title: Identification of the Phenol Functionality in Deprotonated Monomeric and Dimeric Lignin Degradation Products via Tandem Mass Spectrometry Based on Ion-Molecule Reactions with Diethylmethoxyborane.
abstract: Conversion of lignin into smaller molecules provides a promising alternate and sustainable source for the valuable chemicals currently derived from crude oil. Better understanding of the chemical composition of the resulting product mixtures is essential for the optimization of such conversion processes. However, these mixtures are complex and contain isomeric molecules with a wide variety of functionalities, which makes their characterization challenging. Tandem mass spectrometry based on ion-molecule reactions has proven to be a powerful tool in functional group identification and isomer differentiation for previously unknown compounds. This study demonstrates that the identification of the phenol functionality, the most commonly observed functionality in lignin degradation products, can be achieved via ion-molecule reactions between diethylmethoxyborane (DEMB) and the deprotonated analyte in the absence of strongly electron-withdrawing substituents in the ortho- and para-positions. Either a stable DEMB adduct or an adduct that has lost a methanol molecule (DEMB adduct-MeOH) is formed for these ions. Deprotonated phenols with an adjacent phenol or hydroxymethyl functionality or a conjugated carboxylic acid functionality can be identified based on the formation of DEMB adduct-MeOH. Deprotonated compounds not containing the phenol functionality and phenols containing an electron-withdrawing ortho- or para-substituent were found to be unreactive toward diethylmethoxyborane. Hence, certain deprotonated isomeric compounds with phenol and carboxylic acid, aldehyde, carboxylic acid ester, or nitro functionalities can be differentiated via these reactions. The above mass spectrometry method was successfully coupled with high-performance liquid chromatography for the analysis of a complex biomass degradation mixture. Graphical Abstract ᅟ.
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA.
authors.forename: Hanyu
authors.initials: H
authors.lastname: Zhu
authors.forename: Tiffany M
authors.initials: TM
authors.lastname: Jarrell
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Louden
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA.
authors.forename: Joann P
authors.initials: JP
authors.lastname: Max
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Marcum
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Luo
authors.forename: James S
authors.initials: JS
authors.lastname: Riedeman
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA.
authors.forename: Mahdi M
authors.initials: MM
authors.lastname: Abu-Omar
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN, USA. hilkka@purdue.edu.
authors.forename: Hilkka I
authors.initials: HI
authors.lastname: Kenttämaa
keywords: Ion–molecule reactions; Lignin degradation products; Phenol functionality; Phenols