DOI: 10.5281/zenodo.10631885
title: 13C NMR data for the five dissolved organic matter

description: Dissolved organic matter (DOM) is one of the most complex, dynamic, and abundant sources of organic carbon, but its chemical reactivity remains uncertain. Greater insights into DOM structural features could facilitate understanding its synthesis, turnover, and processing in the global carbon cycle. Here we use complementary multiplicity-edited 13C NMR spectra to quantify key substructures assembling the carbon skeletons of DOM from four main Amazon rivers and two mid-size Swedish boreal lakes. We find that one type of reaction mechanism, oxidative dearomatization (ODA), widely used in organic synthesic chemistry to create natural product scaffolds, is likely a key driver for generating structural diversity during processing of DOM that are rich in suitable polyphenolic precursor molecules. Our data suggest a high abundance of tetrahedral quaternary carbons bound to one oxygen and three carbon atoms (OCqC3 units). These units are rare in common biomolecules but could be readily produced by ODA of lignin and tannin derived polyphenols. Tautomerization of (poly)phenols by ODA creates non-planar cyclohexadienones which are subject to immediate and parallel cycloadditions. This combination amounts to a proliferation of structural diversity of DOM compounds from early stages of DOM processing, with an increase in oxygenated aliphatic structures. Overall, we propose that ODA is a key reaction mechanism for complexity acceleration in the processing of DOM molecules, creation of novel oxygenated aliphatic molecules, and that it could be prevalent in nature.
description: Funding provided by: Alexander von Humboldt FoundationCrossref Funder Registry ID: https://ror.org/012kf4317Award Number: 
Funding provided by: Swedish Research Council for Environment Agricultural Sciences and Spatial PlanningCrossref Funder Registry ID: https://ror.org/03pjs1y45Award Number: 2021-0242
Funding provided by: Swedish Research CouncilCrossref Funder Registry ID: https://ror.org/03zttf063Award Number: 2012-00048
Funding provided by: European Research CouncilCrossref Funder Registry ID: https://ror.org/0472cxd90Award Number: 725546
Funding provided by: Ministry of Education of the People's Republic of ChinaCrossref Funder Registry ID: https://ror.org/01mv9t934Award Number: 201806360268
Funding provided by: Coordenação de Aperfeicoamento de Pessoal de Nível SuperiorCrossref Funder Registry ID: https://ror.org/00x0ma614Award Number: 
Funding provided by: Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de JaneiroCrossref Funder Registry ID: https://ror.org/03kk0s825Award Number: 
Funding provided by: National Council for Scientific and Technological DevelopmentCrossref Funder Registry ID: https://ror.org/03swz6y49Award Number: 290004/2014-4
description: These files comprise 13C NMR section integrals for the five DOM, divided into buckets of 0.1 ppm width, and ranging from dC = 0 – 235 ppm. The total integral of these 13C NMR spectra is area normalized to Call = 100% for all five DOM, and to CH0123 according to its proportions. The 13C NMR section integral from dC = 47 - 51 ppm is set to zero for all five 13C NMR spectra of DOM, because of interference from the solvent 12CD3OD, which resonates at dC = 49.0 ppm.