Internal Rotation of Ester Linkage in Phenyl Benzoate and Hydroxybenzoic Acid Dimer as Models of Aromatic Polyesters Using Density Functional Theory

Imase, Tatsuya; Kawauchi, Susumu; Watanabe, Junji

doi:10.1002/1521-3919(20010601)10:5<434::aid-mats434>3.0.co;2-s

Cited by 12 publications

(15 citation statements)

References 8 publications

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“…The rotational states about the bonds in the terephthalate linkage, which is planar, and equal probabilities of conformations in which the ester groups are trans and cis with respect to each other obtained using the PCFF force field, agree with the literature reports 5. The energy barrier for the ϕ 1 ( ϕ 4 ) bond of the terephthalate linkage, as derived using PCFF in our present study, is 11 kcal · mol −1 which is close to that derived from MP2/6‐31G* calculations (10.1 kcal · mol −1 )15 whereas B3LYP/6‐31G* yielded a value of 7.9 kcal · mol −1 14. The energy barrier for the ϕ 2 ( ϕ 3 ) (for the terephthalate linkage as in PCT) reported in the literature falls in the range of 2.4–8.1 kcal · mol −1 14 and our simulations yield a value of 5.24 kcal · mol −1 .…”

Section: Resultssupporting

confidence: 88%

“…The energy barrier for the ϕ 1 ( ϕ 4 ) bond of the terephthalate linkage, as derived using PCFF in our present study, is 11 kcal · mol −1 which is close to that derived from MP2/6‐31G* calculations (10.1 kcal · mol −1 )15 whereas B3LYP/6‐31G* yielded a value of 7.9 kcal · mol −1 14. The energy barrier for the ϕ 2 ( ϕ 3 ) (for the terephthalate linkage as in PCT) reported in the literature falls in the range of 2.4–8.1 kcal · mol −1 14 and our simulations yield a value of 5.24 kcal · mol −1 . This value is in reasonable agreement with the reported value of 4.8 kcal · mol −1 by calculations using MP2/6‐31G*(d 0 )15 and 5.05 kcal · mol −1 using the HF/STO‐3G optimization 16.…”

Section: Resultssupporting

confidence: 85%

“…A comparison of the conformational features of the ester fragments derived from PCFF based simulations here and those reported earlier, is described in brief in order to bring out the ability of this force field to simulate properties of polyesters as in the present study. Ab initio calculations (B3LYP with 6‐31G*) of phenyl benzoate and p ‐hydroxybenzoic acid were reported recently 14. The bond angle ∠C Ph C*O is 111.3° from 6‐31G* optimized geometry, and that derived from PCFF optimization in this study is 112°.…”

Section: Resultssupporting

confidence: 49%

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RIS Models and Unperturbed Chain Properties of Polyesters Containing 1,3‐Cyclobutylene and 1,4‐Cyclohexylene Linkages

Sulatha

Natarajan

2003

Macro Theory & Simulations

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Polyesters containing 1,3‐cyclobutylene and 1,4‐cyclohexylene linkages in the main chain are investigated using conformational energy calculations. Rotational isomeric state (RIS) models are developed for poly(1,4‐cyclohexylenedimethylene terephthalate) (PCT), poly(1,4‐cyclohexylenedimethylene 2,5‐dimethylterephthalate) (DMPCT), poly(1,4‐cyclohexylenedimethylene 1,4‐cyclohexylenedicarboxylate) (PCC), and poly(2,2,4,4‐tetramethyl‐1,3‐cyclobutylene terephthalate) (CBDO). In DMPCT, the ester linkage prefers skewed conformations with respect to the phenyl group to relieve the steric strain caused by the methyl groups. The methyl groups on the cyclobutanediol moiety in CBDO restrict the rotational freedom about the oxycyclobutylene linkage. The unperturbed dimensions as described by characteristic ratio and persistence length are calculated for the trans and cis configurations of these polyesters. CBDO shows highly extended chain conformations among these polyesters indicating relative chain rigidity of the backbone. For DMPCT and PCC, in their trans configuration, the chain dimensions decrease with an increase in temperature while for their cis configurations, the chain dimensions increase with temperature, arising from basic differences in the fragment structures that control the competition of the relative populations as affected by temperature. Temperature has negligible influence on the unperturbed dimensions of both isomeric linkages of CBDO, while this is true for the trans configuration of PCT. The study shows that induction of cyclobutylene groups in the main chain results in a greater rigidity for homopolyesters than for chains with cyclohexylene groups.

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Section: Resultssupporting

confidence: 88%

Section: Resultssupporting

confidence: 85%

Section: Resultssupporting

confidence: 49%

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RIS Models and Unperturbed Chain Properties of Polyesters Containing 1,3‐Cyclobutylene and 1,4‐Cyclohexylene Linkages

Sulatha

Natarajan

2003

Macro Theory & Simulations

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“…For example, the Z conformation in phenyl benzoate is preferred over E by 5-6 kcal/mol; with a rotation barrier of 10-13 kcal/mol. 20 This led us to consider cyclisation of the corresponding ether-tethered substrates.…”

Section: Figurementioning

confidence: 99%

Sequential Claisen Rearrangement and Intramolecular Heck Reaction as a Route to Medium-Ring Oxacycle-Fused Heterocycles

Chattopadhyay¹,

Neogi²,

Singha³

et al. 2008

Synlett

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A synthetic strategy based on tandem application of Claisen rearrangement and intramolecular Heck reaction as key steps has been developed for the synthesis of various hitherto unknown benzoxocine-and benzoxonine-fused coumarin and quinolone derivatives.Various normal-ring-size heterocycle-fused heterocyclic systems display interesting properties and there has been a continuous evolution of newer methodologies for the synthesis of such ring systems. 1 In contrast, medium-ring heterocycle-annulated heterocyclic systems are less known until recently when various metal-catalysed organic transformations made medium-sized rings more accessible. 2 The palladium-catalysed intramolecular Heck-type arylation reaction has been extensively used for the synthesis of heterocyclic rings of varying size and complexity. 3 However, medium-ring formation through such a procedure still poses challenges and therefore remains as an explorable exercise. Whereas with activated olefins (Michael-type olefinic fragments) only one mode of cyclisation (electronic controlled) is mostly observed, 4 mixtures of endo-and exo-cyclisation products are usually formed 5 during medium-sized-ring formation from intramolecular Heck reaction with unactivated olefins. 6 This difference in regioselectivity has been explained by the difficulties associated with the attainment of coplanar eclipsed orientation of the relevant moieties during the carbopalladation step ( Figure 1). However, with the increase in chain length exclusive endo-cyclisation leading to nine-or ten-membered heterocyclic rings has also been observed. 7 Figure 1We have been engaged for some time in the synthesis of medium-ring heterocycle-fused heterocyclic systems culminating in the development of synthetic routes to hitherto unknown oxepin-and oxocin-fused coumarins, 8 quinolones, 9 carbazole 10 and naphthalene derivatives, 11 based on tandem applications of Claisen rearrangement and ring-closing diene-or enyne metathesis. 12 The methodology has found application 13 in the synthesis of other medium-ring heteroannulated compounds. Herein, we report 14 a new methodology for the synthesis of mediumring oxacycle-annulated heterocycles based on tandem Claisen rearrangement 15 and Heck-type arylation reaction as key steps. In view of the known importance of furo-and pyranocoumarins 16 and their isosteric analogues furo-and pyrano-2-quinolones 17 we have chosen coumarin and 2-quinolone as the heterocyclic frameworks for the exploration in the present study.

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“…11,14 Even if the present polymer is nonrigid, but semiflexible, it is still difficult to illustrate the folding lamellar structure. In fact, according to the computer MD simulation, 15,16 only a loose loop comprising more or less than 10 repeating units is allowed. Formation of such a loop would significantly disturb the uniaxial orientational order and so is energetically unfavorable in the nematic liquid crystals.…”

mentioning

confidence: 99%

Aromatic Polyesters with Flexible Side Chains. 8. Studies on Long Periodical Structure Observed in Layered Crystalline Phase

Fu¹,

Nematsu²,

Sone³

et al. 2000

Macromolecules

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Long periodical structure was studied for the crystal of a rigid-rod liquid crystalline BC-6 polyester composed of the 1,4-dihexyl ester of pyromellitic acid and 4,4‘-biphenol with small-angle X-ray scattering (SAXS) and transmission electron microscope (TEM) measurements. The highly oriented crystalline fibers which were prepared by spinning a nematic melt of the sample and succeeding annealing showed well-defined scattering maxima with a spacing in the range of 250−300 Å in the SAXS pattern and the corresponding clear stripes in the TEM photograph. The long spacing is attributed to the crystalline lamellae stacked along the chain axis. This is the first example of long periodical structure in the fully aromatic polymer systems. The origin of the long periodic structure is discussed.

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Internal Rotation of Ester Linkage in Phenyl Benzoate and Hydroxybenzoic Acid Dimer as Models of Aromatic Polyesters Using Density Functional Theory

Cited by 12 publications

References 8 publications

RIS Models and Unperturbed Chain Properties of Polyesters Containing 1,3‐Cyclobutylene and 1,4‐Cyclohexylene Linkages

RIS Models and Unperturbed Chain Properties of Polyesters Containing 1,3‐Cyclobutylene and 1,4‐Cyclohexylene Linkages

Sequential Claisen Rearrangement and Intramolecular Heck Reaction as a Route to Medium-Ring Oxacycle-Fused Heterocycles

Aromatic Polyesters with Flexible Side Chains. 8. Studies on Long Periodical Structure Observed in Layered Crystalline Phase

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