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.

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.

scholarly journals Calculations of hydrogenation enthalpies of hydrocarbons by M06-2X/CBS extrapolated level in the gas phase

2020 ◽  
Vol 44 (11-12) ◽  
pp. 762-768
Author(s):  
AA Khairbek ◽  
M Abd Al-Hakim Badawi
Keyword(s):  
Standard Deviation ◽  
Gas Phase ◽  
Unsaturated Hydrocarbon ◽  
Basis Set ◽  
Basis Sets ◽  
Good Linear ◽  
Complete Basis Set ◽  
The Mean ◽  
Experimental Values ◽  
Linear Correlations

The standard enthalpies of hydrogenation of 29 unsaturated hydrocarbon compounds were calculated in the gas phase by M06-2X theory with the 6-31g(d) and cc-pVXZ, where X = DZ, TZ, QZ, as well as by complete basis set extrapolated level. Geometries of compounds were optimized at the M06-2X/6-31g(d) level. These M06-2X geometries were used in the M06-2X, and extrapolation calculations with cc-pVXZ basis sets. Comparison of calculation and experimental results shows that the mean absolute deviations between the calculated and experimental enthalpies of hydrogenation range from 25.1 to 5.1 kJ mol−1 at M06-2X calculations, and when using cc-pV(DT)Z extrapolated level, the mean absolute deviations have decreased to 2.7. The results of some calculations showed that the deviations from experimental values are located inside the “chemical accuracy” (±1 kcal mol−1≈±4.2 kJ mol−1). Very good linear correlations between experimental and calculated enthalpies of hydrogenation have been obtained at M06-2X/cc-pVTZ and cc-pV(DT)Z extrapolated levels (standard deviation = 3.2 and 3.4 kJ mol−1, respectively).

Gas-phase solvation of N+2 with Ar atoms: a charge switch in the reaction N+2 + Ar → Ar+ …N2

1992 ◽  
Vol 189 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Kenzo Hiraoka ◽  
Toshiharu Mori ◽  
Shinichi Yamabe
Keyword(s):  
Gas Phase ◽  
A Charge

scholarly journals Quantum Calculations to Estimate the Heat of Hydrogenation Theoretically

2020 ◽  
Author(s):  
Ali Amir Khairbek
Keyword(s):  
Unsaturated Hydrocarbon ◽  
Experimental Results ◽  
Basis Set ◽  
Good Linear ◽  
Complete Basis ◽  
Complete Basis Set ◽  
Complete Basis Set Limit ◽  
The Mean ◽  
Experimental Values ◽  
Linear Correlations

Standard enthalpies of hydrogenation of 29 unsaturated hydrocarbon compounds were calculated in the gas phase by CCSD(T) theory with complete basis set cc-pVXZ, where X = DZ, TZ, as well as by complete basis set limit extrapolation. Geometries of reactants and products were optimized at the M06-2X/6-31g(d) level. This M06-2X geometries were used in the CCSD(T)/cc-pVXZ//M06-2X/6-31g(d) and cc-pV(DT)Z extrapolation calculations. (MAD) the mean absolute deviations of the enthalpies of hydrogenation between the calculated and experimental results that range from 8.8 to 3.4 kJ mol−1 based on the Comparison between the calculation at CCSD(T) and experimental results. The MAD value has improved and decreased to 1.5 kJ mol−1 after using complete basis set limit extrapolation. The deviations of the experimental values are located inside the “chemical accuracy” (±1 kcal mol−1 ≈ ±4.2 kJ mol−1) as some results showed. A very good linear correlations between experimental and calculated enthalpies of hydro-genation have been obtained at CCSD(T)/cc-pVTZ//M06-2X/6-31g(d) level and CCSD(T)/cc-pV(DT)Z extrapolation levels (SD =2.11 and 2.12 kJ mol−1, respectively).

ChemInform Abstract: THE STRUCTURE AND REACTIVITY OF ORGANIC IONS IN GAS-PHASE RADIOLYSIS PART 8, THE C7H7(+) ION FROM TOLUENE AND ETHYLBENZENE

1974 ◽  
Vol 5 (36) ◽  
Author(s):  
NOBUO SAGI ◽  
YUKIO YAMAMOTO ◽  
KENJI NAGAOKA ◽  
SETSUO TAKAMUKU ◽  
HIROSHI SAKURAI
Keyword(s):  
Gas Phase ◽  
Organic Ions

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.

Additions and Corrections - Organic Ions in the Gas Phase. VII. Tropylium Ion from Benzyl Chloride and Benzyl Alcohol

1960 ◽  
Vol 82 (24) ◽  
pp. 6427-6427
Author(s):  
Seymour Meyerson ◽  
Paul Rylander ◽  
Ernest Eliel ◽  
John McCollum
Keyword(s):  
Benzyl Alcohol ◽  
Gas Phase ◽  
Benzyl Chloride ◽  
Organic Ions
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