Chemical ionization of phenyl n-propyl ether and methyl substituted analogs: Propene loss initiated by competing proton transfer to the oxygen atom and the aromatic ring

The mechanism of propene loss from protonated phenyl n-propyl ether and a series of mono-, di-, and trimethylphenyl n-propyl ethers has been examined by chemical ionization (CI) mass spectrometry in combination with tandem mass spectrometry experiments. The role of initial proton transfer to the oxygen atom and the aromatic ring, respectively, has been probed with the use of deuterated CI reagents, D₂O, CD₃OD, and CD₃CN (given in order of increasing proton affinity), in combination with deuterium labeling of the β position of the n-propyl group or the phenyl ring. The metastable [M + D]⁺ ions of phenyl n-propyl ether—formed with D₂O as the CI reagent—eliminate C₃H₅D and C₃H₆ in a ratio of 10:90, which indicates that the added deuteron is incorporated to a minor extent in the expelled neutral species. In the experiments with CD₃OD as the CI reagent, the ratio between the losses of C₃H₅D and C₃H₆ from the metastable [M + D]⁺ ions of phenyl n-propyl ether is 18:82, whereas the ratio becomes 27:73 with CD₃CN as the reagent. A similar trend in the tendency to expel a propene molecule that contains the added deuteron is observed for the metastable [M + D]⁺ ions of phenyl n-propyl ether labeled at the β position of the alkyl group. Incorporation of a hydrogen atom that originates from the aromatic ring in the expelled propene molecule is of negligible importance as revealed by the minor loss of C₃H₅D from the metastable [M + H]⁺ ions of C₆D₅OCH₂CH₂CH₃ irrespective of whether H₂O, CH₃OH, or CH₃CN is the CI reagent. The combined results for the [M + D]⁺ ions of phenyl n-propyl ether and deuterium-labeled analogs are suggested to be in line with a model that assumes that propene loss occurs not only from species formed by deuteron transfer to the oxygen atom, but also from ions generated by deuteron transfer to the ring. This is substantiated by the results for the methyl-substituted ethers, which reveal that the position as well as the number of methyl groups bonded to the ring exert a marked effect on the relative importances of the losses of C₃H₅D and C₃H₆ from the metastable [M + D]⁺ ions of the unlabeled methyl-substituted species.     

HOC+: Laboratory observation of a proposed interstellar species

The ion [HOC⁺] together with some [HC⁺O] is generated by the dissociative ionisation of CD₃OH. Collisional activation mass spectral characteristics of the two isomers are reported. ΔH_f ([HOC⁺]) is estimated to be 930 ± 20 kJ mol^?1.     

pH-Metrische Studien an den binären Komplexen von Oxovanadium(IV) mit Hippur- und Anthranilsäure und Pyridin-2-aldoxim

pH-metric studies on the interaction of oxovanadium(IV) with hippuric and anthranilic acids and pyridine-2-aldoxime indicate the formation of monohydroxo derivatives of 1:1 chelates. The equilibrium constants for the reaction, VO²⁺+HA+H₂O?VO(OH)A+2H⁺ have been calculated as 4.47±0.07 and 6.32±0.05 in the 1:1 VO²⁺-hippuric or anthranilic acid systems resp. and for the reaction, VO²⁺+H₂ A ⁺+H₂O?VO(OH)A+3H⁺ as 8.40±0.09 in the 1:1 VO²⁺-pyridine-2-aldoxime hydrochloride system at 30±0.5°C (μ=0.1-KNO₃).     

Heats of formation of iodo-complexes of zinc(II), cadmium(II) and mercury(II) in aqueous solutions

Heats of formation of MeI⁺, MeI₂, MeI₃^? and MeI₄^2? where Me²⁺, Cd²⁺ or Hg²⁺ were determined in acidic solutions by flow microcalorimetry. Some gaps in the literature data were filled. In particular, ΔH₃ for the mercury(II) complex was determined and the ΔH₁, ΔH₂ + ΔH₃, ΔH₄ for zinc(II) complexes were measured in sodium free solutions to avoid ionic couple formation. For cadmium(II) complexes, existing data were confirmed. Thermodynamic functions are discussed in term of hard/soft interactions.     

On the hydrolysis of the titanium(IV) ion in chloride media

Determinations of the [Ti(IV)]/[Ti(III) ratio in solutions of titanium(IV) chloride equilibrated with H₂(g), at 25°C in 3 M (Na)Cl ionic medium, have indicated the predominance of the Ti(OH)₂²⁺ species in the concentration ranges 0.5 ? [H⁺] ? 2 M and 1.5 x 10^?3 ? [Ti(IV)] ? 0.05 M. From the equilibrium data the reduction potential has been evaluated Ti(OH)₂²⁺ + 2 H⁺ + e ? Ti³⁺ + 2H₂O, E_oH = (7.7 ± 0.6) x 10^?3 V. The acidification reactions of Ti(OH)₂²⁺ were also studied in 12 M(Li)Cl medium at 25°C by measuring the redox potential of the Ti(IV)/Ti(III) couple as a function of [H⁺]. The potentiometric data in the acidity range 0.3 ? [H⁺] ? 12 M have been explained by assuming Ti⁴⁺ + e ? Ti³⁺, E_o = 0.202 ± 0.002 V Ti⁴⁺ + H₂O ? TiOH³⁺ + H⁺, log K_a1 = 0.3 ± 0.01 Ti⁴⁺ + 2H₂O ? Ti(OH)₂²⁺ + 2H⁺, log K_a1K_a2 = 1.38 ± 0.05.     

Thermal decomposition of zinc and cadmium zirconyl oxalates

The enthalpy of formation at 298.15 K of the polymer Al₁₃O₄(OH)₂₈(H₂O)³⁺₈ and an amorphous aluminium trihydroxide gel was studied using an original differential calorimetric method, already developed for adsorption experiments, and aluminium-27 NMR spectroscopy data. ΔH_f “Al₁₃” (298.15 K) = ? 602 ± 60.2 kJ mole^?1 and ΔH_f Al(OH)₃ (298.15 K) = ? 51 ± 5 kJ mole^?1. Using theoretical values of ΔG_R “Al₁₃” and ΔG_R Al(OH)₃, we calculated ΔG_f “Al₁₃” (298.15 K) = ? 13282 kJ mole^?1; ΔS_f “Al₁₃” (298.15 K) = + 42.2 kJ mole^?1; ΔG_f Al(OH)₃ (298.15 K) = ? 782.5 kJ mole^?1; and ΔS_f Al(OH)₃ (298.15 K) = + 2.4 kJ mole^?1.     

Reply to comment on the possible role of the reaction H+H2O→H2+OH in the radiolysis of water at high temperatures

In reply to “Comment on the possible role of reaction H+H₂O→H₂+OH in the radiolysis of water at high temperatures” (Bartels, 2009 Comment on the possible role of the reaction H+H₂O→H₂+OH in the radiolysis of water at high temperatures. Radiat. Phys. Chem. 78, 191–194) we present an alternative thermodynamic estimation of the reaction rate constant k. Based on the non-symmetric standard state convention we have calculated that the Gibbs energy of reaction Δ_rG=57.26 kJ mol^?1 and the reaction rate constant k=7.23×10^?5 M^?1 s^?1 at ambient temperature. Re-analysis of the thermodynamic estimation (Bartels, 2009 Comment on the possible role of the reaction H+H₂O→H₂+OH in the radiolysis of water at high temperatures. Radiat. Phys. Chem. 78, 191–194) showed that the upper limit for the rate constant at 573 K is k=1.75×10⁴ M^?1 s^?1 compared to the value predicted by the diffusion-kinetic modelling (3.18±1.25)×10⁴ M^?1 s^?1 (Swiatla-Wojcik, D., Buxton, G.V., 2005. On the possible role of the reaction H+H₂O→H₂+OH in the radiolysis of water at high temperatures. Radiat. Phys. Chem. 74(3–4), 210–219). The presented thermodynamic evaluation of k(573) is based on the assumption that k can be calculated from Δ_rG and the rate constant of the reverse reaction which, as discussed, are both uncertain at high temperatures.     

Rate coefficients for reactions of OH radicals with CH3D,CH2D2, CHD3, and CD4

Fourier transform infrared (FTIR) smog chamber techniques were used to investigate the atmospheric chemistry of the isotopologues of methane. Relative rate measurements were performed to determine the kinetics of the reaction of the isotopologues of methane with OH radicals in cm³ molecule⁻¹ s⁻¹ units: k(CH₃D + OH) = (5.19 ± 0.90) × 10⁻¹⁵, k(CH₂D₂ + OH) = (4.11 ± 0.74) × 10⁻¹⁵, k(CHD₃ + OH) = (2.14 ± 0.43) × 10⁻¹⁵, and k(CD₄ + OH) = (1.17 ± 0.19) × 10⁻¹⁵ in 700 Torr of air diluent at 296 ± 2 K. Using the determined OH rate coefficients, the atmospheric lifetimes for CH_4–xD_x (x = 1–4) were estimated to be 6.1, 7.7, 14.8, and 27.0 years, respectively. The results are discussed in relation to previous measurements of these rate coefficients.     

Kinetics of nucleophilic attack on coordinated organic moieties : XII. Addition of triphenylphosphine to [(C8H11)Co(C5H5)]BF4

A stopped-flow investigation of the reversible addition of Ph₃P to [(C₈H₁₁)Co(C₅H₅)]⁺ indicates the rate law, k_obs = k₁[Ph₃P] + k_?1. The low Δ2 of 21.0 ± 1.2 kJ mol^?1 and the negative ΔS2 of ?114 ± 5 J K^?1 mol^?1 are consistent with rapid addition to the enyl ligand. The higher Δ2 of 86.2 ± 5.1 kJ mol^?1 and the positive ΔS2 of +60 ± 17 J K^?1 mol^?1are as expected for the reverse dissociation. Preliminary studies show that the related complex [(C₇H₉)Co(C₅H₅)]⁺ is at least 65 times more electrophilic towards Ph₃P.     

The platinumcarbon bond strength in Pt(PPh3)2(CH3)I

The enthalpies of reaction 1–3 have been determined

as ΔH(1) = ?176.6 ± 5.4, ΔH(2) = ?107.8 ± 6.0, and ΔH(3) = ?78.9 ± 2.0 kJ mol^?1. The bond dissociation energy difference D₁(PtCH₃) ? D₁(PtI) = +6 ± 5 kJ mol^?1 is calculated, which indicates that the two bonds have very similar strengths.     

Gas-phase solvation of protonated aliphatic amines: methyl,ethyl, n-propyl,and iso-propylamine

The thermodynamic quantities K_{n?1 n}, ΔG⁰_{n?1, n} and ΔS⁰_n?1, n for the gas phase equilibrium reactions RNH⁺₃(RNH₂)_n?1 + RNH₂ = RNH⁺₃(RNH₂)_n, where n ? 3 and R indicates an alkyl group (CH₃, C₂H₅, n-C₃H₇ and iso-C₃H₇), have been determined.     

Second coordination sphere of aluminium and gallium hexacoordination complexes

It is shown by means of ¹⁹F NMR that the hexacoordinated solvates of aluminium and gallium in solutions of methyl, ethyl and n-propyl alcohols form outer-sphere complexes with the halide ions, F^?, Cl^? and Br^?, in which the acidoligands are situated in the second coordination sphere. The outer-sphere complexes are formed on the basis of purely alcoholic solvates, M(ROH)₆³⁺, as well as the complexes containing the mixed coordination sphere, M(ROH)_6?n(H₂O)_n³⁺, and Al(CH₃OH)_6?n(C₂H₅OH)_n²⁺.     

Hydroxo and Chloro Complexes/Ion Interactions of Hf4+ and the Solubility Product of HfO2(am)

The solubility of HfO₂(am) was determined at different equilibration periods from the over- and undersaturation directions, in very acidic to basic solutions (0.1 m HCl to 3.2 m NaOH), and in NaCl solutions ranging in concentrations from very dilute to as high as 5.59 m and in a ${\text{p}}C_{{\text{H}} + }$ range from 1 to 4 to obtain reliable thermodynamic data for the Hf⁴⁺–Cl^?–Na⁺–H⁺–OH^?–H₂O system. The studies indicate that equilibrium is reached rapidly (<5 days) and that HfO₂(am) solubility shows amphoteric behavior. The solubility data obtained in this study, along with the data reported in the literature, at NaOH molalities as high as 21.7 m were interpreted using the ion-interaction model of Pitzer. The log K ⁰ for the solubility of HfO₂(am) [HfO₂(am) + 2H₂O ? Hf⁴⁺ + 4OH^?] was determined to be ?55.1 ± 0.7. The log K ⁰ values for the formation of HfOH³⁺, Hf(OH)⁰ ₄, Hf(OH)₅ ^?, and Hf(OH)₆ ^2? according to the reaction (Hf⁴⁺ + xOH^? ? Hf(OH)^4?x _x) were determined to be 13.8, <44.8, 49.7 ± 0.2, and 51.2 ± 0.2, respectively. The thermodynamic model developed in this study is valid for a wide range of conditions (as high as 0.1 m HCl, 21.7 m NaOH, and 5.59 m NaCl). The binary ion-interaction parameters for Hf⁴⁺–Cl^?, HfOH³⁺–Cl^?, and Hf(OH)^2? ₆–Na⁺ were determined in this study to accurately define the observed solubility behavior of hafnium in various systems.     

Hydrogen migrations in mass spectrometry. II—single and double hydrogen migrations in the electron impact fragmentation of n-propyl benzoate

The sources of the migrant hydrogen atom(s) in reactions (a) and (b) in the electron impact mass spectrum of n-propyl benzoate have been investigated: (a) [C₆H₅CO₂C₃H₇]⁺ →[C₆H₅CO₂H]⁺ + C₃H₆; (b) [C₆H₅CO₂C₃H₇]⁺ → [C₆H₅CO₂H₂]⁺ + C₃H₅^sdot;. Deuterium labelling of the propyl group showed that, for reaction (a) at 70 eV ionizing energy 3 ± 1% of the hydrogen originates from C-1 of the propyl group, 86 ± 4% from C-2 and 11 ± 3% from C-3. The specificity of the transfer from C-2 increases as the internal energy of the fragmenting ions decreases, indicating that the results cannot be rationalized in terms of H/D interchanges between positions in the propyl group, but rather that the reaction involves specific, competing, H transfer reactions from each propyl position, in contrast to the high site specificity characteristic of the McLafferty rearrangement. Reaction (b) involves, almost exclusively, transfer of one hydrogen from C-2 and one from C-3 with only very minor participation of C-1 hydrogens. The [C₆H₅COOH]⁺ ion produced in reaction (a) fragments further to [C₆H₅CO]⁺ + OH. and the labelling results indicate some interchange of the carboxylic hydrogen with (ortho) ring hydrogens for those ions fragmenting in the first drift region. The extent of interchange is less than that observed for fragmentation of the same ion produced by direct ionization of benzoic acid or by reaction (a) in ethyl benzoate.     

Chemical ionization of fluorophenyl n-propyl ethers: Loss of propene from the metastable [M + D]+ ions

Chemical ionization (CI) mass spectrometry with the reagents D₂O, CD₃OD, and CD₃CN (given in order of increasing proton affinity) has been used to generate metastable [M + D]⁺ ions of a series of mono-, di-, and trifluorophenyl n-propyl ethers and analogs labeled with two deuterium atoms at the β position of the alkyl group. Loss of propene is the main reaction of the [M + D]⁺ ions, whereas dissociation with formation of propyl carbenium ions is of minor importance. The combined results reveal that the deuteron added in the CI process can be incorporated in the propene molecules as well as in the propyl carbenium ions. The extent to which the added deuteron is exchanged with the hydrogen atoms of the propyl group is markedly dependent on the position of the fluorine atom(s) on the ring and the exothermicity of the initial deuteron transfer. For 3-fluorophenyl n-propyl ether, exchange is not observed if D₂O is the CI reagent, and occurs only to a minor extent in the experiments with the CI reagents CD₃OD and CD₃CN. Similar results are obtained for the 3,5-difluoro- and 2,4,6-trifluorophenyl ethers, whereas significant exchange is observed prior to the dissociations of the [M + D]⁺ ions of the 4-fluoro- and 2,6-difluorophenyl n-propyl ethers, irrespective of the nature of the CI reagent. These results are discussed in terms of the occurrence of initial deuteron transfer either to the oxygen atom or the aromatic ring followed by formation of an ion/neutral complex of a fluorine-substituted molecule and a secondary propyl carbenium ion. Initial deuteron transfer to the oxygen atom is suggested to yield complexes that can react by exchange between the added deuteron and the hydrogen atoms of the original propyl group prior to dissociation. By contrast, initial deuteron transfer to the ring is suggested to lead to complexes that react further by loss of propene molecules containing only the hydrogen/deuterium atoms of the original propyl entity.     

Hydrolysis of methyltin(IV) trichloride in aqueous NaCl and NaNO3 solutions at different ionic strengths and temperatures

The hydrolysis of methyltin(IV) trichloride (CH₃SnCl₃) has been studied in aqueous NaCl and NaNO₃ solutions (0 < I/mol dm⁻³ ≤ 1), at different temperatures (15 ≤ T/°C ≤ 45) by­potentiometric measurements (H⁺‐glass electrode). By considering the generic hydrolytic <?tw=97.2%>reaction pCH₃Sn³⁺ + qH₂O = (CH₃Sn)_p(OH)_q^3p−q<?tw>­+ qH⁺ (logβ_pq), we have the formation of five species and logβ₁₂ = −3.36, logβ₁₃ = −8.99, logβ₁₄ = −20.27 and logβ₂₅ = −7.61. The first hydrolysis step is measurable only at very low pH values and was not determined: a rough estimate of the hydrolysis constant is logβ₁₁ = −1.5 (± 0.5). The dependence on ionic strength of logβ_pq is quite different in NaNO₃ and NaCl solutions, and the formation at low pH values of the species CH₃Sn(OH)Cl⁺ has been found with logβ = −1.40. Hydrolysis constants strongly depend on temperature and from the relationships logβ_pq = f(T), ΔH ° values have been calculated. Speciation problems of CH₃Sn³⁺ in aqueous solution are discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

Effects of functional group interactions on the gas-phase methylation and dissociation of acids and esters

Functional group interactions have been observed to affect gas-phase ion-molecule chemistry in a quadrupole ion trap mass spectrometer. Gas-phase methylation and collisionactivated dissociation reactions of a series of related acids and esters allows an evaluation of the structural factors that influence reactivity and functional group interactions of these compounds. Examination of the [M+H]⁺ or [M+15]⁺ product ions by collision-activated dissociation has provided insight into the conformations from which diacids and diesters undergo electrophilic addition. Collision-activated dissociation has provided not only more detailed information on the structures of the ions, but also the data necessary for confident mechanistic interpretation. Labeling studies were done to probe fragmentation pathways. Upon activation of the [M+CD₃]⁺ products of dimethyl maleate and dimethyl succinate, formed from reaction of the neutrals with CD₃OCD ₂ ⁺ ions, a rapid interfunctional group methyl transfer causes scrambling of the methyls prior to elimination of dimethyl ether or methanol. The [M+15]⁺ ions of dimethyl maleate are believed to lose dimethyl ether through a rate-determining 1,6-methyl transfer, whereas the [M+15]⁺ ions of dimethyl succinate eliminate methanol through a rate-determining 1,5-proton transfer.     

Possible tests for the mechanisms of ligand exchange in solids: The deaquation-anation of [Cr(NH3)5(H2O)]X3 salts

The possibility of using correlations of ΔH⁺ and ΔH, and of ΔH⁺ and ΔS⁺ to gain insight into the mechanisms of ligand-exchange reactions in solids are discussed. These correlations are tested using literature values for the deaquation-anation reactions of [Cr(NH₃)₅(H₂O)]X₃, where X^? = Cl^?, Br^?, I^? or NO^?₃. The poor agreement in the activation parameters reported in the literature precluded a meaningful test of the ΔH?ΔH^* correlation. This poor agreement suggests that these activation parameters are strongly influenced by experimental factors that have not been controlled in studies to date. nevertheless, there is a linear correlation of ΔH² and ΔS² which gives an isokinetic temperature of 367 ± 11 K. This isokinetic behavior suggests that the same mechanism is operative throughout the series.     

Hydrolysis of dioxouranium(VI): a calorimetric study in NaClaq and NaClO4 aq, at 25 °C

We report the results of a calorimetric study on the hydrolysis of UO₂²⁺ in different ionic media (NaClO_4 aq, NaCl_aq) at 25 °C. Experiments in NaCl were performed at different ionic strength, at I≤1 mol l⁻¹. The species considered in both ionic media were UO₂(OH)⁺, (UO₂)₂(OH)₂²⁺ and (UO₂)₃(OH)₅⁺, and in addition (UO₂)₃(OH)₄²⁺ and (UO₂)₃(OH)₇⁻ in NaCl_aq. The dependence on ionic strength of enthalpy changes in NaCl_aq was expressed by the simple linear equation ΔH_pq=ΔH°_pq+aI^1/2 (a, empirical parameter). Comparison with literature findings is given and some recommended values are reported.     

Potentiometric study of binary complexes of 3-[(1R)-1-hydroxy-2-(methylamino)ethyl]phenol hydrochloride with some lanthanide ions in aqueous and mixed solutions

The complexation of lanthanide ions (Y³⁺, La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Gd³⁺, Tb³⁺, and Dy³⁺) with 3-[(1R)-1-hydroxy-2-(methylamino)ethyl]phenol hydrochloride was studied at different temperatures and different ionic strengths in aqueous solutions by Irving-Rossotti pH titration technique. Stepwise calculation, PKAS and BEST Fortran IV computer programs were used for determination of proton-ligand and metal-ligand stability constants. The formation of species like MA, MA₂, and MA(OH) is considered in SPEPLOT. Thermodynamic parameters of complex formation (ΔG, ΔH, and ΔS) are also evaluated. Negative ΔG and ΔH values indicate that complex formation is favourable in these experimental conditions. The stability of complexes is also studied at in different solvent-aqueous (vol/vol). The stability series of lanthanide complexes has shown to have the “gadolinium break.” Stability of complexes decreases with increase in ionic strength and temperature. Effect of systematic errors like effect of dissolved carbon dioxide, concentration of alkali, concentration of acid, concentration of ligand and concentration of metal have also been explained.