Hydrolysis half-live

Chemical/Physical. The estimated hydrolysis half-life of acetonitrile at 25 °C and pH 7 is >150,000 yr (Ellington et al., 1988). No measurable hydrolysis was observed at 85 °C at pH values 3.26 and 6.99. At 66.0 °C (pH 10.42) and 85.5 °C (pH 10.13), the hydrolysis half-lives based on first-order rate constants were 32.2 and 5.5 d, respectively (Ellington et al., 1987). The presence of hydroxide or hydronium ions facilitates hydrolysis transforming acetonitrile to the intermediate acetamide which undergoes hydrolysis forming acetic acid and ammonia (Kollig, 1993). Acetic acid and ammonia formed react quickly forming ammonium acetate. 

Acrylic acid and ammonium ions (Abdelmagid and Tabatabai, 1982 Brown and Rhead, 1979 Kollig, 1993) were reported as hydrolysis products. The hydrolysis rate constant at pH 7 and hydrolysis half-lives are reduced significantly at varying pHs and temperature. At 88.0 °C and pH values of 2.99 and 7.04, the half-lives were 2.3 and 6.0 d, respectively (Ellington et al., 1986). Decomposes between 175 and 300 °C (NIOSH, 1994). 

Chemical/Physical. 5-BHC dehydrochlorinates in the presence of alkali s. Although no products were reported, the hydrolysis half-lives at pH values of 7 and 9 are 191 d and 11 h, respectively (Worthing and Hance, 1991). 

Surface Water. In a laboratory aquaria containing estuarine water, 43% of dissolved carbaryl was converted to 1-naphthol in 17 d at 20 °C (pH 7.5-8.1). The half life of carbaryl in estuarine water without mud at 8 °C was 38 d. When mud was present, both carbaryl and 1-naphthol decreased to <10% in the estuarine water after 10 d. Based on a total recovery of only 40%, it was postulated that the remainder was evolved as methane (Karinen et al, 1967). The rate of hydrolysis of carbaryl increased with an increase in temperature (Karinen et al., 1967) and in increases of pH values greater than 7.0 (Rajagopal et al, 1984). The presence of a micelle [hexadecyltrimethylammonium bromide (HDATB), 3 x 10 M] in natural waters greatly enhanced the hydrolysis rate. The hydrolysis half-lives in natural water samples with and without HDATB were 0.12-0.67 and 9.7-138.6 h, respectively (Gonzalez et al, 1992). In a sterilized buffer solution, a hydrolysis half-life of 87 h was observed (Ferreira and Seiber, 1981). In the dark. 

In pond water, carbaryl degraded very rapidly to 1-naphthol. The latter degraded, presumably by Flavobacterium sp., into hydroxycinnamic acid, salicylic acid, and an unidentified compound (HSDB, 1989). Four d after carbaryl (30 mg/L and 300 ng/L) was added to Fall Creek water, >60% was mineralized to carbon dioxide. At pH 3, however, <10% was converted to carbon dioxide (Boethling and Alexander, 1979). Under these conditions, hydrolysis of carbaryl to 1-naphthol was rapid. The authors could not determine how much carbon dioxide was attributed to biodegradation of carbaryl and how much was due to the biodegradation of 1-naphthol (Boethling and Alexander, 1979). Hydrolysis half-lives of carbaryl in filtered and sterilized Hickory Hills (pH 6.7) and U.S. Department of Agriculture Number 1 pond water (pH 7.2) were 30 and 12 d, respectively (Wolfe et al., 1978). 

Hydrolysis and photolysis of carbaryl forms 1-naphthol (Wauchope and Haque, 1973 Rajagopal et al., 1984, 1986 Miles et al., 1988 MacRae, 1989 Ramanand et al., 1988a Lewis, 1989 Somasundaram et al, 1991) and 2-hydroxy-l,4-naphthoquinone (Wauchope and Haque, 1973), respectively. In aqueous solutions, carbaryl hydrolyzes to 1-naphthol (Boethling and Alexander, 1979 Vontor et al., 1972), methylamine, and carbon dioxide (Vontor et al., 1972), especially under alkaline conditions (Wolfe et al., 1978). At pH values of 5, 7, and 9, the hydrolysis half-lives at 27 °C were 1,500,15, and 0.15 d, respectively (Wolfe et al., 1978). 

Miles et al. (1988) studied the rate of hydrolysis of carbaryl in phosphate-buffered water (0.01 M) at 26 °C with and without a chlorinating agent (10 mg/L hypochlorite solution). The hydrolysis half-lives at pH 7 and 8 with and without chlorine were 3.5 and 10.3 d and 0.05 and 1.2 d. 

Hydrolyzes in soil and water to carbofuran phenol, carbon dioxide, and methylamine (Rajagopal et al, 1986 Seiber et al, 1978 Somasundaram et al., 1989, 1991). Hydrolysis of carbofuran occurs in both flooded and nonflooded soils, but the rate is slightly higher under flooded conditions (Venkateswarlu et al., 1977), especially when the soil is pretreated with the hydrolysis product, carbofuran phenol (Rajagopal et al., 1986). In addition, the hydrolysis of carbofuran was found to be pH dependent in both deionized water and rice paddy water. At pH values of 7.0, 8.7, and 10.0, the hydrolysis half-lives in deionized water were 864, 19.4, and 1.2 h, respectively. In paddy water, the hydrolysis half-lives at pH values of 7.0, 8.7, and 10.0 were 40, 13.9, and 1.3, respectively (Seiber et al, 1978). 

Chemical/Physical. In an alkaline medium or solvent, carrier, diluent or emulsifier having an alkaline reaction, chlorine will be released (U.S. EPA, 1985). The hydrolysis half-lives of cis-chlordane at pH values of 10.18 (84.0 °C) and 10.85 (65.0 °C) were 1.92 and 16.8 h, respectively (Ellington et al, 1987). 

The hydrolysis half-life in three different natural waters was approximately 48 d at 25 °C (Macalady and Wolfe, 1985). At 25 °C, the hydrolysis half-lives were 120 d at pH 6.1 and 53 d at pH 7.4. At pH 7.4 and 37.5 °C, the hydrolysis half-life was 13 d (Freed et al, 1979). At 25 °C and a pH range of 1-7, the hydrolysis half-life was about 78 d (Macalady and Wolfe, 1983). However, the alkaline hydrolysis rate of chlorpyrifos in the sediment-sorbed phase were found to be considerably slower (Macalady and Wolfe, 1985). In the pH range of 9-13, 3,5,6-trichloro-2-pyridinol and 0,0-diethyl phosphorothioic acid formed as major hydrolysis products (Macalady and Wolfe, 1983). The hydrolysis half-lives of chlorpyrifos in a sterile 1% ethanoFwater solution at 25 °C and pH values of 4.5, 5.0, 6.0, 7.0, and 8.0 were 11, 11, 7.0, 4.2, and 2.7 wk, respectively (Chapman and Cole, 1982). 

In clear and muddy waters, hydrolysis half-lives were 18->50 and 10-25 d, respectively, (Nesbitt and Watson, 1980). 

Chemical/Physical. Hydrolysis in distilled water at 25 °C produced c/5-3-chloro-2-propen-l-ol and HCl. The reported half-life for this reaction is 1 d (Milano et al., 1988 Kollig, 1993). Kim et al. (2003) reported that the disappearance of c/5-1,3-dichloropropylene in water followed a first-order decay model. At 25 and 35 °C, the first-order rate constants were 0.077 and 0.286/d, respectively. The corresponding hydrolysis half-lives were 9.0 and 2.4 d, respectively. 

Chemical/Physical. Under alkaline conditions, diethyl phthalate will initially hydrolyze to ethyl hydrogen phthalate and ethanol. The monoester will undergo hydrolysis forming o-phthalic acid and ethanol (Kollig, 1993). A second-order rate constant of 2.5 x lO /M-sec was reported for the hydrolysis of diethyl phthalate at 30 °C and pH 8 (Wolfe et al, 1980). At 30 °C, hydrolysis half-lives of 8.8 and 18 yr were reported at pH values 9 and 10-12, respectively (Callahan et al., 1979). 

Chemical/Physical. Endosulfan detected in Little Miami River, OH was readily hydrolyzed and tentatively identified as endosulfan diol (Eichelberger and Lichtenberg, 1971). Undergoes slow hydrolysis forming the endosulfan diol and sulfur dioxide (Worthing and Hance, 1991). The hydrolysis half-lives at pH values (temperature) of 3.32 (87.0 °C), 6.89 (68.0 °C), and 8.69 (38.0 °C) were calculated to be 2.7, 0.07, and 0.04 d, respectively (Ellington et al., 1988). Greve and Wit (1971) reported hydrolysis half-lives of P-endosulfan at 20 °C and pH values of 7 and 5.5 were 37 and 187 d, respectively. In a 1 pM sodium bicarbonate buffer solution at pH 8.15 and 28 °C, suspensions of sea sand, titanium dioxide, a-ferric oxide, a-FeOOH, laponite, and silicon dioxide catalyzed the hydrolysis of a-endosulfan to endosulfan diol. The uncatalyzed hydrolysis rate constant and half-life was 4.01 x lO Vsec and 0.20 d, respectively (Walse et al., 2002). 

Chemical/Physical. In an aqueous phosphate buffer solution (0.05 M) containing hydrogen sulfide ion, ethylene dibromide was transformed into 1,2-dithioethane and vinyl bromide. The hydrolysis half-lives for solutions with and without sulfides present ranged from 37 to 70 d and 0.8 to 4.6 yr, respectively (Barbash and Reinhard, 1989). Dehydrobromination of ethylene dibromide to vinyl bromide was observed in various aqueous buffer solutions (pH 7 to 11) in the temperature range of 45 to 90 °C. The estimated half-life for this reaction at 25 °C and pH 7 is 2.5... 

Chemical/Physical. Hydrolyzes in water forming cis-diethyl fumarate, tra/ s-diethyl fumarate (Suffet et ah, 1967), thiomalic acid, and dimethyl thiophosphate (Mulla et al., 1981). The reported hydrolysis half-lives at pH 7.4 and temperatures of 20 and 37.5 °C were 10.5 and 1.3 d, respectively (Freed et al, 1977). In a preliminary study, Librando and Lane (1997) concluded that the hydrolysis of malathion is very sensitive to pH. At pH 8.5, <5% of the malathion remains after 2 d, whereas at pH 5.7, >90% remains after 20 d. 

The hydrolysis half-lives at pH 7.4 and 20 and 37.5 °C were 130 and 27 d, respectively. At pH 6.1 and 20 °C, the hydrolysis half-life was 170 d (Freed et al, 1979). When equilibrated with a prereduced pokkali soil (acid sulfate), parathion instantaneously degraded to aminoparathion. The quick rate of reaction was reportedly due to soil enzymes and/or other heat labile substances. Desethyl aminoparathion was also identified as a metabolite in two separate studies (Wahid and Sethunathan, 1979 Wahid et al., 1980). The half-lives for the degradation of parathion in a silty clay (pH 5.5) and sandy clay (pH 6.9) were 23 and 22 d, respectively (Sattar, 1990). 

Chemical/Physical. The hydrolysis rate constant for 1,2,3-trichloropropane at pH 7 and 25 °C was determined to be 1.8 x lO Vh, resulting in a half-life of 43.9 yr (Ellington et ah, 1988). The hydrolysis half-lives decrease at varying pHs and temperature. At 87 °C, the hydrolysis half-lives at pH values of 3.07, 7.12, and 9.71 were 21.1, 11.6, and 0.03 d, respectively (Ellington et al, 1986). By analogy to l,2-dibromo-2-chloropropane, the following hydrolysis products would be formed 2,3-dichloro-l-propanol, 2,3-dichloropropene, epichlorohydrin, l-chloro-2,3-... 

Chemical/Physical. When an aqueous solution containing triphenyl phosphate (0.1 mg/L) and chlorine (3 to 1,000 mg/L) was stirred in the dark at 20 °C for 24 h, the benzene ring was substituted with one to three chlorine atoms (Ishikawa and Baba, 1988). The reported hydrolysis half-lives at pH values of 8.2 and 9.5 were 7.5 and 1.3 d, respectively (Howard and Doe, 1979). Decomposes at temperatures greater than 410 °C (Dobry and Keller, 1957)... 

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