Wetting behavior of magnesite and dolomite surfaces

Magnesite and dolomite are salt-type minerals that show similar chemical composition and flotation behavior due to same crystal structure, and sparingly soluble nature. The surface properties of minerals play a major role in determining their separation from each other in processes such as flotation. During flotation process, selectivity problem arises between magnesite and associated gangue minerals such as dolomite. There is a close relationship between floatability of minerals and their contact angles. Therefore, surface hydrophobicity of magnesite and dolomite minerals was investigated by contact angle measurements in the absence and presence of flotation reagents.Magnesite and dolomite show hydrophilic properties and they have got a small contact angle (magnesite ∼10.4° and dolomite ∼6.6°) in distilled water in the absence of any surfactant. The contact angle values at the magnesite and dolomite surfaces remained at 9.7°-10.9° in the presence of petroleum sulphonates (R825 and R840) while sodium oleate affected hydrophobicity of magnesite, and the contact angle value increased up to 79°. The contact angle value of 39° at dolomite surface was obtained in the solution of sodium oleate, respectively.     

transformation between diphosphinoamines and iminobiphosphines: a reversible P-N-P <--> N=P-P rearrangement triggered by protonation/deprotonation

The protonation of diphosphinoamines attached to pyridine at the ortho-position quantitatively affords the corresponding iminobiphosphine isomers. The starting material can be recovered quantitatively by deprotonation with base. The system represents a new type of molecular switch.     

Effects of cosolvents cetyltrimethylammonium bromide on the thresholds for nucleation of nitrogen in aqueous solutions

The decomposition of ammonium nitrite in water creates a supersaturated solution of nitrogen. The same process occurs in water-organic solvent mixtures. Acetone, dioxane, dimethylsulfoxide (DMSO) and dimethylformamide (DMF) are the cosolvents used in this study. The limits of supersaturation of nitrogen (C _SL /mol L^–1) were determined in all of these solvent mixtures by releasing the dissolved gas sonicationally and measuring the volume of released gas. C _SL was generally increased in the presence of cosolvents. The effectiveness sequence of organic solvents was found to be as DMF SL and all of the measured quantities of this study were generally affected by micelle formation.     

Synthesis of tricyclic ring systems: [2+2] ketene addition reaction for preparation of tricyclic ketone,alcohol, and lactone derivatives

The addition of dichloroketene to 1,4-cyclohexadiene was examined. Dichloroketene, which was easily prepared from trichloroacetyl chloride and Zn–Cu, reacted with 1,4-cyclohexadiene in the presence of POCl₃ to afford novel racemic products of single addition (5) and double addition (6). The adducts 6 and 7 were reacted separately with MCPBA (meta-chloroperbenzoic acid), H₂O₂, LiAlH₄, and cis-diol 10 was reacted with PCC (pyridinium chlorochromate) to afford lactone, alcohol, and ketone derivatives likely to exhibit biological activity. The structures of all the racemic molecules mentioned in the article were determined from ¹H NMR, ¹³C NMR, MS, and IR data.     

High-Temperature Bromination XIII [1]: Bromination of Dimethyl 7-Oxabicyclo[2.2.1]hepta-2,5-diene-2,3dicarboxylate

The electrophilic addition of bromine to dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate 10 at 0 and –60°C led in high yield to the formation of dibromide 11. However, high-temperature bromination of 10 in carbon tetrachloride at 77°C gave four products 12–15, three of them with nonrearranged skeleton. Similarly, bromination of the dibromides 14 and 15 at 77°C yielded the nonrearranged tetrabromides 13 and 16, respectively. The structure of the tetrabromide 13 was solved by single-crystal X-ray analysis. The formation mechanism is discussed and supported by calculations.     

PN Bond Cleavage during the Insertion of Carbon Fragments into PIIIN Bonds in Bis(diphenylphosphino) Amines

The reaction of tertiary amine functionalized phosphines with aromatic and aliphatic aldehydes gives insertion of carbon fragments into the P^III? N bonds or P^III? N bond cleavage. The reaction of bis(diphenylphosphino) amines, 1a – 1c , with two equiv. of aldehydes in toluene afforded the P^III? N bond inserted products, 2a – 4a, 4b – 6b , and 3c – 5c , in moderate‐to‐good yield. The products were characterized by IR, ¹H‐ and ³¹P‐NMR spectroscopy and elemental analysis.     

Oxidation of Alcohols to Carbonyl Compounds, Benzylic Carbons to their Ketones, and Arenes to their Quinones with Molecular Oxygen in Subcritical Water

Summary. Molecular oxygen is used as an efficient oxidant for the conversion of alcohols into carbonyl compounds, benzylic carbons to their ketones, and arenes to their quinones in subcritical water in the absence of catalysts. The procedure utilizes water and does not require support materials and metal salts.