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EC number: 200-609-3 | CAS number: 65-45-2
Rate constants extrapolated to zero buffer concentration. pKa = 7.54, measured at 100°C, ionic strength 1M.
Hydrolysis occurs under aqueous acid and alkaline conditions at ca. 100°C.
Experimental work has demonstrated hydrolysis under both alkaline and acid conditions, but only at elevated temperatures (ca. 100°C). Reid (Reid, E.E., Am. Chem. J., 1899, 21(4), 281-348) carried out a series of experiments on aromatic amides and demonstrated that ortho-substituted species were significantly stabilised towards hydrolysis. Koshy (Koshy, K.T., J. Pharm. Sci., 1959, 58(5), 560-563) calculated first-order rate constants under acid (1M HClO4, 1.88x10-3min-1) and alkaline (1M NaOH, 0.93x10-3min-1) conditions at 90°C. Bruice et al (Bruice, T.C., et al, J. Org. Chem., 1965, 30(5), 1668-1669) carried out pH dependent hydrolysis studies of several aromatic amides to identify the reaction mechanism, again at elevated temperatures (100°C). The rate constants for salicylamide were determined in the range pH=7.1 - 11.6 and showed an unusual S-shaped curve, which had previously been demonstrated in a similar compound, with similar reaction mechanism (Bender, M.L., et al, J.Am.Chem.Soc., 1963, 85(19), 3017-3024). Both compounds had a constant reaction-rate plateau above the pKa, before increasing under significantly alkaline conditions. The lowest reaction rates were under acid conditions, below the pKa. For the test substance the reaction rates were determined: pH=7.1, 0.013min-1; pH ca. 8-10.6, 0.022min-1; pH=11.6, 0.053min-1. It was mentioned that borate and phosphate buffers were unsuitable due to complexing with o-hydroxyamides. Brodie (Brodie, D.C., et al, J. Am. Pharm. Assoc., 1951, 40(8), 414-415) investigated hydrolysis under physiological conditions in vitro, at room temperature. No hydrolysis was observed in a 4h or 8h period, within experimental error.
The experimental work demonstrated hydrolysis under both alkaline and acid conditions, but only at elevated temperatures (ca. 100 °C). No experimental data under environmentally relevant conditions are available.
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