Interaction of metal cations with functionalised hydrocarbons in the gas phase: further experimental evidence for solvation of metal ions by the hydrocarbon chain.

Relative affinity measurements of monovalent metal ions (= Li(+), Cu(+) and Ag(+)) towards aliphatic amines, alcohols and methyl alkanoates (P) have been performed using the kinetic method on the dissociation of metal bound dimer ions of the type P(1)-M(+)-P(2). It was found that the cations' affinity towards long chain (≥C(4) chain length) n- and s-alkylamines, n-alkanols and methyl n- alkanoates was unexpectedly enhanced. This is attributed to a bidentate interaction of the metal ion with the amine, alcohol or ester functional group and the aliphatic chain, paralleling earlier observations on metal bound nitriles.

Interaction of metal cations with alkylnitriles in the gas phase: solvation of metal ions by the hydrocarbon chain.

Relative affinity measurements of monovalent metal ions (M = Li(+), Na(+), Cu(+)and Ag(+)) toward aliphatic nitriles have been performed using the kinetic method by dissociation of metal bound dimer ions of the type R1C≡N-M(+)-N≡CR(2). It is found, particularly for Cu(+) and Ag(+), that the affinity towards nitriles having long chains (>C(6)) is markedly enhanced. This is attributed to a bidentate interaction of the metal ion with the nitrile moiety and the aliphatic chain.

Generation and Dissociation of RCOOCaCl and other Carboxylate-Substituted Superhalogens: CO Capture and Implications for Structure Analysis.

Carboxylate-substituted superhalogens of the type RCOOMX (M=Mg, Ca, Sr, Ba, Mn, Co, Ni, Zn; X=Cl, Br) are easily accessible in the gas phase by electrospray ionisation. Their collision-induced dissociation (CID) characteristics have been probed by using ion-trap and triple-quadrupole mass analysers with particular emphasis on the behaviour of RCOOCaCl -type ions. In the ion trap these appear to react readily with residual water to yield HOCaCl as the hydrolysis product.

Structure and dissociation characteristics of metal chloride anion clusters containing redox-active metal ions studied by laser desorption and electrospray ionization mass spectrometry and ab initio calculations.

Copper chloride anion clusters with both copper oxidation states can be made by laser desorption of CuCl(2) crystals. We have used this method to study the dissociation characteristics of such cluster ions. The stability and the structure of the observed complexes were probed by ab initio calculations.

Small (poly)unsaturated oxygen containing ions and molecules: a brief assessment of their thermochemistry based on computational chemistry.

The CBS-QB3, CBS-APNO and Gaussian-3 model chemistries have been used to determine the ionic and neutral heats of formation and the adiabatic ionization energies (IE(a)) derived therefrom, for the ca 30 principal isomers of the C(3)H(2)O(*+) and the C(4)H(4)O(*+) families of radical cations. Theory and experiment are in excellent agreement for those molecules whose experimental IE(a) has been accurately measured. In contrast, large deviations from the computed values were found for a great many ionic heats of formation reported in the literature.

On the interaction of peptides with calcium ions as studied by matrix-assisted laser desorption/ionization Fourier transform mass spectrometry: towards peptide fishing using metal ion baits.

In a previous report [J.W. de Beukelaar, J.

Even-electron ions: a systematic study of the neutral species lost in the dissociation of quasi-molecular ions.

The collision-induced dissociations of the even-electron [M + H](+) and/or [M - H](-) ions of 121 model compounds (mainly small aromatic compounds with one to three functional groups) ionized by electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) have been studied using an ion trap instrument, and the results are compared with the literature data. While some functional groups (such as COOH, COOCH(3), SO(3)H in the negative ion mode, or NO(2) in both the positive and negative ion modes) generally promote the loss of neutrals that are characteristic as well as specific, other functional groups (such as COOH in the positive ion mode) give rise to the loss of neutrals that are characteristic, but not specific. Finally, functional groups such as OH and NH(2) in aromatic compounds do not lead to the loss of a neutral that reflects the presence of these substituents.

Site of alkylation of N-methyl- and N-ethylaniline in the gas phase: a tandem mass spectrometric study.

N-Methylaniline (NMA) was ethylated and N-ethylaniline (NEA) was methylated under chemical ionization conditions using C(2)H(5)I and CH(3)I, respectively, as reagent gases. The structures of the resulting m/z 136 adduct ions have been probed using metastable ion and collision-induced dissociation (CID) methods. From the similarity of the spectra obtained and from the presence of structure-diagnostic ions at m/z 59 (CH(3)NHC(2)H(5) (+*)) and m/z 44 (CH(3)NHCH(2) (+)), it is concluded that predominantly N-alkylation occurs in both systems.

Reactions of the ionized enol tautomer of acetanilide: elimination of HNCO via a novel rearrangement.

The reactions of ionised acetanilide, C(6)H(5)NH(=O)CH(3)(.+), and its enol, C(6)H(5)NH(OH)=CH(2)(.+), have been studied by a combination of tandem mass spectrometric and computational methods.

Derivatization of small oligosaccharides prior to analysis by matrix-assisted laser desorption/ionization using glycidyltrimethylammonium chloride and Girard's reagent T.

In matrix-assisted laser desorption/ionization (MALDI) analyses of small oligosaccharides a very large increase in sensitivity (by a factor of 1000) may be obtained by introducing a quaternary ammonium center ('quaternization'). Such a quaternary ammonium center may be introduced into the saccharide by reaction with commercially available glycidyltrimethylammonium chloride (GTMA), or by using Girard's reagent T (Naven and Harvey, Rapid Commun. Mass Spectrom.