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Structures and Chemical Rearrangements of Benzoate Derivatives Following Gas Phase Decarboxylation
Abstract
Decarboxylation of carboxylate ions in the gas phase provides a useful window into the chemistry displayed by these reactive carbanion intermediates. Here, we explore the species generated by decarboxylation of two benzoate derivatives: 2-formylbenzoate (2FBA) and 2-benzoylbenzoate (2BBA). The nascent product anions are transferred to a cryogenic ion trap where they are cooled to ∼15 K and analyzed by their pattern of vibrational bands obtained with IR photodissociation spectroscopy of weakly bound H2 molecules. The structures of the quenched species are then determined by comparison of these spectra with those predicted by electronic structure calculations for local minima on the potential energy surface. The 2-phenide carbanion generated by decarboxylation of 2FBA occurs in two isomeric forms that differ in the orientation of the formyl group, both of which yield a very large (∼110 cm-1) redshift in the stretching frequency of the H2 molecule attached to the anionic carbon center. Although calculated to be a local minimum, the analogous 2-phenide species could not be isolated upon decarboxylation of 2BBA. Rather, the anionic product adopts a ring-closed structure, indicating efficient nucleophilic attack on the pendant phenyl group by the nascent phenide. The barrier for ring closing is evaluated with electronic structure calculations.
... Article likely due to oxidation of NA. 20 Yet, a simultaneous growth of a negative absorption band at 1704 cm −1 , also attributed to the stretching mode of C�O functional groups, indicates a loss of mass due to fractionation or decarboxylation of the complex sample, leading to VOC and CO 2 formation. 33,55,56 Slight positive absorptions at 1404 and 1370 cm −1 , corresponding to the bending modes of aldehydic C−H and O−H product functional groups, further support these observations. 20 These simultaneous processes of oxidation and decarboxylation offset one another, resulting in no measurable mass change in the QCM. Figure 7B shows the vibrational spectroscopy results of 1:5 m-DOM/NA thin film, where distinct features of oxygenated product formation are identified. ...
... This observation is consistent with the gravimetric measurements shown in Figure 5B, in which a lower fraction of mass loss is observed in the sample containing both m-DOM and NA. 20,33,56 The large negative absorption bands at 2962 and 2827 cm −1 are likely due to the loss of C−H stretches due to fractionation and mass loss as VOC. This interpretation is supported by mass loss observed during gravimetric experiments. ...
... Figure 7B also shows a sharp negative absorption at 1707 cm −1 as a result of the loss of C�O species and decarboxylation within m-CDOM. 20,56 The slight positive absorption at 1718 cm −1 can be attributed the reactive uptake of oxygen leading to the formation of carbonyl functional groups, with the concomitant growth of the C�O stretching mode band for aldehyde and ketone products. 20 Small but observable absorptions bands between 1550 and 1400 cm −1 can be attributed to the bending modes of aldehydic C−H and O−H product functional groups. ...
Photochemical aging and photooxidation of atmospheric particles play a crucial role in both the chemical and physical processes occurring in the troposphere. In particular, the presence of organic chromophores within atmospheric aerosols can trigger photosensitized oxidation that drives the atmospheric processes in these interfaces. However, the light-induced oxidation of the surface of atmospheric aerosols, especially those enriched with organic components, remains poorly understood. Herein, we present a gravimetric and vibrational spectroscopy study aimed to investigate the photosensitized oxidation of nonanoic acid (NA), a model system of fatty acids within organic aerosols, in the presence of complex organic photosensitizers and molecular proxies. Specifically, this study shows a comparative analysis of the photosensitized reactions of thin films containing nonanoic acid and four different organic photosensitizers, namely marine dissolved organic matter (m-DOM) and humic acids (HA) as environmental photosensitizers, and 4-imidazolecarboxaldehyde (4IC) and 4-benzoylbenzoic acid (4BBA) as molecular proxies. All reactions show predominant photooxidation of nonanoic acid, with important differences in the rate and yield of product formation depending on the photosensitizer. Limited changes were observed in the organic photosensitizer itself. Results show that, among the photosensitizers examined, 4BBA is the most effective in photooxidizing nonanoic acid. Overall, this work underscores the role of chromophores in the photooxidation of organic thin films and the relevance of such reactions on the surface of aerosols in the marine environment.
... We propose COOH chemistry as a critical modifier in the structural evolution of DOM towards more compact molecules during environmental processing, which increases the average number of chemical bonds between constituent atoms in DOM molecules and the proportions of quaternary and methine carbon units, at the expense of methylene and methyl units (Fig. 2d). For instance, intermediates produced by decarboxylation carry intrinsic energy fostering structural rearrangements 72 . In particular, free radicals have distinct reactivity, with skeletal rearrangements towards higher compaction supported by the higher stability of sterically crowded radical positions, opposite to common chemistry, in which increasing steric demands (for example, entry of new substituents to pre-existing atomic environments in molecules) are difficult to attain 37,61 . ...
Dissolved organic matter (DOM) is one of the most complex, dynamic and abundant sources of organic carbon, but its chemical reactivity remains uncertain1–3. Greater insights into DOM structural features could facilitate understanding its synthesis, turnover and processing in the global carbon cycle4,5. Here we use complementary multiplicity-edited ¹³C nuclear magnetic resonance (NMR) spectra to quantify key substructures assembling the carbon skeletons of DOM from four main Amazon rivers and two mid-size Swedish boreal lakes. We find that one type of reaction mechanism, oxidative dearomatization (ODA), widely used in organic synthetic chemistry to create natural product scaffolds6–10, is probably a key driver for generating structural diversity during processing of DOM that are rich in suitable polyphenolic precursor molecules. Our data suggest a high abundance of tetrahedral quaternary carbons bound to one oxygen and three carbon atoms (OCqC3 units). These units are rare in common biomolecules but could be readily produced by ODA of lignin-derived and tannin-derived polyphenols. Tautomerization of (poly)phenols by ODA creates non-planar cyclohexadienones, which are subject to immediate and parallel cycloadditions. This combination leads to a proliferation of structural diversity of DOM compounds from early stages of DOM processing, with an increase in oxygenated aliphatic structures. Overall, we propose that ODA is a key reaction mechanism for complexity acceleration in the processing of DOM molecules, creation of new oxygenated aliphatic molecules and that it could be prevalent in nature.
We describe an instrumental configuration for the structural characterization of fragment ions generated by collisional dissociation of peptide ions in the typical MS2 scheme widely used for peptide sequencing. Structures are determined by comparing the vibrational band patterns displayed by cryogenically cooled ions with calculated spectra for candidate structural isomers. These spectra were obtained in a linear action mode by photodissociation of weakly bound D2 molecules. This is accomplished by interfacing a Thermo Fisher Scientific Orbitrap Velos Pro to a cryogenic, triple focusing time-of-flight photofragmentation mass spectrometer (the Yale TOF spectrometer). The interface involves replacement of the Orbitrap’s higher-energy collisional dissociation cell with a voltage-gated aperture that maintains the commercial instrument’s standard capabilities while enabling bidirectional transfer of ions between the high-resolution FT analyzer and external ion sources. The performance of this hybrid instrument is demonstrated by its application to the a1, y1 and z1 fragment ions generated by CID of a prototypical dipeptide precursor, protonated L-phenylalanyl-L-tyrosine (H+-Phe-Tyr-OH or FY-H+). The structure of the unusual z1 ion, nominally formed after NH3 is ejected from the protonated tyrosine (y1) product, is identified as the cyclopropane-based product is tentatively identified as a cyclopropane-based product.
While hydrogen tunneling at elevated temperatures has, for instance, often been postulated in biochemical processes, spectroscopic proof is thus far limited to cryogenic conditions, under which thermal reactivity is negligible. We report spectroscopic evidence for H-tunneling in the gas phase at temperatures around 320-350K observed in the isomerization reaction of a hydroxycarbene into an aldehyde. The charge-tagged carbene was generated in situ in a tandem mass spectrometer by decarboxylation of oxo[4-(trimethylammonio)phenyl]acetic acid upon collision induced dissociation. All ion structures involved are characterized by infrared ion spectroscopy and quantum chemical calculations. The charge-tagged phenylhydroxycarbene undergoes 1,2-H-shift to the corresponding aldehyde with a half-life of about 10 s, evidenced by isomer-selective two-color (IR-IR) spectroscopy. In contrast, the deuterated (OD) carbene analogue showed largely reduced 1,2-D-shift reactivity with an estimated half-life of at least 200 seconds under the experimental conditions, and provides clear evidence for hydrogen atom tunneling in the H-isotopologue. This is the first gas-phase spectroscopic confirmation of hydrogen atom tunneling governing 1,2-H-shift reactions at non-cryogenic temperatures, which is of broad significance for a range of (bio)chemical processes, including enzymatic transformations and organocatalysis.
Decarboxylation chemistry has a rich history, and in more recent times, it has been recruited in the quest to develop cheaper, cleaner, and more efficient bond-coupling reactions. Thus, over the past two decades, there has been intense investigation into new metal-catalyzed reactions of carboxylic substrates. Understanding the elementary steps of metal-mediated transformations is at the heart of inventing new reactions and improving the performance of existing ones. Fortunately, during the same time period, there has been a convergence in mass spectrometry (MS) techniques, which allows these catalytic processes to be examined efficiently in the gas phase. Thus, electrospray ionization (ESI) sources have been combined with ion-trap mass spectrometers, which in turn have been modified to either accept radiation from tunable OPO lasers for spectroscopy based structural assignment of ions or to allow the study of ion–molecule reactions (IMR). The resultant “complete” gas-phase chemical laboratories provide a platform to study the elementary steps of metal-catalyzed decarboxylation reactions in exquisite detail.
We have measured the IR Fourier-transform spectra of biologically active benzaldehyde and its derivatives in the gas and liquid phases. For compounds of this class, the role played by C=O, OH, and CH groups in intra- and intermolecular has been analyzed. We have revealed spectral features that characterize the participation of C=O groups of unsubstituted benzaldehyde molecules in the occurrence of intermolecular hydrogen bonds C=O...H-C with the formation of molecular dimers of different types. For 2-hydroxybenzaldehyde molecules, spectral data have been obtained that are indicative of the occurrence of intramolecular hydrogen bonds of the C=O...H-C type in solutions. In 2-methoxybenzaldehyde molecules, no intramolecular hydrogen bonds have been observed.
The fundamental ground tone vibration of H2, HD, and D2 is determined to an
accuracy of 2 x 10^-4 cm^-1 from Doppler-free laser spectroscopy in the
collisionless environment of a molecular beam. This rotationless vibrational
splitting is derived from the combination difference between electronic
excitation from the X^1Sg+, v=0 and v=1 levels to a common EF^1g+, v=0 level.
Agreement within between the experimental result and a full ab initio
calculation provides a stringent test of quantum electrodynamics in a
chemically-bound system.
Positive-mode atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MSn
) was tested for the differentiation of regioisomeric aromatic ketocarboxylic acids. Each analyte forms exclusively an abundant protonated molecule upon ionization via positive-mode APCI in a commercial linear quadrupole ion trap (LQIT) mass spectrometer. Energy-resolved collision-activated dissociation (CAD) experiments carried out on the protonated analytes revealed fragmentation patterns that varied based on the location of the functional groups. Unambiguous differentiation between the regioisomers was achieved in each case by observing different fragmentation patterns, different relative abundances of ion-molecule reaction products, or different relative abundances of fragment ions formed at different collision energies. The mechanisms of some of the reactions were examined by H/D exchange reactions and molecular orbital calculations.
A charge-tagged phenyl pyruvic acid derivative was investigated by tandem-MS, infrared (IR) ion spectroscopy and theory. The tailor-made precursor ions efficiently lose CO2 in collision induced dissociation experiments, offering access to study the secondary decay reactions of the product ions. IR ion spectroscopy provides evidence for the formation of an enol acid precursor ion structure in the gas phase and also indicates the presence of enol products- formed after CO2 loss. Extensive DFT computations however, suggest intermediate generation of hydroxycarbene products, which in turn rearrange in a secondary process to the enol ions detected by IR ion spectroscopy. Quantum mechanical tunneling of the hydroxycarbene can be excluded since no evidence for aldehyde product ion formation could be found. This finding is in contrast to the behavior of methylhydroxycarbene, which cleanly penetrates the energy barrier to form exclusively acetaldehyde at cryogenic temperatures in an argon matrix via quantum mechanical hydrogen tunneling. The results presented here are attributed to the highly excited energy levels of the product ions formed by CID in combination with different barrier heights of the competing reaction channels, which allow exclusive access over one energy barrier leading to the formation of the enol tautomer ions observed.
The single-conformation spectroscopy and infrared-induced conformational isomerization of a model protonated pentapeptide [YGPAA + H]⁺ is studied under cryo-cooled conditions in the gas phase. Building on recent results (DeBlase, A. F.; J. Am. Chem. Soc.2017, 139, 5481−5493), firm assignments are established for the presence of two conformer families with distinct infrared and ultraviolet spectra, using IR–UV depletion spectroscopy. Families (A and B) share a similar structure near the N-terminus but differ in the way that the C-terminal COOH group configures itself (cis versus trans) in forming H-bonds with the peptide backbone. Infrared population transfer (IR-PT) spectroscopy is used to study the IR-induced conformational isomerization following single-conformer infrared excitation. IR-induced isomerization is accomplished in both directions (A → B and B → A) in the hydride stretch region and is used to determine fractional abundances for the two conformer families (FA = 0.65 ± 0.04, FB = 0.35 ± 0.04, 2σ error bars). The time scale for collisional cooling of the room-temperature ions to Tvib = 10 K by cold helium in the octupole trap is established as 1.0 ms. Key stationary points on the isomerization potential energy surface are calculated at the DFT B3LYP/6-31+G(d) G3DBJ level of theory. Using RRKM theory, the energy-dependent isomerization rates and populations are calculated as a function of energy. According to the model, the observed population distribution after collisional cooling is close to that of the 298 K Boltzmann distribution and is in near-quantitative agreement with experiment. On the basis of this success, inferences are drawn for the circumstances that govern the population distribution in the trap, concluding that, in ions the size of [YGPAA + H]⁺ and larger, the observed distributions will be near those at 298 K.
We propose new approximate global multiplicative scaling factors for the DFT calculation of ground state harmonic vibrational frequencies using functionals from the TPSS, M06, and M11 functional families with standard Correlation Consistent cc-pVxZ and aug-cc-pVxZ (x= D, T and Q), 6-311G split valence family, as well as Sadlej, and Sapporo polarized triple- basis sets. Results for B3LYP, CAM-B3LYP, B3PW91, PBEPBE, and PBE0 functionals with these basis sets are also reported. A total of 99 harmonic frequencies were calculated for 26 gas phase organic and non-organic molecules typically found in detonated solid propellant residue. Our proposed approximate multiplicative scaling factors are determined using a least squares approach comparing the computed harmonic frequencies to experimental counterparts well established in the scientific literature. A comparison of our work to previously published global scaling factors is made to verify method reliability and the applicability of our molecular test set.
The silver-catalyzed coupling of arylboronic acids with arylglyoxylic acids was found to be an extremely efficient route for the synthesis of unsymmetrical diaryl ketones. It can be conducted on a gram scale under mild and open-flask conditions with good functional group compatibility, avoiding the addition of expensive and/or toxic metals.
Reductive activation offers an attractive synthetic route for conversion of CO2 to transportable fuels, a process that often involves creation of the formate ion as an intermediate. We carry out an Ar-tagging infrared spectroscopic study of isolated HCO2¯ and its first hydrate, HCO2¯·H2O, and analyze the resulting band patterns with electronic structure and vibrationally anharmonic calculations. Strong vibronic interactions and intramolecular mode couplings are identified that are responsible for the deceptively complex solvation behavior of this familiar ion. In particular, the CH stretch fundamental is found to be anomalously low in energy in the isolated ion and to dramatically blue shift (by hundreds of cm–1) upon solvation. These two effects are traced to the large dependence of the electronic wave function on the CH bond length, reminiscent of the classic curve-crossings that dominate the dissociation behavior of neutral salt molecules.
Carbanions are anions that have a carbon center with an unshared pair of electrons and a formal negative charge. Understanding the reactivity of carbanions is challenging because it depends upon the associated metal and is sensitive to additives, the solvent, temperature, and concentration. Complications in solution due to solvation, counterion effects, and aggregation have hindered our understanding of these species. As a result, the intrinsic reactivity and properties of isolated and truly free carbanions in the gas phase are of interest. Versatile synthetic strategies have been developed for the preparation of a wide variety of gaseous carbanions. This has enabled the reactivities and thermodynamic properties of many carbanions to be experimentally determined. Moreover, because the electron can be viewed as the simplest protecting group, the reactivities and energetics of neutral species such as radicals, biradicals, carbenes, and other fleetingly stable species also can be explored.
The major collision-induced dissociations of PhEt2 involve the losses of H˙, H2, and CH4. Loss of H˙ occurs from the phenyl ring, H2 is eliminated principally by the process PhEt2→ PhC(Et)CHCH2–+ H2, while methane is lost by the stepwise process PhEt2→{Me–[Ph(Et)CCH2]}→(C6H4)–C(Et)CH2+ CH4, in which the second step (deprotonation) is rate-determining. The characteristic fragmentation of both Ph2CH– and Ph3C– is loss of C4H4. This loss occurs without atom randomisation and Dewar benzene intermediates are proposed. The ion Ph3C– also loses C6H6; this is a slow process which is preceded or accompanied by both intra- and inter-ring hydrogen scrambling.
This contribution is very much a personal history of a journey through the wonderful world of anion chemistry, and a tale of how advances in laser technologies, theoretical methods, and computational capabilities continuously enabled advances in our understanding. It is a story of the excitement and joy that come from the opportunity to add to the fabric of science, and to do so by working as a group of excited explorers with common goals. The participants in this journey include me, my students and postdoctoral associates, my collaborators, and our many generous colleagues. It all happened, in the words of the Beatles, "with a little help from my friends." Actually, it was so much more than a little help! Expected final online publication date for the Annual Review of Physical Chemistry Volume 64 is March 31, 2013. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
The use of an ion-trap mass spectrometer to generate daughter spectra of selected parent ions is shown. Ions are created within the trap by electron impact, undesired ions are ejected from the trap, and the selected parent ion undergoes collisionally activated dissociation (CAD). The CAD efficiency can be greatly increased by applying a small supplementary ac voltage of appropriate frequency. The energy transferred to the selected ion, which depends upon the radio frequency voltage applied to the trap as well as the supplementary ac voltage and frequency, is explored with the molecular ions of tetraethylsilane, n-butylbenzene, and nitrobenzene.
Vibrational predissociation spectroscopy of the HOOC(CH2)10COO− and −OOC(CH2)10COO− anions is carried out by predissociation of weakly bound H2 molecules. The HOOC(CH2)10COO− (H2)2 and −OOC(CH2)10COO− (H2)10 cluster ions are formed by H2 attachment to the electrospray-generated bare ions in an ion trap cooled to below 20 K using a closed cycle helium cryostat. The photofragmentation behavior indicates that the H2 binding energy is about 600 cm−1, which is similar in strength to that found in Ar-tagged ions. The spectra indicate that the monoanion adopts a cyclic structure through the formation of an asymmetrical, internal anionic H-bond.Graphical abstract.View high quality image (122K)Research highlights▶ H2 tagging of electrosprayed ions in cryogenically cooled RF ion trap. ▶ Singly and doubly charged ions analyzed by vibrational predissociation spectroscopy. ▶ Characterization of intramolecular hydrogen bonding in cyclic monoanion.
There is significant correspondence between certain skeletal rearrangement processes of close-shell organic anions in the condensed and gas phases. Examples of such correspondence include the acyloin, acyl oxyacetate, anionic oxy Cope, anionic Wolff, benzilic acid, Dieckmann, Lossen, Smiles and Wittig rearrangements. In contrast, there are some rearrangements observed in the condensed phase, which are either minor or do not occur at all in the gas phase. The Favorskii, Tiemann and Carroll rearrangements fall into this category. Finally, there are some gas phase rearrangements which have no condensed phase analogy: for example the negative ion pinacol/pinacolone and Beckmann rearrangements. These, and related processes are discussed in this Review.
Infrared multiple photon dissociation (IRMPD) spectroscopy was used to study formation of b
2+ from nicotinyl-glycine-glycine-methyl ester (NicGGOMe). IRMPD shows that NicGGOMe is protonated at the pyridine ring of the nicotinyl group, and more importantly, that b
2+ from NicGGOMe is not protonated at the oxazolone ring, as would be expected if the species were generated on the conventional b
n
+
/y
n
+ oxazolone pathway, but at the pyridine ring instead. IRMPD data support a hypothesis that formation of b
2+ from NicGGOMe involves mobilization and transfer of an amide position proton during the fragmentation reaction.
Structure of gas-phase arenium ions: The long-standing controversy about the geometry of protonated benzene is unambiguously solved by IR spectroscopy. The first high-resolution gas-phase spectrum of an arenium ion shows that the σ complex (not the π complex; see picture) is the most stable structure of C6H7+.
Temperature-dependent photoelectron spectra of benzoate anion (C6H5CO2(-)) and its three methyl-substituted isomers (o-, m-, p-CH3C6H4CO2(-)) have been obtained using a newly developed low-temperature photoelectron spectroscopy apparatus that features an electrospray source and a cryogenically controlled ion trap. Detachment channels due to removing electrons from the carboxylate group and benzene ring pi electrons were distinctly observed. Well-resolved vibrational structures were obtained in the lower binding energy region due to the OCO bending modes, except for o-CH3C6H4CO2(-), which yielded broad spectra even at the lowest ion trap temperature (18 K). Theoretical calculations revealed a large geometry change in the OCO angles between the anion and neutral ground states, consistent with the broad ground-state bands observed for all species. A strong steric effect was observed between the carboxylate and the methyl group in o-CH3C6H4CO2(-), such that the -CO2(-) group is pushed out of the plane of the benzene ring by approximately 25 degrees and its internal rotational barrier is significantly reduced. The low rotational barrier in o-CH3C6H4CO2(-), which makes it very difficult to be cooled vibrationally, and the strong coupling between the OCO bending and CO2 torsional modes yielded the broad PES spectra for this isomer. It is shown that there is no C-H...O hydrogen bond in o-CH3C6H4CO2(-), and the interaction between the carboxylate and methyl groups in this anion is found to be repulsive in nature.
The (CO2)n- clusters are thought to accommodate the excess electron by forming a localized molecular anion, or "core ion", solvated by the remaining, largely neutral CO2 molecules. Earlier studies interpreted discontinuities in the (CO2)n- photoelectron spectra to indicate that both the CO2- and C2O4- species were present in a size-dependent fashion. Here we use vibrational predissociation spectroscopy to unambiguously establish the molecular structures of the core ions in the 2 < or = n < or = 17 size range. Spectra are reported in the 2300-3800 cm(-1) region, which allows us to independently monitor the contribution of each ion through its characteristic overtone and combination bands. These signature bands are observed to be essentially intact in the larger clusters, establishing that the CO2- and C2O4- molecular ions are indeed the only electron accommodation modes at play. The size dependence of the core ion suggested in earlier analyses of the photoelectron spectra is largely confirmed, although both species are present over a range of clusters near the expected critical cluster sizes, as opposed to the prompt changes inferred earlier. Perturbations in the bands associated with the nominally neutral CO2 "solvent" molecules are correlated with the changes in the molecular structure of the core ion. These observations are discussed in the context of a diabatic model for electron delocalization over the CO2 dimer. In this picture, the driving force leading to the transient formation of the monomer ion is traced to the solvent asymmetry inherent in an incomplete coordination shell.
Gas phase C 6H 7 (+) and C 7H 9 (+) ions are studied with infrared photodissociation spectroscopy (IRPD) and the method of rare gas tagging. The ions are produced in a pulsed electric discharge supersonic expansion source from benzene or toluene precursors. We observe exclusively the formation of either the C 2 v benzenium ion (protonated benzene) or the para isomer of the toluenium ion (protonated toluene). The infrared spectral signatures associated with each ion are established between 750 and 3400 cm (-1). Comparing the gas phase spectrum of the benzenium ion to the spectrum obtained in a superacid matrix [ Perkampus, H. H.; Baumgarten, E. Angew. Chem. Int. Ed. 1964, 3, 776 ], we find that the C 2 v structure of the gas phase species is minimally affected by the matrix environment. An intense band near 1610 cm (-1) is observed for both ions and is indicative of the allylic pi-electron density associated with the six membered ring in these systems. This spectral signature, also observed for alkyl substituted benzenium ions and protonated naphthalene, compares favorably with the interstellar, unidentified infrared emission band near 6.2 microm (1613 cm (-1)).
- J N Louris
- R G Cooks
- J E P Syka
- P E Kelley
- G C Stafford
- J F Todd
Louris, J. N.; Cooks, R. G.; Syka, J. E. P.; Kelley, P. E.; Stafford,
G. C.; Todd, J. F. J. Instrumentation, Applications, and Energy
Deposition in Quadrupole Ion-Trap Tandem Mass-Spectrometry.
Anal. Chem. 1987, 59 (13), 1677−1685.