Site of protonation of benzonitrile hydrogen interchange in the protonated species

Wincel, H.; Fokkens, Roel H.; Nibbering, Nico M. M.

doi:10.1016/1044-0305(90)85039-o

Cited by 18 publications

(10 citation statements)

References 19 publications

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“…13. The IRPD spectra of the H + BN-L dimers confirm the previous indirect mass spectrometric experimental evidence 66 that protonation of BN occurs exclusively at the N end of the CN group, in line with the computational thermochemical prediction. 67,68 It is instructive to compare the structure and bonding of H + BN-W with that of neutral BN-W [50][51][52][53][54] and the BN + -W radical cation 49 to infer the effects of protonation and ionization on the shape of the intermolecular interaction potential and resulting hydration network.…”

Section: Further Discussionsupporting

confidence: 88%

“…[55][56][57][58][59][60][61][62][63] The early low-resolution electronic ultraviolet photodissociation spectrum of H + BN does not unravel the protonation site. 64,65 Mass spectrometric studies using isotopic labelling conclude N-protonation at the CN group, 66 with a recommended PA of 812 kJ mol À1 , 13 in line with previous low-level quantum chemical calculations. 67 In our recent combined IRPD and high-level DFT study of H + BN-L n clusters with L = Ar and N 2 (n r 4), we confirmed for the first time with spectroscopic tools that N-protonation is strongly preferred over C-protontation.…”

Section: Introductionsupporting

confidence: 72%

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Intracluster proton transfer in protonated benzonitrile–(H₂O)_n≤6 nanoclusters: hydrated hydronium core for n ≥ 2

Chatterjee

Dopfer

2019

Phys. Chem. Chem. Phys.

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Section: Further Discussionsupporting

confidence: 88%

Section: Introductionsupporting

confidence: 72%

Intracluster proton transfer in protonated benzonitrile–(H₂O)_n≤6 nanoclusters: hydrated hydronium core for n ≥ 2

Chatterjee

Dopfer

2019

Phys. Chem. Chem. Phys.

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“…The key feature of the plot, though, is that the compounds are separated into two distinct groups, with the smaller group having GB values much higher than would be anticipated, based upon their high IEs and the clear trend in the main group. The reason for the separation is that the smaller group are substituent-protonating, rather than ring-protonating, and their GB values do not reflect the basicity of the ring, which is low because of the EW substituent effect, but that of the substituent itself [21][22][23]. Significantly, all of the compounds from the substituent-protonating group were observed to selfprotonate during Test 1 of the experiments; the only self-protonating dopant not among the substituentprotonating group of Figure 2 was phenyl acetate, which is absent from the plot altogether.…”

Section: Discussion Of Results For Substituted-benzenesmentioning

confidence: 99%

Investigation of substituted-benzene dopants for charge exchange ionization of nonpolar compounds by atmospheric pressure photoionization

Robb

Smith

Blades

2008

J. Am. Soc. Mass Spectrom.

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Atmospheric pressure photoionization (APPI) using a dopant enables both polar and nonpolar compounds to be analyzed by LC/MS. To date, the charge exchange ionization pathway utilized for nonpolar compounds has only been efficient under restrictive conditions, mainly because the usual charge exchange reagent ions-the dopant photoions themselves-tend to be consumed in proton transfer reactions with solvent and/ or dopant neutrals. This research aims to elucidate the factors affecting the reactivities of substituted-benzene dopant ions; another, overriding, objective is to discover new dopants for better implementing charge exchange ionization in reversed-phase LC/MS applications. The desirable properties for a charge exchange dopant include low reactivity of its photoions with solvent and dopant neutrals and high ionization energy (IE). Reactivity tests were performed for diverse substituted-benzene compounds, with substituents ranging from strongly electron withdrawing (EW) to strongly electron donating (ED). The results indicate that both the tendency of a dopant's photoions to be lost through proton transfer reactions and its IE depend on the electron donating/withdrawing properties of its substituent(s): ED groups decrease reactivity and IE, while EW groups increase reactivity and IE. Exceptions to the reactivity trend for dopants with ED groups occur when the substituent is itself acidic. All told, the desirable properties for a charge exchange dopant tend towards mutual exclusivity. Of the singlysubstituted benzenes tested, chloro-and bromobenzene provide the best compromise between low reactivity and high IE. Several fluoroanisoles, with counteracting EW and ED groups, may also provide improved performance relative to the established dopants. . Despite its name, analyte ionization in APPI is mostly due to ion-molecule reactions, following the photoionization of a primary reagent. The primary reagent is usually added purposefully, and is then termed a dopant, though this may not be required if a bulk component of the sample stream itself is photoionizable. Once the primary reagent ions are generated, the ensuing ion-molecule reactions may lead to analyte ionization through either proton transfer or charge exchange (electron transfer), depending upon the properties of the analyte and the chemical environment of the source. In general, polar compounds may be readily Address reprint requests to Michael W. Blades, Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, B.C., Canada, V6T 1Zl, Canada. E-mail: blades@chem.ubc.ca ionizable via either ionization pathway, whereas nonpolar compounds are less amenable to proton transfer and may require charge exchange. To date, the charge exchange ionization pathway has only been efficient under restrictive conditions, mainly because of the tendency of the usual dopant ions to react by proton transfer with reversed-phase solvents and/or dopant neutrals. No study of the factors affecting the reactivity of dopant ions with solvent or dopant neu...

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“…For the tertiary amine derivative, hordenine, it is worth mentioning the formation of (CH 3 ) 2 NH 2 (m/z 46) from MH , since it represents an unusual pathway not observed for any of the other amines. Deuteration of the hydroxy group and chemical ionization with D 2 O as ionizing reagent afforded the MD ions which decompose unimolecularly into ions of m/z 47 and 48 (Fig.…”

Section: Dissociations Of the Metastable Mh Ionsmentioning

confidence: 99%

Gas-phase protonation of arylalkylamines. A metastable ion study

Cardoso

Alexandre

Barros

et al. 1998

Rapid Commun. Mass Spectrom.

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The unimolecular metastable decompositions of protonated arylalkylamines of general formula R and R 5 = H and/or CH 3 ; and n = 1-3, generated by chemical ionization with water and ammonia as ionizing reagents, have been examined via the analysis of the mass-analysed ion kinetic energy spectra of the protonated molecules. The mechanisms proposed have been probed by chemical ionization of the deuterated analogues of the amines with D 2 O and ND 3 . The results show that protonation occurs preferentially on the amino group leading to abundant ions due to ammonia (or amine) loss, although ions resulting from transfer of the proton from the amino group to the aromatic ring, to the hydroxy group para to the aliphatic chain and to the benzylic OH, are also observed. Experimental evidence for H/D exchange between the deuteronated amino group and the aromatic ring is presented, and discussed in terms of the internal energy content of the deuterated ions and structural features of the amines, such as aliphatic chain length and the presence of a second hydroxy group on the aromatic ring. # 1998 John Wiley & Sons, Ltd. Received 3 April 1998; Revised 29 April 1998; Accepted 2 May 1998The site of protonation 1-33 of polyfunctional molecules is a topic of current interest in the field of gas-phase ion chemistry. The research in this area has been focused mainly on two aspects: proton affinity measurements by equilibrium, bracketing or kinetic methods, and structural elucidation of the protonated molecules by several mass spectrometric methods. Proton affinity measurements, in general, provide information on the basicity of the molecule as a whole, and not on specific protonation sites. For polyfunctional molecules the location of the proton in the protonated molecule has been discussed in terms of the proton affinities of each functional group in the molecule 11,13,15,18 by comparison of chemical ionization mass spectra, 5-10 analysis of the mass-analysed ion kinetic energy (MIKE) and MIKE-CID (collision induced dissociation) spectra of the protonated molecules and their labelled analogues, comparison of charge stripping processes, 29 and information provided by neutralization-reionization mass spectra. 12,[30][31][32][33] The present work reports the unimolecular metastable decompositions of protonated molecules of the arylalkylamines given in Table 1, including a group of biologically important amines (biogenic amines) which play significant physiological roles. The protonated molecules of the arylalkylamines were prepared by chemical ionization with water and ammonia as ionizing reagents, in order to evaluate the effect of the exothermicity of the protonation reaction in the dissociations of the metastable MH ions. The compounds studied have essentially two basic sites, the (un)substituted aromatic ring and the aliphatic chain with a terminal amino group, so that any interchange of protons will occur between these two sites. The MIKE spectra of the MD ions of the deuterated arylalkylamines will be discussed in order to eval...

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Site of protonation of benzonitrile hydrogen interchange in the protonated species

Cited by 18 publications

References 19 publications

Intracluster proton transfer in protonated benzonitrile–(H₂O)_n≤6 nanoclusters: hydrated hydronium core for n ≥ 2

Intracluster proton transfer in protonated benzonitrile–(H₂O)_n≤6 nanoclusters: hydrated hydronium core for n ≥ 2

Investigation of substituted-benzene dopants for charge exchange ionization of nonpolar compounds by atmospheric pressure photoionization

Gas-phase protonation of arylalkylamines. A metastable ion study

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Site of protonation of benzonitrile hydrogen interchange in the protonated species

Cited by 18 publications

References 19 publications

Intracluster proton transfer in protonated benzonitrile–(H2O)n≤6 nanoclusters: hydrated hydronium core for n ≥ 2

Intracluster proton transfer in protonated benzonitrile–(H2O)n≤6 nanoclusters: hydrated hydronium core for n ≥ 2

Investigation of substituted-benzene dopants for charge exchange ionization of nonpolar compounds by atmospheric pressure photoionization

Gas-phase protonation of arylalkylamines. A metastable ion study

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Intracluster proton transfer in protonated benzonitrile–(H₂O)_n≤6 nanoclusters: hydrated hydronium core for n ≥ 2

Intracluster proton transfer in protonated benzonitrile–(H₂O)_n≤6 nanoclusters: hydrated hydronium core for n ≥ 2