Methyl p-nitrophenyl

The results are in accordance with those obtained by Taft and colleagues80,81. These authors have measured the 19F NMR chemical shifts of p-FC6H4OH in the presenceof 60 bases including sulphoxides (DMSO, methyl phenyl, methyl p-nitrophenyl, diphenyl, tetramethylene sulphoxide) and determined the association constants K for the hydrogen bond shown in equation 15. 

In the course of this study, the authors determined /Lvalues for dibenzyl, methyl phenyl, methyl p-nitrophenyl, di-p-tolyl, di-isopropyl and tetramethylene sulphoxides and for diethyl, dipropyl and dibutyl sulphites. The /Lscales are applied to the various reactions or the spectral measurements. The /Lscales have been divided into either family-dependent (FD) types, which means two or more compounds can share the same /Lscale, family-independent (FI) types. Consequently, a variety of /Lscales are now available for various families of the bases, including 29 aldehydes and ketones, 17 carboxylic amides and ureas, 14 carboxylic acids esters, 4 acyl halides, 5 nitriles, 10 ethers, 16 phosphine oxides, 12 sulphinyl compounds, 15 pyridines and pyrimidines, 16 sp3 hybridized amines and 10 alcohols. The enthalpies of formation of the hydrogen bond of 4-fluorophenol with both sulphoxides and phosphine oxides and related derivatives fit the empirical equation 18, where the standard deviation is y = 0.983. Several averaged scales are shown in Table 1588. 

Also, Chin s dihydroxy-bridged dicobalt(III) complex 10 provides one of the largest rate enhancements ever observed for phosphodiester hydrolysis [36]. Reaction with the activated phosphodiester methyl(p-nitrophenyl)phosphate (MNPP) yields 11. A crystal structure is available for the analogous dimethylphosphate complex in which the Co ions are 2.9 A apart. At pH 7 and 45 °C 11 releases p-nitrophenolate with k = 0.1 s 1 which corresponds to a nearly 10I2-fold rate enhancement over spontaneous hydrolysis of the substrate. The product of the reaction is a methylphosphate-bridged complex. Based on the pH rate profile and on... 

FIGURE 2. Br0nsted-type plot for reactions of methyl p-nitrophenyl sulfate with amines. The a-nucleophiles are shown as soUd circles. Data taken from Buncel, Chuaqui and Wilson, J. Org. Chem., 45, 3621 and reprinted with permission. Copyright (1980) American Chemical Society... 

Methyl-p-nitrophenyl phosphate coordinated to the two metal centers in 37 undergoes hydrolysis by a two-step addition-elimination mechanism [73]. The free phosphate hydrolyzes by a concerted mechanism. In both phosphate monoester and diester hydrolysis, the two Co(m) centers in 32 and 37 stabilize the five-coordinate phosphate species (transition state or intermediate) by bringing the phosphate and nucleophile together. This stabilization leads to a change in mechanism from dissociative to concerted for a phosphate monoester hydrolysis [96] and from concerted to stepwise for phosphate diester hydrolysis [73]. 

When p-nitro-N,N-dimethylaniline (IVc) was ozonized at 0°C in ethyl acetate, methylene chloride, or methanol, a mixture of products resulted. In addition to the expected side-chain oxidation products— p-nitro-N-methylaniline (Vc), p-nitro-N-methyl formanilide (Vic)—a peroxide compound was formed. This peroxide, which is not formed until the solvents are removed, was shown by a series of experiments (described below) to be identical with di-[(N-methyl-p-nitrophenyl)-aminomethyl] peroxide (VII). Deoxygenation of VII with triethyl phosphite (7) yielded the ether VIII, which in turn decomposed at its melting point to the amine IX. 

C9H12N05P ethyl phosphonic acid, methyl p-nitrophenyl 15536-01-3 388.15 33.250 1,2 17151 C9H1202 3-methoxy-alpha-methylbenzenemethanol 23308-82-9 512.40 45.077 2... 

Reactions at sp centers are associated with small (<10) alpha effects, as typified by those illustrated in Figure 3.3. On the other hand, the rather small value of the alpha effect for the reaction of methyl p-nitrophenyl sulfate is contrasted with the reaction of p-nitrophenyl acetate at an sp center, with butane-2,3-dionemonoximate (Ox )... 

FIGURE 3.3 Br0nsted-type plot of log versus p for the reaction of nucleophiles with methyl p-nitrophenyl sulfate. The a-nucleophiles are shown as solid circles. Source Buncel et al. (1980) by permission of the American Chemical Society. 

Monoclonal antibodies have been raised against jn-nitrophenyl phosphonate (220) to elicit catalytic antibodies capable of hydrolysing jn-nitrophenyl carbonates (221). One of the clones catalysed the hydrolysis of methyl p-nitrophenyl carbonate (221 R = Me) with a rate acceleration (fecat/ uncat) of 6.4 x (f, 20-fold higher than that of a substrate [221 R = (CH2)3CONHMe] congruent with the hapten. This catalytic... 

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