An ion mobility spectrometry/mass spectrometry (IMS/MS) study of the site of protonation in anilines

Karpas, Zeev; Berant, Z.; Stimac, Robert M.

doi:10.1007/bf00674262

Cited by 59 publications

(76 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The measured proton affinity of aniline is 874 kJ/mol (208.8 [42] and 209.5 kcal/mol [43] )and experimental [44] and theoretical [45] studies showed almost equal propensity for protonation at the amino-N-and the para-C-atoms. The proton affinities of the amino group of the nucleobases are lower than for aniline and, moreover, amino group protonation cannot compete with the alternatives (Table 2).…”

Section: Site Of Protonation and Mode Of Initial Fragmentationmentioning

confidence: 99%

Ammonia elimination from protonated nucleobases and related synthetic substrates

Qian

Yang

et al. 2007

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

The results are reported of mass-spectrometric studies of the nucleobases adenine 1h (1, R ϭ H), guanine 2h, and cytosine 3h. The protonated nucleobases are generated by electrospray ionization of adenosine 1r (1, R ϭ ribose), guanosine 2r, and deoxycytidine 3d (3, R ϭ deoxyribose) and their fragmentations were studied with tandem mass spectrometry. In contrast to previous EI-MS studies of the nucleobases, NH 3 elimination does present a major path for the fragmentations of the ions [1h ϩ H] ϩ , [2h ϩ H] ϩ , and [3h ϩ H] ϩ . The ion [2h ϩ H Ϫ NH 3 ] ϩ also was generated from the acyclic precursor 5-cyanoamino-4-oxomethylenedihydroimidazole 13h and from the thioether derivative 14h of 2h (NH 2 replaced by MeS). The analyses of the modes of initial fragmentation is supported by density functional theoretical studies. Conjugate acids 15-55 were studied to determine site preferences for the protonations of 1h, 2h, 3h, 13h, and 14h. The proton affinity of the amino group hardly ever is the substrate's best protonation site, and possible mechanisms for NH 3 elimination are discussed in which the amino group serves as the dissociative protonation site. The results provide semi-direct experimental evidence for the existence of the pyrimidine ring-opened cations that we had proposed on the basis of theoretical studies as intermediates in nitrosative nucleobase deamination. [1,2]. This chemistry has been studied extensively because of the dietary and environmental exposure of humans to these substances [3][4][5]. Toxicological studies of deamination became more significant when it was recognized that endogenous nitric oxide [6,7] causes nitrosation [8,9], and that this process is accelerated by chronic inflammatory diseases [10,11]. It has been known for a long time that deamination of adenine 1, guanine 2, and cytosine 3 (Scheme 1) results in the formation of hypoxanthine, xanthine, and uracil, respectively, and these products are thought to result from DNA base diazonium ions 4-6, respectively, by direct nucleophilic dediazoniation. The discovery of oxanine formation [12][13][14] in the nitrosative deamination of guanine challenged the generality and completeness of this mechanism. Theoretical studies revealed that unimolecular dediazoniation of guaninediazonium ion 5 is accompanied or immediately followed by pyrimidine ringopening [15,16] and that cytosine-catalysis promotes the process [17,18]. The resulting 5-cyanoimino-4-oxomethylene-4,5-dihydroimidazole is a highly reactive intermediate and undergoes acid-catalyzed 1,4-addition via cyano-N or imino-N protonated 5-cyanoimino-4-oxomethylene-4,5-dihydroimidazoles, 9 and 10, respectively [19].Labeling studies support this reaction mechanism for oxanine formation [20]. Moreover, we synthesized 5-cyanoamino-4-imidazolecarboxamide and studied its cyclization chemistry [21] and its proficiency for cross-link formation [22]. The unimolecular dediazoniation of the diazonium ions of adenine and cytosine can proceed without ring-opening but the cations 7 and 11 formed in this...

show abstract

Section: Site Of Protonation and Mode Of Initial Fragmentationmentioning

confidence: 99%

Ammonia elimination from protonated nucleobases and related synthetic substrates

Qian

Yang

et al. 2007

J. Am. Soc. Mass Spectrom.

View full text Add to dashboard Cite

show abstract

“…Structural differences account for the enhanced mobility of protonated cyclic amines [2] and tertiary amines [5] compared to that of normal aliphatic primary amines. On the other hand, charge delocalization led to increased mobility of the ring-protonated conformation of substituted anilines compared to the nitrogen-protonated structure [3] and also explained the enhanced mobility of diamines [2] and aminoalcohols [4]. In the present work IMS measurements were used to gain insights into the structure of some protonated diamines and polyamines.…”

Section: Introductionmentioning

confidence: 95%

The structure of protonated diamines and polyamines

et al. 1994

View full text Add to dashboard Cite

The reduced mobilities in air, at 200~ of six isomeric C7H~sN2 protonated diamines, two triamines (caldine and spermidine), and two tetramines (thermine and spermine) were measured by ion mobility spectrometric (IMS) techniques. The results indicated that all these polyamines undergo proton-induced cyclization, with the proton forming a bridge between two amino groups. It appears as if the favored configuration of the protonated polyamines involves a six-or sevenmembered ring rather than a bridge between the terminal amino groups. It is believed that in the tetramines the cyclic structure is formed between the two central, more basic, secondary amine sites.

show abstract

“…[1–6] Furthermore, competing gas-phase (de)protonation sites can have important analytical implications. For instance, if relative abundances of the (de)protonation sites are dependent on experimental conditions, so too might be the observed spectra from tandem mass spectrometry,[7] ion mobility,[8, 9] or infrared spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Effects of ESI conditions on kinetic trapping of the solution-phase protonation isomer of p-aminobenzoic acid in the gas phase

Patrick

Cismesia

Tesler

et al. 2017

International Journal of Mass Spectrometry

125

View full text Add to dashboard Cite

The effects of electrospray ionization (ESI) solvent and source temperature on the relative abundance of the preferred solution-phase (N-protonated; i.e. amine) versus preferred gas-phase (O-protonated; i.e., acid) isomers of p-aminobenzoic acid (PABA) were investigated. When PABA was electrosprayed from protic solvents (i.e., methanol/water), the infrared multiple photon dissociation (IRMPD) spectrum recorded was consistent with that for O-protonation, according to both calculations and previous studies. When aprotic solvent (i.e., acetonitrile) was used, a different spectrum was recorded and was assigned to the N-protonated isomer. As the amine is the preferred protonation site in solution, this suggests that an isomerization takes place under certain conditions. Photodissociation at the diagnostic band for the O-protonated isomer (NH2 stretching mode) was used to quantify the relative contributions of each isomer to ion signal as a function of ESI conditions. For mixtures of methanol and acetonitrile, the relative contribution of the O-protonated gas-phase structure increased as a function of methanol content. Yet, substituting methanol for water resulted in a marked decrease of isomerization to the O-protonated structure. The source temperature (i.e., temperature of a heated desolvation capillary) was found to play a key role in determining the extent of isomerization, with higher temperatures yielding increased presence of gas-phase structures. These results are consistent with a protic bridge mechanism, in which the ESI droplet temperatures, dependent on endothermic desolvation and radiative heating from the capillary, may determine the isomerization yield.

show abstract

An ion mobility spectrometry/mass spectrometry (IMS/MS) study of the site of protonation in anilines

Cited by 59 publications

References 17 publications

Ammonia elimination from protonated nucleobases and related synthetic substrates

Ammonia elimination from protonated nucleobases and related synthetic substrates

The structure of protonated diamines and polyamines

Effects of ESI conditions on kinetic trapping of the solution-phase protonation isomer of p-aminobenzoic acid in the gas phase

Contact Info

Product

Resources

About