Different Mechanisms of Alkaline and Enzymatic Hydrolysis of the Insensitive Munition Component 2,4-Dinitroanisole Lead to Identical Products

Bridget A. Ulrich, Mallory Palatucci, Jakov Bolotin, Jim C. Spain, Thomas B. Hofstetter

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

The emerging use of 2,4-dinitroanisole (DNAN) in insensitive munitions formulations has caused concern about future contamination of subsurface environments, generating significant interest in understanding and identifying its transformation processes. Here we characterized the C and N isotope fractionation associated with abiotic and biological DNAN hydrolysis through alkaline hydrolysis at high pH as well as enzymatic hydrolysis by Nocardioides sp. JS1661 and partially purified DNAN O-demethylase. Whereas both reactions generated 2,4-dinitrophenol (DNP), compound-specific isotope analysis (CSIA) of DNAN and DNP revealed that these reactions occur by different mechanisms. Alkaline hydrolysis was associated with apparent 13C and 15N kinetic isotope effects (13C-AKIE and 15N-AKIE) of 1.044 ± 0.003 and 1.0027 ± 0.0004, respectively, reflecting the previously postulated nucleophilic aromatic substitution mechanism. Conversely, enzyme-catalyzed DNAN hydrolysis exhibited a 13C-AKIE of 1.027 ± 0.005 and a 15N-AKIE of 1.0032 ± 0.0003. On the basis of these AKIE values and the C and N isotope fractionation of DNP, our results imply that enzymatic O-demethylation of DNAN occurs through a nucleophilic substitution reaction at the aliphatic C of the methoxy group. This work provides a basis for the assessment of DNAN transformation by CSIA, as the C and N isotope fractionation patterns observed in this work are distinct from other hypothesized degradation pathways.

Original languageEnglish (US)
Pages (from-to)456-461
Number of pages6
JournalEnvironmental Science and Technology Letters
Volume5
Issue number7
DOIs
StatePublished - Jul 10 2018
Externally publishedYes

Bibliographical note

Funding Information:
B.A.U. was supported by the Strategic Environmental Research and Development Program (SERDP Project ER-2618).

Publisher Copyright:
© 2018 American Chemical Society.

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