Proton Affinities of Primary Alkanols:  An Appraisal of the Kinetic Method

Holmes, John L.; Aubry, Christiane; Mayer, Paul M.

doi:10.1021/jp984094z

Cited by 44 publications

(87 citation statements)

References 13 publications

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“…For this reason, the first applications of MassKinetics were related to modeling of the kinetic method 79. Probably the best illustration is the case of protonated alcohol clusters,80 studied experimentally by Holmes et al ,81 using metastable ions. In our study, the critical energy and transition state model was taken from Holmes et al 81 and vibrational frequencies were calculated by the (very simple) AM182 molecular orbital method.…”

Section: Applications and Outlookmentioning

confidence: 99%

“…Probably the best illustration is the case of protonated alcohol clusters,80 studied experimentally by Holmes et al ,81 using metastable ions. In our study, the critical energy and transition state model was taken from Holmes et al 81 and vibrational frequencies were calculated by the (very simple) AM182 molecular orbital method. The internal energy distribution of ions leaving the chemical ionization ion source was assumed to be thermal, and the time‐scale was calculated from straightforward instrument parameters.…”

Section: Applications and Outlookmentioning

confidence: 99%

“… Comparison of ln([R 1 OH 2 + ]/[R 2 OH 2 + ]) vs proton affinity plots of obtained experimentally (Holmes et al ,81 shown by +) and calculated by the MassKinetics program (Thomas et al ,80 shown by •) …”

Section: Applications and Outlookmentioning

confidence: 99%

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MassKinetics: a theoretical model of mass spectra incorporating physical processes, reaction kinetics and mathematical descriptions

2001

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A theoretical framework and an accompanying computer program (MassKinetics, www.chemres.hu/ms/ masskinetics) is developed for describing reaction kinetics under statistical, but non-equilibrium, conditions, i.e. those applying to mass spectrometry. In this model all the important physical processes influencing product distributions are considered: reactions, including the effects of acceleration, collisions and photon exchange. These processes occur simultaneously and are taken into account by the master equation approach. The system is described by (independent) product, kinetic energy and internal energy distributions, and the time development of these distributions is studied using transition probability functions. The product distribution at the end of the experiment corresponds to the mass spectrum. Individual elements in this scheme are mostly well known: internal energy-dependent reaction rates are calculated by transition state theory (RRK or RRKM formalisms). In the course of collisions, energy transfer and other processes may occur (the latter usually resulting in the 'loss' of ion signal). Collisions are characterized by their probability and by energy transfer in a single collision. To describe single collisions, three collision models are used: long-lived collision complexes, partially inelastic collisions and partially inelastic collisions with cooling. The latter type has been developed here, and is capable of accounting for cooling effects occurring in collision cascades. Descriptions of photon absorption and emission are well known in principle, and these are also taken into account, in addition to changes in kinetic energy due to external (electric) fields. These changes in the system occur simultaneously, and are described by master equations (a set of differential equations). The usual form of the master equation (taking into account reactions and collisional excitation) was extended to consider also radiative energy transfer, kinetic energy changes, energy partitioning and ion loss collisions. Initial results show that close to experimental accuracy can be obtained with MassKinetics, using few or no adjustable parameters. The model/program can be used to model almost all types of mass spectrometric experiments (e.g. MIKE, CID, SORI and resonant excitation). Note that it was designed for mass spectrometric applications, but can also be used to study reaction kinetics in other non-equilibrium systems.

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Section: Applications and Outlookmentioning

confidence: 99%

Section: Applications and Outlookmentioning

confidence: 99%

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MassKinetics: a theoretical model of mass spectra incorporating physical processes, reaction kinetics and mathematical descriptions

2001

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“…The RAs of the final product ions [ A + H] + and [ B + H] + follow a relationship with the PAs of A and B (Eqn.)

ln ({[A + H]}^{+} / {[B + H]}^{+}) = {P A (A) - P A (B)} / R T_{italiceff}

…”

Section: Resultsmentioning

confidence: 99%

Gas phase retro‐Michael reaction resulting from dissociative protonation: fragmentation of protonated warfarin in mass spectrometry

et al. 2012

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A mass spectrometric study of protonated warfarin and its derivatives (compounds 1 to 5) has been performed. Losses of a substituted benzylideneacetone and a 4-hydroxycoumarin have been observed as a result of retro-Michael reaction. The added proton is initially localized between the two carbonyl oxygens through hydrogen bonding in the most thermodynamically favorable tautomer. Upon collisional activation, the added proton migrates to the C-3 of 4-hydroxycoumarin, which is called the dissociative protonation site, leading to the formation of the intermediate ion-neutral complex (INC). Within the INC, further proton transfer gives rise to a proton-bound complex. The cleavage of one hydrogen bond of the proton-bound complex produces the protonated 4-hydroxycoumarin, while the separation of the other hydrogen bond gives rise to the protonated benzylideneacetone. Theoretical calculations indicate that the 1, 5-proton transfer pathway is most thermodynamically favorable and support the existence of the INC. Both substituent effect and the kinetic method were utilized for explaining the relative abundances of protonated 4-hydroxycoumarin and protonated benzylideneacetone derivative. For monosubstituted warfarins, the electron-donating substituents favor the generation of protonated substituted benzylideneacetone, whereas the electron-withdrawing groups favor the formation of protonated 4-hydroxycoumarin.

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“…The choice of reference analyte and metal mediator is important to the success of the experiment. The KM has been applied to a variety of different molecule types, including amino acids [9], peptides [13], alcohols [14], and drug compounds [15]. For these systems, suitable references were chosen and evaluated-in many cases taken from the set of natural amino acids.…”

mentioning

confidence: 99%

Isomeric discrimination of arginine-containing dipeptides using electrospray ionization-ion trap mass spectrometry and the kinetic method

Schug

Lindner

Lemr

2004

J. Am. Soc. Mass Spectrom.

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The Kinetic Method (KM), applied commonly for thermochemical determinations, is used here for sterically-controlled isomeric determination of N- versus C-terminal Arg-containing dipeptide isomers (ArgX versus XArg; where X = His, Leu, Lys, Pro, Ser, Phe, and Tyr). The KM is offered as an alternate approach to direct collision-induced dissociation (CID) procedures. Through formation, isolation, and dissociation of a sterically-encumbered, metal-centered complex with electrospray ionization ion trap mass spectrometry technology, reference dipeptide molecules are screened to quantitatively differentiate a mixture of isomers based on their arrangement about the metal center. Arg-containing dipeptide molecules are chosen because of their contribution in a wide array of protein and peptide functions. Additionally, problems cited previously for evaluation of systems containing Arg residues (due to the incorporation of the guanidinium moiety) by the KM are addressed. The method is shown to be successful for highlighting favorable reference analytes (e.g., ArgPhe, ArgLeu, ProArg, PheArg, among others) for exceptional discrimination (R(iso) > 2.0) of the majority of N- and C-terminal Arg-containing peptides tested.

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Proton Affinities of Primary Alkanols: An Appraisal of the Kinetic Method

Cited by 44 publications

References 13 publications

MassKinetics: a theoretical model of mass spectra incorporating physical processes, reaction kinetics and mathematical descriptions

MassKinetics: a theoretical model of mass spectra incorporating physical processes, reaction kinetics and mathematical descriptions

Gas phase retro‐Michael reaction resulting from dissociative protonation: fragmentation of protonated warfarin in mass spectrometry

Isomeric discrimination of arginine-containing dipeptides using electrospray ionization-ion trap mass spectrometry and the kinetic method

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