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Pröhm P, Berg W, Rupf SM, Müller C, Riedel S. On pyridine chloronium cations. Chem Sci 2023; 14:2325-2329. [PMID: 36873856 PMCID: PMC9977394 DOI: 10.1039/d2sc06757a] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 02/04/2023] [Indexed: 02/09/2023] Open
Abstract
We present the first solid-state structural evidence of mono- and bis(pyridine)chloronium cations. The latter was synthesized from a mixture of pyridine, elemental chlorine and sodium tetrafluoroborate in propionitrile at low temperatures. The mono(pyridine) chloronium cation was realized with the less reactive pentafluoropyridine, using ClF, AsF5, and C5F5N in anhydrous HF. During the course of this study, we also investigated pyridine dichlorine adducts and found a surprising disproportionation reaction of chlorine that depended on the substitutional pattern of the pyridine. Electron richer dimethylpyridine (lutidine) derivatives favor full disproportionation into a positively and a negatively charged chlorine atom which forms a trichloride monoanion, while unsubstituted pyridine forms a 1 : 1 py·Cl2 adduct.
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Affiliation(s)
- Patrick Pröhm
- Department of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Willi Berg
- Department of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Susanne Margot Rupf
- Department of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Carsten Müller
- Department of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Sebastian Riedel
- Department of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
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2
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Østergaard LF, Hammerum S. Secondary kinetic deuterium isotope effects on unimolecular cleavage reactions: Zero-point vibrational energy and qualitative RRKM theory. MASS SPECTROMETRY REVIEWS 2021; 40:821-839. [PMID: 33615519 DOI: 10.1002/mas.21660] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 09/02/2020] [Accepted: 09/02/2020] [Indexed: 06/12/2023]
Abstract
Secondary kinetic isotope effects arise as the result of transition-state zero-point vibrational energy differences. Unimolecular simple cleavage reactions of gas-phase ions in mass spectrometers allow detailed studies of isotope effects on competing reactions, particularly when examined in intramolecular competition experiments where interpretation requires very few simplifying assumptions. The zero-point energy differences reflect changes of isotope sensitive vibrational properties, and both α- and β-secondary deuterium isotope effects are related to the sp 3 → sp 2 hybridization changes that accompany bond cleavage. Deuterium substitution three bonds or more removed from the bond broken also gives rise to isotope effects, but their origin is less easily interpreted. The magnitude and variation of the observed effects depend not only on zero-point energy differences; a number of additional factors play a role. The influence of the critical energy, the excess energy, the size of the reactant, and the presence of competing reactions can be rationalized within a simple, qualitative RRKM framework. The distinction between kinetic and thermodynamic isotope effects is not always obvious.
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Affiliation(s)
- Lars F Østergaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen Ø, DK-2100, Denmark
| | - Steen Hammerum
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, Copenhagen Ø, DK-2100, Denmark
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3
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Tang C, Tan J, Zhang P, Fan Y, Yu Z, Peng X. Energy-dependent normal and unusually large inverse chlorine kinetic isotope effects of simple chlorohydrocarbons in collision-induced dissociation by gas chromatography-electron ionization-tandem mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2020; 55:e4521. [PMID: 32567160 DOI: 10.1002/jms.4521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 03/19/2020] [Accepted: 03/27/2020] [Indexed: 06/11/2023]
Abstract
Kinetic isotope effects (KIEs) occurring in mass spectrometry (MS) can provide in-depth insights into the fragmentation behaviors of compounds of interest in MS. Yet, the fundamentals of KIEs in collision-induced dissociation (CID) in tandem mass spectrometry (MS/MS) are unclear, and information about chlorine KIEs (Cl-KIEs) of organochlorines in MS is particularly scarce. This study investigated the Cl-KIEs of dichloromethane, trichloroethylene, and tetrachloroethylene during CID using gas chromatography-electron ionization triple-quadrupole MS/MS. Cl-KIEs were evaluated with MS signal intensities. All the organochlorines presented large inverse Cl-KIEs (<1, the departures of Cl-KIEs from 1 denote the magnitudes of Cl-KIEs), showing the largest magnitudes of 0.797, 0.910, and 0.892 at the highest collision energy (60 eV) for dichloromethane, trichloroethylene, and tetrachloroethylene, respectively. For dichloromethane, both intra-ion and inter-ion Cl-KIEs were studied, within the ranges of 0.820-1.020 and 0.797-1.016, respectively, showing both normal and inverse Cl-KIEs depending on collision energies. The observed Cl-KIEs generally declined from large normal to extremely large inverse values with increasing collision energies from 0 to 60 eV but were inferred to be independent of MS signal intensities. The Cl-KIEs are dominated by critical energies at low internal energies of precursor ions, resulting in normal Cl-KIEs; while at high internal energies, the Cl-KIEs are controlled by rotational barriers (or looseness/tightness of transition states), which lead to isotope-competitive reactions in dechlorination and thereby inverse Cl-KIEs. It is concluded that the Cl-KIEs may depend on critical energies, bond strengths, available internal energies, and transition state looseness/tightness. The findings of this study yield new insights into the fundamentals of Cl-KIEs of organochlorines during CID and may be conducive to elucidating the underlying mechanisms of KIEs in collision-induced and photo-induced reactions in the actual world.
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Affiliation(s)
- Caiming Tang
- State Key Laboratory of Organic Geochemistry, Guangzhou Instituteof Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
| | - Jianhua Tan
- Guangzhou Quality Supervision and Testing Institute, Guangzhou, 510110, China
| | - Peilin Zhang
- Guangzhou Quality Supervision and Testing Institute, Guangzhou, 510110, China
| | - Yujuan Fan
- State Key Laboratory of Organic Geochemistry, Guangzhou Instituteof Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Zhiqiang Yu
- State Key Laboratory of Organic Geochemistry, Guangzhou Instituteof Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
| | - Xianzhi Peng
- State Key Laboratory of Organic Geochemistry, Guangzhou Instituteof Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
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4
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Campi B, Frascarelli S, Pietri E, Massa I, Donati C, Bozic R, Bertelloni S, Paolicchi A, Zucchi R, Saba A. Quantification of dehydroepiandrosterone in human serum on a routine basis: development and validation of a tandem mass spectrometry method based on a surrogate analyte. Anal Bioanal Chem 2017; 410:407-416. [PMID: 29110028 DOI: 10.1007/s00216-017-0731-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 09/30/2017] [Accepted: 10/26/2017] [Indexed: 01/17/2023]
Abstract
In the clinical laboratories, dehydroepiandrostenedione (DHEA) is usually quantified by immunoassay-based methods, which are often affected by cross-reactivity with endogenous interferences, such as 4-androsten-3β-ol-17-one. The interfering compounds lead to a poor accuracy of the measurements, mainly at a low concentration level. The present paper describes a validated method based on tandem mass spectrometry coupled to liquid chromatography, for the accurate quantification of DHEA in serum. The peculiarity of this method is the use of calibrators and quality controls prepared by adding measured amounts of DHEA-D5, a stable isotope-labeled analogue of DHEA, to real serum from healthy subjects. DHEA-D5 is used in place of DHEA, which is usually present in unstripped serum at physiological levels, as it has the same basic structure, provides an equivalent instrumental response, and can be easily distinguish by DHEA by mass spectrometry due to its different m/z value. The method proved to be sensitive, with a LLOD of 0.09 ng/mL and a LLOQ of 0.23 ng/mL, and selective, with overall performances that allow its use on a routine basis.
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Affiliation(s)
- Beatrice Campi
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Via Savi 10, 56126, Pisa, Italy
| | - Sabina Frascarelli
- Department of Surgical, Medical and Molecular Pathology and Critical Care Medicine, University of Pisa, Via Savi 10, 56126, Pisa, Italy
| | - Elisabetta Pietri
- Department of Medical Oncology, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Via Piero Maroncelli 40, 47014, Meldola, Forlì-Cesena, Italy
| | - Ilaria Massa
- Unit of Biostatistics and Clinical Trials, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Via Piero Maroncelli 40, 47014, Meldola, Forlì-Cesena, Italy
| | - Caterina Donati
- Oncology Pharmacy Laboratory, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Via Piero Maroncelli 40, 47014, Meldola, Forlì-Cesena, Italy
| | - Roberto Bozic
- Perkin Elmer Italia S.p.A, Viale dell'Innovazione 3, 20125, Milan, Italy
| | - Silvano Bertelloni
- Pediatric Division, Department of Obstetrics, Gynecology and Pediatrics, St. Chiara University Hospital, Via Roma 67, 56126, Pisa, Italy
| | - Aldo Paolicchi
- Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Via Savi 10, 56126, Pisa, Italy.,Laboratory of Clinical Pathology, Department of Laboratory Medicine, St. Chiara University Hospital, Via Roma 67, 56126, Pisa, Italy
| | - Riccardo Zucchi
- Department of Surgical, Medical and Molecular Pathology and Critical Care Medicine, University of Pisa, Via Savi 10, 56126, Pisa, Italy
| | - Alessandro Saba
- Department of Surgical, Medical and Molecular Pathology and Critical Care Medicine, University of Pisa, Via Savi 10, 56126, Pisa, Italy. .,Laboratory of Clinical Pathology, Department of Laboratory Medicine, St. Chiara University Hospital, Via Roma 67, 56126, Pisa, Italy.
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Bain RM, Yan X, Raab SA, Ayrton ST, Flick TG, Cooks RG. On-line chiral analysis using the kinetic method. Analyst 2016; 141:2441-6. [PMID: 26979554 DOI: 10.1039/c6an00100a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Chiral analysis of constituents in solution-phase reaction mixtures can be performed by tandem mass spectrometry using the kinetic method to determine the enantiomeric excess (ee).
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Affiliation(s)
- Ryan M. Bain
- Department of Chemistry
- Purdue University
- West Lafayette
- USA
| | - Xin Yan
- Department of Chemistry
- Purdue University
- West Lafayette
- USA
| | | | | | | | - R. Graham Cooks
- Department of Chemistry
- Purdue University
- West Lafayette
- USA
- Center for Analytical Instrumentation Development
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6
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Kanchi V, Shin JW. Kinetic Method Analysis of the Effect of cis- and trans-Hydroxylation on the Proton Affinity of Proline. Aust J Chem 2015. [DOI: 10.1071/ch15047] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Proton affinities of proline and hydroxyproline were measured using the Cooks’ kinetic method. The measurements show that hydroxylation increases the proton affinity, which is consistent with X3LYP computation results. This work supports findings from a previous study (S. Mezzache et al., Rapid Commun. Mass Spectrom. 2005, 19, 2279) that modification of proline increases its proton affinity, but it does not provide compelling evidence for the prediction in the same study that proton affinity of the molecule is substantially influenced by intramolecular interactions involving the proton. PBE1PBE calculations suggest that isotropic polarizability rather than intramolecular hydrogen-bonding interactions provides a more suitable diagnosis for trends in proton affinity changes associated with modifications.
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7
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Ashtekar K, Marzijarani NS, Jaganathan A, Holmes D, Jackson JE, Borhan B. A new tool to guide halofunctionalization reactions: the halenium affinity (HalA) scale. J Am Chem Soc 2014; 136:13355-62. [PMID: 25152188 PMCID: PMC4183602 DOI: 10.1021/ja506889c] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2014] [Indexed: 01/15/2023]
Abstract
We introduce a previously unexplored parameter-halenium affinity (HalA)- as a quantitative descriptor of the bond strengths of various functional groups to halenium ions. The HalA scale ranks potential halenium ion acceptors based on their ability to stabilize a "free halenium ion". Alkenes in particular but other Lewis bases as well, such as amines, amides, carbonyls, and ether oxygen atoms, etc., have been classified on the HalA scale. This indirect approach enables a rapid and straightforward prediction of chemoselectivity for systems involved in halofunctionalization reactions that have multiple nucleophilic sites. The influences of subtle electronic and steric variations, as well as the less predictable anchimeric and stereoelectronic effects, are intrinsically accounted for by HalA computations, providing quantitative assessments beyond simple "chemical intuition". This combined theoretical-experimental approach offers an expeditious means of predicting and identifying unprecedented reactions.
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Affiliation(s)
- Kumar
Dilip Ashtekar
- Department
of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | | | - Arvind Jaganathan
- Engineering
and Process Sciences, The Dow Chemical Company, Midland, Michigan 48674, United States
| | - Daniel Holmes
- Department
of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - James E. Jackson
- Department
of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Babak Borhan
- Department
of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
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8
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Perrin CL. Secondary equilibrium isotope effects on acidity. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2010. [DOI: 10.1016/s0065-3160(08)44003-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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9
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Schug KA, Maier NM, Lindner W. Deuterium isotope effects observed during competitive binding chiral recognition electrospray ionization--mass spectrometry of cinchona alkaloid-based systems. JOURNAL OF MASS SPECTROMETRY : JMS 2006; 41:157-61. [PMID: 16421872 DOI: 10.1002/jms.983] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Deuterium isotope effects are reported for binding between tert-butylcarbamoyl-quinine/quinidine chiral selectors and isotopomeric quasienantiomers of N-(3,5-dinitrobenzoyl)leucine measured using electrospray ionization-mass spectrometry (ESI-MS) and competitive binding. Evaluation of mixtures of each selector with one labeled and one unlabeled enantiomeric selectand of identical configuration showed a significant difference in measured ion abundances of diastereomeric complexes between the selector and each selectand. It was found that in some cases, the complex containing the nondeuterated selectand was 15% more abundant than its deuterated counterpart. On the basis of an assessment of solution- and gas-phase isotope effects reported in the literature, a series of control experiments were performed to study the origin of the effects. On the basis of these measurements, our preliminary conclusion is that the differing gas-phase physicochemical nature of the deuterated versus nondeuterated selectand represents the strongest contribution to the observed effect in this chiral molecular recognition system.
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Affiliation(s)
- Kevin A Schug
- University of Vienna, Department of Analytical Chemistry and Food Chemistry Währingerstrasse 38, A-1090 Vienna, Austria.
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10
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Norrman K, Sølling TI, McMahon TB. Isomerization of the protonated acetone dimer in the gas phase. JOURNAL OF MASS SPECTROMETRY : JMS 2005; 40:1076-87. [PMID: 15971295 DOI: 10.1002/jms.883] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Mass spectrometry-based methods have been employed in order to study the reactions of non- (h(6)/h(6)), half (d(6)/h(6)), and fully (d(6)/d(6)) deuterium labeled protonated dimers of acetone in the gas phase. Neither kinetic nor thermodynamic isotope effects were found. From MIKES experiments (both spontaneous and collision-induced dissociations), it was found that the relative ion yield (m/z 65 vs m/z 59) from the dissociation reaction of half deuterium labeled (d(6)/h(6)) protonated dimer of acetone is dependent on the internal energy. A relative ion yield (m/z 65 vs m/z 59) close to unity is observed for cold, nonactivated, metastable ions, whereas the ion yield is observed to increase (favoring m/z 65) when the pressure of the collision gas is increased. This is in striking contrast to what would be expected if a kinetic isotope effect were present. A combined study of the kinetics and the thermodynamics of the association reaction between acetone and protonated acetone implicates the presence of at least two isomeric adducts. We have employed G3(MP2) theory to map the potential energy surface leading from the reactants, acetone and protonated acetone, to the various isomeric adducts. The proton-bound dimer of acetone was found to be the lowest-energy isomer, and protonated diacetone alcohol the next lowest-energy isomer. Protonated diacetone alcohol, even though it is an isomer hidden behind many barriers, can possibly account for the observed relative ion yield and its dependence on the mode of activation.
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Affiliation(s)
- K Norrman
- The Danish Polymer Centre, Risø National Laboratory, DK-4000 Roskilde, Denmark.
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11
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Santos LS, Catharino R, Eberlin MN. The proton-bound dimer of acetone. JOURNAL OF MASS SPECTROMETRY : JMS 2005; 40:127-128. [PMID: 15643641 DOI: 10.1002/jms.791] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
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12
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Gozzo FC, Santos LS, Augusti R, Consorti CS, Dupont J, Eberlin MN. Gaseous Supramolecules of Imidazolium Ionic Liquids: ?Magic? Numbers and Intrinsic Strengths of Hydrogen Bonds. Chemistry 2004; 10:6187-93. [PMID: 15515085 DOI: 10.1002/chem.200305742] [Citation(s) in RCA: 219] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Electrospray ionization mass spectrometry (ESI-MS) is found to gently and efficiently transfer small to large as well as singly to multiply charged [X+]n[A-]m supramolecules of imidazolium ion (X+) ionic liquids to the gas phase, and to reveal "magic numbers" for their most favored assemblies. Tandem mass spectrometric experiments (ESI-MS/MS) were then used to dissociate, via low-energy collision activation, mixed and loosely bonded [A- - - -X- - - -A']- and [X- - - -A- - - -X']+ gaseous supramolecules, as well as their higher homologues, and to estimate and order via Cooks' kinetic method (CKM) and B3LYP/6-311G(d,p) calculations the intrinsic solvent-free magnitude of hydrogen bonds. For the five anions studied, the relative order of intrinsic hydrogen-bond strengths to the 1-n-butyl-3-methylimidazolium ion [X1]+ is: CF3CO2- (zero) > BF4- (-3.1) > PF6- (-10.0) > InCl4- (-16.4) and BPh4- (-17.6 kcal mol(-1)). The relative hydrogen-bond strength for InCl4- was measured via CKM whereas those for the other anions were calculated and used as CKM references. A good correlation coefficient (R=0.998) between fragment ion ratios and calculated hydrogen-bond strengths and an effective temperature (Teff) of 430 K demonstrate the CKM reliability for measuring hydrogen-bond strengths in gaseous ionic liquid supramolecules. Using CKM and Teff of 430 K, the intrinsic hydrogen-bond strengths of BF4- for the three cations investigated is: 1-n-butyl-3-methyl-imidazolium ion (0) > 1,3-di-[(R)-3-methyl-2-butyl]-imidazolium ion (-2.4) > 1,3-di-[(R)-alpha-methylbenzyl]-imidazolium ion (-3.0 kcal mol(-1)). As evidenced by "magic" numbers, greater stabilities are found for the [(X1)2(BF4)3]- and [(X1)5A4]+ supramolecules (A not equal InCl4-).
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Affiliation(s)
- Fabio C Gozzo
- Thomson Mass Spectrometry Laboratory, Institute of Chemistry, State University of Campinas, UNICAMP, 13083-970 Campinas, SP, Brazil
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13
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Sorrilha AEPM, Santos LS, Gozzo FC, Sparrapan R, Augusti R, Eberlin MN. Intrinsic Reactivity of Gaseous Halocarbocations toward Model Aromatic Compounds. J Phys Chem A 2004. [DOI: 10.1021/jp0488822] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ana E. P. M. Sorrilha
- Institute of Chemistry, State University of Campinas (UNICAMP), 13083-970 Campinas, SP Brazil, and Department of Chemistry, Federal University of Minas Gerais (UFMG), 31270-901 Belo Horizonte, MG Brazil
| | - Leonardo S. Santos
- Institute of Chemistry, State University of Campinas (UNICAMP), 13083-970 Campinas, SP Brazil, and Department of Chemistry, Federal University of Minas Gerais (UFMG), 31270-901 Belo Horizonte, MG Brazil
| | - Fábio C. Gozzo
- Institute of Chemistry, State University of Campinas (UNICAMP), 13083-970 Campinas, SP Brazil, and Department of Chemistry, Federal University of Minas Gerais (UFMG), 31270-901 Belo Horizonte, MG Brazil
| | - Regina Sparrapan
- Institute of Chemistry, State University of Campinas (UNICAMP), 13083-970 Campinas, SP Brazil, and Department of Chemistry, Federal University of Minas Gerais (UFMG), 31270-901 Belo Horizonte, MG Brazil
| | - Rodinei Augusti
- Institute of Chemistry, State University of Campinas (UNICAMP), 13083-970 Campinas, SP Brazil, and Department of Chemistry, Federal University of Minas Gerais (UFMG), 31270-901 Belo Horizonte, MG Brazil
| | - Marcos N. Eberlin
- Institute of Chemistry, State University of Campinas (UNICAMP), 13083-970 Campinas, SP Brazil, and Department of Chemistry, Federal University of Minas Gerais (UFMG), 31270-901 Belo Horizonte, MG Brazil
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14
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Meurer EC, Gozzo FC, Augusti R, Eberlin MN. The kinetic method as a structural diagnostic tool: ionized alpha-diketones as loosely one-electron bonded diacylium ion dimers. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2003; 9:295-304. [PMID: 12939482 DOI: 10.1255/ejms.563] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The kinetic method is used to corroborate the description of ground state ionized alpha-diketones as loosely electron-bonded acylium ion dimers: R(1)-C=O(+)---e(-)---(+)O=C-R(2). The abundance ratio of both the acylium ion fragments R(1)CO(+) and R(2)CO(+) (summed to those of their respective secondary fragments) formed upon low energy (5 eV) collision-induced dissociation of several ionized alpha-diketones is found to correlate linearly with the ionization energies (IEs) of the corresponding R(1)CO(.) and R(2)CO(.) free radicals as predicted by density functional theory calculations at the B3LYP/6-311++G(d,p) level. However, when these abundances are taken from 70 eV electron ionization mass spectra, lower and sometimes inverted ratios (2,3-pentanedione and 2,3-hexanedione) are observed. Inverted ratios are also observed via charge-exchange mass spectrometry/mass spectrometry (MS/MS) experiments for ionized 2,3-pentanodione formed with relatively high internal energies. Ionized alpha-diketones are found to display an effective temperature of 1705 K, which indicates an intermediate loosely-bonded nature. B3LYP/6-311++G(d,p) optimized geometries and charge and spin densities also corroborate the description of ground state ionized alpha-diketones as loosely electron-bonded diacylium ion dimers.
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Affiliation(s)
- Eduardo C Meurer
- State University of Campinas - UNICAMP, Institute of Chemistry CP6154, 13083-970 Campinas, SP Brazil
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16
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Current literature in mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2001; 36:1324-1333. [PMID: 11754125 DOI: 10.1002/jms.99] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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