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.

Gas phase ion equilibria studies of the proton in hydrogen sulfide and hydrogen sulfide – water mixtures. Stabilities of the hydrogen bonded complexes: H+(H2S)x(H2O)y

1977 ◽  
Vol 55 (1) ◽  
pp. 24-28 ◽  
Author(s):  
Kenzo Hiraoka ◽  
Paul Kebarle
Keyword(s):  
Hydrogen Sulfide ◽  
Temperature Dependence ◽  
Gas Phase ◽  
Ion Source ◽  
Cluster Ions ◽  
Exchange Reactions ◽  
Pulsed Electron Beam ◽  
Mixed Cluster ◽  
Association Reaction ◽  
Gas Phase Ion

The temperature dependence of the equilibria [Formula: see text] was measured for n = 1 to 5 in a pulsed electron beam mass spectrometer with a high pressure ion source. The ΔHn+1,n values obtained were (2,1) 15.4, (3,2) 9.1, (4,3) 8.4, (5,4) 6.7 kcal/mol. Possible structures of the clustered ions are proposed.Addition of water vapor leads to mixed cluster ions such as H+(H2S)x(H2O)y, with x + y from 1 to 6, observed as the ion source temperature was decreased to −100 °C. The temperature dependence of the equilibria for the exchange reactions [Formula: see text]and the association reaction [Formula: see text]were also measured. For all ions measured, the hydration process is energetically more favorable than the solvation by H2S.

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.

Hydrogen bonding solvent effect on the basicity of primary amines CH3NH2, C2H5NH2, and CF3CH2NH2

1981 ◽  
Vol 59 (1) ◽  
pp. 151-155 ◽  
Author(s):  
Yan K. Lau ◽  
P. Kebarle
Keyword(s):  
Free Energy ◽  
Energy Difference ◽  
Ion Source ◽  
Primary Amines ◽  
Hydration Free Energy ◽  
Ion Hydration ◽  
Free Energy Difference ◽  
Source Pressure ◽  
Pulsed Electron Beam ◽  
Good Agreement

The equilibria RNH3+(H2O)n−1 + H2O = RNH3+(H2O)n were measured for R = CH3, C2H5, and CF3CH2 from n = 1 to n = 3 with a pulsed electron beam high ion source pressure mass spectrometer. The proton and hydrate transfer equilibria CH3NH3+(H2O)n + C2H5NH2 = CH3NH2 + C2H5NH3+(H2O)n were measured for n = 0 to n = 3. These data allow the evaluation of ΔH0 and ΔG0 for the reactions: R0NH3+(H2O)n + RNH3+ = R0NH3+ + RNH3+(H2O)n. ΔH0 = δΔH00,n(RNH3+), ΔG = δΔG00,n(RNH3+). These data are compared with δΔE0,3 (STO-3G) evaluated by Hehre and Taft. In general good agreement is observed at n = 3. The δΔH00,3(RNH3+) ≈ δΔE0,3(RNH3+) are also found close to the ion hydration free energy difference in aqueous solutions.

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.

scholarly journals THE STUDY OF ELECTRICALLY DISCHARGED O2 BY MEANS OF AN ISOTHERMAL CALORIMETRIC DETECTOR

1959 ◽  
Vol 37 (10) ◽  
pp. 1680-1689 ◽  
Author(s):  
L. Elias ◽  
E. A. Ogryzlo ◽  
H. I. Schiff
Keyword(s):  
Gas Phase ◽  
Molecular Oxygen ◽  
Surface Recombination ◽  
Negative Temperature ◽  
Recombination Coefficient ◽  
Third Order ◽  
Atom Concentration ◽  
Electrodeless Discharge ◽  
First Order ◽  
A Value

Molecular oxygen was subjected to an electrodeless discharge in the pressure range 0.1–3 mm Hg. The oxygen atom concentration was measured as a function of time in a flow system by means of a movable atom detector which consisted of a platinum wire coated with a suitable catalyst for atom recombination. The atom concentration was calculated from the heat liberated when the detector was operated under isothermal conditions. The surface recombination was found to be first order in the atom concentration. A value of 7.7 × 10−5 was obtained for the recombination coefficient (γ) on Pyrex. No temperature dependence for γ was observed. The gas phase recombination of oxygen atoms was found to be consistent with the mechanism[Formula: see text]The rate constant for the third-order reaction was found to have a value of 1.0 × 1014 cc2 mole−2 sec−1, and a small negative temperature dependence.Evidence was also obtained for the presence of considerable amounts of excited molecular oxygen in electrically activated O2.

Ion molecule reactions in ethane. Thermochemistry and structures of the intermediate complexes: C4H11+ and C4H10+ formed in the reactions of C2H5+ and C2H4+ with C2H6

1980 ◽  
Vol 58 (21) ◽  
pp. 2262-2270 ◽  
Author(s):  
K. Hiraoka ◽  
P. Kebarle
Keyword(s):  
Low Temperature ◽  
Rate Constant ◽  
Reaction System ◽  
Major Product ◽  
Ion Source ◽  
Source Pressure ◽  
Pulsed Electron Beam ◽  
Ion Molecule Reactions ◽  
High Temperature Reaction ◽  
Induced Dipole

The reactions of C2H5+ and C2H4+ with ethane were studied in a pulsed electron beam high ion source pressure mass spectrometer. Ethane at variable pressures in the 10–100 m Torr range in ~5 Torr hydrogen was used in experiments covering the temperature range −145 to 400 °C. Reaction [7]: C2H5+ + C2H6 = sec-C4H9+ + H2 was found to have a rate constant whose magnitude decreased with temperature: k7 = 10−5.12 T−2 (molecule−1 cm3 s−1). The reaction proceeds via a C4H11+ (b) intermediate, which at low temperature can be stabilized and becomes the major product. The rate constant for thermal decomposition of C4H11(b) by reaction [6t]: C4H11+ (b) = sec-C4H9+ + H2 could be measured. The activation energy was found to be E6t = 9.6 kcal/mol. From consideration of the above data and the known ΔH7, it was concluded that C4H11+ (b) has the structure[Formula: see text]Before dissociation to sec-C4H9+ + H2, this ion rearranges to[Formula: see text]The barrier for this rearrangement is ~9.6 kcal/mol.C2H4+ reacts with C2H6 to give C4H10+ (d) at low temperatures. At high temperatures C4H10+ (d) becomes an intermediate in the dissociation to sec-C3H7+ + H2. The formation of C4H10+ at low temperature has a rate constant whose magnitude decreases with temperature. The temperature dependence of the equilibrium constant K10 for the reaction [10]: C2H4+ + C2H6 = C4H10+ (d) could be determined. This led to ΔH10 = −15.3 kcal/mol. The rate constant for the high temperature reaction [11]: C2H4+ + C2H6 = sec-C3H7+ + H2 was k11 = 8.4 × 10−10 exp (−3.9/RT kcal/mol) (molecule−1 cm3 s−1). A potential energy diagram for the reaction system is proposed. C4H10+ (d) is probably a complex between C2H4+ and C2H6 held largely by ion induced dipole process. Reaction [11] probably proceeds via C4H10+ (d) → n-C4H10+ → sec-C3H7+ + H2. The barrier between C7H10+ (d) and n-C4H10+ is ~20 kcal/mol.

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.

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