| In vitro: |
| Journal of Molecular Structure: THEOCHEM, 1998, 432(3):247-255. | | Internal rotation barriers: ab initio calculations on substituted ethyl benzoates and benzoic acids as models for polyester flexibility.[Reference: WebLink] |
METHODS AND RESULTS:
The rotational barriers of several ortho and para substituted ethyl benzoates (EB) and benzoic acids (BA), used as models for internal rotation in PET polymers, have been calculated at the SCF and MP2 levels. Since there were no experimental data available on internal rotations in EB and BA, barriers to rotation in benzaldehyde and three similar compounds were calculated as benchmarks and compared with experimental data. Calculated barriers in the benzaldehydes were within 1 kcal/mol of the experimental values. The tentative conclusion from the rotation barrier results on model compounds is that PET-type polymers made from high-rotation-barrier monomers like ortho-hydroxy-terephthalic acid should have larger internal barriers to rotation than unsubstituted PET, leading to more rigid polymers with higher glass transition temperatures, Tg, and an altered degree of crystallinity. We found an unexpectedly low barrier to rotation of 2.3 kcal/mol for ortho X-CH3, compared to about 5 kcal/ mol for ortho X-H.
CONCLUSIONS:
Based on these model studies, we would expect that a PET-type polymer made from ortho-methyl substituted terephthalate would be more flexible, would have a lower glass transition temperature and different degree of crystallinity with accompanying change in void space. | | Chinese journal of entomology, 1990. | | Ethyl benzoate: an impact ovipositional attractant of the oriental fruit fly, Dacus dorsalis Hendel.[Reference: WebLink] |
METHODS AND RESULTS:
Analysis and bioassays of extracts of guava fruits using GC and GC/MS showed that the oviposition attractant of Dacus dorsalis [Bactrocera dorsalis] consisted of several components, including ethyl benzoate. |
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