Equilibrium constants have been measured for proton transfer reactions between protonated methanol or protonated formic acid with propylene, trans-2-butene, cyclopropane, methylcyclopropane, and ethane. The single ion source of a mass spectrometer was used as reactor. From the free energies of reaction and assuming negligible entropy change, proton affinities have been determined for the above compounds assuming A//f(7-C3H7+) to be 191.7 kcal/mol. Heats of formation of the various protonated ions calculated from these values show that protonated cyclopropane and methylcyclopropane have heats of formation different from that of the propyl or butyl ions showing that the ring structure for these ions is maintained. The heat of formation of C2H7+ is about 0.2 kcal/mol less than that of C2H5+. This is in accord with the postulated instability of C2H7+. This research has been directed toward establishing thermodynamic properties of certain interesting hydrocarbon positive ions for which no suitable values have yet been determined. Several investigators have postulated protonated cyclopropane or methylcyclopropane as intermediate in the solvolysis of norbornyl derivatives,1 in the addition of acids,2-4 acetyl chloride,3
In carbon monoxide at pressures above 0.2 torr, the principal product ion is C20 2+ formed by a threebody process. The rate constant for the reaction is 1.43X1O--'8 cm 6 molecule-2 ·secl • Above about 0.8 torr, the reaction appears to approach equilibrium with an equilibrium constant of 1482 referred to 1 atm as standard. At pressures of methane above 0.2 torr and small additions of CO, the only reaction observed in the protonation of CO by CH.+ with a rate constant of 5.54X1o--10 cm s molecule-I·sec-I . All other reactions are endothermic and are not observed. At pressures of carbon monoxide above 0.2 torr, the addition of small amounts of methane results in an H-atom transfer reaction to CO+ with a rate constant of 13.7X1O--I0 cm s molecule-I·sec l • In addition, C20 2 + reacts to form HCO+, C2HsO+, and CsHsO+ with rate constants of 9.44,4.37, and 0.76X10-IO cm S molecule-I'sec l , respectively.The origin of chemical binding is analyzed with the help of variational reasoning for the ground state of the hydrogen molecule-ion. The bond-parallel component of the kinetic-energy integral is shown to be the critical term. The effect of electron sharing on this term is such that the variation process yields, at all internuclear distances, a lower energy for the molecule than for the separated atoms. This appears to be paradoxical in as much as, at the equilibrium distance, the potential part of the binding energy is negative and the kinetic part is positive. The paradox is resolved by showing that the actual values of the potential and kinetic binding energy are the result of a scale variation which is similar to that found in the isolated atom and contracts the wavefunction towards the two nuclei. The variational origin of this redistribution of the kinetic-and potential-energy integrals, which establishes the virial relationship, is analyzed. It is concluded that the variational facts are inadequately described by the view that the chemical bond is formed "because the potential energy can be lowered through accumulation of charge in the bond." Rather, the accumulation of charge in the bond is essential for chemical binding because it profoundly influences the behavior of the kinetic-energy integral under scale variations.
By employing elevated pressures in the ion source of a quadrupole mass filter, it is shown that D3S+ does not transfer a deuteron to D2O and that D3O+ transfers a deuteron to D2S. Studies were carried out in most instances under conditions where the reactant ion undergoes 30–60 collisions before reacting. Thus, most excess energy should have been removed. The transfer of deuteron from D3O+ to D2S appears to go to equilibrium with an equilibrium constant of 14.4 which corresponds to a heat of reaction of 1.8 kcal/mole. From this we deduce the proton affinity of water to be 168 kcal/mole.
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