Diazen und andere Distickstoffhydride: Bildungswärmen, Dissoziationsenergien, Auftrittspotentiale, Protonenaffinitäten [1] / Diazene and other Dinitrogen Hydrides: Heats of Formation, Dissoziation Energies, Appearance Potentials, Proton Affinities [1]

1979 ◽  
Vol 34 (10) ◽  
pp. 1385-1390 ◽  
Author(s):  
Nils Wiberg ◽  
Gerd Fischer ◽  
Heinz Bachhuber
Keyword(s):  
Hydrogen Atom ◽  
Proton Affinity ◽  
Heat Of Formation ◽  
Heats Of Formation ◽  
Proton Affinities ◽  
Kcal Mole ◽  
Energy Data

AbstractIonisation and appearance potentials were obtained for diazene HN = NH (prepared by thermolysis of TOSN2H2M, M = Li, Na, K), isodiazene H2N = N (prepared by thermolysis of TOSN2H2CS and N2H4 microwave radiolysis, respectively), and other hydrides N2Hn (cf. Table I). The following energy data (kcal/mole) have been determined for diazene: heat of formation (32), enthalpy of isomerisation to isodiazene (13), NN-dissoziation energy (122), NH-dissoziation energy (81), hydrogen atom affinity (45), proton affinity (176).

Photoionisation von Methanol und Formaldehyd / Photoionisation of Methanol and Formaldehyd

1971 ◽  
Vol 26 (12) ◽  
pp. 2047-2057 ◽  
Author(s):  
Peter Warneck
Keyword(s):  
Spectral Region ◽  
Heat Of Formation ◽  
Heats Of Formation ◽  
Kcal Mole ◽  
Yield Curves ◽  
Dissociation Energies ◽  
Fragment Ions

Photoions produced in methanol and formaldehyde by radiation in the spectral region 450 - 1150 Å were analyzed mass spectrometrically and their relative yields were determined as a function of wavelength. First ionisation potentials were determined and the ion yield curves were interpreted in terms of ionisation processes in conjunction with other data. Fragment ions were detected on mass numbers 31, 30, 29, 15, and 14 for methanol, and 29, 2, and 1 for formaldehyde. The associated appearence potentials were determined and were used to calculate heats of formation of the ions CH2OH+ and HCO+, and the radicals CH3, CH2, and HCO. The most important result appears to be the heat of formation found for HCO: ΔHB = 0.43 ± 0.07 eV, corresponding to 9.9 ± 1.6 kcal/mole, as well as the associated dissociation energies for HCO and formaldehyde. Previously existing discrepancies concerning these quantities are thereby clarified

ENERGETICS OF FORMATION OF SOME OXYGENATED IONS AND THE PROTON AFFINITIES OF CARBONYL COMPOUNDS

1966 ◽  
Vol 44 (14) ◽  
pp. 1625-1632 ◽  
Author(s):  
A. G. Harrison ◽  
A. Ivko ◽  
D. Van Raalte
Keyword(s):  
Gas Phase ◽  
Electron Impact ◽  
Carbonyl Compounds ◽  
Heats Of Formation ◽  
Proton Affinities ◽  
Mechanism Of Formation ◽  
Kcal Mole ◽  
Impact Processes

The energetics and mechanism of formation of ions of m/e 31, 45, and 59 from a number of alcohols, ethers, and esters have been studied. The following ionic heats of formation have been obtained: CH2=OH+, 176 kcal/mole; CH3O+, 213 kcal/mole; CH3CH=OH+, 145 kcal/mole; CH2=OCH3+, 170 kcal/mole; (CH3)2C=OH+, 125 kcal/mole; CH3CH2CH=OH+, 131 kcal/mole; CH3CH=OCH3+, 135 kcal/mole; CH2=OC2H5+, 144 kcal/mole. It is concluded that with the exception of CH3O+ the alkoxy ions probably are not formed by electron impact processes. The gas-phase proton affinities of a number of carbonyl compounds are estimated.

Ion-molecule reactions with carbon chain molecules: reactions with diacetylene and the diacetylene cation

1986 ◽  
Vol 64 (4) ◽  
pp. 641-648 ◽  
Author(s):  
Seksan Dheandhanoo ◽  
Leonard Forte ◽  
Arnold Fox ◽  
Diethard K. Bohme
Keyword(s):  
Carbon Chain ◽  
Heat Of Formation ◽  
Buffer Gas ◽  
Proton Affinities ◽  
Chain Molecules ◽  
Ion Flow ◽  
Molecule Reaction ◽  
Ion Molecule Reactions ◽  
A Value ◽  
Selected Ion Flow Tube

Reactions of hydrocarbon and carbon/nitrogen ions with diacetylene and of the diacetylene radical cation with various molecules have been examined with a view to molecular growth by ion–molecule reaction. Measurements were performed with a Selected-Ion Flow Tube (SIFT) apparatus at 296 ± 2 K of the rate constants and product distributions for the reactions of C+, CH3+, C2H2+, C3H+, CN+, C2N+, and C2N2+ with C4H2 and of C4H2+ with H2, CO, C2H2, C2N2, and C4H2. Condensation and association reactions which build up the carbon content of the ion were observed to compete with charge transfer. For the reactions of CN+ and C2N2+ with C4H2 this growth involved the addition of cyanide to the carbon chain. The kinetics of protonation of diacetylene were also investigated. It was possible to bracket the proton affinity of diacetylene between the known proton affinities of HCN and CH3OH with a value for PA(C4H2) = 177 ± 5 kcal mol−1, which results in a heat of formation for C4H3+ of 305 ± 5 kcal mol−1. Numerous secondary association reactions were observed to form adduct ions in helium buffer gas at total pressures of a few tenths of a Torr with rates near the collision rate. This was the case for C6H4+ (C4H2+•C2H2), C7H5+ (C3H3+•C4H2), C8H4+ (C4H2+•C4H2), C8H5+ (C4H3+•C4H2), C9H3+ (C5H+•C4H2), C9H4+ (C5H2+•C4H2), C9H5 (C5H3+•C4H2), C10H4+ (C6H2+•C4H2), C10H5+ (C6H3+•C4H2), C11H7+ (C3H3+•(C4H2)2), C12H6+ (C4H2+•(C4H2)2), C9H3N+ (HC5N+•C4H2), and C10H4N+ (C2N+•(C4H2)2) where the reactants are indicated in parentheses. The observed high rates of association imply the formation of chemical bonds in the adduct ions but the structures of these ions were not resolved experimentally. In most instances there seems little basis for preferring acyclic over cyclic adduct ions.

A thermodynamic study of the dimerization of cyclopentadiene

1968 ◽  
Vol 21 (7) ◽  
pp. 1789 ◽  
Author(s):  
AG Turnbull ◽  
HS Hull
Keyword(s):  
Liquid Phase ◽  
Rate Constant ◽  
Vapour Pressure ◽  
Boiling Point ◽  
Strain Energy ◽  
Order Rate Constant ◽  
Adiabatic Calorimeter ◽  
Thermodynamic Study ◽  
Heats Of Formation ◽  
Kcal Mole

The heat of dimerization of cyclopentadiene to endo-dicyciopentadiene in the liquid phase at 25� was measured in an adiabatic calorimeter to be -9.22 � 0.3 kcal/mole monomer. The rate of dimerization in the liquid phase at 25� was followed with a dilatometer and the initial second-order rate constant found to be 4.99 x 10-5. mole-l min-l. The vapour pressure of endo-dicyclopentadiene, measured by a boiling point method in the range 77.5-149.6�, gave the relation (p in torr): RInp ? 11342/T -2.6505In T + 54.7855 The standard heats of formation of solid, 31.1 � 0.5 kcal/mole, and gaseous, 42.2 � 0. 6 kcal/mole, endo-dicyclopentadiene were derived, and the strain energy and dimerization equilibria discussed.

Heat of Formation of the HCO Radical

1974 ◽  
Vol 29 (2) ◽  
pp. 350-351 ◽  
Author(s):  
P. Warneck
Keyword(s):  
Formic Acid ◽  
Heat Of Formation ◽  
Kcal Mole

From the threshold of OH+ formation in the photoionisation of formic acid the heat of formation of the HCO radical is determined as 10.2 Kcal/mole, in agreement with the earlier value derived from photoionisation of formaldehyde

ENERGETICS AND MECHANISM OF HYDRONIUM ION FORMATION BY ELECTRON IMPACT

1963 ◽  
Vol 41 (12) ◽  
pp. 3118-3126 ◽  
Author(s):  
D. Van Raalte ◽  
A. G. Harrison
Keyword(s):  
Water Molecule ◽  
Electron Impact ◽  
Proton Affinity ◽  
Mass Spectra ◽  
Kcal Mole ◽  
Deuterium Labelling ◽  
Ion Formation ◽  
Hydronium Ion

The reactions leading to formation of the hydronium ion in the mass spectra of a number of alcohols and formate esters have been elucidated through a study of appearance potentials and metastable transitions and by the use of deuterium labelling. The results lead to ΔHf(H3O+) = 157 ± 3 kcal/mole corresponding to a proton affinity of the gaseous water molecule of 151 ± 3 kcal/mole.

Experimental and theoretical studies of proton removal from propene

1978 ◽  
Vol 56 (1) ◽  
pp. 131-140 ◽  
Author(s):  
Gervase I. Mackay ◽  
Min H. Lien ◽  
Alan C. Hopkinson ◽  
Diethard K. Bohme
Keyword(s):  
Proton Affinity ◽  
Electron Affinity ◽  
Rate Constants ◽  
Equilibrium Constants ◽  
Standard Free Energy ◽  
Proton Transfer Reaction ◽  
Heat Of Formation ◽  
Molecular Orbital Calculations ◽  
Standard Free Energy Change ◽  
Methyl Proton

The kinetics and energetics of proton removal from propene, which contains several sites of different acidities, were investigated both theoretically and experimentally. Rate and equilibrium constants were measured for the proton-transfer reaction [Formula: see text]at 296 ± 2 K using the flowing afterglow technique. The rate constants were determined to be kforward = (1.1 ± 0.3) × 10−9 cm3 molecule−1 s−1 and kreverse = (5.4 ± 1.9) × 10−10 cm3 molecule−1 s−1. The ratio of rate constants, kf/kr = 2.1 ± 0.7, was found to be in agreement with the equilibrium constant, K = 2.2 ± 0.8, determined from equilibrium concentrations. Abinitio molecular orbital calculations predicted the removal of a methyl proton from propene to yield the allyl anion to be energetically favoured. This prediction was supported by measurements of deuteron removal from CD3CHCH2. The measured value of K corresponds to a standard free energy change, ΔG0298, of −0.44 ± 0.14 kcal mol−1 which provided values for the standard enthalpy change ΔH0298 = +0.5 ± 0.4 kcal mol−1, the proton affinity, PA298(C3H5−) = 391 ± 1 kcal mol−1, the heat of formation, ΔH0f,298(C3H5−) = 29.0 ± 0.8 kcal mol−1, and the electron affinity EA(CH2CHCH2) = 12.4 ± 1.9 kcal mol−1. The experimentally established value for the proton affinity of the allyl anion was in reasonable accord with the value of 422.3 kcal mol−1 determined by calculation. The electron affinity of the allyl radical derived in this study is supported by previous calculations and several limiting values obtained experimentally.

Sign in / Sign up

Export Citation Format

Share Document