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Gaseous fragment ions generated in mass spectrometers may be employed as "building blocks" for the synthesis of novel molecules on surfaces using ion soft-landing. A fundamental understanding of the reactivity of the fragment ions is required to control bond formation of deposited fragments in surface layers. The fragment ion [B12X11]− (X = halogen) is formed by collision-induced dissociation (CID) from the precursor [B12X12]2− dianion. [B12X11]− is highly reactive and ion soft-landing experiments have shown that this ion binds to the alkyl chains of organic molecules on surfaces. In this work we investigate whether specific modifications of the precursor ion affect the chemical properties of the fragment ions to such an extent that attachment to functional groups of organic molecules on surfaces occurs and binding of alkyl chains is prevented. Therefore, a halogen substituent was replaced by a thiocyanate substituent. CID of the precursor [B12I11(SCN)]2− ion preferentially yields the fragment ion [B12I8S(CN)]−, which shows significantly altered reactivity compared to the fragment ions of [B12I12]2−. [B12I8S(CN)]− has a previously unknown structural element, wherein a sulfur atom bridges three boron atoms. Gas-phase reactions with different neutral reactants (cyclohexane, dimethyl sulfide, and dimethyl amine) accompanied by theoretical studies indicate that [B12I8S(CN)]− binds with higher selectivity to functional groups of organic molecules than fragment ions of [B12I12]2− (e.g., [B12I11]− and [B12I9]−). These findings were further confirmed by ion soft-landing experiments, which showed that [B12I8S(CN)]− ions attacked ester groups of adipates and phthalates, whereas [B12I11]− ions only bound to alkyl chains of the same reagents. [ABSTRACT FROM AUTHOR]

Biomass‐derived degraded lignin and cellulose serve as possible alternatives to fossil fuels for energy and chemical resources. Fast pyrolysis of lignocellulosic biomass generates bio‐oil that needs further refinement. However, as pyrolysis causes massive degradation to lignin and cellulose, this process produces very complex mixtures. The same applies to degradation methods other than fast pyrolysis. The ability to identify the degradation products of lignocellulosic biomass is of great importance to be able to optimize methodologies for the conversion of these mixtures to transportation fuels and valuable chemicals. Studies utilizing tandem mass spectrometry have provided invaluable, molecular‐level information regarding the identities of compounds in degraded biomass. This review focuses on the molecular‐level characterization of fast pyrolysis and other degradation products of lignin and cellulose via tandem mass spectrometry based on collision‐activated dissociation (CAD). Many studies discussed here used model compounds to better understand both the ionization chemistry of the degradation products of lignin and cellulose and their ions' CAD reactions in mass spectrometers to develop methods for the structural characterization of the degradation products of lignocellulosic biomass. Further, model compound studies were also carried out to delineate the mechanisms of the fast pyrolysis reactions of lignocellulosic biomass. The above knowledge was used to assign likely structures to many degradation products of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

Diagnostic gas‐phase ion‐molecule reactions serve as a powerful alternative to collision‐activated dissociation for the structural elucidation of analytes when using tandem mass spectrometry. The use of such ion‐molecule reactions has been demonstrated to provide a robust tool for the identification of specific functional groups in unknown ionized analytes, differentiation of isomeric ions, and classification of unknown ions into different compound classes. During the past several years, considerable efforts have been dedicated to exploring various reagents and reagent inlet systems for functional‐group selective ion‐molecule reactions with protonated analytes. This review provides a comprehensive coverage of literature since 2006 on general and predictable functional‐group selective ion‐molecule reactions of protonated analytes, including simple monofunctional and complex polyfunctional analytes, whose mechanisms have been explored computationally. Detection limits for experiments involving high‐performance liquid chromatography coupled with tandem mass spectrometry based on ion‐molecule reactions and the application of machine learning to predict diagnostic ion‐molecule reactions are also discussed. [ABSTRACT FROM AUTHOR]