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Zhang B, Burchill L, Altalhi WAO, Ma HZ, O'Hair RAJ. A fixed-charge model of the N-protomer of 4-aminobenzoic acid to facilitate the study of the unimolecular and bimolecular chemistry of its "neutral" carboxylic acid group. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2024; 38:e9681. [PMID: 38355884 DOI: 10.1002/rcm.9681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 11/24/2023] [Accepted: 11/25/2023] [Indexed: 02/16/2024]
Abstract
RATIONALE There are a growing number of examples of protomers formed via electrospray ionization (ESI) that do not fragment under mobile proton conditions, giving rise to distinct tandem mass spectra. To model the N-protomer of 4-aminobenzoic acid, here we study the gas-phase unimolecular and bimolecular chemistry of the 4-(carboxyphenyl)trimethylammonium ion. METHODS 4-(Carboxyphenyl)trimethylammonium iodide was synthesized, purified via recrystallization and transferred to the gas phase via ESI. 4-(Carboxyphenyl)trimethylammonium ion, 7, was mass selected and subjected to collision-induced dissociation and ion-molecule reactions in a linear ion trap mass spectrometer. RESULTS The major fragmentation channel for the fixed-charge cation 7 is methyl radical loss, whereas loss of trimethylamine and CO2 represents minor pathways. The free carboxylic acid functional group of 7 is unreactive toward a number of neutral reagents (methanol, acetone, acetonitrile, and N,N'-diisopropylcarbodiimide). 7 reacts very slowly with trimethylborate via addition-elimination, consistent with density functional theory (DFT) calculations that show this reaction is slightly endothermic. The deuterated cation 7(D) undergoes slow D/H exchange with ethanol, and DFT calculations reveal that a flip-flop mechanism operates. CONCLUSIONS The free carboxylic group of 7 is not very reactive toward neutral reagents in the gas phase.
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Affiliation(s)
- Beiang Zhang
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Laura Burchill
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Weam A O Altalhi
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
- Department of Chemistry, Prince Sattam Bin Abdulaziz University, Hotat Bani Tamim, Saudi Arabia
| | - Howard Z Ma
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
| | - Richard A J O'Hair
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria, Australia
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2
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Raczyńska ED, Gal JF, Maria PC. Enhanced Basicity of Push-Pull Nitrogen Bases in the Gas Phase. Chem Rev 2016; 116:13454-13511. [PMID: 27739663 DOI: 10.1021/acs.chemrev.6b00224] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nitrogen bases containing one or more pushing amino-group(s) directly linked to a pulling cyano, imino, or phosphoimino group, as well as those in which the pushing and pulling moieties are separated by a conjugated spacer (C═X)n, where X is CH or N, display an exceptionally strong basicity. The n-π conjugation between the pushing and pulling groups in such systems lowers the basicity of the pushing amino-group(s) and increases the basicity of the pulling cyano, imino, or phosphoimino group. In the gas phase, most of the so-called push-pull nitrogen bases exhibit a very high basicity. This paper presents an analysis of the exceptional gas-phase basicity, mostly in terms of experimental data, in relation with structure and conjugation of various subfamilies of push-pull nitrogen bases: nitriles, azoles, azines, amidines, guanidines, vinamidines, biguanides, and phosphazenes. The strong basicity of biomolecules containing a push-pull nitrogen substructure, such as bioamines, amino acids, and peptides containing push-pull side chains, nucleobases, and their nucleosides and nucleotides, is also analyzed. Progress and perspectives of experimental determinations of GBs and PAs of highly basic compounds, termed as "superbases", are presented and benchmarked on the basis of theoretical calculations on existing or hypothetical molecules.
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Affiliation(s)
- Ewa D Raczyńska
- Department of Chemistry, Warsaw University of Life Sciences (SGGW) , ul. Nowoursynowska 159c, 02-776 Warszawa, Poland
| | - Jean-François Gal
- Institut de Chimie de Nice (ICN) - UMR CNRS 7272, University Nice Sophia Antipolis , Parc Valrose, 06108 Nice Cedex 2, France
| | - Pierre-Charles Maria
- Institut de Chimie de Nice (ICN) - UMR CNRS 7272, University Nice Sophia Antipolis , Parc Valrose, 06108 Nice Cedex 2, France
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3
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Samet M, Buhle J, Zhou Y, Kass SR. Charge-Enhanced Acidity and Catalyst Activation. J Am Chem Soc 2015; 137:4678-80. [DOI: 10.1021/jacs.5b01805] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Masoud Samet
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jordan Buhle
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Yunwen Zhou
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Steven R. Kass
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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Komasa A, Katrusiak A, Kaźmierczak M, Dega-Szafran Z, Szafran M. Spectroscopic, structural and theoretical investigation of bis(4-trimethylammoniumbenzoate) hydroiodide hydrate. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2015; 136 Pt B:1149-1156. [PMID: 25459511 DOI: 10.1016/j.saa.2014.09.138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 09/05/2014] [Accepted: 09/18/2014] [Indexed: 06/04/2023]
Abstract
The structure of bis(4-trimethylammoniumbenzoate) hydroiodide hydrate 1 has been studied by X-ray diffraction, B3LYP/6-311G(d,p) calculations, FTIR, Raman and NMR spectroscopic techniques. The crystal is polar in monoclinic space group Cc. Two 4-trimethylammoniumbenzoate moieties are joined by a short and asymmetric hydrogen bond of 2.45(2) Å. Water molecules are gradually released from the structure, causing shifts in the position of iodine anions, which induces their disorder. The water molecule interacts with 4-trimethylammoniumbenzoate moiety and iodide anion via two O(3)-H(1)⋯O(1) and O(3)-H(2)⋯I(1) hydrogen bonds of lengths 2.70(3) and 3.51(1) Å. Hydrogen bonds in theoretically predicted structures of 2 and 3 (in vacuum), and 4, 5 (in DMSO) optimized by the B3LYP/6-311G(d,p) approach are slightly longer than in crystal 1. The FTIR spectrum of 1 shows a broad and intense absorption in the 1500-400 cm(-1) region, typical of short hydrogen bonds assigned to the νas(OHO)+γ(OHO) vibrations. The correlations between the experimental (13)C and (1)H chemical shifts (δexp) of the investigated compound in DMSO and the GIAO/B3LYP/6-311G(d,p) magnetic isotropic shielding constants (σcalc) calculated by using the screening solvation model (COSMO) are linear, δexp=a+b σcalc, and they well reproduce the experimental chemical shifts.
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Affiliation(s)
- Anna Komasa
- Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61614 Poznan, Poland.
| | - Andrzej Katrusiak
- Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61614 Poznan, Poland
| | - Michał Kaźmierczak
- Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61614 Poznan, Poland
| | - Zofia Dega-Szafran
- Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61614 Poznan, Poland
| | - Mirosław Szafran
- Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61614 Poznan, Poland
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DFT study on foscarnet as an antiviral drug: Conformer analysis, gas phase acidity, metal ion affinity and influence of metal complexation on gas phase acidity. J Mol Struct 2015. [DOI: 10.1016/j.molstruc.2014.09.075] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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6
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Structure of methyl 3-(trimethylammonium)benzoate iodide studied by X-ray diffraction, DFT calculations, NMR and FTIR spectra. J Mol Struct 2012. [DOI: 10.1016/j.molstruc.2012.02.051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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7
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Szafran M, Katrusiak A, Dega-Szafran Z, Komasa A, Kowalczyk I. Structure of methyl 4-(trimethylammonium)benzoate iodide studied by X-ray diffraction, DFT calculations, NMR and FTIR spectra. J Mol Struct 2011. [DOI: 10.1016/j.molstruc.2011.09.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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8
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Ducháčková L, Kadlčíková A, Kotora M, Roithová J. Oxygen Superbases as Polar Binding Pockets in Nonpolar Solvents. J Am Chem Soc 2010; 132:12660-7. [DOI: 10.1021/ja103744f] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Lucie Ducháčková
- Department of Organic Chemistry, Charles University in Prague, Hlavova 8, 12843 Prague 2, Czech Republic
| | - Aneta Kadlčíková
- Department of Organic Chemistry, Charles University in Prague, Hlavova 8, 12843 Prague 2, Czech Republic
| | - Martin Kotora
- Department of Organic Chemistry, Charles University in Prague, Hlavova 8, 12843 Prague 2, Czech Republic
| | - Jana Roithová
- Department of Organic Chemistry, Charles University in Prague, Hlavova 8, 12843 Prague 2, Czech Republic
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9
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Manríquez R, López-Dellamary FA, Frydel J, Emmler T, Breitzke H, Buntkowsky G, Limbach HH, Shenderovich IG. Solid-State NMR Studies of Aminocarboxylic Salt Bridges in l-Lysine Modified Cellulose. J Phys Chem B 2008; 113:934-40. [DOI: 10.1021/jp8081968] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ricardo Manríquez
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany; Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Kilómetro 15.5, Carretera Guadalajara-Nogales, Guadalajara, C.P. 45020, Jalisco, México; Institut für Physikalische Chemie, Universität Jena, Helmholtzweg 4, D-07743, Jena, Germany; and V.A. Fock Institute of Physics, St.Petersburg State University, Ulianovskaya 1, 198504 St. Petersburg, Russian Federation
| | - Fernando A. López-Dellamary
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany; Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Kilómetro 15.5, Carretera Guadalajara-Nogales, Guadalajara, C.P. 45020, Jalisco, México; Institut für Physikalische Chemie, Universität Jena, Helmholtzweg 4, D-07743, Jena, Germany; and V.A. Fock Institute of Physics, St.Petersburg State University, Ulianovskaya 1, 198504 St. Petersburg, Russian Federation
| | - Jaroslaw Frydel
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany; Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Kilómetro 15.5, Carretera Guadalajara-Nogales, Guadalajara, C.P. 45020, Jalisco, México; Institut für Physikalische Chemie, Universität Jena, Helmholtzweg 4, D-07743, Jena, Germany; and V.A. Fock Institute of Physics, St.Petersburg State University, Ulianovskaya 1, 198504 St. Petersburg, Russian Federation
| | - Thomas Emmler
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany; Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Kilómetro 15.5, Carretera Guadalajara-Nogales, Guadalajara, C.P. 45020, Jalisco, México; Institut für Physikalische Chemie, Universität Jena, Helmholtzweg 4, D-07743, Jena, Germany; and V.A. Fock Institute of Physics, St.Petersburg State University, Ulianovskaya 1, 198504 St. Petersburg, Russian Federation
| | - Hergen Breitzke
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany; Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Kilómetro 15.5, Carretera Guadalajara-Nogales, Guadalajara, C.P. 45020, Jalisco, México; Institut für Physikalische Chemie, Universität Jena, Helmholtzweg 4, D-07743, Jena, Germany; and V.A. Fock Institute of Physics, St.Petersburg State University, Ulianovskaya 1, 198504 St. Petersburg, Russian Federation
| | - Gerd Buntkowsky
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany; Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Kilómetro 15.5, Carretera Guadalajara-Nogales, Guadalajara, C.P. 45020, Jalisco, México; Institut für Physikalische Chemie, Universität Jena, Helmholtzweg 4, D-07743, Jena, Germany; and V.A. Fock Institute of Physics, St.Petersburg State University, Ulianovskaya 1, 198504 St. Petersburg, Russian Federation
| | - Hans-Heinrich Limbach
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany; Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Kilómetro 15.5, Carretera Guadalajara-Nogales, Guadalajara, C.P. 45020, Jalisco, México; Institut für Physikalische Chemie, Universität Jena, Helmholtzweg 4, D-07743, Jena, Germany; and V.A. Fock Institute of Physics, St.Petersburg State University, Ulianovskaya 1, 198504 St. Petersburg, Russian Federation
| | - Ilja G. Shenderovich
- Institut für Chemie und Biochemie, Freie Universität Berlin, Takustrasse 3, D-14195 Berlin, Germany; Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Kilómetro 15.5, Carretera Guadalajara-Nogales, Guadalajara, C.P. 45020, Jalisco, México; Institut für Physikalische Chemie, Universität Jena, Helmholtzweg 4, D-07743, Jena, Germany; and V.A. Fock Institute of Physics, St.Petersburg State University, Ulianovskaya 1, 198504 St. Petersburg, Russian Federation
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Fattahi A, Tavasoli E. Conversion of a weak organic acid to a super acid in the gas phase. J PHYS ORG CHEM 2008. [DOI: 10.1002/poc.1292] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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11
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Raczyńska ED, Gal JF, Maria PC, Zientara K, Szelag M. Application of FT-ICR-MS for the study of proton-transfer reactions involving biomolecules. Anal Bioanal Chem 2007; 389:1365-80. [PMID: 17786415 DOI: 10.1007/s00216-007-1508-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2007] [Revised: 07/06/2007] [Accepted: 07/12/2007] [Indexed: 10/22/2022]
Abstract
Fourier transform ion cyclotron resonance mass spectrometry, combined with modern ionization (fast atom bombardment , electrospray ionization, matrix-assisted laser desorption-ionization), fragmentation (collision-induced dissociation, surface-induced dissociation, one-photon ultraviolet photodissociation, infrared multiphoton dissociation, blackbody infrared radiative dissociation, electron-capture dissociation), and separation (high-performance liquid chromatography, liquid chromatography, capillary electrophoresis) techniques is now becoming one of the most attractive and frequently used instrumental platforms for gas-phase studies of biomolecules such as amino acids, bioamines, peptides, polypeptides, proteins, nucleobases, nucleosides, nucleotides, polynucleotides, nucleic acids, saccharides, polysaccharides, etc. Since it gives the possibilities to trap the ions from a few seconds up to thousands of seconds, it is often applied to study ion/molecule reactions in the gas phase, particularly proton-transfer reactions which provide important information on acid-base properties. These properties determine in part the three-dimensional structure of biomolecules, most of their intramolecular and intermolecular interactions, and consequently their biological activity. They also indicate the form (unionized, zwitterionic, protonated, or deprotonated) which the biomolecule may take in a nonpolar environment.
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Affiliation(s)
- E D Raczyńska
- Department of Chemistry, Warsaw University of Agriculture (SGGW), 02-726 Warsaw, Poland.
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12
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Ren J. Polar Group Enhanced Gas-Phase Acidities of Carboxylic Acids: An Investigation of Intramolecular Electrostatic Interaction. J Phys Chem A 2006; 110:13405-11. [PMID: 17165865 DOI: 10.1021/jp0624855] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We studied the effects of polar groups on the gas-phase acidities of carboxylic acids experimentally and computationally. In this connection, the gas-phase acidities (DeltaH(acid), the enthalpy of deprotonation, and DeltaG(acid), the deprotonation free energy) of borane-complexed methylaminoacetic acid ((CH(3))2N(BH(3))CH(2)CO(2)H) and methylthioacetic acid (CH(3)S(BH(3))CH(2)CO(2)H) were measured using the kinetic method in a flowing afterglow-triple quadrupole mass spectrometer. The values of DeltaH(acid) and DeltaG(acid) of (CH(3))2N(BH(3))CH(2)CO(2)H were determined to be 328.8 +/- 1.9 and 322.1 +/- 1.9 kcal/mol, and those of CH(3)S(BH(3))CH(2)CO(2)H were determined to be 325.8 +/- 1.9 and 319.2 +/- 1.9 kcal/mol, respectively. The theoretical enthalpies of deprotonation of (CH(3))2N(BH(3))CH(2)CO(2)H (329.2 kcal/mol) and CH(3)S(BH(3))CH(2)CO(2)H (325.5 kcal/mol) were calculated at the B3LYP/6-31+G(d) level of theory. The calculated enthalpies of deprotonation of N-oxide-acetic acid (CH(3)NOCH(2)CO(2)H, 329.4 kcal/mol) and S-oxide-acetic acid (CH(3)SOCH(2)CO(2)H, 328.6 kcal/mol) are comparable to the experimental results for borane-complexed methylamino- and methylthioacetic acids. The enthalpy of deprotonation of sulfone-acetic acid (CH(3)SO2CH(2)CO(2)H, 326.1 kcal/mol) is about 2 kcal/mol lower than the S-oxide-acetic acid. The calculated enthalpy of deprotonation of sulfoniumacetic acid, (CH(3))2S+CH(2)CO(2)H, is 243.0 kcal/mol. Compared to the corresponding reference molecules, CH(3)NHCH(2)CO(2)H and CH(3)SCH(2)CO(2)H, the dipolar group and the monopolar group substituted carboxylic acids are stronger acids by 11-14 and 97 kcal/mol, respectively. We correlated the changes of the acidity upon a polar group substitution to the electrostatic free energy within the carboxylate anion. The acidity enhancements in polar group substituted carboxylic acids are the results of the favorable electrostatic interactions between the polar group and the developing charge at the carboxyl group.
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Affiliation(s)
- Jianhua Ren
- Department of Chemistry, University of the Pacific, Stockton, California 95211, USA.
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Gattin Z, Kovačević B, Maksić ZB. Cooperative Intramolecular Hydrogen Bonding Effect and Basicity -An Ab Initio and DFT Study of the Superbasic Properties ofN-[(Dimethylamino)alkyl]-2,3-diaminocycloprop-2-ene-1-imines. European J Org Chem 2005. [DOI: 10.1002/ejoc.200500054] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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14
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Wong RL, Williams ER, Counterman AE, Clemmer DE. Evaluation of ion mobility spectroscopy for determining charge-solvated versus salt-bridge structures of protonated trimers. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2005; 16:1009-19. [PMID: 15914022 DOI: 10.1016/j.jasms.2005.03.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Revised: 03/21/2005] [Accepted: 03/24/2005] [Indexed: 05/02/2023]
Abstract
The cross sections of five different protonated trimers consisting of two base molecules and trifluoroacetic acid were measured by using ion mobility spectrometry. The gas-phase basicities of these five base molecules span an 8-kcal/mol range. These cross sections are compared with those determined from candidate low-energy salt-bridge and charge-solvated structures identified by using molecular mechanics calculations using three different force fields: AMBER*, MMFF, and CHARMm. With AMBER*, the charge-solvated structures are all globular and the salt-bridge structures are all linear, whereas with CHARMm, these two forms of the protonated trimers can adopt either shape. Globular structures have smaller cross sections than linear structures. Conclusions about the structure of these protonated trimers are highly dependent on the force field used to generate low-energy candidate structures. With AMBER*, all of the trimers are consistent with salt-bridge structures, whereas with MMFF the measured cross sections are more consistent with charge-solvated structures, although the assignments are ambiguous for two of the protonated trimers. Conclusions based on structures generated by using CHARMm suggest a change in structure from charge-solvated to salt-bridge structures with increasing gas-phase basicity of the constituent bases, a result that is most consistent with structural conclusions based on blackbody infrared radiative dissociation experiments for these protonated trimers and theoretical calculations on the uncharged base-acid pairs.
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Affiliation(s)
- Richard L Wong
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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15
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Vianello R, Liebman JF, Maksić ZB. In Search of Ultrastrong Brønsted Neutral Organic Superacids: A DFT Study on Some Cyclopentadiene Derivatives. Chemistry 2004; 10:5751-60. [PMID: 15484200 DOI: 10.1002/chem.200400337] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
An efficient but reasonably accurate B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) computational procedure showed that pentasubstituted cyclopentadienes such as (CN)5C5H, (NO2)5C5H, and (NC)5C5H containing strongly electron-withdrawing groups are neutral organic superacids of unprecedented strength. The boldface denotes the atom attached to the cyclopentadiene framework. All of them exhibit prototropic tautomerism by forming somewhat more stable structures with C=NH, NO2H, and N=CH exocyclic fragments, respectively. The acidity (DeltaH(acid)) of these is lower, but only to a rather small extent. The DeltaH(acid) enthalpies of these last three tautomers are estimated to be 271, 276, and 282 kcal mol(-1), respectively. Hence, the most stable tautomers of (CN)5C5H and (NC)5C5H represent a legitimate target for synthetic chemists. On the other hand, (NO2)5C5H is less suitable for practical applications, because of its high energy density. The origin of the highly pronounced acidity of these compounds was analyzed by using the recently developed triadic formula. It is found that very high Koopmans' ionization energy (IE)n(Koop) of conjugate bases exerts a decisive influence on acidity. It follows as a corollary that the overwhelming effect leading to very high acidity is due to the properties of the final state. An alternative picture is offered by homodesmotic reactions, wherein the cyclic systems are compared with their linear counterparts. It is found that the acidity of cyclopentadiene (CP) is a consequence of aromatic stabilization in the CP- anion. The extreme acidity of pentacyanocyclopentadiene (CN)5C5H is due to aromatization of the five-membered ring and a strong anionic resonance effect in the resultant conjugate base. The neutral organic superacids predicted by the present calculations may help to bridge the gap between existing very strong acids and bases.
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Affiliation(s)
- Robert Vianello
- Quantum Organic Chemistry Group, Division of Organic Chemistry and Biochemistry, Ruder Bosković Institute, P.O. Box 180, HR-10 002 Zagreb, Croatia
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Dunbar RC. BIRD (blackbody infrared radiative dissociation): evolution, principles, and applications. MASS SPECTROMETRY REVIEWS 2004; 23:127-158. [PMID: 14732935 DOI: 10.1002/mas.10074] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Blackbody infrared radiative dissociation (BIRD) describes the observation of ion-dissociation reactions at essentially zero pressure by the ambient blackbody radiation field, which is usually studied in the ion-trapping ion cyclotron resonance (ICR) mass spectrometer. A brief summary of the historical context and evolution is provided. Focussing on the quantitative observation of the temperature dependence of BIRD rates, methods are developed for connecting BIRD observations with activation parameters and dissociation thermochemistry. Three regimes are differentiated and described, comprising large molecules, small molecules, and intermediate-sized molecules. The different approaches to interpreting BIRD kinetics in those three regimes are discussed. In less than a decade since its inception, this approach to studying gas-phase ions has spread over a wide variety of applications, which are surveyed. Some major areas of activity are: the characterization of solvent-molecule detachment from solvated ions; dissociation reactions of biomolecules (polypeptides, oligonucleotides, complexes involving polysaccharides) and the structural information to be deduced from them; and dissociations of proton-bound and metal-ion-containing complexes. Studies of blackbody-radiation-driven evaporation of water molecules from large water-cluster ions are surveyed briefly. Several techniques related to BIRD are noted, including collisional dissociation in the FT-ICR ion trap; high-pressure thermal dissociation in quadrupole ion traps and in heated inlet capillary regions; hot-filament-assisted dissociation; and infrared multiphoton dissociation (IRMPD).
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Affiliation(s)
- Robert C Dunbar
- Chemistry Department, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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Mora AJ, Delgado G, Ramı́rez BM, Rincón L, Almeida R, Cuervo J, Bahsas A. The role of H-bonding in the structure of the 4-piperidinecarboxylic acid monohydrate. J Mol Struct 2002. [DOI: 10.1016/s0022-2860(02)00217-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Gal JF, Maria PC, Raczyńska ED. Thermochemical aspects of proton transfer in the gas phase. JOURNAL OF MASS SPECTROMETRY : JMS 2001; 36:699-716. [PMID: 11473393 DOI: 10.1002/jms.202] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The beginning of the twentieth century saw the development of new theories of acidity and basicity, which are currently well accepted. The thermochemistry of proton transfer in the absence of solvent attracted much interest during this period, because of the fundamental importance of the process. Nevertheless, before the 1950s, few data were available, either from lattice energy evaluations or from calculations using the emerging molecular orbital theory. Advances in mass spectrometry during the last 40 years allowed studies of numerous systems with better accuracy. Thousands of accurate gas-phase acidities or basicities are now available, for simple atomic and molecular systems and for large biomolecules. The intrinsic effect of structure on the Brønsted basic or acidic properties of molecules and the influence of solvents have been unravelled. In this tutorial, the basics of the thermodynamic principles involved are given, and the mass spectrometric techniques are briefly reviewed. Advances in the design and measurements of gas-phase superacids and superbases are described. Recent studies concerning biomolecules are also evoked.
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Affiliation(s)
- J F Gal
- Chimie des Matériaux Organiques et Métalliques, Université de Nice--Sophia Antipolis, 06108 Nice Cedex 2, France.
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Affiliation(s)
- K M Ervin
- Department of Chemistry and Chemical Physics Program, University of Nevada, Reno, Nevada 89557, USA.
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Broadus KM, Kass SR. Probing Electrostatic Effects: Formation and Characterization of Zwitterionic Ions and Their “Neutral” Counterparts in the Gas Phase. J Am Chem Soc 2000. [DOI: 10.1021/ja0016708] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Katherine M. Broadus
- Contribution from the Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
| | - Steven R. Kass
- Contribution from the Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455
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Wang XB, Broadus KM, Wang LS, Kass SR. Photodetachment of the First Zwitterionic Anions in the Gas Phase: Probing Intramolecular Coulomb Repulsion and Attraction. J Am Chem Soc 2000. [DOI: 10.1021/ja001943z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Xue-Bin Wang
- Department of Physics, Washington State University 2710 University Drive, Richland, Washington 99352 W. R. Wiley Environmental Molecular Science Laboratory MS K8-88, Pacific Northwest National Laboratory P.O. Box 999, Richland, Washington 99352 Department of Chemistry, University of Minnesota Minneapolis, Minnesota 55455
| | - Katherine M. Broadus
- Department of Physics, Washington State University 2710 University Drive, Richland, Washington 99352 W. R. Wiley Environmental Molecular Science Laboratory MS K8-88, Pacific Northwest National Laboratory P.O. Box 999, Richland, Washington 99352 Department of Chemistry, University of Minnesota Minneapolis, Minnesota 55455
| | - Lai-Sheng Wang
- Department of Physics, Washington State University 2710 University Drive, Richland, Washington 99352 W. R. Wiley Environmental Molecular Science Laboratory MS K8-88, Pacific Northwest National Laboratory P.O. Box 999, Richland, Washington 99352 Department of Chemistry, University of Minnesota Minneapolis, Minnesota 55455
| | - Steven R. Kass
- Department of Physics, Washington State University 2710 University Drive, Richland, Washington 99352 W. R. Wiley Environmental Molecular Science Laboratory MS K8-88, Pacific Northwest National Laboratory P.O. Box 999, Richland, Washington 99352 Department of Chemistry, University of Minnesota Minneapolis, Minnesota 55455
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