Ab‐initio electrostatic molecular potential contour maps for initiation step and Ab‐Initio MRD‐CI calculations for propagation step of cationic polymerization of oxetanes

Kaufman, Joyce J.; Hariharan, P. C.; Roszak, Szczepan; Keegstra, Phillip B.

doi:10.1002/masy.19860060130

Cited by 9 publications

(3 citation statements)

References 15 publications

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“…In a series of contributions by Kaufman et al [ 285 , 286 , 287 ], QCC have been employed to investigate the mechanism of cyclic oxetane-based monomers. The reactivity in the cationic polymerization of these types of monomers is screened on the basis of the electrostatic molecular potential contour maps constructed via ab initio calculation with explicit accounting for a proton in the calculations.…”

Section: Case Studies For Connection Of Computational Chemistry and Kinetic Modelingmentioning

confidence: 99%

Connecting Gas-Phase Computational Chemistry to Condensed Phase Kinetic Modeling: The State-of-the-Art

et al. 2021

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In recent decades, quantum chemical calculations (QCC) have increased in accuracy, not only providing the ranking of chemical reactivities and energy barriers (e.g., for optimal selectivities) but also delivering more reliable equilibrium and (intrinsic/chemical) rate coefficients. This increased reliability of kinetic parameters is relevant to support the predictive character of kinetic modeling studies that are addressing actual concentration changes during chemical processes, taking into account competitive reactions and mixing heterogeneities. In the present contribution, guidelines are formulated on how to bridge the fields of computational chemistry and chemical kinetics. It is explained how condensed phase systems can be described based on conventional gas phase computational chemistry calculations. Case studies are included on polymerization kinetics, considering free and controlled radical polymerization, ionic polymerization, and polymer degradation. It is also illustrated how QCC can be directly linked to material properties.

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Section: Case Studies For Connection Of Computational Chemistry and Kinetic Modelingmentioning

confidence: 99%

Connecting Gas-Phase Computational Chemistry to Condensed Phase Kinetic Modeling: The State-of-the-Art

et al. 2021

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“…We had derived, implemented, tested, and used successfully [3-51 this new computational strategy for ab initio MRD-CI calculations for molecular decompositions of large molecules [3] and intermolecular reactions [4,5] of large systems. The advantage is that the transformations from integrals over atomic orbitals to integrals over molecular orbitals (the most demanding part of the calculations in terms of storage) need only be carried out for the localized orbitals included explicitly in the MRD-CI calculations.…”

Section: Mrnimentioning

confidence: 99%

Ab initio MRD–CI calculations on cubane (neutral, carbocation, carboanion) and dissociation of nitrocubanes based on localized orbitals

Chapman

Kaufman

Buenker

1991

Int J of Quantum Chemistry

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Ab initio MRMI calculations based on localized orbitals were carried out for cubane (neutral, carbocation, carboanion) both in our customary MODPOT basis set and in an all-electron 4-31G basis set. The calculated MRHI charge distributions on C1 (the skeletal atom from which the H -or H + was removed) (ab initio MODPOT neutral 4.221, carbocation 3.796, carboanion 4.282; all-electron 4-31G neutral 6.171, carbocation 5.717, carboanion 6.078) indicate that the + or -charge does not remain localized on C1 but redistributes itself. This has significant implications for preparative reactions of energetically substituted cubanes. The MRD-CI population analyses differ somewhat from the SCF population analyses, especially in the calculated total overlap populations. To investigate this effect on electrostatic molecular potential contour (EMPC) maps generated from SCF or MRHI wave functions, we wrote additional routines to calculate EMPC maps from MRE-CI wave functions. The EMPC maps generated from SCF or MRD-CI wave functions are different if the molecule needs an MRD-CI multideterminant wave function to describe it adequately. The EMPC map is a one-electron property. One-electron properties are derived from the 1-matrix. The 1-matrix is different for SCF or MRD-CI wave functions. Thus, all the one-electron properties (EMPC maps, population analyses, bond deviation indices, etc.) are different when calculated from SCF or MRD-CI wave functions if MRD-CI wave functions are necessary to describe a system properly. We calculate these one-electron properties from the 1-matrix from the final natural orbitals. Our preliminary calculations for the 3C-NOz dissociation pathway indicate it takes more energy to dissociate a >C-N02 bond in 1-nitrocubane than in octanitrocubane. Even in their ground electronic states at equilibrium geometry, both 1-nitrocubane and octanitrocubane require MRD-CI wave functions to describe them properly. The c2 of the single determinant SCF wave function is only 0.8401 for 1-nitrocubane and 0.8300 for octanitrocubane. There are contributions from skeletal excitations as there are for cubane itself as well as excitations involving the nitrogroup.As the >C-N02 bond in nitrocubane is dissociated to 8.00 bohrs, the cz of the SCF contribution drops to only 0.4606 (1-nitrocubane) and 0.4445 (octanitrocubane). At this C1-N1 intermolecular distance, the largest excitations are in the CI-NI bond: (CI-NI)' + (Cl-N?)', (CI-Nl) -+ (Cl -N;). We also calculated the first electronically excited state for the >C-N02 dissociation pathway for selected points for both 1-nitrocubane and octanitrocubane.

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“…2) based on localized molecular orbitals, including explicitly in the CI the localized occupied and virtual molecular orbitals in the reaction region and folding the remainder of the occupied localized molecular orbitals into an effective CI Hamiltonian [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Ab Intitio MRD-CI calculations on protonated cyclic ethers. I. Protonation pathways involve multipotential surfaces (protonation of oxetane). II. Differences from SCF in dominant configurations upon opening non-protonated oxirane rings (epoxides)

Kaufman

Hariharan

Roszak

et al. 1987

Int. J. Quantum Chem.

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Ab‐initio electrostatic molecular potential contour maps for initiation step and Ab‐Initio MRD‐CI calculations for propagation step of cationic polymerization of oxetanes

Cited by 9 publications

References 15 publications

Connecting Gas-Phase Computational Chemistry to Condensed Phase Kinetic Modeling: The State-of-the-Art

Connecting Gas-Phase Computational Chemistry to Condensed Phase Kinetic Modeling: The State-of-the-Art

Ab initio MRD–CI calculations on cubane (neutral, carbocation, carboanion) and dissociation of nitrocubanes based on localized orbitals

Ab Intitio MRD-CI calculations on protonated cyclic ethers. I. Protonation pathways involve multipotential surfaces (protonation of oxetane). II. Differences from SCF in dominant configurations upon opening non-protonated oxirane rings (epoxides)

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