Consecutive loss of two benzyl radicals from the [M + Na]+ adduct ions of pyrogallol tribenzyl ether and its derivatives

Dietmar Kuck; Sandra Heitkamp; Matthias Letzel; Ishtiaq Ahmed; Karsten Krohn

doi:10.1177/1469066717729300

Consecutive loss of two benzyl radicals from the [M + Na]⁺ adduct ions of pyrogallol tribenzyl ether and its derivatives

Eur J Mass Spectrom (Chichester). 2018 Feb;24(1):23-32. doi: 10.1177/1469066717729300. Epub 2017 Sep 4.

Authors

Dietmar Kuck¹, Sandra Heitkamp¹, Matthias Letzel^{1

2}, Ishtiaq Ahmed^{3

4}, Karsten Krohn³

Affiliations

¹ 1 Department of Chemistry, Bielefeld University, Bielefeld, Germany.
² 2 Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Münster, Germany.
³ 3 Department of Chemistry, University of Paderborn, Paderborn, Germany.
⁴ 4 Institute for Biological Interfaces, Karlsruhe Institute of Technology, Karlsruhe, Germany.

PMID: 29041811
DOI: 10.1177/1469066717729300

Abstract

The electrospray ionization-collision-induced dissociation mass spectra of nine pyrogallol tribenzyl ethers, 2-10, and a catechol dibenzyl ether, 11, that bear various functional groups or larger structural extensions have been studied with respect to the occurrence of a highly characteristic consecutive loss of two benzyl radicals from the sodiated molecular ions, [M + Na]⁺. It is shown that this specific fragmentation reaction strongly dominates other fragmentation routes, such as loss of carbon monoxide, formaldehyde and water. In addition, elimination of benzaldehyde occurs as a minor fragmentation channel in most cases. In contrast to these aryl-benzyl ethers, the consecutive two-fold loss of C₇H₇^• is suppressed in the [M + Na]⁺ ions of dibenzyl ethers derived from multiply benzylated gallocatechin and catechin, where the elimination of benzyl alcohol prevails the primary fragmentation almost completely. The secondary fragmentation of the [M + Na]⁺ ions, which also comprises the two-fold loss of C₇H₇^•, as well as a remarkable primary fragmentation of a flavene-based congener leading to particularly stable sodium-free chromylium product ions is also presented. † Deceased.

Keywords: Electrospray mass spectrometry; benzoquinones; benzyl aryl ethers; benzyl radicals; collision-induced dissociation; homolytic cleavage; phenoxy radicals; sodiated molecules.