Binding energies and stabilities of potassium ion complexes with ethylene diamine and dimethoxyethane (glyme) from measurements of the complexing equilibria in the gas phase

1976 ◽  
Vol 54 (16) ◽  
pp. 2594-2599 ◽  
Author(s):  
W. R. Davidson ◽  
P. Kebarle
Keyword(s):  
Phase Equilibria ◽  
Gas Phase ◽  
Ion Source ◽  
Potassium Ion ◽  
Binding Energies ◽  
Ethylene Diamine ◽  
Bidentate Ligands ◽  
Source Pressure ◽  
The Third ◽  
Monodentate Ligands

The temperature dependence of the gas phase equilibria [Formula: see text] where en = ethylene diamine were measured for n = 1 to n = 3. The equilibrium K+ + dimethoxyethane [Formula: see text] K+(dimethoxyethane) was also determined. The measurements were made with a high ion source pressure mass spectrometer equipped with a thermionic potassium ion emitter. The resulting ΔH0, ΔG0, and ΔS0 values are compared with the corresponding values for monodentate ligands like H2O, NH3, CH3OCH3 etc. determined in earlier work. As expected, the bidentate ligands lead to considerably stronger (0,1) interactions. Dimethoxyethane leads to a stronger complex than ethylene diamine. The third molecule of ethylene diamine leads to much weaker binding than is observed for the first two molecules. Explanation of the observed effects is given on basis of electrostatic and steric arguments.

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.

Kinetics and Temperature Dependence of the Hydration of NO+ in the Gas Phase

1973 ◽  
Vol 51 (3) ◽  
pp. 456-461 ◽  
Author(s):  
Margaret A. French ◽  
L. P. Hills ◽  
P. Kebarle
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Rate Constants ◽  
Room Temperature ◽  
Transfer Reaction ◽  
Negative Temperature ◽  
Ion Source ◽  
Third Order ◽  
The Third ◽  
Kinetics Of

The kinetics of the atmospherically important hydration sequence: NO+(H2O)n−1 + H2O = NO+(H2O)n and the transfer reaction NO+(H2O)n + H2O = HNO2 + H+(H2O)n were examined in nitrogen containing small quantities of NO and H2O with a pulsed high pressure ion source mass spectrometer. The room temperature mechanism and rate constants were found to be in agreement with earlier work in other laboratories. The temperature dependence of the reaction was examined for the range 27–157 °C. The transfer reaction does not occur at higher temperatures so that the NO+ hydration equilibria for n = 1 and 2 could be measured leading to ΔH1,0 = 18.5 and ΔH2,1 = 16.1 kcal/mol. The third order forward clustering rate constants were found to have negative temperature coefficients.

Gas phase ion equilibria: heats of formation of acylium ions RCO+ and protonated acids RC(OH)2+; gas phase catalysis of proton shift RC(OH)2+ → RCO(OH2)+

1979 ◽  
Vol 57 (24) ◽  
pp. 3205-3215 ◽  
Author(s):  
W. R. Davidson ◽  
S. Meza-Höjer ◽  
P. Kebarle
Keyword(s):  
Gas Phase ◽  
Negative Temperature ◽  
Ion Source ◽  
Activation Energy Barrier ◽  
Third Order ◽  
Source Pressure ◽  
Pulsed Electron Beam ◽  
Proton Shift ◽  
Gas Phase Ion ◽  
Good Agreement

The equilibria [2]: [Formula: see text] for R = CH3, C2H5, and C6H5 were studied in a pulsed electron beam high ion source pressure mass spectrometer. van't Hoff plots led to ΔH2 values: (CH3), 24.6; (C2H5), 22.7; (C6H5), 21.9 kcal/mol. ΔHf(RC(OH)2+) were obtained from gas phase basicity ladders combined with the new ΔHf(t-butyl+) = 163 kcal/mol (Beauchamp). The ΔHf(RC(OH)2+) were: (CH3), 71.3; (C2H5), 63.6; (C6H5), 95.5 kcal/mol. Combination of ΔH2 with ΔHf(RC(OH)2+) leads to ΔHf(RCO+): (CH3), 153.7; (C2H5), 144; (C6H5), 174.6 kcal/mol. These results are in agreement with selected data from appearance potentials. The energies and structures of the participants in reaction [2] were calculated by MINDO/3 and STO-3G. MINDO/3 gave good agreement with ΔH2. The establishment of the equilibria [2] was unusually slow. A study of the kinetics revealed that k2f is approximately third order, unusually small, and has an unusually large negative temperature coefficient. Furthermore, reaction [2] was found to be catalyzed by RCOOH. An explanation of these observations is given by assuming that the proton shift RCO(OH2)+ → RC(OH)2+ has a large activation energy barrier in the gas phase. This barrier is removed by formation of a hydrogen bonded complex with RCOOH.

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.

Formation of tert-butyl cation in methane

1976 ◽  
Vol 54 (11) ◽  
pp. 1739-1743 ◽  
Author(s):  
K. Hiraoka ◽  
P. Kebarle
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Arrhenius Plot ◽  
Ion Source ◽  
Probable Mechanism ◽  
Positive Temperature ◽  
Phase Reaction ◽  
Source Pressure ◽  
Gas Phase Reaction ◽  
Pure Methane

The reactions of CH3+ with pure methane in the torr range show an interesting temperature dependence. C2H5+ is formed at all temperatures by the well known reaction: CH3+ + CH4 = C2H5+ + H2. In the lowest temperature interval studied (105–125 K) C2H5+ adds two CH4 molecules to give a C4H13+ species. At higher temperatures only one CH4 molecule is added on. The resulting C3H9+ then reacts with one more CH4 molecule according to reaction 6.[Formula: see text]The rate constant k6 is found to be second order and has a positive temperature dependence. An Arrhenius plot gives:[Formula: see text]At temperatures above 200 K reaction 6 ceases to occur since C3H9+, being unstable at high temperatures, decomposes to s-C3H7+ + H2.The reactions were studied using ultra pure methane irradiated with electrons in a pulsed beam high ion source pressure mass spectrometer.The gas phase reaction mechanism for the formation of t-C4H9+ is found to bear close re-semblance to the probable mechanism by which the t-C4H9+ ion is formed from methane dissolved in superacid media.

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