Meerwein reaction of phosphonium ions with epoxides and thioepoxides in the gas phase

Meurer, Eduardo C.; Chen, Hao; Riter, Leah S.; Cooks, R. Graham; Eberlin, Marcos N.

doi:10.1016/j.jasms.2003.11.006

Cited by 15 publications

(13 citation statements)

References 44 publications

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“…156 Neste estudo, a superfície de energia potencial e a energia dos intermediários de reação em fase gasosa foram calculadas e os estados de transição caracterizados pela freqüência vibracional negativa. Os dados teóricos demonstraram que a reação de CH 3 P(O)OCH3 + com epóxidos e tioepóxidos é exotérmica, o que corrobora os resultados obtidos experimentalmente por EM.…”

Section: Reações íOn-moléculaunclassified

Aplicação da química quântica computacional no estudo de processos químicos envolvidos em espectrometria de massas

Vessecchi¹,

Galembeck²,

Lopes³

et al. 2008

Quím. Nova

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Recebido em 4/7/07; aceito em 14/11/07; publicado na web em 19/3/08 APPLICATION OF COMPUTATIONAL QUANTUM CHEMISTRY TO CHEMICAL PROCESSES INVOLVED IN MASS SPECTROMETRY. The field of application of mass spectrometry (MS) has increased considerably due to the development of ionization techniques. Other factors that have stimulated the use of MS are the tandem mass spectrometry (MS/MS) and sequential mass spectrometry (MS n ) techniques. However, the interpretation of the MS/MS and MS n data may lead to speculative conclusions. Thus, various quantum chemical methods have been applied for obtaining high quality thermochemical data in gas phase. In this review, we show some applications of computational quantum chemistry to understand the formation and fragmentation of gaseous ions of organic compounds in a MS analysis.Keywords: theoretical calculations; fragmentation studies; protonation site. INTRODUÇÃONo século passado, vários métodos e técnicas para obtenção de parâmetros moleculares aplicando a química quântica a sistemas multi-eletrônicos foram desenvolvidos. Este desenvolvimento foi fortemente impulsionado pelo aumento do poder computacional, conforme previsto pela Lei de Moore, 1 bem como pelo desenvolvimento de novos métodos computacionais e aperfeiçoamento daqueles já existentes. Atualmente, parâmetros como a energia de um sistema em uma dada geometria e freqüências vibracionais podem auxiliar na determinação da estrutura e das propriedades químicas de intermediários e de possíveis estados de transição para um dado caminho de reação, além de assistirem na obtenção de correlações entre as entalpias de reação e a temperatura, efeitos isotópicos e energias de dissociação. Comumente, nos estudos químico-quântico computacionais utiliza-se como modelo uma molécula isolada no vácuo. Há, portanto, certas similaridades entre estas condições e as condições de baixas pressões no interior de um espectrômetro de massas, onde ocorrem vários fenômenos em fase gasosa.3 Neste contexto, é possível utilizar estes métodos para se estimar uma série de parâmetros de interesse de um espectroscopista de massas, auxiliando na compreensão tanto dos fenômenos de geração de íons como nos processos de fragmentação dos mesmos.Em processos de ionização, por exemplo, é possível obter parâmetros como a energia de ionização adiabática, basicidade e afinidade protônica, entre outros. 4 No caso de substâncias que apresentam vários grupos funcionais ácidos e/ou básicos em suas estruturas, muitas vezes é difícil se identificar qual é o sítio mais suscetível à protonação ou à desprotonação, 5 mesmo existindo na literatura extensas compilações sobre acidez e basicidade em fase gasosa.6 Em princípio, a suscetibilidade à protonação apresentada por dois grupos funcionais diferentes em uma mesma estrutura quími-ca pode ser estimada a partir da diferença entre suas basicidades em fase gasosa. Entretanto, quando os grupos funcionais são parecidos, tal como os nitrogênios de cadeia lateral e de anel de histamina ou pirimidinas, a identificação do sítio m...

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Section: Reações íOn-moléculaunclassified

Aplicação da química quântica computacional no estudo de processos químicos envolvidos em espectrometria de massas

Vessecchi¹,

Galembeck²,

Lopes³

et al. 2008

Quím. Nova

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“…Ion-molecule reactions can be fast, efficient, and highly specific, properties which often are paramount to molecular characterization experiments. Ion-molecule reactions have been used for isomer differentiation [11][12][13][14], functional group identification [15][16][17][18][19][20], and detailed structural elucidation [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Functional Group Selective Ion–Molecule Reactions of Trimethyl Borate in Different Ion Trap Mass Spectrometers

Habicht

Vinueza

Amundson

et al. 2011

J. Am. Soc. Mass Spectrom.

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We report here a comparison of the use of diagnostic ion-molecule reactions for the identification of oxygen-containing functional groups in Fourier-transform ion cyclotron resonance (FTICR) and linear quadrupole ion trap (LQIT) mass spectrometers. The ultimate goal of this research is to be able to identify functionalities in previously unknown analytes by using many different types of mass spectrometers. Previous work has focused on the reactions of various boron reagents with protonated oxygen-containing analytes in FTICR mass spectrometers. By using a LQIT modified to allow the introduction of neutral reagents into the helium buffer gas, this methodology has been successfully implemented to this type of an ion trap instrument. The products obtained from the reactions of trimethyl borate (TMB) with various protonated analytes are compared for the two instruments. Finally, the ability to integrate these reactions into LC-MS experiments on the LQIT is demonstrated.

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“…Ethylnitrilium ion (CH 3 Ϫ C ϵ N ϩ H and its canonical form CH 3 Ϫ C ϩ ϭ NH) resembles acylium ions that have been known to efficiently undergo the gas-phase Meerwein reaction with epoxides in the gas phase [21,22]. The formation of the Meerwein reaction products of epoxides I-IV with ethylnitrilium ion were confirmed by the exact mass measurements within an error of 3.6 ppm.…”

Section: Atmospheric Pressure Gas-phase Meerwein Reaction Of Epoxidesmentioning

confidence: 76%

“…The reaction proceeds by an initial O-acylation followed by an intramolecular nucleophilic attack. This results in three-to-fivemembered ring expansion to yield cyclic 1,3-dioxolanylium ions [21][22][23]. This structure-selective reaction, which displays many features common to those of transacetalization reactions of acylium ions with acetals and analogs [1], has been demonstrated to be very useful for both characterization and selective screening of specific compounds such as warfare agents [24].…”

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confidence: 99%

Gas-phase Meerwein reaction of epoxides with protonated acetonitrile generated by atmospheric pressure ionizations

Liu

Kord

2010

J. Am. Soc. Mass Spectrom.

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Ethylnitrilium ion can be generated by protonation of acetonitrile (when used as the LC-MS mobile phase) under the conditions of atmospheric pressure ionizations, including electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) as well as atmospheric pressure photoionization (APPI). Ethylnitrilium ion (CH 3 Ϫ C ϵ N ϩ H and its canonical form CH 3 Ϫ C ϩ ϭ NH) is shown to efficiently undergo the gas-phase Meerwein reaction with epoxides. This reaction proceeds by the initial formation of an oxonium ion followed by three-to-five-membered ring expansion via an intramolecular nucleophilic attack to yield the Meerwein reaction products. The density functional theory (DFT) calculations at the B3LYP/6-311ϩG(d,p) level show that the gas-phase Meerwein reaction is thermodynamically favorable. Collision-induced dissociation (CID) of the Meerwein reaction products yields the net oxygen-by-nitrogen replacement of epoxides with a characteristic mass shift of 1 Da, providing evidence for the cyclic nature of the gas-phase Meerwein reaction products. The gas-phase Meerwein reaction offers a novel and fast LC-MS approach for the direct analysis of epoxides that might be of genotoxic concern during drug development. Understanding and utilizing this unique gas-phase ion/molecule reaction, the sensitivity and selectivity for quantitation of epoxides can be enhanced. (J Am Soc Mass Spectrom 2010, 21, 1802-1813) © 2010 American Society for Mass Spectrometry G as-phase ion/molecule reactions are fast, efficient, and highly sensitive to the fine structural variations such as relative positions of functional groups. Their product distributions often provide diagnostic information for structural characterization of both reactant ions and neutral molecules [1][2][3][4]. Ion/ molecule reactions have also contributed significantly to the elucidation of organic reaction mechanisms, helping to bridge the gap between gas-phase ion chemistry and condensed-phase organic chemistry. It also provides access to key properties and intrinsic reactivities of a great variety of solvent-and counterion-free gaseous ions and, as such, constitutes a powerful tool for chemical studies. Many classic organic reactions have been studied in the gas phase using the mass spectrometric methods [5][6][7][8][9][10][11][12][13][14]. Recently, with the advent of electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), mass spectrometry has been widely used as an analytical tool for the study of atmospheric pressure ion/molecule reactions. These gas-phase reactions can even yield detailed information regarding the individual reaction step of the catalytic cycles, and thus allow the study of transient intermediates that have not been accessible previously by the condensed-phase techniques [15,16].Epoxides are common reagents or key intermediates in a wide variety of synthetically important condensedphase reactions, including asymmetric synthesis via the opening of the oxirane ring [17][18][19]. For example, Meerwein fi...

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Meerwein reaction of phosphonium ions with epoxides and thioepoxides in the gas phase

Cited by 15 publications

References 44 publications

Aplicação da química quântica computacional no estudo de processos químicos envolvidos em espectrometria de massas

Aplicação da química quântica computacional no estudo de processos químicos envolvidos em espectrometria de massas

Comparison of Functional Group Selective Ion–Molecule Reactions of Trimethyl Borate in Different Ion Trap Mass Spectrometers

Gas-phase Meerwein reaction of epoxides with protonated acetonitrile generated by atmospheric pressure ionizations

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