Structure and formation of gaseous [C4H5O]+ Ions. II–Ions of the type HCC?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}(OH)(CH3)

Loss of an alkyl group X? from acetylenic alcohols HC?C? CX(OH)(CH₃) and gas phase protonation of HC?C? CO? CH₃ are both shown to yield stable HC?C? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}(OH)(CH₃) ions. Ions of this structure are unique among all other [C₄H₅O]⁺ isomers by having m/z 43 [C₂H₃O]⁺ as base peak in both the metastable ion and collisional activation spectra. It is concluded that the composite metastable peak for formation of m/z 43 corresponds to two distinct reaction profiles which lead to the same product ion, CH₃\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O, and neutral, HC?CH. It is further shown that the [C₄H₅O]⁺ ions from related alcohols (like HC?C? CH(OH)(CH₃)) which have an α-H atom available for isomerization into energy rich allenyl type molecular ions, consist of a second stable structure, H₂C?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? C(OH)?CH₂.     

Structure and formation of gaseous [C4H5O]+ ions. I—isomeric ions of the type C3H5\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O

Characterization of [C₄H₅O]⁺ ions in the gas phase using their collisional activation spectra shows that the four C₃H₅\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O isomers CH₂?C(CH₃)\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O, CH₂?CHCH₂\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O, CH₃CH?CH\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O and ?? \documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O are stable for ≥ 10^?5 s. It is concluded further from the characteristic shapes for the unimolecular loss of CO from C₃H₅\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O ions generated from a series of precursor molecules that the CH₂?CH(CH₃)\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O- and CH₂?CHCH₂\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O-type ions dissociate over different potential surfaces to yield [allyl]⁺ and [2-propenyl]⁺ [C₃H₅]⁺ product ions respectively. Cyclopropyl carbonyl-type ions lose CO with a large kinetic energy release, which points to ring opening in the transition state, whereas this loss from CH₃CH?CH\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O-type ions is proposed to occur via a rate determining 1,2-H shift to yield 2-propenyl cations.     

A photoionization study of the [C7H8]\documentclass{article}\pagestyle{empty}\begin{document}$\mathop +\limits_.$\end{document} ion formed from some monosubstituted alkyl benzenes

Appearance potentials for the [C₇H₈]\documentclass{article}\pagestyle{empty}\begin{document}$\mathop +\limits_.$\end{document}ion produced in the fragmentation of n-butyl benzene, iso-butyl benzene and n-pentyl benzene have been measured by photon impact. The results indicate that, at threshold, the fragment ion has the toluene molecular ion structure.     

The vinyloxonium cation, \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 2} = {\rm CH - }\mathop {\rm O}\limits^{\rm + } {\rm H}_{\rm 2}$\end{document}, a stable [C2H5O]+ species in the gas phase

The charge stripping mass spectra of [C₂H₅O]⁺ ions permit the clear identification of four distinct species: \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} - {\rm O - }\mathop {\rm C}\limits^{\rm + } {\rm H}_{\rm 2}$\end{document}, \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} - \mathop {\rm C}\limits^{\rm + } {\rm H - OH}$\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 2} = {\rm CH - }\mathop {\rm O}\limits^{\rm + } {\rm H}_{\rm 2}$\end{document}. The latter, the vinyloxonium ion, has not been identified before. It is generated from ionized n-butanol and 1,3-propanediol. Its heat of formation is estimated to be 623±12 kJ mol^?1. The charge stripping method is more sensitive to these ion structures than conventional collisional activation, which focuses attention on singly charged fragment ions.     

Structures and formation of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 4}} {\rm H}_{{\rm 8}} } \right]_{}^{_.^ + } $\end{document} ions

Several \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 4}} {\rm H}_{{\rm\ 8}} } \right]_{}^{_.^ + } $\end{document} ion isomers yield characteristic and distinguishable collisional activation spectra: \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm 1-butene} } \right]_{}^{_.^ + } $\end{document} and/or \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm 2-butene} } \right]_{}^{_.^ + } $\end{document} (a-b), \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm isobutene} } \right]_{}^{_.^ + } $\end{document} (c) and [cyclobutane]⁺ (e), while the collisional activation spectrum of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm methylcyclopropane} } \right]_{}^{_.^ + } $\end{document} (d) could also arise from a combination of a-b and c. Although ready isomerization may occur for \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 4}} {\rm H}_{{\rm 8}} } \right]_{}^{_.^ + } $\end{document} ions of higher internal energy, such as d or e → a, b, and/or c, the isomeric product ions identified from many precursors are consistent with previously postulated rearrangement mechanisms. 1,4-Eliminations of HX occur in 1-alkanols and, in part, 1-buthanethiol and 1-bromobutane. The collisional activation data are consistent with a substantial proportion of 1,3-elimination in 1- and 2-chlorobutane, although 1,2-elimination may also occur in the latter, and the formation of the methylcycloprpane ion from n-butyl vinyl ether and from n-butyl formate. Surprisingly, cyclohexane yields the \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm linear butene} } \right]_{}^{_.^ + } $\end{document} ions a-b, not \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm cyclobutane} } \right]_{}^{_.^ + } $\end{document}, e.     

Ein neues Gemischtvalentes Oxoniobat: Sr7Nb24+Nb45+O21 \documentclass{article}\pagestyle{empty}\begin{document}$ \widehat = $\end{document} Sr1,167 NbO3,5

A New Mixed Valence Strontium Niobium Oxide Sr₇Nb₂⁴⁺Nb₄⁵⁺O₂₁ \documentclass{article}\pagestyle{empty}\begin{document}$ \widehat = $\end{document} Sr_1.167NbO_3.5 The unknown compound Sr₇Nb₆O₂₁ kristallisiert nach Einkristall-Röntgenbeugungsdaten rhomboedrisch (Raumgruppe C? R3 ; a = 16,450(5) Å, α = 19,85(1)° trigonale Aufstellung: a = 5,670(1), c = 48,364(13) Å). The compound is built up by perovskite blocks with a width of 6 octahedra. The crystal chemistry especially of the interspace between those blocks is discussed in respect to related compounds.     

Applications of NMR spectroscopy of chiral association complexes 5. Stereodynamics and diastereotopism in chiral 1,3-dienes \documentclass{article}\pagestyle{empty}\begin{document}${\rm HOCMe}_{\rm 2} \rlap{--} ({\rm CCl =\!= CCl\rlap{--})}_{\rm 2} {\rm X}$\end{document}

The barriers to partial rotation around the central single bond in chiral dienes \documentclass{article}\pagestyle{empty}\begin{document}${\rm HOCMe}_{\rm 2} \rlap{--} ({\rm CCl =\!= CCl\rlap{--})}_{\rm 2} {\rm X}$\end{document} have been determined by coalescence of either ¹H NMR signals (X = CH₂OCH₃) or ¹³C NMR signals (X = H). In the presence of the optically active shift reagent (+) ? Eu(hfbc)₃ all ¹H signals were split at temperatures where the interconversion of enantiomers is slow. The temperature dependence of these spectra also yielded free activation enthalpies for the enantiomerizations which were in agreement with the ones obtained without Eu(hfbc)₃. The assignment of the four methyl resonances appearing in the presence of (+) ? Eu(hfbc)₃ at low temperature was possible by gradually increasing the rate of enantiomerization or gradually replacing the optically active auxiliary compound by the racemic one.     

Gas phase isomerization of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 14}} } \right]_{}^{_.^ + } $\end{document} ions generated from adamantanoid compounds

\documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 14}} } \right]_{}^{_.^ + } $\end{document} ions have been generated from a number of adamantanoid compounds, both by ionization and ionization followed-by fragmentation. Metastable ion abundance ratios of competitive reactions indicate the decomposition of these ions from common structures in all cases.     

Differentiation of tautomers by ion cyclotron resonance spectrometry: \documentclass{article}\pagestyle{empty}\begin{document}${\rm (CH}_{\rm 3} {\rm)}_{\rm 2} \mathop {\rm N}\limits^{\rm + } {\rm = CH}_{\rm 2} {\rm vs H}_{\rm 3} {\rm C}\mathop {\rm N}\limits^{\rm + } {\rm H = CHCH}_{\rm 3}$\end{document}

Ion cyclotron resonance spectrometry and deuterium labeling have been used to determine that nondecomposing \documentclass{article}\pagestyle{empty}\begin{document}${\rm (CH}_{\rm 3} {\rm)}_{\rm 2} \mathop {\rm N}\limits^{\rm + } {\rm = CH}_{\rm 2}$\end{document} ions do not isomerize to \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} {\rm CH = }\mathop {\rm N}\limits^{\rm + } {\rm HCH}_{\rm 3}$\end{document}.     

Stable γ-distonic oxonium ions: R\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^ + $\end{document}HCHR′ĊH2CHR″ and their characteristic reaction

The γ-distonic radical ions R$ \mathop {\rm O}\limits^ + $CHR′CH₂?HR″ and their molecular ion counterparts R$ \mathop {\rm O}\limits^{{\rm + } \cdot } $CHR′CH₂CH₂R″ have been studied by isotopic labelling and collision-induced dissociation, applying a potential to the collision cell in order to separate activated from spontaneous decompositions. The stability of CH₃$ \mathop {\rm O}\limits^ + $HCH(CH₃)CH₂?HCH₃, C₂H₅$ \mathop {\rm O}\limits^ + $HCH(CH₃)CH₂?HCH₃, CH₃$ \mathop {\rm O}\limits^ + $HCH(CH₃)CH₂?H₂, CH₃$ \mathop {\rm O}\limits^ + $HCH₂CH₂?HCH₃ and C₂H₅$ \mathop {\rm O}\limits^ + $HCH₂CH₂?HCH₃, has been demonstrated and their characteristic decomposition, alcohol loss, identified. For all these γ-distonic ions, the 1,4-H abstraction leading to their molecular ion counterpart exhibits a primary isotope effect.     

Electrochemical Study on Hydrogen Evolution and \begin{document}${\rm C}\rm{O}$\end{document}\begin{document}$_\rm{2}$\end{document} Reduction on Pt Electrode in Acid Solutions with Different pH

Hydrogen evolution reaction (HER) is the major cathodic reaction which competes \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} reduction reaction (\begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} RR) on Pt electrode. Molecular level understanding on how these two reactions interact with each other and what the key factors are of \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} RR kinetics and selectivity will be of great help in optimizing electrolysers for \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} reduction. In this work, we report our results of hydrogen evolution and \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} reduction on Pt(111) and Pt film electrodes in \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} saturated acid solution by cyclic voltammetry and infrared spectroscopy. In solution with pH > 2, the major process is HER and the interfacial pH increases abruptly during HER; \begin{document}${\rm C}\rm{O}_\rm{ad}$\end{document} is the only adsorbed intermediate detected in \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} reduction by infrared spectroscopy; the rate for \begin{document}${\rm C}\rm{O}_\rm{ad}$\end{document} formation increases with the coverage of UPD-H and reaches maximum at the onset potential for HER; the decrease of \begin{document}${\rm C}\rm{O}_\rm{ad}$\end{document} formation under HER is attributed to the available limited sites and the limited residence time for the reduction intermediate (\begin{document}$\rm{H}_\rm{ad}$\end{document}), which is necessary for \begin{document}${\rm C}\rm{O}_\rm{2}$\end{document} adsorption and reduction.     

[C3H3O]+ ions; reacting and non-reacting configurations

Three [C₃H₃O]⁺ ion structures have been characterized. The most stable of these is \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 2} = {\rm CH} - \mathop {\rm C}\limits^ + = {\rm O} $\end{document} its heat of formation ΔH_f was measured as 749±5 kJ mol^?1. In the μs time frame this ion fragments exclusively by loss of CO, a process which also dominates its collisional activation mass spectrum. The other stable [C₃H₃O]⁺ structures, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}\equiv \mathop {\rm C}\limits^ + - {\rm CHOH} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 2} = {\rm C} = \mathop {\rm C}\limits^{\rm + } - {\rm OH}, $\end{document}, were generated from some acetylenic and allenic precursor ions; their heats of formation were estimated to be 830 and 880 kJ mol^?1 respectively. The former ion was also produced by the gas phase protonation of propynal. These ions show loss of C₂H₂ and CO in both their metastable ion and collisional activation mass spectra. The broad Gaussian-type metastable peak for the loss of CO was shown to consist of two components corresponding to gragmentations having different activation energies.     

Potential energy profiles for unimolecular reactions of organic ions: [C3H8N]+ and [C3H7O]+

The unimolecular decompositions of two isomers of [C₃H₈N]⁺, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} {\rm CH} = \mathop {\rm N}\limits^ + {\rm H}_2 $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} \mathop {\rm N}\limits^ + {\rm H = CH}_{\rm 2} $\end{document}, are discussed in terms of the potential energy profile over which reaction may be considered to occur. The energy needed to promote slow (metastable) dissociations of either ion is found to be less than that required to cause isomerization to the other structure. This finding is supported by the observation of different decomposition pathways, different metastable peak shapes for C₂H₄ loss, the results of ²H labelling studies, and energy measurements on the two ions. The corresponding potential energy profile for decomposition of the oxygen analogues, \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} {\rm CH}_{\rm 2} {\rm CH =\!= }\mathop {\rm O}\limits^ + {\rm H} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} \mathop {\rm O}\limits^ + {\rm = CH}_{\rm 2} $\end{document}, is compared and contrasted with that proposed for the [C₃H₈N]⁺ isomers. This analysis indicates that for the oxygen analogues, the energy needed to decompose either ion is very similar to that required to cause isomerization to the other structure. Consequently, dissociation of either ion is finely balanced with rearrangement to the other and similar reactions are observed. Detailed mechanisms are proposed for loss of H₂O and C₂H₄ from each ion and it is shown that these mechanisms are consistent with ²H and ¹³C labelling studies, the kinetic energy release associated with each decomposition channel, the relative competition between H₂O and C₂H₄ loss and energy measurements.     

The gas phase ion chemistry of the acetyl cation and isomeric [C2H3O]+ ions. On the structure of the [C2H3O]+ daughter ions generated from the enol of acetone radical cation

Methods are described for the unequivocal identification of the acetyl, [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document} ?O] (a), 1-hydroxyvinyl, [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH] (b), and oxiranyl, (d), cations. They involve the careful examination of metastable peak intensities and shapes and collision induced processes at very low, high and intermediate collision gas pressures. It will be shown that each [C₂H₃O]⁺ ion produces a unique metastable peak for the fragmentation [C₂H₃O]⁺ → [CH₃]⁺+CO, each appropriately relating to different [C₂H₃O]⁺ structures. [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] ions do not interconvert with any of the other [C₂H₃O]⁺ ions prior to loss of CO, but deuterium and ¹³C labelling experiments established that [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH] (b) rearranges via a 1,2-H shift into energy-rich leading to the loss of positional identity of the carbon atoms in ions (b). Fragmentation of b to [CH₃]⁺+CO has a high activation energy, c. 400 kJ mol^?1. On the other hand, , generated at its threshold from a suitable precursor molecule, does not rearrange into [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH], but undergoes a slow isomerization into [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] via [CH₂\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}HO]. Interpretation of results rests in part upon recent ab initio calculations. The methods described in this paper permit the identification of reactions that have hitherto lain unsuspected: for example, many of the ionized molecules of type CH₃COR examined in this work produce [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OH] ions in addition to [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] showing that some enolization takes place prior to fragmentation. Furthermore, ionized ethanol generates a, b and d ions. We have also applied the methods for identification of daughter ions in systems of current interest. The loss of OH^˙ from [CH₃COOD]^+˙ generates only [CH₂?\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? OD]. Elimination of CH₃^˙ from the enol of acetone radical cation most probably generates only [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}?O] ions, confirming the earlier proposal for non-ergodic behaviour of this system. We stress, however, that until all stable isomeric species (such as [CH₃? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^{\rm + } $\end{document}?C:]) have been experimentally identified, the hypothesis of incompletely randomized energy should be used with reserve.     

An investigation of the decomposition of the intermediate ions produced by electron-impact. II—[C7H7]+ ions from several halogenotoluenes

The structure and decomposition of the [C₇H₇]⁺ ions produced by electron-impact from o-, m- and p-chlorotoluene, o-, m- and p-bromotoluence, and p-iodotoluence, have been investigated. By determining the relative abundance of normal and metastable ions, these [C₇H₇]⁺ ions at electron energy of 20 eV are shown to be so-called ‘tropylium ions’. The amount of the internal energy of the [C₇H₇]⁺ ion estimated by the relative ion abundance ratios, ? [C₅H₅]⁺/[C₇H₇]⁺ and m*/[C₇H₇]⁺ for the decomposition \documentclass{article}\pagestyle{empty}\begin{document}$ [{\rm C}_{\rm 7} {\rm H}_{\rm 7}]^ + \mathop \to \limits^{m^* } [{\rm C}_{\rm 5} {\rm H}_{\rm 5}]^ + + {\rm C}_{\rm 2} {\rm H}_{\rm 2} $\end{document}, is in the order iodotoluene > bromotoluene > chlorotoluene. The heats of formation of the activated complexes for the reaction \documentclass{article}\pagestyle{empty}\begin{document}$ [{\rm C}_{\rm 7} {\rm H}_{\rm 7}]^ + \mathop \to \limits^{m^* } [{\rm C}_{\rm 5} {\rm H}_{\rm 5}]^ + + {\rm C}_{\rm 2} {\rm H}_{\rm 2} $\end{document} were estimated. The values suggest that the decomposing [C₇H₇]⁺ ions from various halogenotoluenes are identical in structure.     

Structure and formation of gaseous [C4H5O]+ ions. III—Ions derived from unsaturated ethers

The abundant [C₄H₅O]⁺ (m/z 69) ions found in the 70 eV mass spectra of a series of acetylenic, allenylic and unsaturated cyclic ethers are shown to have the following structures: HC?C? \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}H? OCH₃ (e), H₂C?C?—OCH₃ (f), (g) and H? C?C? CH₂—O\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}H₂ (h). Of these, the cyclic ion g is the most stable: its ion enthalpy (≥ 165 kcal mol^?1) is close to that found for the acyclic C₃H₅\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}? O isomers identified in a previous study. Evidence that these four isomeric [C₄H₅O]⁺ ions are stable species with lifetimes ≥ 10^?5 s is obtained from their collisional activation spectra, the shape of the metastable peaks and the associated kinetic energy release values for the common loss of CO, thermochemical information and analysis of deuterium and carbon-13 labelled precursor molecules. It is further shown that loss of X? from ethers of the type X? C?C? CH₂OCH₃ involves isomerization into energy rich allenyl type ions [(X)HC?C?CHOCH₃]⁺˙ . These ions undergo loss of X? by simple bond cleavage, yielding, e type product ions, when the C? X bond strength is relatively low (X?I, Br). When X?Cl and especially CH₃ or H, X? is only lost after rearrangement yielding the cyclic product ion g. The mechanism for this cyclization reaction is related to that proposed in a previous study for the ester→ acid isomerization in the molecular ions of the esters of α, β-unsaturated carboxylic acids.     

Gas phase ion chemistry of methyl acetate,methyl propanoate and their enolic tautomers. An experimental approach

From a combination of isotopic substitution, time-resolved measurements and sequential collision experiments, it was proposed that whereas ionized methyl acetate prior to fragmentation rearranges largely into \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_3 \mathop {\rm C}\limits^ + ({\rm OH}){\rm O}\mathop {\rm C}\limits^{\rm .} {\rm H}_2 $\end{document}, in contrast, methyl propanoate molecular ions isomerize into \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^. {\rm H}_2 {\rm CH}_2 \mathop {\rm C}\limits^ + ({\rm OH}){\rm OCH}_3 $\end{document}. Metastably fragmenting methyl acetate molecular ions are known predominantly to form H₂?OH together with \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_3 - \mathop {\rm C}\limits^ + = {\rm O} $\end{document}, whereas ionized methyl propanoate largely yields H₃CO˙ together with \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_3 {\rm CH}_2 - \mathop {\rm C}\limits^ + = {\rm O} $\end{document}. The observations were explained in terms of the participation of different distonic molecular ions. The enol form of ionized methyl acetate generates substantially more H₃CO˙ in admixture with H₂?OH than the keto tautomer. This is ascribed to the rearrangement of the enol ion to the keto form being partially rate determining, which results in a wider range of internal energies among metastably fragmenting enol ions. Extensive ab initio calculations at a high level of theory would be required to establish detailed reaction mechanisms.     

"Dry" NiCo\begin{document}$_\textbf{2}$\end{document}O\begin{document}$_\textbf{4}$\end{document} Nanorods for Electrochemical Non-enzymatic Glucose Sensing

A rod-like NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} modified glassy carbon electrode was fabricated and used for non-enzymatic glucose sensing. The NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} was prepared by a facile hydrothermal reaction and subsequently treated in a commercial microwave oven to eliminate the residual water introduced during the hydrothermal procedure. Structural analysis showed that there was no significant structural alteration before and after microwave treatment. The elimination of water residuals was confirmed by the stoichiometric ratio change by using element analysis. The microwave treated NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} (M-NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document}) showed excellent performance as a glucose sensor (sensitivity 431.29 \begin{document}$\mu $\end{document}A\begin{document}$\cdot$\end{document}mmol/L\begin{document}$^{-1}$\end{document}\begin{document}$\cdot$\end{document}cm\begin{document}$^{-2}$\end{document}). The sensing performance decreases dramatically by soaking the M-NiCo\begin{document}$_2$\end{document}O\begin{document}$_4$\end{document} in water. This result indicates that the introduction of residual water during hydrothermal process strongly affects the electrochemical performance and microwave pre-treatment is crucial for better sensory performance.     

Roaming Dynamics of H+C\begin{document}$_{2}$\end{document}D\begin{document}$_{2}$\end{document} Reaction on Fundamental-Invariant Neural Network Potential Energy Surface

We performed extensive quasiclassical trajectory calculations for the H+C\begin{document}$_2$\end{document}D\begin{document}$_2$\end{document}\begin{document}$\rightarrow$\end{document}HD+C\begin{document}$_2$\end{document}D/D\begin{document}$_2$\end{document}+C\begin{document}$_2$\end{document}H reaction based on a recently developed, global and accurate potential energy surface by the fundamental-invariant neural network method. The direct abstraction pathway plays a minor role in the overall reactivity, which can be negligible as compared with the roaming pathways. The acetylene-facilitated roaming pathway dominates the reactivity, with very small contributions from the vinylidene-facilitated roaming. Although the roaming pathways proceed via the short-lived or long-lived complex forming process, the computed branching ratio of product HD to D\begin{document}$_2$\end{document} is not far away from 2:1, implying roaming dynamics for this reaction is mainly contributed from the long-lived complex-forming process. The resulting angular distributions for the two product channels are also quite different. These computational results give valuable insights into the significance and isotope effects of roaming dynamics in the biomolecular reactions.     

Kinetics and mechanism of the reactions of the superoxide ion in solutions. I. Absorption spectra and interaction with solvents and cations

Absorption spectra of the superoxide ion have been studied in dimethylformamide (DMF) and acetonitrile (AN). It was found that the superoxide ion existed in equilibrium with an ion pair in AN (K_eq = 20M^?1, Bu₄N⁺ is the cation) and as “free” (solvated) ion in DMF. The addition of DMF caused the destruction of an ion pair in AN. The addition of the proton donors HX (water or ethanol) to the \documentclass{article}\pagestyle{empty}\begin{document}${\rm O}_{\rm 2}^{\overline {\rm .} }$\end{document} solutions in DMF and AN caused the formation of new ion pairs (Bu₄N⁺\documentclass{article}\pagestyle{empty}\begin{document}${\rm O}_{\rm 2}^{\overline {\rm .} }$\end{document})₂HX. The equilibrium constants of these ion pairs were determined in DMF and AN.