,N, N -tetra-methyldiamidophosphorochloridate (80) (TMDAPC) with analysis in terms of the extended Grunwald-Winstein equation has been reported (Scheme 19). The stereochemistry of nucleophilic attack at tetracoordinate phosphorus was also discussed." The initial reaction of bis (2,4-dinitrophenyl) phosphate (BDNPP) (81) with hydroxylamine involves release of 1 mol 2,4-dinitrophen-oxide ion and formation of a phosphorylated hydroxylamine (82), which reacts readily with further NH2OH, giving the monoester (83). The intermediate (82) also breaks down by two other independent reactions one involves intramolecular displacement of aryloxide ion (83) and the other involves migration of the 2,4-dinitrophenyl group from O to N and formation of phosphorylated 2,4-dinitrophenylhydroxylamine (84) (Scheme 20)." ... 

The displacement of substituted phenoxide ions from aryl monophosphate monoanions by nicotinamide (Equation 38) has a PLg of -0.95. Reaction of substituted pyridines with 2,4-dinitrophenyl-phosphate monoanion has a 3 of 0.56. Using effective charge data from Scheme 1 construct a combined effective charge map for the... 

The Role of Nucleophile Solvation. The value of = 0 for the reaction of substituted pyridines with 2,4-dinitrophenyl phosphate (76) is puzzling. If the value of is a measure of the amount of the bond formation to the nucleophile in the transition state, this value might be taken to mean that there is no bond formation to the nucleophile in the transition state. This is obviously not the case, because there is a large increase in the rate of disappearance of the phosphate ester with increasing concentration of the nucleophile the reactions follow simple second-order kinetics. 

---