The gas-phase acidities of long chain alcohols

Higgins, P.R.; Bartmess, John E.

doi:10.1016/s0168-1176(98)00125-6

Cited by 21 publications

(23 citation statements)

References 25 publications

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“…4). Interpretation of these spectra in the context of the kinetic method21 indicates a GA order of GA(DIPP‐Gly) > GA(DIPP‐ β ‐Ala) > GA(DIPP‐Aba). Since the distances between the diisopropyloxyphosphoryl group and the carboxyl group of DIPP‐Gly, DIPP‐ β ‐Ala and DIPP‐Aba progressively increase by one methylene group, this result is consistent with an effect due to the electron‐withdrawing ability of the DIPP group which influenced the carboxyl acidity.…”

Section: Resultsmentioning

confidence: 99%

Sensitivity improvement of amino acids by N‐terminal diisopropyloxyphosphorylation in electrospray ionization mass spectrometry

Chen

Zhang

Chen

et al. 2004

Rapid Comm Mass Spectrometry

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With the introduction of a diisopropyloxyphosphoryl (DIPP) group at the N-terminus of amino acids, the signal response in electrospray ionization mass spectrometry can be enhanced by 10-100-fold in positive mode and even more in negative mode. An enhancement of proton affinity due to the N-terminal DIPP derivatization was considered to be responsible for the sensitivity improvement in positive mode, which was supported by kinetic method studies. Two possible mechanisms, i.e., an increase in gas-phase acidity due to the introduction of the electron-withdrawing DIPP group, and the effect of pH on the formation of anions of amino acids and their phosphorylated derivatives, were considered for the signal response enhancement in negative mode.

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Section: Resultsmentioning

confidence: 99%

Sensitivity improvement of amino acids by N‐terminal diisopropyloxyphosphorylation in electrospray ionization mass spectrometry

Chen

Zhang

Chen

et al. 2004

Rapid Comm Mass Spectrometry

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“…Catalán concluded that intramolecular hydrogen bonding -O Ð Ð Ð H 3 Cincreased the acidities beyond C 4 over that expected from the linear correlation. Higgins and Bartmess 68 also noted that the acidity-ionization energy correlation broke down beyond the C 4 alkanol.…”

Section: Methodsmentioning

confidence: 95%

Linear free energy correlations in mass spectrometry

Harrison

1999

J. Mass Spectrom.

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“…Because the present goal is merely to obtain physically reasonable parameters for model calculations, a single conformation has been chosen for each species. For the n-alkanols and n-alkoxides, stretched conformations are used (neglecting intramolecular interactions between the alkyl chain and the oxygen so that the reverse activation energies due to those interactions in the actual alkanols [42] are excluded in the model). Vibrational frequencies are calculated at the HF/6-31G* level and are scaled by a factor of 0.89 [43].…”

Section: Model Systemsmentioning

confidence: 99%

Microcanonical analysis of the kinetic method. The meaning of the “apparent entropy”

Ervin

2002

J. Am. Soc. Mass Spectrom.

135

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A rigorous analysis of the kinetic method is carried out using Rice-Ramsperger-KasselMarcus (RRKM) theory of microcanonical statistical unimolecular dissociation rates. The model employs a kinetics treatment appropriate for metastable ion dissociation. Protonbound alkoxide dimer anions are used as model systems, with realistic vibrational and rotational parameters calculated by ab initio methods for the cluster ion and transition states leading to the competitive dissociation channels. The numerical simulations show that the kinetic method plots of ln(I 2 /I 1 ) versus ⌬⌬H are nearly linear but can exhibit significant curvature. The apparent entropy obtained in the extended kinetic method is not approximately equal to the thermodynamic entropy difference for dissociation, ⌬⌬S(T), or for activation, ⌬⌬S ‡ (T), either at the effective temperature or at any fixed equilibrium temperature. Instead, the apparent entropy term can be related to the ratio of the microcanonical sum of states of the dissociation transition states for the kinetically selected internal energy of the dissociating ions. (J Am Soc Mass Spectrom 2002, 13, 435-452)

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The gas-phase acidities of long chain alcohols

Cited by 21 publications

References 25 publications

Sensitivity improvement of amino acids by N‐terminal diisopropyloxyphosphorylation in electrospray ionization mass spectrometry

Sensitivity improvement of amino acids by N‐terminal diisopropyloxyphosphorylation in electrospray ionization mass spectrometry

Linear free energy correlations in mass spectrometry

Microcanonical analysis of the kinetic method. The meaning of the “apparent entropy”

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