A combined X-ray crystallography and theoretical study of PPh2CH2SPh and PPh2C6H4SMe ligands

Abstract

The solid-state structures of compounds PPh₂CH₂SPh (1) and PPh₂C₆H₄SMe (2) were determined by single crystal X-ray diffraction. Experimental results on the molecular structures of compounds 1 and 2 were supported by Hirshfeld surface analysis and Density Functional Theory (DFT). The computed values calculated at DFT level using B3LYP function with 6-311++G (3df, 3pd) (P, S) and 6-31G* (C, H) basis sets are in good agreement with the experimental results.     

Catalytic Transesterification of Coconut Oil in Biodiesel Production: A Review

Catalysis Surveys from Asia - Biodiesel is one of the renewable energy (RE) sources that has received much interest due to its promising properties. Recently, the use of coconut oil as biodiesel...     

Antibacterial and antioxidant activity of naphthofuranquinones from the twigs of tropical mangrove Avicennia officinalis

Abstract

Mangrove plants are endowed with various biologically active compounds which have potent antibacterial and antioxidant properties. In present study, a bioactivity-guided fractionation for antibacterial and antioxidant active metabolites from the twigs of Avicennia officinalis collected from Kuala Selangor Nature Park, Selangor, Malaysia gave 13 major fractions. The antibacterial activity of A. officinalis fractions using well-diffusion showed strong selectivity on the Gram-positive bacteria (Staphylococcus epidermidis, S. aureus and Bacillus subtilis) with minimum inhibition concentration (MIC) values of 0.156-5.00?mg/mL. However, no antibacterial activities were observed on the Gram-negative bacteria (Vibrio cholera, Enterobacter cloacae and Escherichia coli). The active antibacterial fractions were further isolated using several chromatographic techniques to give two naphthofuranquinones, namely, avicenol C (1) and stenocarpoquinone B (2). Meanwhile, the antioxidant activity of A. officinalis fractions were evaluated using DPPH radical scavenging assay exhibited low antioxidant activities. Molecular structure of the naphthofuranquinones was elucidated using 1?D and 2?D NMR spectroscopy.     

Enzymatic synthesis of kojic acid esters and their potential industrial applications

In this paper, enzymatic methods for the synthesis of 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one (kojic acid) esters are reviewed. Important process parameters related to the synthesis of kojic acid esters such as the type of immobilized lipase, solvent, temperature, initial water activity, water content, pH, metal salts, enzyme loading, substrates mole ratio, and acyl donors are highlighted and discussed. The properties of kojic acid esters related to their solubility, stability, cytotoxicity, depigmenting activity, tyrosinase inhibitory, metal-chelating, anti-oxidant, and other biological activities are also highlighted. At present, kojic acid and its esters are widely used in cosmetic and skin health industries as skin whitening agents. The advantages and disadvantages of various kojic acid esters are compared and possible industrial applications of these derivatives are also discussed.     

Phase behavior and crystal morphology in poly(ethylene succinate) biodegradably modified with tannin

Specific interactions, growth kinetics, and dendritic morphology in poly(ethylene succinate) (PESu) biodegradably modified with various contents of tannic acid (TA) were characterized using differential scanning analysis, Fourier-transform infrared (FTIR) spectroscopy, polarized-light optical microscopy, and atomic force microscopy. Strong interactions and highly retarded growth between PESu and a macromolecular ester with polyphenol groups, TA, interaction-induced highly retarded growth rates for the PESu/TA (80:20) composition are proven to lead to single-crystal-like dendrites when crystallized at high crystallization temperature (T _c). At T _c = 70 °C, the growth rate for neat PESu is 12 μm/min while it is dramatically depressed to one tenth-fold at 1.5 μm/min with 20 wt.% TA in the blend. Strong specific interactions between the carbonyl group of polyesters and the phenolic hydroxyl group of TA are confirmed by (1) the blend’s glass transition temperature (T _g)–composition relationship exhibits a sigmoidal curve, well fitted by the Kwei T _g model for miscible blends with large negative q = −90; (2) thermal analysis on crystal melting revealed an interaction parameter χ = −0.64 between PESu and TA; and (3) IR peak shifting analyzed using two-dimensional FTIR technique. A comparative blend of another polyester poly(hexamethylene sebacate) with TA, lacking the specific interactions, does not exhibit such single crystals upon similar melt crystallization.