Hydrolysis half-life

Discrimination between exposed and unexposed areas in this process requires the selection of thia zolidine compounds that do not readily undergo alkaline hydrolysis in the absence of silver ions. In a study of model compounds, the rates of hydrolysis of model /V-methyl thia zolidine and A/-octadecyl thiazolidine compounds were compared (47). An alkaline hydrolysis half-life of 33 min was reported for the /V-methyl compound, a half-life of 5525 min (3.8 days) was reported for the corresponding V/-octadecyl compound. Other factors affecting the kinetics include the particular silver ligand chosen and its concentration (48). Polaroid Spectra film introduced silver-assisted thiazolidine cleavage to produce the yellow dye image (49), a system subsequentiy used in 600 Plus and Polacolor Pro 100 films. 

Methyl parathion is rapidly degraded in natural water systems. The degradation of methyl parathion occurs much more rapidly in alkaline (pH 8.5) than in neutral (pH 7) or acidic (pH 5) conditions (Badawy and El-Dib 1984). A hydrolysis half-life of 72-89 days was calculated for fresh water at 25° C and pH<8 (EPA 1978c Mabey and Mill 1978) compared with about 4 days at 40° C and pH>8 (EPA 1978c). 

One example of a reactive ortho-hydroxybenzyl derivatives is the Koshland reagent I (Fig. 11.1).11 13 Its hydrolysis half-life in water (pH 3.5 and 25 °C) is... 

Very small changes in acidity greatly affect chemical reactions and the form of chemical species in solution. For example, the hydrolysis half-life of hydrogen cyanide is greater than 100,000 years at pH 4 but drops to about 10 years at pH 9.39... 

Methoxychlor. Methoxychlor is strongly adsorbed to the soil and does not leach, and volatilization is slow. There is no evidence for oxidation, and although photolysis is rapid in aquatic systems, it is assumed not to occur in the soil environment. The hydrolysis half-life is a year in aquatic systems (33) and probably longer in soil systems because of adsorption. Biodegradation does occur in soil systems, however, with a half-life of from 1 to 3 weeks (34). Methoxychlor would not persist in the soil environment. 

Since the active ester end of the molecule is subject to hydrolysis (half-life of about 20 minutes in phosphate buffer at room temperature conditions), it should be coupled to an amine-containing protein or other molecule before the photolysis reaction is done. During the initial coupling procedure, the solutions should be protected from light to avoid decomposition of the phenyl azide group. The degree of derivatization should be limited to no more than a 5- to 20-fold molar excess of sulfo-SBED over the quantity of protein present to prevent possible precipitation of the modified molecules. For a particular protein, studies may have to be done to determine the optimal level of modification. 

Decomposition rates Negligible rate of hydrolysis Half-life of 80 days in air with photochemically produced hydroxyl radicals Mabey and Mill 1978 Hampson 1980... 

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. 

In distilled water, acrolein is hydrolyzed to p hydroxypropionaldehyde (Burczyk et ah, 1968 Reinert and Rodgers, 1987 Kollig, 1993). The estimated hydrolysis half-life in water is 22 d (Burczyk et al, 1968). Bowmer and Higgins (1976) reported a disappearance half-life of 69 and 34 d in buffered water at pH values of 5 and 8.5, respectively. 

The hydrolysis rate constant for acrylonitrile at pH 2.87 and 68 °C was determined to be 6.4 x 10 Vh, resulting in a half-life of 4.5 d. At 68.0 °C and pH 7.19, no hydrolysis or disappearance was observed after 2 d. However, when the pH was raised to 10.76, the hydrolysis half-life was calculated to be 1.7 h (Ellington et al., 1986). Acrylonitrile hydrolyzes to acrylamide which undergoes additional hydrolysis forming acrylic acid and ammonia (Kollig, 1993). 

Chemical/Physical. Hydrolysis under alkaline conditions will yield allyl alcohol (Hawley, 1981). The estimated hydrolysis half-life in water at 25 °C and pH 7 is 2.0 yr (Mabey and Mill, 1978). 

Chemical/Physical. Benzyl butyl phthalate initially hydrolyzes to butyl hydrogen phthalate. This compound undergoes additional hydrolysis yielding o-phthalic acid, 1-butanol, and benzyl alcohol (Kollig, 1993). Gledhill et al. (1980) reported the hydrolysis half-life is >100 d. 

Photolytic. When an aqueous solution containing a-BHC was photooxidized by UV light at 90-95 °C, 25, 50, and 75% degraded to carbon dioxide after 4.2, 24.2, and 40.0 h, respectively (Knoevenagel and Himmelreich, 1976). In basic, aqueous solutions, a-BHC dehydrochlorinates forming pentachlorocyclohexene before being transformed to trichlorobenzenes. In a buffered aqueous solution at pH 8 and 5 °C, the calculated hydrolysis half-life is 26 yr (Ngabe et al., 1993). 

Chemical/Physical. Kollig (1993) reported that bis(2-chloroisopropyl) ether is subject to hydrolysis forming HCl and the intermediate (2-hydroxyisopropyl-2-chloroisopropyl) ether. The intermediate compound undergoes hydrolysis yielding bis(2-hydroxyisopropyl) ether. Van Duuren et al. (1972) reported a hydrolysis half-life of 21 h at 25 °C and pH 7. 

Chemical/Physical. Although no products were identified, the estimated hydrolysis half-life in water at 25 °C and pH 7 is 44 yr (Mabey and Mill, 1978). Bromochloromethane reacts with bisulfide ion (HS ), produced by microbial reduction of sulfate, forming 1,3,5-trithiane and dithiomethane. Estimated reaction rate constants at 25 and 35 °C were 7.29 x 10 and 2.42 x 10 VM-sec, respectively (Roberts et al, 1992). 

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. 

Chemical/Physical. Under laboratory conditions, carbon tetrachloride partially hydrolyzed in aqueous solutions forming chloroform and carbon dioxide (Smith and Dragun, 1984). Complete hydrolysis yields carbon dioxide and HCl (Ellington et al., 1993 Kollig, 1993). The estimated hydrolysis half-life in water at 25 °C and pH 7 is 7,000 yr (Mabey and Mill, 1978) and 40.5 yr (Jeffers et al., 1989 Ellington et al, 1993). The estimated hydrolysis half-life reported by Mabey and Mill (1978) was based on second-order neutral kinetics. Jeffers et al. (1996) reported that hydrolysis of carbon tetrachloride is first-order, contrary to findings of Mabey and Mill (1978). Jeffers et al. (1996) report that the extrapolated environmental half-life at 25 °C is 40 years. 

Chlordane is subject to hydrolysis via the nucleophilic substitution of chlorine by hydroxyl ions to yield 2,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methano-l//-indene which is resistant to hydrolysis (Kollig, 1993). The hydrolysis half-life at pH 7 and 25 °C was estimated to be >197,000 yr (Ellington et ah, 1988). 

Chemical/Physical. Chlorination of 2-chloroethyl vinyl ether to a-chloroethyl ethyl ether or P-chloroethyl ethyl ether may occur in water treatment facilities. The alpha compound is very unstable in water and decomposes almost as fast as it is formed (Summers, 1955). Although stable in NaOH solutions, in dilute acid solutions hydrolysis yields acetaldehyde and chlorohydrin (Windholz et al., 1983). At pH 7 and 25 °C, the hydrolysis half-life is 175 d (Jones and Wood, 1964). 

Chloroprene is subject to hydrolysis forming 3-hydroxypropene and HCl. The reported hydrolysis half-life at 25 °C and pH 7 is 40 yr (Kollig, 1993). 

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). 

Chemical/Physical. Anticipated products from the reaction of 1,2-dichlorobenzene with ozone or OH radicals in the atmosphere are chlorinated phenols, ring cleavage products, and nitro compounds (Cupitt, 1980). Based on an assumed base-mediated 1% disappearance after 16 d at 85 °C and pH 9.70 (pH 11.26 at 25 °C), the hydrolysis half-life was estimated to be >900 yr (Ellington et al, 1988). 

Chemical/Physical. A glass bulb containing air and 1,1-dichloroethane degraded outdoors to carbon dioxide and HCl. The half-life for this reaction was 17 wk (Pearson and McConnell, 1975). Hydrolysis of 1,1-dichloroethane under alkaline conditions yielded vinyl chloride, acetaldehyde, and HCl (Kollig, 1993). The reported hydrolysis half-life at 25 °C and pH 7 is 61.3 yr (Jeffers et al., 1989). 

Hydrolysis of 1,2-dichloroethane under alkaline and neutral conditions yielded vinyl chloride and ethylene glycol, respectively, with 2-chloroethanol, and ethylene oxide forming as the intermediates under neutral conditions (Ellington et al, 1988 Jeffers et al, 1989 Kollig, 1993). The reported hydrolysis half-life in distilled water at 25 °C and pH 7 is 72.0 yr (Jeffers et al, 1989), but in a 0.05 M phosphate buffer solution the hydrolysis half-life is 37 yr (Barbash and Reinhard, 1989). Based on a measured hydrolysis rate constant of 1.8 x 10 at 25 °C and pH 7, the half-life is 71.5 yr (Jeffers and Wolfe, 1996). 

Chemical/Physical. Reacts rapidly with water forming HCl and formaldehyde (Fishbein, 1979 Ton et al., 1974). Ton et al. (1974) reported a hydrolysis half-life of 38 sec for sj/ 3-dichloromethyl ether at 20 °C. 

Slowly hydrolyzes in water and in acidic media but is more rapidly hydrolyzed under alkaline conditions to dimethyl hydrogen phosphate and dichloroacetaldehyde (Capel et al., 1988 Hartley and Kidd, 1987 Worthing and Hance, 1991). In the Rhine River (pH 7.4), the hydrolysis half-life of dichlorvos was 6 h (Capel et al, 1988). 

Chemical/Physical. Diuron decomposes at 180 to 190 °C releasing dimethylamine and 3,4-dichlorophenyl isocyanate. Dimethylamine and 3,4-dichloroaniline are produced when hydrolyzed or when acids or bases are added at elevated temperatures (Sittig, 1985). The hydrolysis half-life of diuron in a 0.5 N NaOH solution at 20 °C is 150 d (El-Dib and Aly, 1976). When diuron was pyrolyzed in a helium atmosphere between 400 and 1,000 °C, the following products were identified dimethylamine, chlorobenzene, 1,2-dichlorobenzene, benzonitrile, a trichlorobenzene, aniline, 4-chloroaniline, 3,4-dichlorophenyl isocyanate, bis(l,3-(3,4-dichlorophenyl)urea), 3,4-dichloroaniline, and monuron [3-(4-chlorophenyl)-l,l-dimethylurea] (Gomez et al., 1982). Products reported from the combustion of diuron at 900 °C include carbon monoxide, carbon dioxide, chlorine, nitrogen oxides, and HCl (Kennedy et al., 1972a). 

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