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Thin films derived by the deposition of charged microdroplets generated in the ESI source of a mass spectrometer act as highly concentrated reaction vessels in which the final products of an ion-molecule reaction can be isolated by their precipitation onto a solid surface under ambient conditions. In this study, the ESI Z-spray source supplied to a Q-TOF Ultima mass spectrometer was used to investigate the d-fructose acid-catalyzed reactions by microdroplets deposition onto a stainless-steel target surface. High conversion ratios of d-fructose into 5-hydroxymethylfuraldehyde (5-HMF), 5-methoxymethylfuraldehyde (5-MMF), and difructrose anhydrides (DFAs) were obtained with HCl and KHSO

The occurrence of N-heterocyclic carbenes in imidazolium-based ionic liquids has long been discussed, but no spectroscopic evidence has been reported yet due to their transient nature. The insertion of an ionizable acid group into the cation scaffold of an ionic liquid which acts as a charge tag allows for the direct detection of free carbenes by mass spectrometry.Three different Brønsted acidic ionic liquids were synthesized: 1-methyl-3-carboxymethylimidazolium chloride (MAICl), 1-methyl-3-carboxymethylimidazolium acetate (MAIAc) and the corresponding 2-(3-methyl-1H-imidazol-3-ium-1-yl)acetate zwitterion (MAI - H). The speciation of these compounds was then analysed by electrospray ionization ion-trap mass spectrometry in the negative ion mode.The C2-H deprotonation of the imidazolium cation leading to the formation of the corresponding carbene is highly affected by the basic properties of the counter-anion. In the case of MAICl and MAI - H ionic liquids, no charged species corresponding to the free N-heterocyclic carbene was detected. On the contrary, in the presence of a sufficiently basic anion, such as acetate of MAIAc ionic liquid, an intense signal related to the free carbenic species was observed without the addition of an external base.In situ formation of free N-heterocyclic carbenes from Brønsted acidic ionic liquids was demonstrated, highlighting the crucial role of anion basicity in promoting the C2-H proton abstraction from imidazolium cations with a carboxylic side chain.

The reactivity of [NaL·ClO2]− cluster anions (L = ClOx−; x = 0–3) with sulphur dioxide has been investigated in the gas phase by ion–molecule reaction experiments (IMR) performed in an in-house modified Ion Trap mass spectrometer (IT-MS). The kinetic analysis revealed that SO2 is efficiently oxidised by oxygen-atom (OAT), oxygen-ion (OIT) and double oxygen transfer (DOT) reactions. The main difference from the previously investigated free reactive ClO2− is the occurrence of intracluster OIT and DOT processes, which are mediated by the different ligands of the chlorite anion. This gas-phase study highlights the importance of studying the intrinsic properties of simple reacting species, with the aim of elucidating the elementary steps of complex processes occurring in solution, such as the oxidation of sulphur dioxide.

A gas‐phase investigation of the D‐fructose dehydration reaction in the presence of base has been performed by the joint application of mass spectrometric techniques and theoretical calculations. Protonated addition products of D‐fructose and base were generated in the gas phase by electrospray ionization using several bases of different proton affinity. The intermediates, products and decomposition channels were investigated by ion trap mass spectrometry. Electronic structure calculations allowed the identification of the ionic intermediates and products of a selected system containing NH3, helping to rationalize the observed reaction pathways. The obtained results show that the final product, the protonated 5‐hydroxymethyl‐2‐furaldheyde [5‐HMF]H+, is better formed using selected bases and only if these remain clustered until the end of the dehydration process.

The reactivity of carbonate cluster ions with sulfur dioxide has been investigated in the gas phase by mass spectrometric techniques. SO2 promotes the displacement of carbon dioxide from carbonate clusters through a stepwise mechanism, leading to the quantitative conversion of the carbonate aggregates into the corresponding sulfite cluster ions. The kinetic study of the reactions of positive, negative, singly, and doubly charged ions reveals very fast and efficient processes for all the carbonate ions.

The creation of carbon–carbon bonds is still a highly required topic in organic chemistry for the capacity to give a wide variety of new products of industrial value. Accordingly, the Knoevenagel condensation between activated methylene compounds and aldehydes is one of the most known carbon coupling reactions. In this work, the catalytic activity of imidazolium-based ionic liquids (1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-methyl-3-carboxymethylimidazolium chloride) was studied under solvent-free conditions and compared with that of sodium salts (sodium chloride, sodium acetate). Mass spectrometric techniques were used to monitor the formation of the reaction products and to detect the key intermediates of the process. Based on the catalyst employed different reaction mechanisms were highlighted, thus laying the foundation for the design of more specific and efficient catalysts.

The synthesis of cationic mono oxo MoIV PNP pincer complexes of the type [Mo(PNPMe-iPr)(O)X]+ (X = I, Br) from [Mo(PNPMe-iPr)(CO)X2] is described. These compounds are coordinatively unsaturated and feature a strong Mo≡O triple bond. The formation of these complexes proceeds via cationic 14e intermediates [Mo(PNPMe-iPr)(CO)X]+ and requires both molecular oxygen and water. ESI MS measurements with 18O labeled water (H2 18O) and molecular oxygen (18O2) indicates that water plays a crucial role in the formation of the Mo≡O bond. A plausible mechanism based on DFT calculations is provided. The X-ray structure of [Mo(PNPMe-iPr)(O)I]SbF6 is presented.

Unprecedented hydrolysis reactions are observed in the gas phase in clusters containing doubly-charged vanadium oxides and hydroxide anions, SO2 and H2O. The experimental and computational study shows the cooperative effects of the vanadium species, V2O62− and HV3O92−, and sulfur dioxide on the enhancement of the hydrogen bonds of water that allows the acid–base reaction and charge separation in the doubly-charged ion.

The reactivity of transition metal dioxide anions of cobalt, nickel, copper and zinc with sulfur dioxide has been investigated in the gas phase by mass spectrometric techniques and theoretical calculations. Dioxide anions of the late transition metals Cu and Zn promote an unprecedented fast and efficient oxidation to the sulfate radical anion through a double oxygen transfer, whereas the earlier transition metals Ni and Co only undergo the addition of two SO2 molecules. The ligation of a water molecule to ZnO2 − switches the reaction path to a single oxygen anion transfer, forming SO3 −.

The gas-phase reactivity of doubly-charged vanadium hydroxides anions with SO2 has been studied by experimental and computational methods. The obtained results highlight the role of sulfur dioxide in promoting unprecedented bond-forming reactions, which produce singly-charged products by breaking the Vx Oy skeleton or a terminal V-O bond.

Unprecedented redox reactions of chromium oxide anions have been observed in the gas phase and investigated by mass spectrometric techniques and electronic structure calculations. The effective oxidizing and reducing power of chromium oxide anions is unravelled by sulfur dioxide: CrO4 − and CrO2 − generate CrO3 − as the reduction and oxidation product, respectively, together with SO3 and SO as the oxidation and reduction products of SO2, respectively. Computations predict that the reactions of CrO4 − and CrO2 − proceed through rather stable ion-dipole complexes and that CrO4 - produces also a strongly bound [CrSO6] - species.

Seeking promising molecular species with huge energy release and significant kinetic stability continues to be a hot topic and a great challenge in the field of high-energy density materials (HEDMs). CO4 is the first high-order carboxide that has the potential as an energetic molecule. However, the intrinsic kinetic stability of its two most studied energy-rich isomers, i.e., 11 (monocyclic) and 12 (bicyclic), has remained quite unclear in spite of numerous studies. This has greatly hindered the quantitative stability assessment of 11 and 12 under various conditions as well as the justification of their prospect as energetic candidates. In this work, for the first time we report the rate-determining transition states associated with the CO2-elimination from 11 and 12. The thermodynamics of 11 and 12 was described using G3B3, CBS-QB3, G4, W1BD, CCSD(T)/CBS and CASPT2/CBS, while the kinetic stability was analyzed based on broken-symmetry UCCSD(T)/CBS and CASPT2/CBS single-point energy calculations on UB3LYP geometries. The rate-determining barriers for the dissociation of 11 and 12 into CO2 + 1O2 at 298 K were found to amount to 28.7 and 14.7 kcal mol−1 at the CASPT2(18e,12o)/CBS level of theory, and 23.5 and 21.1 kcal mol−1 at the UCCSD(T)/CBS level of theory, respectively. 11 is a kinetically stable energetic molecule, which releases 45.2 kcal mol−1 upon dissociation into CO2 + 1O2 at the CASPT2(18e,12o)/CBS level and 38.9 kcal mol−1 at the UCCSD(T)/CBS level, and could serve as a rigid energetic building block for larger oxocarbons. The bicyclic 12 releases much higher energy, 79.3 kcal mol−1 at the CASPT2(18e,12o)/CBS level and 73.4 kcal mol−1 at the CASPT2-corrected UCCSD(T)/CBS level whereas the barrier for dissociation is lower than that of monocyclic 11.

Fulminates containing the CNO(-) ion have been widely utilized as high-energy density materials (HEDMs) for more than 120 years. Yet no purely covalently bound CNO molecule, i.e., nitrile oxide, is known to behave as an HEDM. In this study, we performed a thorough investigation of the potential energy surface of nitrile oxide ONCNO and related isomers, applying various sophisticated methods including G4, CBS-QB3, W1BD, CCSD(T)/CBS, and CASPT2/CBS. The Gibbs free energy calculations showed that the decomposition of ONCNO to the considerably endothermic products CNO + NO is favored compared to that into the highly exothermic products CO2 + N2. Thus, ONCNO fails to be the long expected nitrile oxide HEDM. However, with the rate-determining barrier of 23.3 kcal mol(-1) at the W1BD level, ONCNO should be experimentally accessible.

The new nitrogen-rich oxide N 3 O has been detected in the gas phase by mass spectrometric experiments. The radical has been assigned a minimum lifetime of 0.7 μs and an open-chain NNNO structure in the quartet state. Structures and energies of the N 3 O + precursor ion and the N 3 O radical have been investigated by ab initio calculations.

H 2 O 2 + ions are shown to be formed in ionized O2/CH4 mixtures from the secondary reaction of CH2O+ with O2. By high-resolution mass spectrometric techniques, the peroxide HOOH structure and the H2CO structure of ionized formaldehyde are assigned to the [H2O2]+ ions and the [CH2O]+ reactants, respectively. The [CH4O2]+ intermediate of the reaction between O 2 + and CH4 is characterized as a mixture of the loosely bound [ CH 4 O 2 ] + complex and the theoretically predicted insertion product CH3OOH+. The CH3OOH+ intermediate, precursor of the most abundant ionic product CH2OOH+, has been characterized for the first time as a long-lived species.

The new radical HONF has been detected in the gas phase by neutralization-reionization mass spectrometry (NRMS). The radical has been identified and directly characterized as a gaseous isolated species, having a lifetime of at least 1 microsecond and a linear cis-trans structure of H-O-N-F connectivity. Detection of this molecule, which is highly unstable towards the dissociation into HF and NO and kinetically sufficiently stable to be observed, represents an advance in the search for high-energy species.

The HOOO− anion, the conjugate base of dihydrogen trioxide, HOOOH, is suggested as a key intermediate in ozonation reactions relevant to atmospheric chemistry, water purification, preparative organic chemistry, etc. Whereas recent theoretical calculations characterize HOOO− as a long-lived metastable species, so far the anion proved experimentally elusive, defying attempts at its direct detection even in solution, where it should be stabilized by solvation. We report the preparation and the proof-positive detection of HOOO− as an isolated species with a lifetime >0.8 μs. The preparation proved particularly difficult, since the only viable approach is the indirect route involving the preliminary formation of HOOO upon neutralization of HOOO+, followed by electron attachment to the radical, utilizing neutralization–reionization ( + NR − ) mass spectrometry. Direct two-electron reduction of the HOOO+ cation to the HOOO− anion by the vertical process typical of charge reversal (CR) experiments proved inefficient. This observation, and application of neutral and ion decomposition difference (NIDD) mass spectrometry, pioneered by Schwarz and coworkers [Int. J. Mass Spectrom. Ion Processes 172 (1998) 181] suggest that the geometries of HOOO+ and HOOO− are significantly different, whereas that of the HOOO radical is structurally intermediate between them, which accounts for the diversity of the Franck–Condon factors characterizing the mutual vertical transitions of the three species. This inference is consistent with the available optimized geometries of HOOO and HOOO+, computed at various levels of theory, and with that of the anion recently reported by Plesnicar et al. [J. Am. Chem. Soc. 124 (2002) 8462].

The oxidation of SO2 by nonmetal oxoanions in the gas phase is investigated in an experimental and theoretical study of the structure of the species involved and the reaction kinetics and mechanism. SO3 , SO3(.-) and SO4(.-) are efficiently produced by reaction of On XO(-) anions (X=Cl, Br, and I; n=0 and 1) with SO2 ; XO(-) ions mainly react to give SO3 by oxygen-atom transfer, whereas OXO(-) ions mainly give SO3(.-) by oxygen-anion transfer. On descending the halogen group from chlorine to iodine, the SO3 /SO3(.-) ratio decreases and increases for reactions involving XO(-) and OXO(-) anions, respectively, whereas the formation of SO4(.-) is particularly significant with OIO(-). Kinetic factors play a major role in the reactions of On XO(-), depending on the halogen atom and its oxidation state.

The new radical FBNCO and the new cation FBNCO+, containing all the p-block elements, have been identified in the gas phase, as species having a dissociation energy of 50 and 161 kcal mol−1, respectively.

Although suggested by Lewis in 1924 and theoretically predicted, O4 has so far proved extremely elusive, defying all attempts at the positive experimental detection of a bound, intact O4 species. The search has now been brought to an end by the conclusive proof, achieved by neutralization-re-ionization mass spectrometry, of the existence of intact O4 as a gas-phase species with a lifetime in excess of 1 μs, whose dissociation requires overcoming a barrier of the order of 10 kcal mol-1 .

Recent mass spectrometric studies of simple inorganic species (both charged and neutral) of main-group elements are reviewed, focusing attention on radicals and ions of interest to the chemistry of the atmosphere and its pollution. The examples illustrated concern the detection of HO 3 , hydrogen trioxide, the O 2 /O 3 isotope exchange and its charged intermediate O 5 + , the reactions promoted by ionization of ozone/halocarbon mixtures in atmospheric gases, the ion chemistry of NO x oxides, and that of elemental chlorine and chlorine fluoride. Among the results of specific interest to gas-phase ion chemistry, the examples illustrated concern the intracluster ligand-switching reactions in ternary NO + complexes, the NO 2 + reactivity towards ethylene and acetylene, the gas-phase basicity of Cl 2 , the formation and characterization of Cl 2 X + ions (X = Cl, F) and of [H 3 C-Cl-Cl] + , a new isomer of protonated dichloromethane.

Charged species structurally related to several isomers of Cl(2)O(2), of considerable importance in atmospheric chemistry, were obtained by chemical ionization (CI) and characterized by collisionally activated dissociation (CAD) mass spectrometry. The ClOClO(+) and [Cl(2)-O(2)](+) species were prepared by positive ion Cl(2)/CI of ClO(2) and O(2), respectively, whereas the ClClO(2)(+) isomer proved an elusive species of considerably lower stability. The ClClO(2)(-) anion was obtained from the negative ion Cl(2)/CI of ClO(2). The formation process, structure and stability of the ions are discussed in connection with available theoretical results and related to the recent preparation of (Cl(2)O(2))(+)SbF(6)(-) and (Cl(2)O(2))(+)Sb(2)F(11)(-) salts in the solid phase. Copyright 1999 John Wiley & Sons, Ltd.

Gaseous [HN2O5]+ ions formed upon addition of NO2+ to nitric acid have been studied by mass spectrometric and computational methods. The results from MIKE, CAD and FT-ICR spectrometry and calculations at the B3LYP 6-311++G(3df, 3dp)//6-311G(d,p) level of theory show that the most stable adduct formed is an electrostatic HNO3·NO2+ complex where NO2+ is coordinated to the nitro group of nitric acid. Consequently, the nitro group is the energetically preferred protonation site of N2O5, whose experimental proton affinity (PA) amounts to 189.8 ± 2 kcal mol-1, vs theoretically computed values ranging from 182 to 188 kcal mol-1. Addition of NO2+ to XNO2 molecules (X = CH3O, C2H5O and NH2) also yields electrostatic complexes where the nitronium ion is coordinated to the NO2 group. The most stable [HN2O4]+ ion from the addition of NO+ to HNO3 is also identified as a cluster characterized by coordination of the nitrosonium ion to the nitro group, whose almost thermoneutral isomerization into a cluster where a nitro...

It has long been assumed that ionizing neutral acetonitrile produces ions with the same atomic connectivity, CH(3)CN(+*). Recent calculations on the C(2)H(3)N(+*) potential energy surface have suggested that it may be difficult to generate pure CH(3)CN(+*) when ionizing acetonitrile. We have probed the interconversion of CH(3)CN(+*) and its lower energy isomer CH(2)CNH(+*) by calculation, collision-induced dissociation mass spectrometry and ion-molecule reaction. The latter ion, ionized ketenimine, is co-generated upon electron or chemical ionization of neutral acetonitrile in the ion source of a mass spectrometer. An estimate of the ratio of the two isomers can be obtained from their respective ion-molecule reactions with CO(2) or COS. CH(3)CN(+*) reacts by proton-transfer with CO(2) and charge transfer with COS, whereas CH(2)CNH(+*) is unreactive.

The activation of C-halogen bonds by the SO

The activation of C-halogen bonds by the SO.+ radical cation is investigated in the gas phase. The CCl bond of CH2 Cl2 is activated by fast and effective chloride-ion transfer, whereas the CF bond of CH2 F2 is activated by a very slow fluoride-ion transfer. In both cases, thermodynamic and kinetic factors account for the type of process and the observed selectivity, that is, carbon-halogen versus carbon-hydrogen activation, mainly owing to the presence of the sulfur atom. The cleavage of the CCl bond of CH2 Cl2 by SO.+ is a rare example of a very effective and selective chloride-ion abstraction by a metal-free, sulfur-centred radical cation.

The H(.)-atom transfer (HAT) reaction is investigated in the gas phase, starting from two different entrance channels, O(2)(.+)/CH(2)X(2) and CH(2)X(2)(.+)/O(2) (X=F, Cl), that correspond to a step of hydride transfer and to HAT, respectively. Analysis of the spin and charge along the reaction pathway shows that HAT occurs through the same reacting configuration, irrespective of whether the reactants are formed within the complex or are free isolated species.

The reactivity of the two diatomic congeneric systems [CO](·+) and [SiO](·+) towards methane has been investigated by means of mass spectrometry and quantum-chemical calculations. While [CO](·+) gives rise to three different reaction channels, [SiO](·+) reacts only by hydrogen-atom transfer (HAT) from methane under thermal conditions. A theoretical analysis of the respective HAT processes reveals two distinctly different mechanistic pathways for [CO](·+) and [SiO](·+), and a comparison to the higher metal oxides of Group 14 emphasizes the particular role of carbon as a second-row p element.

The gas-phase ion chemistry of H 2 N-NO 2 (1) has been studied with mass spectrometric and ab initio theoretical methods. The H 2 N 2 O 2 .+ molecular ion is formed upon electron-impact ionization of 1, whose photoelectron (PE) spectra have been recorded. From the onset of the PE bands the ionization energy of 1 has been estimated to be 11.02±0.06 eV. Reaction of 1 with gaseous BrOnsted acid such as H 3 + , CH 5 + , H 3 O + , and i-C 3 H 7 + , etc., gives protonated adducts [H 2 N-NO 2 ]H +

The Proton Affinity and Gas-Phase Basicity of Sulfur Dioxide

Recent mass spectrometric studies of species and processes relevant to the chemistry of atmospheres are reported. New species have been detected, including HO3; a stratospheric reservoir of OH radicals; the [H2O+O2-] charge transfer complex, central to the atmospheric photonucleation theory; and the OSOSO oxide and its cation, likely present in the Io's atmosphere. As to ionic processes, a new route to tropospheric N2O in air ionized by lightning and coronas is reported, as well as the complex chemistry promoted by ionization of ozone/freon and ozone/carbonyl sulfide mixtures and the formation of O5+, relevant to the problem of 18O excess in stratospheric ozone.

The room-temperature C-H activation of ethane by metal-free SO2 center dot+ radical cations has been investigated under different pressure regimes by mass spectrometric techniques. The major reaction channel is the conversion of ethane to ethylene accompanied by the formation of H2SO2 center dot+ the radical cation of sulfoxylic acid. The mechanism of the double C-H activation, in the absence of the single activation product HSO2+, is elucidated by kinetic studies and quantum chemical calculations. Under near single-collision conditions the reaction occurs with rate constant k = 1.0 x 10(-9) (+/-30%) cm(3) s(-1) molecule(-1), efficiency = 90%, kinetic isotope effect k(H)/k(D)=1.1, and partial H/D scrambling. The theoretical analysis shows that the interaction of SO2 center dot+ with ethane through an oxygen atom directly leads to the C-H activation intermediate. The interaction through sulfur leads to an encounter complex that rapidly converts to the same intermediate. The double C-H activation occurs by a reaction path that lies below the reactants and involves intermediates separated by very low energy barriers, which include a complex of the ethyl cation suitable to undergo H/D scrambling. Key issues in the observed reactivity are electron-transfer processes, in which a crucial role is played by geometrical constraints. The work shows how mechanistic details disclosed by the reactions of metal-free electrophiles may contribute to the current understanding of the C-H activation of ethane.

[CH3SO2]+, [CH3SO3H2]+ and [CH3SO2OCH3H]+, positive even-electron ions from hexavalent sulfur compounds, have been studied by Fourier transform ion cyclotron resonance and collision-induced dissociation (CID). These ions showed no evidence of undergoing S → O methyl group shift, at variance with easy skeletal rearrangements frequently postulated for ionized sulfones and sulfonyl derivatives. A proton affinity value of 184 ± 2 kcal mol−1 has been obtained for methanesulfonic acid by the bracketing procedure, but the site of proton attachment in [CH3SO3H2]+ ions could not be established, either by CID or kinetic evidence. The methylation of SO2 by (CH3)2F+ ions has been ascertained to yield [CH3SO2]+ ions methylated on oxygen, in analogy to the same reaction observed in a superacid medium.

Where does rain come from? The first experimental evidence for the existence of the (H(2)O(+)O(2)(-)) charge transfer complex, predicted to play a key role as a nucleation center for atmospheric vapor photonucleation (see picture), is provided by the powerful neutralization - reionization mass spectrometric technique.

This paper deals with electrospray ionization mass spectrometry (ESIMS), small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) measurements in order to provide information on the existence, aggregation, composition, and structure of the two-component aggregates of sodium glycocholate (NaGC) and sodium glycodeoxycholate (NaGDC) in the gas and solution phases. Five samples, containing 100% NaGC and 100% NaGDC, and NaGDC/NaGC molar ratios of 3 (75D), 1 (50D), and 1/3 (25D), have been analyzed by ESIMS in positive-ion detection mode starting from 10(-3) and 10(-2) M total bile salt concentration in aqueous solutions. Generally, dimers or trimers prevail in the 100% NaGC or NaGDC samples, respectively, as observed in the preceding one-component ESIMS measurements and in agreement with the proposed micellar aggregate structures in aqueous solution. Moreover, it is observed that the composition of multimers in the samples 75D, 50D, and 25D deviates from the one expected on the basis of a random association of the monomers, the NaGDC contribution generally prevailing on the NaGC one. It happens also under the same percentage condition (50D sample), in agreement with a greater aggregation ability of NaGDC with respect to NaGC. SAXS and DLS data were recorded on six samples containing a NaGC+NaGDC 40 mM total concentration, one bile salt having 40, 32, 24, 16, 8, and 0 mM concentration and the other the complementary one, keeping constant the NaCl concentration (0.6 M). The NaGDC 40 mM sample presents SAXS curves in agreement with a cylindrical shape of the aggregates as shown in a previous paper. For the bile salt mixtures, the progressive decrease of the sizes and change of the aggregate morphology, toward a globular-like geometry, are observed by increasing the NaGC fraction, thus confirming the hypothesis about the ability of trihydroxy salts to inhibit the growth of dihydroxy salt aggregates. Fits on the basis of cylindrical model can be accomplished for all the SAXS spectra, however, when the extracted cylinder parameters are used to estimate theoretical hydrodynamic radii a reasonable agreement is obtained only for the samples at high fraction of NaGDC (NaGDCor=24 mM).

The new radical HS(4) containing three sulfur-sulfur bonds has been detected in the gas phase by mass spectrometric experiments. Structures and energies of HS(4) in the three oxidation states +/0/- have been investigated by ab initio calculations. HS(4) is characterized by the HSSSS open-chain structure, and it is stable toward dissociation into S(2) and HS(2) by 23 kcal mol(-1). The first detection of HS(4)(-), the conjugate base of the strong acid H(2)S(4) is also reported.

A precise jab to methane: The SO(2)(*+) radical cation (see figure) effectively activates CH(4) at room temperature through a [H(3)C(*)...HOSO(+)] methyl intermediate isolated in the gas phase by mass spectrometry. Methanol and ionized methyl hydrogen sulfoxylate, CH(3)OSOH(*+), are formed by selective, direct attack of the incipient methyl radical at the O atom of the intermediate. The reaction shows radical and charge effects in the activation of methane by metal-free radical cations.

A novel O-H bond activation reaction is reported: thermal SO2 center dot+ radical cations activate water in the gas phase forming OH center dot radicals with 100% efficiency.