Alumina-supported Mn(II), Co(II), Ni(II) and Cu(II) N,N-bis(salicylidene)-2,2-dimethylpropane-1,3-diamine complexes: Synthesis, characterization and catalytic oxidation of cyclohexene with tert-butylhydroperoxide and hydrogen peroxide

New square-planar manganese(II), copper(II), nickel(II) and cobalt(II) complexes of a tetradentate Schiff-base ligand “N,N-bis(salicylidene)-2,2-dimethylpropane-1,3-diamine, H₂[salpnMe₂]” have been prepared and characterized by elemental analyses, IR, UV–Vis, conductometric and magnetic measurements. The results suggest that the symmetrical Schiff-base is a bivalent anion with tetradentate N₂O₂ donors derived from the phenolic oxygen and azomethine nitrogen. The formulae was found to be [M(salpnMe₂)] for the 1:1 non-electrolytic complexes. Alumina-supported metal complexes (ASMC; [M(salpnMe₂)/Al₂O₃]) catalyze the oxidation of cyclohexene with tert-buthylhydroperoxide (TBHP) and hydrogen peroxide. Oxidation of cyclohexene with TBHP gave 2-cyclohexene-1-one, 2-cyclohexene-1-ol and 1-(tert-butylperoxy)-2-cyclohexene whereas, oxidation with H₂O₂ resulted in the formation of cyclohexene oxide and cyclohexene-1,2-diol. Manganese(II) complex supported on alumina “[Mn(salpnMe₂]–Al₂O₃” shows significantly higher catalytic activity than other catalysts.     

Reduction of formaldehyde emission from plywood

The aim of this work is to evaluate performances of tannin-based resins designed as adhesive in the plywood production. For this purpose, a part of phenol formaldehyde (PF) and melamine formaldehyde (MF) in the classic adhesive formulation was replaced by tannin. The physical properties of the formulated resins (rheological characterization, etc.) were measured. In order to analyze the mechanical performance of tannin-based resins, plywood panels were produced and the mechanical properties including tensile strength wood failure and three-point bending strength were investigated. The performance of these panels is comparable to those of plywood panels made by commercial PF and MF. The results showed that the plywood panels bonded with tannin–PF (PFT) and tannin–MF (MFT) resins exhibited better mechanical properties in comparison to the plywood panels made of commercials PF and MF. The introduction of small properties of tannin in PF and MF resins contribute to the improvement of the water performance of these adhesives. The formaldehyde emission levels obtained from panels bonded with tannin-based resins were lower than those obtained from panels bonded with control PF and MF. Although there are no actual reaction at all between PF, MF, and tannin, addition of tannin significantly improves the water resistance of PF and MF resins. This is a novel finding that manifests the possibility of replacing a convention PF and MF resins by tannin. Modified adhesive is one of the goals in the plywood production without changing any of their production conditions with improvement to their overall properties.     

Solvent-free,mild, facile,and rapid one-pot three-component synthesis of some novel imidazo[2,1-b]naphtho[1,2-e][1,3] thiazin-10-ones using p-TSA

Novel [2,1-b]naphtho[1,2-e][1,3]thiazin-10-ones were synthesized in 63–89% yield via a three-component reaction of an aromatic aldehyde, β -naphthol, and thiohydantoin in the presence of 10 mol% p-toluene sulfonic acid under solvent-free conditions. This is the first protocol to be reported for the synthesis of the title compounds. The significant features of the present protocol are simplicity, high yields, eco-friendliness, and convenient purification that does not require chromatography.     

Preparation and characterization of nano-porous silica aerogel from rice husk ash by drying at atmospheric pressure

Silica aerogel, a mesoporous material, was prepared from rice husk ash by sol–gel method and dried under atmospheric pressure. In this method, rice husk ash, which is rich in silica, was extracted with sodium hydroxide solution to produce a sodium silicate solution. This solution was neutralized with acid to form a silica hydrosol, and a small amount of tetraethyl silicate (TEOS) to form a gel. The aged gel was washed carefully by distilled water and ethanol and finally dried under atmospheric air. The prepared silica aerogels were characterized by XRF, FT-IR, TG, DTA, DTG, XRD, BET and SEM measurements. The synthesized TEOS-doped silica aerogel was a light solid with specific surface area of 315 m²/g, pore volume 0.78 cm³/g, average pore size 9.8 nm, bulk density 0.32 g/cm³ and porosity 85%.