Homogeneous Hydrolysis Rate Constants—part Ii: Additions, Corrections and Halogen Effects

Abstract

Neutral and alkaline rate constants were measured for 14 halogenated hydrocarbons, and new or revised rate constants were determined for hexachloroethane, trichloroethene, and 1,2-dichloroethane. These results include the effects of F or Br substitution for Cl in halogenated methanes, ethanes, and ethenes. The brominated ethanes and ethenes are more reactive than the corresponding chlorinated compounds, due to lower activation energies and higher activation entropies. Fluorine substitution increases the activation energy for some of the ethanes and greatly decreases reactivity for most of the compounds studied. However, fluorodichloromethane is about as reactive as chloroform. Complex reactions were observed in alkaline solutions of vinyl chloride and 1,2-dichlorotrifluoroethane.

Solvation Effects on Kinetics of Methylene Chloride Reactions in Sub- and Supercritical Water: Theory, Experiment, and Ab Initio Calculations

“…Our final objective is to then use these results, along with experimental temperature profiles, to generate engineering-oriented global kinetic rate expressions for the hydrolysis reaction of CH 2 Cl 2 . A more complete reaction network has also been developed for CH 2 Cl 2 hydrolysis and its products based on our experimental data and studies in the literature and is presented by Marrone et al 5 Although there have been several studies of subcritical liquid and vapor hydrolysis of various chlorinated hydrocarbons, 6,7 only a few have been carried out at supercritical conditions.…”

Low‐Temperature Thermal Remediation: Gaining Traction as a Green Remedial Alternative

“…In 1990, the USEPA conducted a pathway analysis associated with the hydrolysis of acrylonitrile and several pesticides along with various chlorinated alkanes: carbon tetrachloride (CT), chloroform (CF), 1,2‐dichlorothane (1,2‐DCA), methylene chloride (MC), 1,1,1‐trichloroethane (1,1,1‐TCA), 1,1,2‐trichloroethane (1,1,2‐TCA), 1,1,1,2‐tetrachloroethane (1,1,1,2‐TCA), and 1,1,2,2‐tetrachloroethane (1,1,2,2‐TCA) (Kollig et al 1990). A number of other studies have also presented temperature effects and reaction by‐products for hydrolysis and dehydrohalogenation reactions (Mabey and Mill ; Gerkens and Franklin ; Jeffers et al ; Washington ; Jeffers and Wolfe ; Pagan et al ).…”

“…Using the Arrhenius equation and published values for A and E A (Jeffers et al ; Washington ; Jeffers and Wolfe ), Figure summarizes the calculated hydrolysis half‐lives for a number of chlorinated compounds that might be expected at neutral groundwater pH and temperatures ranging from 10 °C to 95 °C. The figure shows that moderate increases in temperature can shorten abiotic half‐lives by orders of magnitude.…”

Temperature‐Activated Auto‐Decomposition Reactions: An Under‐Utilized In Situ Remediation Solution

“…Despite the low incidence of selection as a primary remediation solution, there has been a significant amount of research done on the breakdown pathways associated with the hydrolysis of several chlorinated alkanes, acrylonitrile, and several pesticides (Kollig et al 1990). A number of other studies have also presented temperature effects and reaction end products for hydrolysis and dehydrohalogenation reactions (Mabey and Mill 1978; Gerkens and Franklin 1989; Jeffers et al 1989; Washington 1995; Jeffers and Wolfe 1996; Pagan et al 1998).…”

“…where K is the rate constant, A is the frequency factor, relating to the collision of molecules involved in the reaction, E A is the activation energy, R is the universal gas constant, and T is the absolute temperature. Using the Arrhenius equation and published values for A and E A (Washington 1995;Jeffers et al 1989;Jeffers and Wolfe 1996), Table 1 summarizes the calculated half-lives for a number of chlorinated alkanes that might be expected at neutral groundwater pH and temperatures ranging from 10 to 95 °C. As shown, the halflives at a temperature representative of many groundwater systems (~10 °C) ranged from 1.3 x 10 14 to 16 d, with chlorinated alkenes being highly recalcitrant to hydrolysis and certain chlorinated alkanes much more amenable.…”