Position-specific isotope effects during alkaline hydrolysis of 2,4-dinitroanisole resolved by compound-specific isotope analysis, 13C NMR, and density-functional theory

Chunlei Wang, Linnea J. Heraty, Adam F. Wallace, Changjie Liu, Xiaoqiang Li, Gregory P. McGovern, Juske Horita, Mark E. Fuller, Paul B. Hatzinger, Neil C. Sturchio

Research output: Contribution to journalArticlepeer-review

Abstract

Compound-specific isotope analysis (CSIA), position-specific isotope analysis (PSIA), and computational modeling (e.g., quantum mechanical models; reactive-transport models) are increasingly being used to monitor and predict biotic and abiotic transformations of organic contaminants in the field. However, identifying the isotope effect(s) associated with a specific transformation remains challenging in many cases. Here, we describe and interpret the position-specific isotope effects of C and N associated with a SN2Ar reaction mechanism by a combination of CSIA and PSIA using quantitative 13C nuclear magnetic resonance spectrometry, and density-functional theory, using 2,4-dinitroanisole (DNAN) as a model compound. The position-specific 13C enrichment factor of O–C1 bond at the methoxy group attachment site (εC1) was found to be approximately -41‰, a diagnostic value for transformation of DNAN to its reaction products 2,4-dinitrophenol and methanol. Theoretical kinetic isotope effects calculated for DNAN isotopologues agreed well with the position-specific isotope effects measured by CSIA and PSIA. This combination of measurements and theoretical predictions demonstrates a useful tool for evaluating degradation efficiencies and/or mechanisms of organic contaminants and may promote new and improved applications of isotope analysis in laboratory and field investigations.

Original languageEnglish
Article number130625
JournalChemosphere
Volume280
DOIs
StatePublished - Oct 2021

Keywords

  • 2,4-Dinitroanisole
  • C NMR
  • Density-functional theory
  • Stable isotopes

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