Acetonitrile and N-Chloroacetamide Formation from the Reaction of Acetaldehyde and Monochloramine

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• 作者：Susana Y. Kimura ; Trang Nha Vu ; Yukako Komaki ; Michael J. Plewa ; Benito J. Mari帽as
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：August 18, 2015
• 年：2015
• 卷：49
• 期：16
• 页码：9954-9963
• 全文大小：385K
• ISSN：1520-5851

文摘

Nitriles and amides are two classes of nitrogenous disinfection byproducts (DBPs) associated with chloramination that are more cytotoxic and genotoxic than regulated DBPs. Monochloramine reacts with acetaldehyde, a common ozone and free chlorine disinfection byproduct, to form 1-(chloroamino)ethanol. Equilibrium (K₁) and forward and reverse rate (k₁,k_鈥?) constants for the reaction between initial reactants and 1-(chloroamino)ethanol were determined between 2 and 30 掳C. Activation energies for k₁ and k_鈥? were 3.04 and 45.2 kJ路mol^鈥?, respectively, and enthalpy change for K₁ was 鈭?2.1 kJ路mol^鈥?. In parallel reactions, 1-(chloroamino)ethanol (1) slowly dehydrated (k₂) to (chloroimino)ethane that further decomposed to acetonitrile and (2) was oxidized (k₃) by monochloramine to produce N-chloroacetamide. Both reactions were acid/base catalyzed, and rate constants were characterized at 10, 18, and 25 掳C. Modeling for drinking water distribution system conditions showed that N-chloroacetamide and acetonitrile concentrations were 5鈥? times higher at pH 9.0 compared to 7.8. Furthermore, acetonitrile concentration was found to form 7鈥?0 times higher than N-chloroacetamide under typical monochloramine and acetaldehyde concentrations. N-chloroacetamide cytotoxicity (LC₅₀ = 1.78 脳 10^鈥? M) was comparable to dichloroacetamide and trichloroacetamide, but less potent than N,2-dichloroacetamide and chloroacetamide. While N-chloroacetamide was not found to be genotoxic, N,2-dichloroacetamide genotoxic potency (5.19 脳 10^鈥? M) was on the same order of magnitude as chloroacetamide and trichloroacetamide.