Studies on aliphatic polyesters. Part II: Ab initio, density functional and force field studies of model molecules with two carboxyl groups

Johanna Blomqvist, Berit Mannfors, Lars-Olof Pietilä (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

This paper is a continuation of our study on the ester bond energetics. Here, model molecules for structural units of biodegradable polyglycolic and polylactic acids (HC(=O)–O–CH2–C(=O)–O–CH3 and HC(=O)–O–CH(CH3)–C(=O)–O–CH3), which contain two carboxyl groups in close vicinity to one another, have been considered. Rotations about the neighbouring C(sp3)–O(sp3) and C(sp3)–C(sp2) bonds adjacent to the CH2 or CH(CH3) group have been studied quantum chemically by ab initio and density functional methods (MP2, B3-LYP and B-LYP), using the standard Gaussian-type basis set 6-31G(d), as well as by the PCFF (Polymer CFF) force field. The quantum chemical results mostly are in good agreement with each other. However, for the C–O rotations, the Density Functional Theory (DFT) barriers are 0.5–3.1 kcal/mol lower than the corresponding MP2 ones. The conformational dependency of bond lengths, valence angles, and that of atomic charges also is similar in the MP2 and DFT methods. The changes in bond lengths with conformation are small, but the valence angles vary more and especially in high-energy states with low population they may open as much as 18°. The conformational dependence of the most significant atomic CHELPG charges also was found to be small, and the largest relative changes occurred in small charges that do not have a major impact on the electrostatic potential. The PCFF force field produced torsional energetics that was in serious disagreement with the quantum chemical results, especially in the case of the C–C rotations. By reoptimizing the pertinent torsion parameters of the PCFF force field, these disagreements could be removed.

Original languageEnglish
Pages (from-to)359 - 374
Number of pages16
JournalJournal of Molecular Structure: THEOCHEM
Volume531
Issue number1-3
DOIs
Publication statusPublished - 2000
MoE publication typeA1 Journal article-refereed

Fingerprint

Polyesters
polyesters
carboxyl group
field theory (physics)
Polymers
Bond length
Molecules
Density functional theory
polymers
density functional theory
Polyglycolic Acid
valence
molecules
Structural Models
Carbon Monoxide
Static Electricity
Torsional stress
Electron energy levels
torsion
Conformations

Cite this

@article{a76447a8edc6478ebf411d17e3c7acbe,
title = "Studies on aliphatic polyesters. Part II: Ab initio, density functional and force field studies of model molecules with two carboxyl groups",
abstract = "This paper is a continuation of our study on the ester bond energetics. Here, model molecules for structural units of biodegradable polyglycolic and polylactic acids (HC(=O)–O–CH2–C(=O)–O–CH3 and HC(=O)–O–CH(CH3)–C(=O)–O–CH3), which contain two carboxyl groups in close vicinity to one another, have been considered. Rotations about the neighbouring C(sp3)–O(sp3) and C(sp3)–C(sp2) bonds adjacent to the CH2 or CH(CH3) group have been studied quantum chemically by ab initio and density functional methods (MP2, B3-LYP and B-LYP), using the standard Gaussian-type basis set 6-31G(d), as well as by the PCFF (Polymer CFF) force field. The quantum chemical results mostly are in good agreement with each other. However, for the C–O rotations, the Density Functional Theory (DFT) barriers are 0.5–3.1 kcal/mol lower than the corresponding MP2 ones. The conformational dependency of bond lengths, valence angles, and that of atomic charges also is similar in the MP2 and DFT methods. The changes in bond lengths with conformation are small, but the valence angles vary more and especially in high-energy states with low population they may open as much as 18°. The conformational dependence of the most significant atomic CHELPG charges also was found to be small, and the largest relative changes occurred in small charges that do not have a major impact on the electrostatic potential. The PCFF force field produced torsional energetics that was in serious disagreement with the quantum chemical results, especially in the case of the C–C rotations. By reoptimizing the pertinent torsion parameters of the PCFF force field, these disagreements could be removed.",
author = "Johanna Blomqvist and Berit Mannfors and Lars-Olof Pietil{\"a}",
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doi = "10.1016/S0166-1280(00)00453-X",
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Studies on aliphatic polyesters. Part II : Ab initio, density functional and force field studies of model molecules with two carboxyl groups. / Blomqvist, Johanna; Mannfors, Berit; Pietilä, Lars-Olof (Corresponding Author).

In: Journal of Molecular Structure: THEOCHEM, Vol. 531, No. 1-3, 2000, p. 359 - 374.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Studies on aliphatic polyesters. Part II

T2 - Ab initio, density functional and force field studies of model molecules with two carboxyl groups

AU - Blomqvist, Johanna

AU - Mannfors, Berit

AU - Pietilä, Lars-Olof

PY - 2000

Y1 - 2000

N2 - This paper is a continuation of our study on the ester bond energetics. Here, model molecules for structural units of biodegradable polyglycolic and polylactic acids (HC(=O)–O–CH2–C(=O)–O–CH3 and HC(=O)–O–CH(CH3)–C(=O)–O–CH3), which contain two carboxyl groups in close vicinity to one another, have been considered. Rotations about the neighbouring C(sp3)–O(sp3) and C(sp3)–C(sp2) bonds adjacent to the CH2 or CH(CH3) group have been studied quantum chemically by ab initio and density functional methods (MP2, B3-LYP and B-LYP), using the standard Gaussian-type basis set 6-31G(d), as well as by the PCFF (Polymer CFF) force field. The quantum chemical results mostly are in good agreement with each other. However, for the C–O rotations, the Density Functional Theory (DFT) barriers are 0.5–3.1 kcal/mol lower than the corresponding MP2 ones. The conformational dependency of bond lengths, valence angles, and that of atomic charges also is similar in the MP2 and DFT methods. The changes in bond lengths with conformation are small, but the valence angles vary more and especially in high-energy states with low population they may open as much as 18°. The conformational dependence of the most significant atomic CHELPG charges also was found to be small, and the largest relative changes occurred in small charges that do not have a major impact on the electrostatic potential. The PCFF force field produced torsional energetics that was in serious disagreement with the quantum chemical results, especially in the case of the C–C rotations. By reoptimizing the pertinent torsion parameters of the PCFF force field, these disagreements could be removed.

AB - This paper is a continuation of our study on the ester bond energetics. Here, model molecules for structural units of biodegradable polyglycolic and polylactic acids (HC(=O)–O–CH2–C(=O)–O–CH3 and HC(=O)–O–CH(CH3)–C(=O)–O–CH3), which contain two carboxyl groups in close vicinity to one another, have been considered. Rotations about the neighbouring C(sp3)–O(sp3) and C(sp3)–C(sp2) bonds adjacent to the CH2 or CH(CH3) group have been studied quantum chemically by ab initio and density functional methods (MP2, B3-LYP and B-LYP), using the standard Gaussian-type basis set 6-31G(d), as well as by the PCFF (Polymer CFF) force field. The quantum chemical results mostly are in good agreement with each other. However, for the C–O rotations, the Density Functional Theory (DFT) barriers are 0.5–3.1 kcal/mol lower than the corresponding MP2 ones. The conformational dependency of bond lengths, valence angles, and that of atomic charges also is similar in the MP2 and DFT methods. The changes in bond lengths with conformation are small, but the valence angles vary more and especially in high-energy states with low population they may open as much as 18°. The conformational dependence of the most significant atomic CHELPG charges also was found to be small, and the largest relative changes occurred in small charges that do not have a major impact on the electrostatic potential. The PCFF force field produced torsional energetics that was in serious disagreement with the quantum chemical results, especially in the case of the C–C rotations. By reoptimizing the pertinent torsion parameters of the PCFF force field, these disagreements could be removed.

U2 - 10.1016/S0166-1280(00)00453-X

DO - 10.1016/S0166-1280(00)00453-X

M3 - Article

VL - 531

SP - 359

EP - 374

JO - Computational and Theoretical Chemistry

JF - Computational and Theoretical Chemistry

SN - 2210-271X

IS - 1-3

ER -