Center for Molecular Modeling - F. De Vleeschouwer

Reversibility from DFT-Based Reactivity Indices: Intramolecular Side Reactions in the Polymerization of Poly(vinyl chloride)

wim — Mon, 03 Oct 2011 12:04:01 +0000

F. De Vleeschouwer, A. Toro-Labbe, S. Gutierrez-Oliva, V. Van Speybroeck, M. Waroquier, P. Geerlings, F. De Proft

Journal of Physical Chemistry A

113 (27), 7899-7908

2009

Abstract

A detailed investigation of the kinetic irreversibility−reversibility concept is presented on the basis of the analysis of four side reactions occurring in the polymerization of poly(vinyl chloride), the intramolecular 1,5- and 1,6-backbiting and 1,2- and 2,3-Cl shift side reactions. Density functional theory-based reactivity indices combined with an analysis of the reaction force are invoked to probe this concept. The reaction force analysis is used to partition the activation and reaction energy and characterize the behavior of reactivity indices along the three reaction regions that are defined within this approach. It has been observed that in the reactant and product regions mainly geometric rearrangements take place, whereas in the transition state region changes in the electronic bonding pattern occur; here most changes of the electronic properties are observed. The kinetic irreversibility−reversibility of the reactions is confirmed and linked to the differences in the Fukui function and dual descriptor of the radical centers associated with the initial and final species.

DOI

http://dx.doi.org/10.1021/jp900884z

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09 j. phys. chem. A 113(27)7899 de vleeshouwer.pdf

An Intrinsic Radical Stability Scale from the Perspective of Bond Dissociation Enthalpies: A Companion to Radical Electrophilicities

wim — Mon, 03 Oct 2011 09:43:49 +0000

F. De Vleeschouwer, V. Van Speybroeck, M. Waroquier, P. Geerlings, F. De Proft

Journal of Organic Chemistry

73 (22) 9109-9120

2008

Abstract

Bond dissociation enthalpies (BDEs) of a large series of molecules of the type A−B, where a series of radicals A ranging from strongly electrophilic to strongly nucleophilic are coupled with a series of 8 radicals (CH2OH, CH3, NF2, H, OCH3, OH, SH, and F) also ranging from electrophilic to nucleophilic, are computed and analyzed using chemical concepts emerging from density functional theory, more specifically the electrophilicities of the individual radical fragments A and B. It is shown that, when introducing the concept of relative radical electrophilicity, an (approximately) intrinsic radical stability scale can be developed, which is in good agreement with previously proposed stability scales. For 47 radicals, the intrinsic stability was estimated from computed BDEs of their combinations with the strongly nucleophilic hydroxymethyl radical, the neutral hydrogen atom, and the strongly electrophilic fluorine atom. Finally, the introduction of an extra term containing enhanced Pauling electronegativities in the model improves the agreement between the computed BDEs and the ones estimated from the model, resulting in a mean absolute deviation of 16.4 kJ mol−1. This final model was also tested against 82 experimental values. In this case, a mean absolute deviation of 15.3 kJ mol−1 was found. The obtained sequences for the radical stabilities are rationalized using computed spin densities for the radical systems.

DOI

http://dx.doi.org/10.1021/jo802018b

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08 j. org. chem. 73(22)9109 de vleeshouwer.pdf

First Principles Based Group Additive Values for the Gas Phase Standard Entropy and Heat Capacity of Hydrocarbons and Hydrocarbon Radicals

wim — Mon, 03 Oct 2011 09:39:25 +0000

M. Sabbe, F. De Vleeschouwer, M-F. Reyniers, M. Waroquier, G.B. Marin

Journal of Physical Chemistry A

112 (47), 12235-12251

2008

Abstract

In this work a complete and consistent set of 95 Benson group additive values (GAVs) for standard entropies S° and heat capacities Cp° of hydrocarbons and hydrocarbon radicals is presented. These GAVs include 46 groups, among which 25 radical groups, which, to the best of our knowledge, have not been reported before. The GAVs have been determined from a set of B3LYP/6-311G(d,p) ideal gas statistical thermodynamics values for 265 species, consistently with previously reported GAVs for standard enthalpies of formation. One-dimensional hindered rotor corrections for all internal rotations are included. The computational methodology has been compared to experimental entropies (298 K) for 39 species, with a mean absolute deviation (MAD) between experiment and calculation of 1.2 J mol−1 K−1, and to 46 experimental heat capacities (298 K) with a resulting MAD = 1.8 J mol−1 K−1. The constructed database allowed evaluation of corrections on S° and Cp° for non-nearest-neighbor effects, which have not been determined previously. The group additive model predicts the S° and Cp° within 5 J mol−1 K−1 of the ab initio values for 11 of the 14 molecules of the test set, corresponding to an acceptable maximal deviation of a factor of 1.6 on the equilibrium coefficient. The obtained GAVs can be applied for the prediction of S° and Cp° for a wide range of hydrocarbons and hydrocarbon radicals. The constructed database also allowed determination of a large set of hydrogen bond increments, which can be useful for the prediction of radical thermochemistry.

DOI

http://dx.doi.org/10.1021/jp807526n

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08 j. phys. chem. A 112(47)12235 sabbe.pdf

Electrophilicity and nucleophilicity index for radicals

wim — Mon, 03 Oct 2011 07:44:56 +0000

F. De Vleeschouwer, V. Van Speybroeck, M. Waroquier, P. Geerlings, F. De Proft

Organic Letters

9 (14), 2721-2724

2007

Abstract

Radicals can be regarded as electrophilic/nucleophilic, depending on their tendency to attack sites of relatively higher/lower electron density. In this paper, an electrophilicity scale, global as well as local, and a nucleophilicity scale for 35 radicals is reported. The global electrophilicity scale correlates well with the nucleophilicity scale, suggesting that these concepts are inversely related.

DOI

http://dx.doi.org/10.1021/ol071038k

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07 org. lett. 9(14)2721 de vleeshouwer.pdf

Validation of DFT-Based Methods for Predicting Qualitative Thermochemistry of Large Polyaromatics

wim — Mon, 22 Aug 2011 14:21:05 +0000

K. Hemelsoet, F. De Vleeschouwer, V. Van Speybroeck, F. De Proft, P. Geerlings, M. Waroquier

ChemPhysChem

12(6), 1100-1108

2011

Abstract

We present a validation of computationally efficient density functional-based methods for the reproduction of relative bond dissociation energies of large polyaromatic hydrocarbons. Through the calculation of intrinsic radical stabilities and the computation of spin densities, the extent of delocalization of the unpaired electron in the benzylic radicals is examined. We focus on the influence of the level of theory choice applied for the geometry optimization and the role of van der Waals corrections on thermochemical properties. The dispersion effects mainly influence the energetics, causing a small upward shift of the bond dissociation energies. The long-range corrected CAM-B3LYP functional does not improve the traditional B3LYP results for the geometry description of the large delocalized radicals, however a non-negligible influence was encountered when applied for the energetics. It is reported that the f polarization functions present in the 6-311+G(3df,2p) basis set lead to an erroneous trend when combined with the B2PLYP functional for the computation of the single point energies.

DOI

http://dx.doi.org/10.1002/cphc.201000788

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11 chemphyschem 12, 1100 hemelsoet.pdf

Standard enthalpy of formation, entropy and heat capacity of hydrocarbons and hydrocarbon radicals: first principles group additive values

samuel — Thu, 06 Feb 2020 14:41:45 +0000

M. Sabbe, F. De Vleeschouwer, V. Van Speybroeck, M. Waroquier, M-F. Reyniers, G.B. Marin

ISBN/ISSN:

Talk

Conference / event / venue

Thermodynamics 2007

Rueil-Malmaison, France

Wednesday, 26 September, 2007 to Friday, 28 September, 2007

Electrophilicity and Nucleophilicity Index for Radicals

wim — Tue, 18 Oct 2011 08:01:50 +0000

F. De Vleeschouwer, V. Van Speybroeck, M. Waroquier, P. Geerlings, F. De Proft

Poster

Conference / event / venue

DFT2007

Amsterdam, the Netherlands

Sunday, 26 August, 2007 to Thursday, 30 August, 2007