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

Abstract

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-1) constants for the reaction between initial reactants and 1-(chloroamino)ethanol were determined between 2 and 30 °C. Activation energies for k1 and k-1 were 3.04 and 45.2 kJ·mol(-1), respectively, and enthalpy change for K1 was -42.1 kJ·mol(-1). 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 °C. Modeling for drinking water distribution system conditions showed that N-chloroacetamide and acetonitrile concentrations were 5-9 times higher at pH 9.0 compared to 7.8. Furthermore, acetonitrile concentration was found to form 7-10 times higher than N-chloroacetamide under typical monochloramine and acetaldehyde concentrations. N-chloroacetamide cytotoxicity (LC50 = 1.78 × 10(-3) 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 × 10(-3) M) was on the same order of magnitude as chloroacetamide and trichloroacetamide.

Chlorination of Amino Acids: Reaction Pathways and Reaction Rates

“…T his result is consistent with previous reports that the formation of N-chloraldimines from the chloramination of aldehydes in aqueous solutions is very slow. 27,38 T herefore, N-chloroisobutyraldimine was produced in anhydrous conditions;…”

Quantification by SIFT-MS of volatile compounds produced by the action of sodium hypochlorite on a model system of infected root canal content

“…A major question that needs further investigation is how these volatile nitrogenous compounds are formed and whether their direct analysis by SIFT-MS in the headspace may offer insight into the reactions of NaOCl with proteins and amino acids. One possible explanation for the formation of CH 3 CN is by the reaction of NaOCl with aldehydes and monochloramines, which has previously been investigated using solid phase microextraction (SPME) and GC-MS [ 46 ]. Note that acetaldehyde is present in the headspace of our samples.…”

Reductive Dechlorination of Chloroacetamides with NaBH4 Catalyzed by Zero Valent Iron, ZVI, Nanoparticles in ORMOSIL Matrices Prepared via the Sol-Gel Route

“…Recently it was shown that ZVI-NPs entrapped in sol-gel matrices can be used as effective heterogeneous catalysts for reductive dehalogenation reactions (RDH) of halo-acetic acids [31]. The high yields and the stability of the catalyst suggest its plausible use for the reduction of the more toxic and very abundant chloroacetamides family of pollutants [2,[32][33][34]. To the best of our knowledge, there has been no attempt to date to utilize ZVI-NPs as a catalyst in the reductive dehalogenation of chloroacetamides.…”

“…More than half a century ago it was proposed to study each halogenated compound independently of its homologue hydrocarbon series [1]. While there are number of halogenated pollutants that are monitored by the health authorities, e.g., halo-acetic acids, others which appear on the EPA's (United States Environmental Protection Agency) contaminant candidate list await proper directives and legislation, e.g., halo-acetamides which are formed during chlorination of drinking water [2]. Halo-organic compounds can be reduced electro-chemically [3,4], photo-chemically [5], radiolytically [6], and by a variety of reducing agents [7].…”