Towards a general scheme for estimating the heats of formation of organic ions in the gas phase. Part I. Odd-electron cations

1981 ◽  
Vol 59 (1) ◽  
pp. 80-93 ◽  
Author(s):  
John L. Holmes ◽  
Mervin Fingas ◽  
F. P. Lossing
Keyword(s):  
Gas Phase ◽  
General Scheme ◽  
Double Bond Position ◽  
Heats Of Formation ◽  
Organic Cations ◽  
Aliphatic Aldehydes ◽  
Aliphatic Ketones ◽  
Alkanoic Acids ◽  
Correction Terms ◽  
Aliphatic Ethers

It is shown that gas-phase heats of formation of homologous odd-electron organic cations can be well represented by an equation of the form ΔHf[ion]+• = A − Bn + C/n, where A, B, and C are constants and n is the total number of atoms in the molecule. Values for A, B, and C have been determined for the linear homologous series: alkanes, olefins, alkynes, alkanols, aliphatic ethers, aliphatic aldehydes, aliphatic ketones, alkanoic acids, alkyl chlorides, bromides, and iodides. For each of these series, correction terms for chain branching, double-bond position, and asymmetry effects are also given. These equations can be applied to molecules containing 40 or more atoms. The data base for this work is also presented.

Towards a general scheme for estimating the heats of formation of organic ions in the gas phase. Part II. The effect of substitution at charge-bearing sites

1982 ◽  
Vol 60 (18) ◽  
pp. 2365-2371 ◽  
Author(s):  
John L. Holmes ◽  
F. P. Lossing
Keyword(s):  
Gas Phase ◽  
General Scheme ◽  
Heats Of Formation ◽  
Organic Ions ◽  
Good Linear ◽  
Ionic Size ◽  
A Charge ◽  
Linear Correlations ◽  
Multiple Substitution

The effects on ionic heats of formation of the multiple substitution of -CH3, -OH, or -OCH3 groups, in place of H atoms, are described. It is shown that for all three substituents, good linear correlations exist between ΔHf(ion) and the logarithm of the number of atoms in the ion (i.e. a quantity proportional to ionic size). The changes in ΔHf(ion) resulting from successive substitutions at a charge-bearing atom or π-system essentially depend only upon the specific nucleophilic character of the group and the size of the resultant ion. Examples are given of the utility of these correlations in estimating new ionic heats of formation.

Temperature-dependence study of the gas-phase reactions of atmospheric Cl atoms with a series of aliphatic aldehydes

2006 ◽  
Vol 40 (21) ◽  
pp. 3845-3854 ◽  
Author(s):  
Carlos A. Cuevas ◽  
Alberto Notario ◽  
Ernesto Martínez ◽  
José Albaladejo
Keyword(s):  
Temperature Dependence ◽  
Gas Phase ◽  
Gas Phase Reactions ◽  
Aliphatic Aldehydes ◽  
Cl Atoms

The gas phase reactions of hydroxyl radicals with a series of aliphatic ethers over the temperature range 240-440 K

1988 ◽  
Vol 20 (1) ◽  
pp. 41-49 ◽  
Author(s):  
Timothy J. Wallington ◽  
Renzhang Liu ◽  
Philippe Dagaut ◽  
Michael J. Kurylo
Keyword(s):  
Gas Phase ◽  
Hydroxyl Radicals ◽  
Gas Phase Reactions ◽  
Temperature Range ◽  
Aliphatic Ethers

Absolute gas-phase acidities of CH3NH2, C2H5NH2, (CH3)2 NH, and (CH3)3N

1976 ◽  
Vol 54 (10) ◽  
pp. 1624-1642 ◽  
Author(s):  
Gervase I. Mackay ◽  
Ronald S. Hemsworth ◽  
Diethard K. Bohme
Keyword(s):  
Equilibrium Constant ◽  
Gas Phase ◽  
Equilibrium Constants ◽  
Heats Of Formation ◽  
Molecular Orbital Calculations ◽  
Electron Affinities ◽  
Flowing Afterglow ◽  
Experimental Assessment ◽  
Gas Phase Acidity ◽  
Conjugate Bases

The flowing afterglow technique has been employed in measurements of the rate and equilibrium constants at 296 ± 2 K for reactions of the type[Formula: see text]and[Formula: see text]where R1 and R2 may be H, CH3, or C2H5. The equilibrium constant measurements provided absolute values for the intrinsic (gas-phase) acidities of the Brønsted acids CH3NH2, C2H5NH2, (CH3)2NH, and (CH3)3N, the heats of formation of their conjugate bases, and the electron affinities of the corresponding radicals R1R2N. Proton removal energies, ΔG0298/(kcal mol−1), were determined to be 395.7 ± 0.7 for [Formula: see text] 391.7 ± 0.7 for [Formula: see text] 389.2 ± 0.6 for [Formula: see text] and > 396 for [Formula: see text] Heats of formation, ΔH0f.,298, were determined to be 30.5 ± 1.5 for CH3NH−, 21.2 ± 1.5 for C2H5NH−, and 24.7 ± 1.4 for (CH3)2N−. Electron affinities (in kcal mol−1) were determined to be 13.1 ± 3.5 for CH3NH, 17 ± 4 for C2H5NH, and 14.3 ± 3.4 for (CH3)2N. These results quantify earlier conclusions regarding the intrinsic effects of substituents on the gas-phase acidity of amines and provide an experimental assessment of recent molecular orbital calculations of proton removal energies for alkylamines.

Sulfenic acids in the gas phase. Preparation, ionization energies and heats of formation of methane-, ethene-, and benzenesulfenic acid

1988 ◽  
Vol 53 (9) ◽  
pp. 2140-2158 ◽  
Author(s):  
František Tureček ◽  
Libor Brabec ◽  
Tomáš Vondrák ◽  
Vladimír Hanuš ◽  
Josef Hájíček ◽  
...  
Keyword(s):  
Experimental Data ◽  
Gas Phase ◽  
Radical Cations ◽  
Appearance Energy ◽  
Heats Of Formation ◽  
Ionization Energies ◽  
Flash Vacuum Pyrolysis ◽  
Vacuum Pyrolysis ◽  
Mndo Calculations ◽  
Sulfenic Acids

Methane-, ethene-, and ethynesulfenic acids were generated in the gas phase by flash-vacuum pyrolysis of the corresponding tert-butyl sulfoxides at 400 °C and 10-4 Pa. Benzenesulfenic acid was prepared from phenyl 3-buten-1-yl sulfoxide at 350 °C and 10-4 Pa. The sulfenic acids were characterized by mass spectrometry Threshold ionization energies (IE) were measured as IE(CH3SOH) = 9·07 ± 0·03 eV, IE(CH2=CHSOH) = 8·70 ± 0·03 eV, IE(HCCSOH) = 8·86 ± 0·04 eV, and IE(C6H5SOH) = 8·45 + 0·03 eV. Radical cations [CH3SOH].+, [CH2=CHSOH].+, and [HCCSOH].+ were generated by electron-impact-induced loss of propene from the corresponding propyl sulfoxides and their heats of formation were assessed by appearance energy measurements as 685, 824, and 927 kJ mol-1, respectively. Heats of formation of the neutral sulfenic acids and the S-(O) (C), S-(O) (Cd), S-(O) (Ct) and S-(O) (CB) group equivalents were determined. The experimental data, supported by MNDO calculations, point to sulfenate-like structures (R-S-OH) for the sulfenic acids under study.

Computational Determination of Heats of Formation of Energetic Compounds

1995 ◽  
Vol 418 ◽  
Author(s):  
Peter Politzer ◽  
Jane S. Murray ◽  
M. Edward Grice
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Functional Group ◽  
Solid Phase ◽  
Heats Of Formation ◽  
Energetic Compounds ◽  
Phase Data ◽  
Heats Of Vaporization ◽  
Group Effects

AbstractA recently-developed density functional procedure for computing gas phase heats of formation is briefly described and results for several categories of energetic compounds are summarized and discussed. Liquid and solid phase values can be obtained by combining the gas phase data with heats of vaporization and sublimation estimated by means of other relationships. Some observed functional group effects upon heats of formation are noted.

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