Prediction of Heat and Free Energies of Organic Compounds

Franklin, J. L.

doi:10.1021/ie50473a041

Cited by 256 publications

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“…The most interesting property of the energies of the saturated hydrocarbons is that they obey an additivity relation wherein one assigns fixed energies to the CH3, CH2, CH, and C groups (15). The most important property of the topological atom is that its properties, including its energy, are determined by its spatial distribution of charge, that is, by its form in real space.…”

Section: Atomic Energiesmentioning

confidence: 99%

Properties of atoms and bonds in carbocations

Bader¹

1986

Can. J. Chem.

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The quantum theory of atoms in molecules defines structures for and determines the properties of the atoms and bonds in the series of carbocations [(CH3),CH3_,]+ with n = 0-3, and their parent hydrocarbons. In this theory, an atom in a molecule and its properties are defined by quantum mechanics. The quantum condition defining the atom is given in terms of a property derived from the charge density, as are the other concepts of the molecular structure hypothesis. In terms of the amount of electronic charge density accumulated between the carbon nuclei and its spatial distribution, a C-C bond of the carbocations exhibits an order greater than one. There is a transfer of charge from the hydrogens of methyl to the central carbon that destroys the axial symmetry of these C-C bonds and concentrates the charge in a plane perpendicular to the plane of substitution, in a manner consistent with the hyperconjugative mechanism of electron transfer. The positive charge of a carbocation is thus delocalized over all the atoms in the molecule, and the extent of this delocalization increases with increased methyl substitution. The electron population of each atom in a carbocation increases with this increase in the delocalization of positive charge and its energy is correspondingly decreased (the atom becomes more stable). These effects are most pronounced for the carbon atom bearing the methyl groups and they account for the observed increase in the relative stabilities of the carbocations with increasing methyl substitution. The electron populations and energies of the atoms in saturated hydrocarbons are also determined. The group additivity scheme for the energy in the homologous series of normal alkanes is predicted and explained in terms of the properties of the quantum atoms. It is the possibility of such transferability of the quantum atoms and their properties between systems that identifies them with the atoms of chemistry.R. F. W. BADER. Can. J. Chem. 64, 1036 (1986).La thCorie quantique des atomes dans les molCcules dCfinit les structures et dCtermine les properiCtCs des atomes et des liaisons dans une sCrie de carbocations [(CH~),CH~-~]+, dans lesquels n = 0-3, ainsi que dans leurs hydrocarbures de base. Dans cette thCorie, la condition quantique qui dCfinit l'atome ainsi que les autres concepts de l'hypothbse relative i la structure molCculaire sont dCfinies en fonction d'une propriCtC dCrivCe de la densit6 de charge. En termes de la densit6 de la charge Clectronique qui est accumulCe entre les noyaux de carbone et de leur distribution spatiale, une liaison C-C des carbocations prksente un ordre qui est plus grand que un. I1 se produit un transfert de charge des hydrogbnes du mCthyle vers le carbone central et ceci dCtruit la symktrie axiale de ces liaisons C-C et concentre la charge dans un plan perpendiculaire au plan de la substitution, d'une manikre qui est en accord avec le mecanisme d'hyperconjugaison de transfert Clectronique. La charge positive d'un carbocation est donc dClocalisCe sur tous les atomes de la...

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Section: Atomic Energiesmentioning

confidence: 99%

Properties of atoms and bonds in carbocations

Bader¹

1986

Can. J. Chem.

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“…The first group comprises methods in which the increments are ascribed to certain groups of atoms or bonds (see e.g. [26][27][28][29]). In the second group, the atoms or bonds are categorized according to their saturation degree.…”

Section: Theoretical Background Of the Superposition-additive Approachmentioning

confidence: 99%

Superposition-additive approach in the description of thermodynamic parameters of formation and clusterization of substituted alkanes at the air/water interface

Vysotsky

Belyaeva

Fomina

et al. 2012

Journal of Colloid and Interface Science

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“…Partial mass spectra of p-methylethylbenzenes Estimation of Heats of Formation AHf(7-mecylcoheptatriene) has been previously estimated (12) to be 37.2 kcal/mole using Franklin's group equivalent method (17). By the same method AHl(spiro[2.4]-heptal,.…”

Section: VIImentioning

confidence: 99%

AN ELECTRON IMPACT STUDY OF SOME C₈H_I0 ISOMERS

Meyer¹,

Haynes²,

McLean³

et al. 1965

Can. J. Chem.

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The mass spectra of I-, 2-, and 6-methylspiro[2.4]hepta-l,3-diene have been lneas~~red and found to be very similar to the spectra of 7-methylcycloheptatriene and the isomeric alkyl benzenes. It is concluded that in all cases the major part of the fragmentation occurs b y identical paths involving identical intermediates. This conclusion is supported by deuterium labelling and appearance potential data. On the other hand the mass spectrum of 2,5-dimethyl-1,5-hexadien-3-yne, an acyclic CeHlo isomer, shows a number of significant differences in its fragmentation pattern. These differences are reflected in the energetics of ion formation and it is concluded that in this case the fragmentation proceeds through different intermediates.

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Prediction of Heat and Free Energies of Organic Compounds

Cited by 256 publications

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Properties of atoms and bonds in carbocations

Properties of atoms and bonds in carbocations

Superposition-additive approach in the description of thermodynamic parameters of formation and clusterization of substituted alkanes at the air/water interface

AN ELECTRON IMPACT STUDY OF SOME C₈H_I0 ISOMERS

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Prediction of Heat and Free Energies of Organic Compounds

Cited by 256 publications

References 0 publications

Properties of atoms and bonds in carbocations

Properties of atoms and bonds in carbocations

Superposition-additive approach in the description of thermodynamic parameters of formation and clusterization of substituted alkanes at the air/water interface

AN ELECTRON IMPACT STUDY OF SOME C8HI0 ISOMERS

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AN ELECTRON IMPACT STUDY OF SOME C₈H_I0 ISOMERS