In this study, maleinized soybean oil triglycerides (SOMA) were reacted with epoxidized soybean oil triglycerides (ESO) to give plant oil-based thermoset polymers. To increase fracture toughness of the product, different amounts of SOMA was replaced by maleic anhydride grafted polypropylene (MMPP) (Epolene E43, maleate content 2.9%, M n ¼ 3900 and Polybond 3200, maleate content 1%, M n ¼ 1,10,000). The improvement in mechanical properties was monitored. The characterizations of the products were done by DMA, DSC, TGA, and IR spectroscopy. ESO-SOMA and ESO-SOMA-MMPP polymers are crosslinked rigid infusible polymers. ESO-SOMA-MMPP(E43) and ESO-SOMA-MMPP(PB3200) showed a phase change at 146 and 169 C, respectively, probably due to the melting transition of the MMPP backbone. Storage moduli of the two polymers at 35 C were 54.6 and 246.1 MPa, respectively. Storage moduli and the impact strength of the polymers increased with MMPP content and with MMPP molecular weight.
[reaction: see text] The stereochemistries of [3,3] sigmatropic Johnson-Claisen (J-C) rearrangements of six intermediates studied in the synthesis of gelsemine were modeled using DFT methodology. The possible origins of the rearrangement stereoselectivity are explored and compared with the experimentally suggested rationalizations by Danishefsky et al. (J. Am. Chem. Soc. 2002, 124, 9812-9824). In the intermediate used for the J-C rearrangement in the Danishefsky synthesis (3), the closure is inhibited by the repulsive interactions between the enolate terminus and the carbon atoms of the double bond as well as with the hydrogen on C7. The closure is favored by stabilizing interactions between the enolate terminus and the H's of the oxetane ring.
The Claisen rearrangement of 1-methyl-2-isopropyoxycarbonyl-6-propyl allyl vinyl ether catalyzed by copper(II) bisoxazoline (Cu-box) has been investigated using density functional theory. Both the phenyl- and tert-butyl-substituted Cu-box systems have been studied. Three different reaction media (vacuum, CH2Cl2, CH3CN) have been considered. In vacuum, the phenyl Cu-box catalyzed reaction yields a (1R,6R) configured major product with a low selectivity. The solvent induces a higher selectivity and a reversal of the absolute configuration (1S,6S). However, the tert-butyl Cu-box catalyzed reaction yields (1R,6R) as the major product both in the gas phase and in the solvent with a good selectivity. Although chair-like TSs are lower in energy than boat-like TSs, the energy difference is small. This is because in the presence of the catalyst the distance between the allyl and vinyl parts of the substrate is relatively large, and thus the steric repulsion between them is smaller than would normally be expected for boat-like structures. The enantioselectivity of tert-butyl Cu-box originates from the steric interactions between the substrate and the catalyst, which are less important for the phenyl Cu-box where the enantioselectivity is determined by the solvent effects.
T he purpose of crystal engineering is to explore new materials with striking properties that can be used in a variety of implementation areas. Metal complexes with an important place in crystal engineering consist of anions or molecules called ligands, which bind to a metal cation and metal atom at the center of symmetry. Metal complexes have been the subject of interest with the diversity of their structures for many years. The structures of metal complexes were determined to be influenced by the biological and physical properties of metal cations, ligands and intermolecular interactions [1][2][3][4]. Medical inorganic chemistry, which has an important place in materials science, is a multidisciplinary field consisting of chemistry, pharmacology, toxicology, and biochemistry. Medical chemists focus on the design and synthesis of new metal-based molecules with greater enhanced biological activity, better selectivity, low toxicity and multiple roles of mechanical effects to overcome the Article History:
[reaction: see text] We comment on the effects of angular substitution on the outcome of a Pb(OAc)4 (LTA) mediated heterodomino reaction, with selected bicyclic unsaturated 1,2-diols, which is considered to proceed through a series of transformations in a single vessel. The first two, oxidative and pericyclic, are followed by the key step, an electrophilic addition of LTA to the olefin, responsible for the course of the domino process. In this study, the electrophilic addition of LTA to the double bond has been modeled with B3LYP, where the 6-31G* basis set is used for C, O, and H atoms and the LANL2DZ method is used for Pb. The modeling in the gaseous phase and in solution has revealed the concerted nature of the addition of LTA to the double bond of the intermediate. The fact that LTA adds from the same side as the substituent R, for R=H and from the opposite side when R=CH3 has been attributed to steric hindrance, which causes deformation of the olefinic intermediate.
In this study 4-methylpyridine (4MP), 4-vinylpyridine (4VP) and poly(4-vinylpyridine) (P4VP) were separately reacted with epoxidized soybean oil triglycerides (ESO) to give plant oil based thermoset polymers. The addition reaction of pyridine with epoxide followed by a rearrangement results in formation of pyridone units and these were polymerized via a Diels-Alder reaction. DMA, DSC, TGA and IR spectroscopy were used for the characterization of the products. 4MP-ESO, P4VP-ESO and P4VP-ESO-in situ polymers were crosslinked yielding rigid infusible polymers. Glass transition temperatures (T g ) of 4MP-ESO and P4VP-ESO-in situ were found as À10.5 and 70.5 (32.3 as shoulder) C respectively, by DMA analysis. Storage moduli of 4MP-ESO and P4VP-ESO-in situ at 25 C were 13.7 and 187.2 MPa, respectively.
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