Center for Molecular Modeling - FWO UGent/VUB (3G011909) B/09984/*

Cationic ring-opening polymerization of 2-propyl-2-oxazolines: Understanding structural effects on polymerization behavior based on molecular modeling

wim — Mon, 10 Jun 2013 13:23:46 +0000

H. Goossens, S. Catak, M. Glassner, V. De La Rosa, B. Monnery, F. De Proft, V. Van Speybroeck, R. Hoogenboom

ACS Macro Letters

2, 651-654

2013

Abstract

The surprising difference in the cationic ring-opening polymerization rate of 2-cyclopropyl-2-oxazoline versus 2-n-propyl-2-oxazoline and 2-isopropyl-2-oxazoline was investigated both experimentally and theoretically. The polymerization kinetics of all three oxazolines were experimentally measured in acetonitrile at 140 °C, and the polymerization rate constant (kp) was found to decrease in the order c-PropOx > n-PropOx > i-PropOx. Theoretical free energy calculations confirmed the trend for kp, and a set of DFT-based reactivity descriptors, electrostatics, and frontier molecular orbitals were studied to detect the factors controlling this peculiar behavior. Our results show that the observed reactivity is dictated by electrostatic effects. More in particular, the charge on the nitrogen atom of the monomer, used to measure its nucleophilicity, was the most negative for c-PropOx. Furthermore, the electrophilicity of the cations does not change substantially, and thus, the nucleophilicity of the monomers is the driving factor for kp.

DOI

http://dx.doi.org/10.1021/mz400293y

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13_ACSMacroLetters_2,651_Goossens.pdf

Trans Effect and Trans Influence: Repulsion, rather than Competition for Donation

michel — Fri, 12 Apr 2013 10:16:37 +0000

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

Physical Chemistry Chemical Physics (PCCP)

15 (40), 17354-17365

2013

Abstract

The trans effect and trans influence were investigated and rationalized in the aminolysis, a typical nucleophilic substitution reaction, of trans-TPtCl2NH3 complexes (T = NH3, PH3, CO and C2H4) using energy decomposition analysis, both along the reaction paths and on the stationary points, and Natural Orbital for Chemical Valence analysis. In order to scrutinize the underlying principles and the origin of the kinetic trans effect, plausible structural constraints were introduced in the decomposition analysis, which allowed eliminating the distance dependence of the interaction energy components. It was established that the trans effect can be rationalized with the interaction of the TPtCl2 and NH3 fragments in the reactant state and TPtCl2 and (NH3)2 fragments in the transition state. It was evinced quantitatively that the σ-donor ability of T indeed controls the stability of the reactant, whereas in the case of π-acids, backdonation stabilizes the transition state, for which conceptually two mechanisms are available: intrinsic and induced π-backdonation. In the destabilization of the reactant and also in the labilization of the leaving group (trans influence) repulsion plays a more important role than orbital sharing effects, which are the cornerstones of the widely accepted interpretations of the trans influence, such as competition for donation or limitation of the donation of the leaving group by the trans ligand T. This repulsive interaction was rationalized both in terms of donated electron density and also in the molecular orbital framework. NOCV orbitals indeed clearly show that the σ-trans effect can be envisioned as a donation from the trans ligand not only to the metal but also to the σ* orbital of the metal-leaving group bond, which manifests as a repulsion between the metal and the leaving group.

DOI

http://dx.doi.org/10.1039/C3CP52383G

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13_PCCP_15(40)17354_pinter.pdf

Synthesis of 2-Hydroxy-1,4-oxazin-3-ones through Ring Transformation of 3-Hydroxy-4-(1,2-dihydroxyethyl)--lactams and a Study of Their Reactivity

michel — Fri, 13 Jul 2012 11:46:22 +0000

K. Mollet, H. Goossens, N. Piens, S. Catak, M. Waroquier, V. Van Speybroeck, M. D'Hooghe, N. De Kimpe

Chemistry - A European Journal

19 (10), 3383-3396

2013

Abstract

The reactivity of 3-hydroxy-4-(1,2-dihydroxyethyl)-β-lactams with regard to the oxidant sodium periodate was evaluated, unexpectedly resulting in the exclusive formation of new 2-hydroxy-1,4-oxazin-3-ones through a C3C4 bond cleavage of the intermediate 4-formyl-3-hydroxy-β-lactams followed by a ring expansion. This peculiar transformation stands in sharp contrast with the known NaIO4-mediated oxidation of 3-alkoxy- and 3-phenoxy-4-(1,2-dihydroxyethyl)-β-lactams, which exclusively leads to the corresponding 4-formyl-β-lactams without a subsequent ring enlargement. In addition, this new class of functionalized oxazin-3-ones was further evaluated for its potential use as building blocks in the synthesis of a variety of differently substituted oxazin-3-ones, morpholin-3-ones and pyrazinones. Furthermore, additional insights into the mechanism and the factors governing this new ring-expansion reaction were provided by means of density functional theory calculations.

DOI

http://dx.doi.org/10.1002/chem.201203314

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13_chem_eur_ j_19(10)3383_Mollet.pdf

Symposium on Molecular Electrostatic Potentials

wim — Thu, 23 Oct 2014 07:38:28 +0000

Brussels, Belgium

Wednesday, 22 October, 2014

Participant(s)

T. Verstraelen

Project ref.

FWO mandaat, FWO UGent/VUB (3G011909) B/09984/*, Alliantie (DEF09) I/00048/02

Conference reference

Symposium on Molecular Electrostatic Potentials

ICSHM2013

wim — Mon, 12 Aug 2013 13:43:25 +0000

Ghent, Belgium

Sunday, 16 June, 2013 to Thursday, 20 June, 2013

Participant(s)

T. De Meyer, H. Goossens

Project ref.

BOF mandaat, FWO UGent/VUB (3G011909) B/09984/*

Conference reference

ICSHM2013

FWO-VUB (3G011909)

wim — Tue, 23 Apr 2013 13:36:47 +0000

Project promotor

V. Van Speybroeck, M. Waroquier

Financierende instantie

FWO

Project data

01/01/2009 to 31/12/2012

Bedrag

€163 920,00

Project titel

Chemical reactivity from an ab-initio molecular dynamics and Density Functional Perspective : methodological aspects and applications in organic, inorganic and biochemistry.

Personeel

H. Goossens

Extra info

UGent (CMM) - VUB

Project ref.

FWO UGent/VUB (3G011909) B/09984/*

Visiting Paul Ayers (McMaster)

wim — Mon, 08 Apr 2013 14:02:40 +0000

Hamilton, Ontario, Canada

Monday, 29 April, 2013 to Monday, 13 May, 2013

Participant(s)

T. Verstraelen

Project ref.

FWO mandaat, FWO UGent/VUB (3G011909) B/09984/*

DFT-2011

wim — Thu, 24 Jan 2013 14:26:24 +0000

Athenes, Greece

Monday, 29 August, 2011 to Monday, 5 September, 2011

Participant(s)

H. Goossens

Project ref.

FWO UGent/VUB (3G011909) B/09984/*, Alliantie (DEF09) I/00048/02

Conference reference

DFT-2011

TACC-2012

wim — Thu, 17 Jan 2013 11:03:56 +0000

University of Pavia, Italy

Sunday, 2 September, 2012 to Friday, 7 September, 2012

Participant(s)

K. De Wispelaere, H. Goossens

Project ref.

FWO UGent/VUB (3G011909) B/09984/*, FWO mandaat

Conference reference

TACC-2012

MolSim-2013

wim — Thu, 17 Jan 2013 10:52:01 +0000

ACMM, University of Amsterdam (NL)

Monday, 7 January, 2013 to Friday, 18 January, 2013

Participant(s)

S. Vandenbrande, H. Goossens

Project ref.

FWO UGent/VUB (3G011909) B/09984/*, BOF-ERC I/00057/02

Conference reference

Molsim-2013