Showing papers on "Bond-dissociation energy published in 1971"
TL;DR: In this paper, photon absorption at threshold wavelengths has been used to prepare I−, Br−, and F− ions with approximately room-temperature thermal energies, as verified by retarding potential measurements.
Abstract: Ion‐pair formation by photon absorption at threshold wavelengths has been used to prepare I−, Br−, and F− ions with approximately room‐temperature thermal energies, as verified by retarding‐potential measurements. The primary ions were accelerated and their reactions with halogen molecules studied at laboratory kinetic energies from 0.0 to about 4.0 eV. Thresholds were determined for endoergic reactions of the type X−+Y2→X+Y2 −, where X may be the same as Y. At least two reactions were used in determining each electron affinity. The agreement was good in all cases. The values of electron affinity obtained are 3.08±0.1 eV for F2, 2.38±0.1 eV for Cl2, 2.51±0.1 eV for Br2, and 2.58±0.1 eV for I2. Interhalogen molecular ions such as IBr− were also observed, and measurement of the threshold for formation gave the value 2.7±0.2 eV for the electron affinity of IBr. The retarding‐potential measurements of F− from F2 strongly support a value for the dissociation energy of F2 in the neighborhood of 1.6 eV.
147 citations
TL;DR: In this paper, the authors measured the A−(H2O)n−1−1 + H2O n−1+ H 2O n −1−H 2O = A−H n−n− 1 + H 2 O n− 1 −1 −H 2 O−n −1+H 2 N−1
Abstract: By measuring the A−(H2O)n−1 + H2O = A−(H2O)n equilibria in the gas phase and their temperature dependence, the equilibrium constants and ΔHn, n–1 and ΔSn, n–1 for some of the hydrates of NO2−, NO3−, CN−, and OH− were determined. Available thermochemical data are used for the evaluation of the total heats of hydration of the above ions. The total heats of hydration were then compared with the ΔH1,0. Relative to the total hydration energies the ΔH1,0 of the above ions were found larger than the ΔH1,0 of the halide ions.An approximate linear correlation was found to exist between ΔH1,0 of negative ions and the heterolytic bond dissociation energy D(A−–H+). With this relationship independent estimates for the electron affinities of NO2 and NO3 could be obtained.The ΔHn, n–1 of OH− were found in essential agreement with earlier measurements from this laboratory and in disagreements with recent measurements (Friedman) which gave much higher values.
116 citations
TL;DR: In this paper, the absorption spectrum of diatomic argon in the 780-1080 A region has been re-analysed using the Rydberg-Klein-Rees method.
Abstract: The absorption spectrum of diatomic argon in the 780–1080 A region has been re-analysed using the Rydberg-Klein-Rees method. The results of this study together with an analysis of the equilibrium and transport properties of gaseous argon have been used to establish a potential energy function which is consistent with all the available data. The dissociation energy of the argon dimer is estimated at some 7 per cent greater than that indicated in previous analyses of the spectroscopic data.
113 citations
TL;DR: In this article, the far ultra-violet continuum of nitric oxide was assigned to the dimer by obtaining the following experimental evidence: (a) the intensity of the spectrum is proportional to [NO]2; (b) the possibility that the carrier may be some other known oxide of nitrogen was eliminated; (c) from the temperature dependence the enthalpy change accompanying dissociation was 2.24 (± 0.1 ) kcal/mol (100-140 K).
Abstract: The far ultra-violet continuum of nitric oxide was assigned to the dimer by obtaining the following experimental evidence : (a) the intensity of the spectrum is proportional to [NO]2; (b) the possibility that the carrier may be some other known oxide of nitrogen was eliminated; (c) from the temperature dependence the enthalpy change accompanying dissociation was 2.24 (±0.1 ) kcal/mol (100–140 K), in good agreement with 2.4 (±0.2) kcal/mol deduced from the dimer infra-red intensities4; (d) approximate upper and lower limits to the dissociation constant, and the temperature dependence, were consistent with Guggenheim's5 method of analyzing the second virial coefficients by means of the principle of corresponding states.
An absolute scale of dissociation constants was fixed from the excess of the reduced second virial coefficient at its normal boiling point, and the temperature dependence found spectroscopically. The dissociation energy of the dimer is 1.6 (±0.1) kcal/mol. Evidence for substantial population of excited states of the dimer at 300 K was discussed. The dimer continuum exhibits a maximum at 2050 A, and the oscillator strength of the system was recorded as 0.26.
112 citations
TL;DR: In this article, a kinematic separation of reactive and nonreactive scattering has been proposed, showing that the angular distributions of reactive scattering peak at right angles to the initial relative velocity vector, and that only a small fraction of the available energy appears in product translational motion.
Abstract: Crossed‐beam studies have been made of the reactions of H and D atoms with K2, Rb2, and Cs2. The hydrogen atoms were generated by thermal dissociation of molecules in a tungsten oven at ∼ 2200–2900°K, the alkali dimers by association of atoms in a supersonic beam expanded from a nozzle at ∼ 900°K. Surface ionization detectors were unable to distinguish among alkali atoms, dimers, and alkali hydrides. However, a kinematic separation of reactive and nonreactive scattering proved to be feasible, owing to the disparity in reactant masses and parity in product masses. The angular distributions of reactive scattering peak at right angles to the initial relative velocity vector. A kinematic analysis indicates that only a small fraction of the available energy appears in product translational motion. This implies that either the vibrational and/or rotational excitation of the product alkali hydride is very high (∼ 30–40 kcal/mole), comparable to or possibly even larger than its dissociation energy, or the product...
54 citations
TL;DR: In this article, the Hartree-Fock energy curves for the X 2 Π and 2 Σ + states of HF + were calculated for an analysis of the photoelectron spectra of HF.
45 citations
TL;DR: In this paper, the authors reported ab initio quantum potential surfaces for the ground and first excited states of the CH2+ molecular ion, and the relationship between these calculations and the dissociation energy of CH3 radical is discussed.
45 citations
36 citations
30 citations
TL;DR: In this article, the thermal elimination of HF from 1,2-difluoroethane has been studied in a static system over the temperature range 734-820°K, with a rate constant of 2.303RT in kcal/mole.
Abstract: The kinetics of the thermal elimination of HF from 1,2-difluoroethane
have been studied in a static system over the temperature range 734–820°K. The reaction was shown to be first order and homogeneous, with a rate constant of
where θ = 2.303RT in kcal/mole. The A-factor falls within the normal range for such reactions and is in line with transition state theory; the activation energy is similarly consistent with an estimate based on data for the analogous reactions of ethyl fluoride and other alkyl halides. The above activation energy has been compared with values of the critical energy calculated from data on the decomposition of chemically activated 1,2-difluoroethane by the RRKM theory and the bond dissociation energy, D(CH2FCH2F) = 88 ± 2 kcal/mole, derived. It follows from thermochemistry that ΔHf0(CH2F) = -7.8 and D(CH2FH) = 101 ± 2 kcal/mole. Bond dissociation energies in fluoromethanes and fluoroethanes are discussed.
24 citations
TL;DR: In this article, the nature of the metal-metal bond in a series of binuclear metal carbonyls M2(CO)10(M2= Mn2, Tc2, Re2, and MnRe) is described by application of the selfconsistent charge and configuration (SCCC) molecular orbital method.
Abstract: The nature of the metal–metal bond in a series of binuclear metal carbonyls M2(CO)10(M2= Mn2, Tc2, Re2, and MnRe) is described by application of the self-consistent charge and configuration (SCCC) molecular orbital method. Good correlation between calculated quantities such as orbital energies and overlap populations and experimental quantities such as photoionization spectra and bond dissociation energies are obtained. It is suggested that the term ‘unsupported’ metal–metal bond, especially for atoms of the first transition series requires modification because of the important contribution to the metal–metal bond energy of the cross-interaction between a metal atom and ligands directly bonded to the other metal atom.
TL;DR: In this article, the infrared spectra of α-methanol and α−methanol d3 were measured in the range 400-20 cm−1 at 100 and 150°K and seven intermolecular vibrations were observed.
Abstract: The infrared spectra of α‐methanol and α‐methanol‐d3 have been measured in the range 400–20 cm−1 at 100 and 150°K. Seven intermolecular vibrations are expected and were observed. The CH3 internal rotations were not observed. A normal coordinate analysis of the spectra has been made assuming that the potential energy has the symmetry C2h, that is, is independent of the position of the hydrogen atom in the hydrogen bond. The hydrogen‐bond stretching force constant is 0.346 mdyn A−1, which is about twice the value for the hydrogen bond in ice. This does not correlate well with the effect of hydrogen bonding on the OH stretching frequencies, nor with the dissociation energy of the dimers of methanol and water in the vapor. However, the heat of sublimation of methanol at 0°K indicates that about 8.5 kcal mole−1 are required to break the hydrogen bonds, compared with only 5.66 kcal mole−1 in ice, which is consistent with the higher force constant for methanol.
TL;DR: In this article, a multiconfiguration valence bond calculation using accurate AO bases has been carried out for F2 and F2 - ion, and a dissociation energy of at least 1·06 eV is predicted for the F2 ion.
Abstract: Multiconfiguration valence bond calculations using accurate AO bases have been carried out for F2 and F2 -. A dissociation energy of at least 1·06 eV is predicted for the F2 - ion. Lattice energy calculations together with this value lead to an approximate value of ΔG = -16 kcal mole-1 for the reaction The true value may be much closer to zero.
TL;DR: In this paper, the dependence of the instantaneous bond dissociation energies (ibde) of the carbon-carbon single bonds on the bond overlaps has been discussed, and it has been found that the following relationship E(C-C)IBD = (372.3 Sc-c−143.7) kcal mole obtained by the least squares method fits the experimental energies with a standard deviation of 0.5 kcal mole.
TL;DR: In this paper, the rate of decomposition of the n-propyl radical was determined as a function of temperature and pressure, and limiting high-pressure and low-pressure kinetic parameters were obtained.
Abstract: The results of the previous paper are analyzed to yield information about the reactions of the n-propyl and i-propyl radicals. The various combination and disproportionation reactions are considered. The rate of decomposition of the n-propyl radical was determined as a function of temperature and pressure, and limiting high-pressure and low-pressure kinetic parameters were obtained. The high-pressure activation energy is 32.6 kcal mol−1, and this leads to a value of 24.3 kcal mol−1 for the dissociation energy of the C—C bond in the n-propyl radical, to 22.2 kcal mol−1 for its heat of formation, and to 99.1 kcal mol−1 for the primary C—H dissociation energy in propane. Entropy changes are also calculated from the results.For the decomposition of the i-propyl E∞ = 38.7 kcal mol−1, and this leads to 37.7 kcal mol−1 for the C—H bond dissocation energy in this radical and to 19.3 kcal mol−1 for its heat of formation. The secondary C—H dissociation energy in propane is calculated to be 96.2 kcal mol−1. Correspo...
TL;DR: In this paper, the velocity distribution of the recoiling chlorine atoms from the laser induced photodissociation of Cl2 at 3471 A using a time-of-flight technique is described.
Abstract: The measurement and analysis of the velocity distribution of the recoiling chlorine atoms from the laser induced photodissociation of Cl2 at 3471 A using a time‐of‐flight technique is described. The expected velocity distribution is numerically calculated from the experimental geometry by appropriate center‐of‐mass (c.m.)‐laboratory (LAB) coordinate transformations. By making the measurements at moderate densities in the interaction zone, the elastic scattering of Cl atoms by Cl2 molecules is observed. Since scattering angles in c.m. correspond to velocity changes in LAB coordinates, the direct recoil signal must be corrected for the effects of multiple elastic scattering. Careful comparison of expected and observed velocity profiles enables one to deduce directly the energy state of the products, the bond dissociation energy D0 ○, and the rainbow scattering angle. The analysis on Cl2 yields D0 ○ (Cl–Cl)=57.05±0.2 kcal/mole, which is in excellent agreement with the JANAF value of 57.04±0.06 kcal/mole and ...
TL;DR: In this paper, the standard enthalpy of sublimation of germanium difluoride has been determined using both mass spectrometric and vacuum balance techniques, and a value of Δ H ° sub (GeF 2,c,298.15 K) = (20.5 ± 1.8) kcal mol −1 was obtained.
TL;DR: In this paper, appearance potentials for the ions M2Me3+ of the title compounds have been measured, and used in combination with accurate thermochemical data to obtain the corresponding metal-metal bond dissociation energies.
Abstract: Appearance potentials for the ions M2Me3+ of the title compounds have been measured, and used in combination with accurate thermochemical data to obtain the corresponding metal–metal bond dissociation energies. For the bonds M1–M2, D(W–M2) > D(Mo–M2) > D(Cr–M2)(M2= Ge or Sn); and D(M1–Sn) > D(M1–Ge) > D(M1–Si). Raman and i.r. spectra have been recorded also for these compounds, and the metal–metal stretching modes (165–195 cm–1) have been assigned.
TL;DR: The orbiting resonance theory of hydrogen-atom recombination predicts a non-statistical ortho-to-para ratio for the molecular hydrogen formed via this mechanism, but the predicted ratio changes very drastically due to a recent increase of only 4 cm −1 in the experimental ground-state dissociation energy of H 2 (X 1 Σ g + ).
TL;DR: In this paper, the standard enthalpy of combustion of liquid cyclopropylamine, ΔHoo(298.15 K), was found to be −(532.20 ± 0.10) kcal mol−1 by oxygen-bomb combustion calorimetry.
TL;DR: In this article, a phase shift method has been used to study the bimolecular and termolecular reactions of Hg(3P0) with NH3, and the dissociation energy of the complex is estimated to be 5.0 kcal mole−1.
TL;DR: In this article, the first aluminum resonance doublet and the A2∑+ → X2 ∑+ bands of AlO emitted from a bydrogen flame at atmospheric pressure have been measured at various temperatures between 2300° and 2700°K.
TL;DR: The enthalpies of formation of crystalline (107·6 ± 1·7 kJ mol−1) and gaseous (+18 ± 2·5 kJmol−1)[π-C3H5PdCl]2 have been determined by differential scanning calorimetry as discussed by the authors.
Abstract: The enthalpies of formation of crystalline (–107·6 ± 1·7 kJ mol–1) and gaseous (+18 ± 2·5 kJ mol–1)[π-C3H5PdCl]2 have been determined by differential scanning calorimetry. A minimum value of 237 kJ mol–1 is calculated for the palladium–allyl bond dissociation energy.
TL;DR: A self-consistent bond energy scheme has been constructed for organo-mercury compounds and some associated bond dissociation energies have been calculated as mentioned in this paper, which yields a standard enthalpy of formation Δ H ° f (HgPh 2,c) = (67.6±1.9) kcal mol −1.
TL;DR: In this paper, the rates of reaction with sodium atoms of the compounds Me3MCl and Me2MCl2 (M = Ge, Sn) have been measured and the gradations in velocity constants along the Group IV series were discussed in terms of bond dissociation energies, concluding that the reaction rate of trimethylchlorostannane is high and reasons for this behaviour are discussed.
TL;DR: In this paper, the mass spectral cracking pattern of CH3CF3 and the appearance potentials of the ions CF3+, CH 3CF2+, CH3 CF3+ and CH 3 CF2+ have been determined.
TL;DR: In this paper, the 1-and 2-isomers of B5Hin8X were determined by electron impact methods and compared with the results obtained by extended Huckel calculations.
TL;DR: In this paper, a reduction in the B-F bond dissociation energy was observed upon complexation of BF3 with ethyl ether, and the reduction was further observed upon BF3 complexation with BF4.
Abstract: A reduction in the B–F bond dissociation energy is observed upon complexation of BF3 with ethyl ether.