Gamma Radiolysis of Phenyl-Substituted TODGAs: Part II

ABSTRACT

The radiolytic degradation chemistry of three phenylated analogs of N,N,N’,N’-tetraoctyl diglycolamide (TODGA) was investigated: 2-(2-(di-n-octylamino)-2-oxoethoxy)-N,N-di-n-octyl-2-phenylacetamide (PhTODGA), which has a phenyl substituent bound to a central methylene, 2-(2-(di-n-octylamino)-2-oxo-1-phenylethoxy)-N,N-di-n-octylpropanamide (PhMeTODGA), which also contains a methyl substituent bound to the methylene on the other side of the ether moiety, and, 2-(2-N-n-hexyl-N-phenylamino)-2-oxoethoxy)-N-n-hexyl-N-phenylacetamide (DHDPDGA), which has phenyl substituents located on the amide groups instead of the central methylenes. In Part II of this series of papers radiolytic degradation products were identified after separation with liquid chromatography by High Resolution, Accurate-Mass mass spectrometry and collision-induced dissociation. At least twenty-two radiolytic degradation products were identified for PhTODGA, twenty-nine for PhMeTODGA, and over three dozen for DHDPDGA. The suite of radiolytic degradation products of these three investigated ligands was significantly larger than has been reported for previously studied diglycolamides, owing to their asymmetric nature, and to the identification of several new degradation mechanisms, including addition of methyl, hydroxyl, and nitrogen oxide radicals, that have not been previously reported for diglycolamides. Degradation products that contained addition of a NO₂ or NO₃ group were particularly prevalent for DHDPDGA, likely due to the phenyl side-groups. Several of these newly observed mechanisms do not appear to depend on the presence of the phenyl groups, suggesting these novel mechanisms may apply to other diglycolamides

KEYWORDS:

• Radiolysis
• radical chemistry
• TODGA
• diglycolamides

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07366299.2023.2221290

Additional information

Funding

The gamma-ray irradiation and UHPLC-ESI-MS experiments performed at Idaho National Laboratory were supported by the US Department of Energy (US-DOE), Assistant Secretary for Nuclear Energy, under the Fuel Cycle R&D Program, Idaho Operations Office Contract DE-AC07-05ID14517. Additional financial support for this research was provided by the European Commission: projects SACSESS and GENIORS, Grant No. 323282 and 755171, respectively.