Table 1.
Rate constants for PPlγ catalyzed hydrolysis of aryl phosphates and aryl methylphosphonates (25 °C, pH 8.0, 100 mM buffer (2-amino-2-methyl-1,3-propanedio), 1 mM MnCl2, I = 0.45 M (NaCl)), and for the reaction of hydroxide with aryl methylphosphonates (25 °C, I=0.1M (NaCl)).
| Aryl group | Phenol pKa(a) | PP1γ-catalyzed phosphonate hydrolysis (kcat/KM, M-1 s-1) | PP1γ-catalyzed phosphonate hydrolysis (kcat/KM, M-1 s-1) | kHO- catalyzed phosphonate hydrolysis (M-1 s-1) |
|---|---|---|---|---|
| 4-nitro-3-fluoro | 6.10 | - | 60±2 | 6.2±0.2×10-5 |
| 4-nitro | 7.01 | 820±20 | 40±2 | 1.18±0.01×10-5 |
| 3-nitro-4-chloro | 7.54 | 640±20 | - | - |
| 3-nitro | 8.14 | 450±20 | 9.5±0.9 | 2.9±0.2×10-6(b) |
| 3,4-dichloro | 8.32 | 520±50 | - | - |
| 3-chloro | 8.82 | 370±10 | 12.6±0.7 | 6.2±0.2×10-7(b) |
| 3-fluoro | 9.00 | 200±20 | - | - |
| 4-chloro | 9.30 | 260±30 | 9.8±0.2 | 3.6±0.4×10-7(b) |
| 4-fluoro | 9.78 | 104±17 | - | |
| Phenol | 9.97 | 94±12 | 3±1 | 1.2±0.2×10-7(b) |
| 4-methyl | 10.15 | 100±3 | 3.2±0.2 |
(a)
pKas were measured by spectrophotometric titration at 25 °C
(b)
extrapolated from measurements in 0.1 M NaOH at higher temperatures.