Charge distribution and chemical effects. V. Modified population analysis. Application to carbon-13 nuclear magnetic resonance shifts

Fliszár, Sándor; Goursot, Annick; Dugas, Hermann

doi:10.1021/ja00821a002

Cited by 55 publications

(51 citation statements)

References 5 publications

(6 reference statements)

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“…This procedure alnouiits to an experimental partitioning of Mulliken overlap populations. The result, p = (30.3 _f 0.3) x lo-, electron equals, within experimental uncertainty, that found by similar procedures for I3C resonance shifts (6,26,27) and adiabatic ionization potentials (28), i.e., p = 30.12 x lo-, electron. Consequently, the charges derived from eqs.…”

Section: Appendixsupporting

confidence: 83%

“…[5] and [6], where N = number of H atoms attached to C and p = 30.12 x electron is the departure from the usual halving of the C H overlap population, for one C-H bond. (The reasons leading to this type of analysis are given in detail elsewhere (5,6).) The same carbon atomic charges are also obtained from C-13 nmr shifts (6) (eq.…”

Section: Coulomb Interactionsmentioning

confidence: 99%

“…Indeed, the C and H charges derived from optimized STO-3G, Hoylands' bond-order (23), 7 .~3~1 3 .~ (24), and 6-31G nb itiitio calculations are in all cases in a ratio (k) of l : 1.3: 0.86: 0.84, after readjustment through eqs. [5] and [6], evidently without any change in their relative ordering (5). Here, the search for the best k yields k = 0.7-0.95 (depending upon whether or not one or another compound is left out of thecorrelation), with an insignificant improvement in the calculations of the AHrO's, the average deviation being now 0.15 kcal/mol.…”

Section: Experimental Verificationsmentioning

confidence: 99%

“…[5] and [6]. For the other molecules, carbon atoinic charges were derived from 13C nmr shifts, using eq.…”

Section: Appendixmentioning

confidence: 99%

“…Consequently, the charges derived from eqs. [5] and [6] are appropriate for the problem at hand and are adequately represented by 13C resonance shifts, through eq. [7], as was done in eqs.…”

Section: Appendixmentioning

confidence: 99%

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Charge distributions and chemical effects. XIX. Analysis of 'bonded' and 'non-bonded' energy contributions in saturated hydrocarbons

Fliszár¹,

Béraldin²

1979

Can. J. Chem.

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Total Coulomb interactions between non-bonded atoms behave in general in a 'quasiadditive' fashion, not only in simple linear and branched paraffins, but also in polycyclic hydrocarbons constructed from chair and boat cyclohexane rings. Because of their relative insensitivity to structural features, they cannot be regarded as being the leading terms in the explanation of energetic effects related to structural changes. The prime factors governing molecular stabilities, as well as the explanation of the structural effects which are at their origin, are found in the behavior of the charge dependent energy contributions associated with bonded atoms, i.e., in the chemical bonds themselves.Can. J. Chem. 57, 1772 (1979). Les sommes des interactions Coulombiennes entre atomes non liCs se comportent en general de manikre "quasi additive", tout aussi bien dans les paraffines lintaires et ramifiees que dans les hydrocarbures polycycliques constitues d'anneaux cyclohexaniques en forme chaise ou bateau. En raison de leur faible sensibiliti aux modifications structurales, ces interactions ne peuvent jouer de r6le preponderant dans leur interpretation. Les principaux facteurs determinant les stabilitts moleculaires, ainsi que l'explication des effets structuraux qui sont a leur origine, se retrouvent dans le comportement des contributions tnergetiques associees aux charges des atomes lies, c'est-a-dire dans les liaisons chimiques elles-m@mes. This particular choice is not restrictive because atomization energies (AE,:';) of vibrationless mole-order. Let X be a molecular property and ~( 2 )~ cules can be derived from the corresponding standard X(l) the for ethane and enthalpies of formation AH,' (gas, 298.16 K) and methane. If X i s e x a c t l~ additive, then appropriate spectroscopic data (eq. [I]; C n i = total [21 x = (1 -m )~( 2 ) + (n -2 + zm) number of atoms in the molecule, T = 298.16 K).where X(2) -X(l) is the change in X going from + H~ -H~ -5CniRT/2 methane to ethane, i.e., the contribution of one CH, Here we investigate saturated hydrocarbons group. The meaning of eq. [2] is obvious for nonCnH2,,+, -,,, considering both simple paraffins and cyclic compounds (m = 0). or c~clohexane (m = l), six-membered cyclic compounds, including poly-which consists of n -2 + 2m = 6 CH2 groups, cyclic hydrocarbons (m = number of cycles) such as the (1 -m)X(2) term of eq. [21 cancels. Decalin is adamantane, bicyclo[2.2.2]octane, iceane, etc. Atten-con~tructed from two c~clohexane units. In this case tion is focussed on energy partitioning and additivity n -2 + 2m accounts for 12 CH2 groups, but One rules involving AE, *.additional ethane X(2) contribution (i.e., that of two CH, and two H atoms) is subtracted with respect Formulation of Additivity to cyclohexane, i.e., a total of 2X(2) contributions Because of our central interest in additivity, a few with respect to noncyclic alkanes. Similar arguments preliminary remarks about its formulation are in applied to other polycyclic saturated hydrocarbons

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Section: Appendixsupporting

confidence: 83%

Section: Coulomb Interactionsmentioning

confidence: 99%

Section: Experimental Verificationsmentioning

confidence: 99%

“…[5] and [6]. For the other molecules, carbon atoinic charges were derived from 13C nmr shifts, using eq.…”

Section: Appendixmentioning

confidence: 99%

Section: Appendixmentioning

confidence: 99%

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Charge distributions and chemical effects. XIX. Analysis of 'bonded' and 'non-bonded' energy contributions in saturated hydrocarbons

Fliszár¹,

Béraldin²

1979

Can. J. Chem.

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Influence of γ-hydrogens (hydrogens three bonds away) in calculating13C chemical shifts of acyclic alkanes and alcohols

Saikia¹,

Suryanarayana²

1999

Magn. Reson. Chem.

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The 13C NMR chemical shifts of acyclic alkanes and alcohols are reproduced by an equation having two parameters, the charge on the carbon atom as calculated by iterative partial equalization of orbital electronegativity and the effective number of hydrogen atoms three bonds away from the carbon atom under consideration. The data sets consist of 183 carbons of all alkane isomers up to C8 and 184 carbons of aliphatic alcohol isomers up to C8 . The alkane carbons are correlated with a correlation coefficient of 0.994 and a standard deviation of 1.06 ppm and the alcohol carbons with a correlation coefficient of 0.997 and a standard deviation of 1.37 ppm. The influence of effective number of hydrogen atoms three bonds away is discussed in terms of 1,4 steric interactions in the molecules. Copyright © 1999 John Wiley & Sons, Ltd.

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On the definition of the atomic charge. Relationship between13C NMR chemical shifts, dipole moments, and charges in saturated hydrocarbons

Monaco

1998

Int. J. Quant. Chem.

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ABSTRACT:The problem of defining a reliable quantum mechanical charge by comparison with one-electron properties is analyzed, and it is stressed that properties involving the virtual space are not suited to that end. Particular attention is devoted to the relationship between charges and chemical shifts for the case of saturated hydrocarbons. A simple explanation of the Grant and Paul ␣ effect is suggested, which can also account for the modified population analysis proposed by Fliszar. Moreover thé vexata quaestio of the direction of the C-H bond dipole moment has been reexamined. Ž q y . The awkward theoretical prediction C -H can be reconciled with the one based on Ž y q . experimental data and electronegativities C -H if one considers that the former is determined by an hydridization contribution to the dipole moment, which tend to cancel in a summation over all the bonds formed by each atom.

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Charge distribution and chemical effects. V. Modified population analysis. Application to carbon-13 nuclear magnetic resonance shifts

Cited by 55 publications

References 5 publications

Charge distributions and chemical effects. XIX. Analysis of 'bonded' and 'non-bonded' energy contributions in saturated hydrocarbons

Charge distributions and chemical effects. XIX. Analysis of 'bonded' and 'non-bonded' energy contributions in saturated hydrocarbons

Influence of γ-hydrogens (hydrogens three bonds away) in calculating13C chemical shifts of acyclic alkanes and alcohols

On the definition of the atomic charge. Relationship between13C NMR chemical shifts, dipole moments, and charges in saturated hydrocarbons

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