Relative methylmercury cation affinities in the gas phase determined by high pressure mass spectrometry

1981 ◽  
Vol 59 (12) ◽  
pp. 1779-1786 ◽  
Author(s):  
John A. Stone ◽  
Dena E. Splinter
Keyword(s):  
High Pressure ◽  
Gas Phase ◽  
External Rotation ◽  
Equilibrium Constants ◽  
Partition Functions ◽  
Pulsed Electron Beam ◽  
Nitrogen Bases ◽  
Relative Affinity ◽  
The Difference ◽  
Soft Acid

A pulsed electron beam, high pressure mass spectrometer has been used to determine equilibrium constants for the exchange of CH3Hg+ between bases; [Formula: see text] A series of aromatic, hydrocarbon bases has been studied at 417 K and several nitrogen bases have been studied at 580 K. There is a good linear correlation between differences in CH3Hg+ affinity (ΔG0) and H+ affinity for bases in each series. The single sulfur base examined ((C3H7)2S) shows anomalously high relative affinity for CH3Hg+ compared with H+ while two oxygen bases (CH3COOCH3 and C6H5NO2) show lesser relative affinity. These results are in qualitative agreement with the hard–soft acid base theory. ΔH0 and ΔS0 values have been obtained from Arrhenius plots. For a pair of aromatic bases (toluene–ethylbenzene) ΔH0 is of the same magnitude as that for H+ and ΔS0 may be calculated using partition functions for translation and external rotation. For toluene/methylacetate the difference in binding energy is much greater for H+ than for CH3Hg+ and a similar calculation of ΔS0 gives a result not consistent with the experimental value.

Intrinsic Acidities of α, β, γ Chlorosubstituted Aliphatic Acids from Gas Phase Equilibrian Mesurements

1974 ◽  
Vol 52 (5) ◽  
pp. 861-863 ◽  
Author(s):  
R. Yamdagni ◽  
P. Kebarle
Keyword(s):  
Proton Transfer ◽  
Gas Phase ◽  
Equilibrium Constants ◽  
Transfer Reactions ◽  
Pulsed Electron Beam ◽  
Aliphatic Acids ◽  
Gas Phase Acidity ◽  
Proton Transfer Reactions ◽  
The Difference ◽  
Acidity Scale

Measurements of the proton transfer equilibria: A1− + A2H = A2− with a pulsed electron beam high pressure mass spectrometer were extended to α, β, γ chlorosubstituted aliphatic acids. The equilibrium constants were used to evaluate ΔG0 for the proton transfer reactions. Assuming ΔG ≈ ΔH and using standard acids AH for which the difference between the bond dissociation energy D(A—H) and the electron affinity of A, EA(A) was known one could evaluate the corresponding difference for the newly measured acids and place them on an absolute acidity scale. The gas phase acidity was observed to increase in the order: acetic, propionic, butyric, γ-Cl butyric, β-Cl butyric, β-Cl propionic, α-Cl butyric, α-Cl propionic, α-Cl acetic. The gas phase acidities are compared with those observed in aqueous solution. The effects of the Cl substituent parallel those in solution but are much larger. The attenuation occurring in solution is attributed to weaker hydrogen bonding of the chloro stabilized acid anions to water molecules.

Solvation of Cl− and O2− with H2O, CH3OH, and CH3CN in the gas phase

1973 ◽  
Vol 51 (15) ◽  
pp. 2507-2511 ◽  
Author(s):  
R. Yamdagni ◽  
J. D. Payzant ◽  
P. Kebarle
Keyword(s):  
High Pressure ◽  
Temperature Dependence ◽  
Gas Phase ◽  
Experimental Technique ◽  
Equilibrium Constants ◽  
Ion Source ◽  
Mass Spectrometric ◽  
Mass Spectrometric Detection ◽  
Free Energies

Determination of the temperature dependence of the equilibrium constants Kn,n−1 for the reactions A −Bn = A −Bn−1 + B where A− equals Cl− and O2− and B is HOH, CH3OH, or CH3CN leads to the corresponding ΔH0n−1, ΔG0n−1,n, and ΔS0n−1,n values. The experimental technique is based on mass spectrometric detection of ions escaping from a high pressure ion source. At n = 1, Cl− is solvated most strongly by methanol, then CH3CN and HOH. At higher n a cross over is observed with water becoming the best solvent. These results are in agreement with the positive transfer enthalpies and free energies for Cl− from the liquid solvents HOH → CH3OH and HOH → CH3CN reported in the literature.O2− is solvated more strongly than Cl− appearing thus as an ion of "size" intermediate between Cl− and F− Again CH3OH gives the highest interaction for n = 1, however for n > 1 water gives stronger interactions.

Alkylation of benzene by alkyl cations. Stability of the tert-butyl benzenium ion

1982 ◽  
Vol 60 (18) ◽  
pp. 2325-2331 ◽  
Author(s):  
D. K. Sen Sharma ◽  
S. Ikuta ◽  
P. Kebarle
Keyword(s):  
Gas Phase ◽  
Equilibrium Constants ◽  
Ion Source ◽  
Phase Reaction ◽  
Source Pressure ◽  
Pulsed Electron Beam ◽  
Gas Phase Reaction ◽  
Alkyl Cations ◽  
Alkylation Of Benzene ◽  
Energy Formula

The kinetics and equilibria of the gas phase reaction [1] tert-C4H9+ + C6H6 = tert-C4H9C6H6+ were studied with a high ion source pressure pulsed electron beam mass spectrometer. Equilibria [1] could be observed in the temperature range 285–325 K. van't Hoff plots of the equilibrium constants led to [Formula: see text] and [Formula: see text]. The rate constants at 305 K were klf = 1.5 × 10−28 molecules−2 cm6 s−1 and klr = 2.9 × 10−1 molecules−1 cm3 s−1. tert-C4H9C6H6+ dissociates easily via [lr] not only because of the low dissociation energy [Formula: see text] but also because of the unusually favorable entropy [Formula: see text]. The occurrence of transalkylation reactions: tert-C4H9C6H6+ + alkylbenzene = tert-C4H9 alkylbenzene+ + benzene, was discovered in the present work.

scholarly journals The adsorption of non-polar gases on alkali halide crystals

1939 ◽  
Vol 173 (954) ◽  
pp. 349-367 ◽  
Keyword(s):  
Gas Phase ◽  
Three Dimensional ◽  
Adsorbed Layer ◽  
Partition Functions ◽  
Configurational Energy ◽  
Adsorbed Gas ◽  
The Difference ◽  
Gas Layer ◽  
Alkali Halide Crystals ◽  
Made In

In recent years many important theoretical advances have been made in the application of quantum statistics to adsorption problems. Fowler (1935), adopting the Langmuir picture of a monomolecular adsorbed gas layer, derived from purely statistical considerations the equation p = ( θ /1- θ ) ((2 πm ) 3/2 ( kT ) 5/2 )/ h 3 ( b g ( T )/ v s ( T ) e -x/kT , in which the undetermined constants of Langmuir’s original equation (1918) are given explicitly in terms of the partition functions, b g ( T ) and v s ( T ) belonging to atoms in the gas phase and in the adsorbed layer respectively and x , which is the difference in energy of an atom in the gas phase and in the lowest adsorption level on the surface. In subsequent developments the change in the energy of adsorption as a function of θ (the fraction of the surface covered) has been introduced in the above equation using ( a ) the Bragg and Williams approximations (Fowler 1936 a ) and ( b ) the Bethe method (Peierls 1936) to determine the configurational energy. Further applications and extensions of these methods to special adsorption problems have been carried through by Roberts (1937) and by Wang (1937), and Rushbrooke (1938) has examined the validity of the assumption, which is implicit in all this work, namely, that v s ( T ) is independent of the configuration. In addition, an approach to the solution of the statistical configuration problem when molecules condense in two layers simultaneously has recently been made by Cernuschi (1938) and developed by Dube (1938). In order to evaluate correctly the summations v s ( T ) occurring in equation (1), the Schrödinger equation for an atom moving in the three-dimensional potential field of the substrate should be solved, but this has so far proved prohibitively difficult. In the past it has been customary, and for practical purposes it is possibly generally sufficient, to substitute classical partition functions for these summations.

Kinetics and Rate Constants of Reactions Leading to Hydration of and in Gaseous Oxygen, Argon, and Helium Containing Traces of Water

1972 ◽  
Vol 50 (14) ◽  
pp. 2230-2235 ◽  
Author(s):  
J. D. Payzant ◽  
A. J. Cunningham ◽  
P. Kebarle
Keyword(s):  
High Pressure ◽  
Electron Beam ◽  
Gas Phase ◽  
Mass Spectrometer ◽  
Rate Constants ◽  
Gas Phase Reactions ◽  
Third Order ◽  
Gaseous Oxygen ◽  
Time Resolved ◽  
Pulsed Electron Beam

The rate constants for the forward and reverse components of gas phase reactions:[Formula: see text]were measured with a pulsed electron beam, time resolved detection high pressure mass spectrometer at 300 °K. O2, Ar, and He at pressures from 1–7 Torr were used as third gas M. The forward reactions were found to be third order and the reverse reactions second order. Establishment of the equilibria could also be observed.

Gas Phase Solvation of the Ammonium Ion by NH3 and H2O and Stabilities of Mixed Clusters NH4+ (NH3)n(H2O)w

1973 ◽  
Vol 51 (19) ◽  
pp. 3242-3249 ◽  
Author(s):  
J. D. Payzant ◽  
A. J. Cunningham ◽  
P. Kebarle
Keyword(s):  
Gas Phase ◽  
Pure Water ◽  
Equilibrium Constants ◽  
Ion Source ◽  
Ammonium Ion ◽  
Water Ligand ◽  
Ligand Complex ◽  
Ionic Charge ◽  
The Difference ◽  
Mixed Clusters

The gas phase equilibria[Formula: see text]and those leading to mixed clusters like[Formula: see text]were measured with a pulsed electron beam high pressure ion source mass spectrometer. The ion source contained pure ammonia or mixtures of ammonia and water vapor at pressures in the Torr range. Determination of the temperature dependence of the equilibrium constants led to the evaluation of ΔG0, ΔH0, and ΔS0 values for the equilibria from n = 1 to 4 and w = 1 to 5. The ΔG0 values for the NH4+(NH3)n equilibria were in good agreement with previous determinations from this laboratory. Fair agreement was observed for the ΔH0 and ΔS0 values. Comparison with the corresponding results for NH4+(H2O)w showed that the ΔHn,n−1 and ΔG0n,n−1 were larger than ΔHw,w−1 and ΔG0w,w−1. The difference was largest for the first step (1,0) and decreased progressively until a reversal with water values becoming larger occurred at the (5,4) step. The stronger hydrogen bonds of NH3 to NH4+ for low ligand numbers is explained by the greater basicity of NH3. As the ionic charge becomes dispersed and more distant stronger interactions are obtained with water which gives stronger H bonds in the absence of positive ionic charge. Breaks in the ΔHn,n−1 values indicate existence of a relatively stable NH4+(NH3)4 symmetric ion. A much smaller and less distinct break is observed with pure water ligands.The mixed ammonia–water clusters show similar effects. The addition of a NH3 molecule to a pure water ligand complex gives the strongest interaction. The addition of H2O to a pure ammonia cluster gives the weakest interaction. The above effect is strongest at lowest ligand numbers. The difference decreases gradually and becomes reversed for more than four ligands.

The Hydrogen Bond Energies in ClHCl− and Cl−(HCl)n

1974 ◽  
Vol 52 (13) ◽  
pp. 2449-2453 ◽  
Author(s):  
R. Yamdagni ◽  
P. Kebarle
Keyword(s):  
Gas Phase ◽  
Equilibrium Constants ◽  
Bond Energies ◽  
Gas Phase Reactions ◽  
Weakly Bound ◽  
Pulsed Electron Beam ◽  
Large N ◽  
Different Temperatures ◽  
Hydrogen Bond Energies

The equilibrium constants for the gas phase reactions: Cl−(HCl)n = Cl−(HCl)n−1 + HCl, (n, n−1) were measured at different temperatures with a pulsed electron beam high pressure mass spectrometer. This allowed determination of ΔGn,n−10, ΔHn,n−10, and ΔSn,n−10 for reactions with n = 1 to n = 4. The enthalpy change for the reaction: (ClHCl)− = Cl− + HCl was ΔH1.00 = 23.7 kcal/mol. This value is much higher than the literature value of 14.2 kcal/mol based on Born cycles. The stabilities of the Cl−(HCl)n clusters are compared with those of OH−(H2O)n and Cl−(H2O)n measured earlier. It is found that the (ClHCl)− is nearly as stable as the (HOHOH)− species but that the stabilities of the higher Cl−(HCl)n clusters decreases much more rapidly than that of OH−(H2O)n. The initial strong interaction in (ClHCl) is assumed to be due to the high polarizability of Cl. For large n this effect becomes unimportant. Cl−HOH is much more weakly bound than (ClHCl)−, however, at high n the Cl−(H2O)n interactions become more favorable.

Stabilities of complexes (N2)nH+, and (O2)nH+ for n = 1 to 7 based on gas phase ion-equilibria measurements

1979 ◽  
Vol 57 (16) ◽  
pp. 2159-2166 ◽  
Author(s):  
K. Hiraoka ◽  
P. P. S. Saluja ◽  
P. Kebarle
Keyword(s):  
Electron Beam ◽  
Gas Phase ◽  
Equilibrium Constants ◽  
Ion Source ◽  
Large Decrease ◽  
Proton Affinities ◽  
Source Pressure ◽  
Pulsed Electron Beam ◽  
The Stability ◽  
Gas Phase Ion

The equilibria Bn−1H+ + B = BnH+ for B = N2, CO, and O2 were measured with a pulsed electron beam high ion source pressure mass spectrometer. Equilibria up to n = 7 could be observed. van't Hoff plots of the equilibrium constants lead to ΔGn−1,n0, ΔHn−1,n0, and ΔSn−1,n0. While the proton affinities increase in the order O2 < N2 < CO, the stabilities of the B2H+ towards dissociation to BH+ + B increase in the reverse order, i.e. CO < N2 < O2. The stabilities towards dissociation of B for BnH+ where n > 2 are much lower for all three compounds; however for N2 and CO the stability decreases only very slowly from n = 3 to n = 6, then there is a large fall off for n = 7. The (O2)nH+ clusters show large decrease of stabilities as n increases. The BnH+ (for n > 3) of CO are more stable than those of N2 or O2. The above experimental results can be partially explained with the help of results from molecular orbital STO-3G calculations for B, BH+, and B2H+ and general considerations. BH+ and B2H+ for CO and N2 are found to be linear while those for O2 are bent. The most stable O2H+ is a triplet, while (O2)2H+ is a quintuplet.

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