RESUMO

Petroleum-based plastics dominate everyday life, necessitating the exploration of natural polymers as alternatives. Starch, abundant and biodegradable, is a promising raw material. However, understanding the molecular mechanisms underlying starch plasticization has proven challenging. To address this, we employ molecular dynamics simulations, focusing on amylose as a model. Our comprehensive evaluation revealed that chain size affects solubility, temperature influenced diffusivity and elastic properties, and oleic acid expressed potential as an alternative plasticizer. Furthermore, blending glycerol or oleic acid with water suggested the enhancement amylose's elasticity. These findings contribute to the design of sustainable and improved biodegradable plastics.

Assuntos

Plásticos Biodegradáveis , Amido , Amilose , Ácido Oleico , Glicerol , Simulação de Dinâmica Molecular , Plásticos

RESUMO

The cation of the title solvated salt, C42H42N2P2 (2+)·2Br(-)·2CH2Cl2, lies on a crystallographic twofold rotation axis. The 1,2-di-amino-cyclo-hexane fragment has a chair conformation with two N atoms in a transoid conformation [N-C-C-N = 163.4 (2)°]. In the crystal, the cations are linked to the anions by N-H⋯Br and C-H⋯Br hydrogen bonds, forming a chain structure along the c axis. The di-chloro-methane mol-ecule takes part in the hydrogen-bond network through C-H⋯π and C-H⋯Br inter-actions.

RESUMO

In the title compound, C28H22OP2, each of the P atoms has an almost perfect pyramidal geometry, with C-P-C angles varying from 100.63 (10) to 102.65 (9)°. In the crystal, neighbouring mol-ecules are linked via weak C-H⋯π inter-actions, forming supra-molecular chains along the b-axis direction.

RESUMO

In the title salt, C23H21NOP(+)·Br(-), the dihedral angles between the phenyl rings are 70.41 (18), 73.6 (2) and 80.85 (19)°. In the crystal, neighboring mol-ecules are linked through an N-H⋯Br hydrogen bond and four weak C-H⋯Br contacts, forming a three-dimensional network.

RESUMO

Kinetic modeling using nonlinear differential equations is proposed to analyze the spontaneous generation of enantiomeric excess in the autocatalytic addition of diisopropylzinc to prochiral pyrimidine carbaldehydes (Soai reaction). Our approach reproduces experimentally observed giant chiral amplification from an initial enantiomeric excess of <10(-6)% to >60%, high sensitivity and positive response to the presence of minute amounts of chiral initiator at concentrations <10(-14) M, and spontaneous absolute asymmetric synthesis from achiral starting conditions. From our numerical simulations using kinetic schemes derived from the Frank model, including stereospecific autocatalysis and mutual inhibition, we have shown that it is possible to reproduce the mirror-symmetry-breaking behavior of the Soai reaction under batch conditions leading to a bimodal enantiomeric product distribution. Mirror-symmetry breaking was found to be resistant to a loss of stereoselectivity up to 30%. While the mutual inhibition between enantiomers seems to originate from the presence of dimerization equilibria, the exact nature of the autocatalytic stereoselective process still remains to be revealed. From the kinetic viewpoint, simple autocatalysis involving monomers as the catalytic species is consistent with all reported experimental effects of the Soai reaction.

RESUMO

Dichloro and chloromethyl Ga(III) complexes of general formulae [XClGa-eta2-{R2P(E)NP(E'R'2-E,E'}](X = Cl, R, R'= Ph, E, E'= O (1), S (2), Se (3); R = Ph, R'= OEt, E = O, E'= S (4); R = Me, R'= Ph, E, E'= S (5) and X = Me, E, E'= O (6), S (7), Se (8)) were synthesised by either metathesis reactions between GaCl3 and the potassium salt of the ligand (X = Cl) or by methane eliminations from in situ prepared GaMe2Cl and the protonated ligands LH (X = Me). Redistribution reaction of (3) in either CDCl3 or THF afforded the solvent-free tetracoordinate gallium spirocycle cation [Ga-{eta2-{Ph2P(Se)NP(Se)Ph2-Se,Se'})2]+ (9+). The molecular structures of complexes 2, 4, 5, 7 and 9(+) show non-planar gallacycle rings.