Synthesis, Spectral, Thermal and CO2 Absorption Studies on Birnessites Type Layered MnO6 Oxide

Birnessite type layered MnO₆ oxides with increased crystallinity were synthesized from six carbohydrates and three dihydric phenols viz., dextrose, starch, fructose, galactose, maltose, lactose, catechol, resorcinol, quinol and KMnO₄ through the formation of a sol–gel. All of the MnO₆ oxides were characterized by powder XRD. The strong signal at 2θ ~ 12° corresponding to 7.4 Å refers to the Mn–Mn distance between the adjacent layers. The interlayer volume is dispersed with K⁺ ions and H₂O molecules. The presence of interlayer K⁺ ions is indicated by a signal at 25°, corresponding to a distance of 3.5 Å. IR spectra of the oxides show signature bands at ca. 500 cm^?1 due to the stretching modes occurring for MnO₆ entity. A broad band observed at ca. 3300 cm^?1 is due to interlayer water molecules. Thermal analysis indicated three stage decomposition with the formation of MnO₂ at ca. 600 °C through the intermediate formation of Mn(OH) _n . The MnO₆ exhibited a remarkable CO₂ scrubbing ability, which has also been investigated.     

Crystal and molecular structures of 1,4-dihydro-6-methyl-5-N,N-diethylcarbamoyl-4-phenyl-2(3H)-pyrimidinethione (1) and 1,4-dihydro-6-methyl-5-N-methyl carbamoyl-4-(2′-nitrophenyl)-2(3H)-pyrimidinethione hemihydrate (2)

The crystal structure of 1,4-dihydro-6-methyl-5-N,N-diethylcarbamoyl-4-phenyl-2(3H)-pyrimidinethione, C₁₆ H ₂₁ N ₃OS (1), is monoclinic, space group P2₁/n, a = 6.818(1), b = 13.211(2), c = 18.807(3) Å, = 99.53(1)°, V = 1670.6(4) ų, Z = 4 and d _cal = 1.206 Mg/m³, R = 0.042 (wR = 0.119) for 190 parameters and 2560 observations with I 2(I) and 1,4-dihydro-6-methyl-5-N-methyl carbamoyl-4-(2-nitrophenyl)-2(3H)-pyrimidinethione hemihydrate, C₁₃ H ₁₄N₄O₃S 0.5H₂O, (2), is triclinic, space group P1, a = 7.513(1), b = 14.381(2), c = 15.506(2)Å, = 114.95(2), = 98.11(1), = 93.55(1)°, V = 1490.0(3) ų, Z = 4 and d _cal = 1.406 Mg/m³, R = 0.062 (wR = 0.165) for 388 parameters and 3094 observations with I 2(I).The compound 2 crystallized having two molecules in the asymmetric unit, which can be regarded as monohydrated dimers, and forming a hydrate. The conformation of the central heterocyclic ring (1,4-dihydropyrimidine) in both compounds was found to be close to a half-chair conformation. The 2-nitrophenyl substituent in 2 is in the axial synperiplanar orientation. In both compounds, the conformation of the 3-substituted carbamoyl group appears to be influenced by hydrogen bonding with anticlinal orientation observed for carbonyl groups serving as hydrogen bonding acceptors.     

Steady nonlinear hydromagnetic flow and heat transfer over a stretching surface of variable temperature

The steady nonlinear hydromagnetic flow of an incompressible, viscous and electrically conducting fluid with heat transfer over a surface of variable temperature stretching with a power-law velocity in the presence of variable transverse magnetic field is analysed. Utilizing similarity transformation, governing nonlinear partial differential equations are transformed to nonlinear ordinary differential equations and they are numerically solved using fourth-order Runge–Kutta shooting method. Numerical solutions are illustrated graphically by means of graphs. The effects of magnetic field, stretching parameter and Prandtl number on velocity, skin friction, temperature distribution and rate of heat transfer are discussed.