Sequence analysis and kinetic study of the polymerization of 1,4-bis(hydroxydimethylsilyl)benzene with sir2Cl2

²⁹Si NMR rate studies of the bulk reaction of 1,4-bis(hydroxydimethylsilyl)benzene (BHB) with dichlorodimethylsilane, dichloromethylphenylsilane, and dichlorodiphenylsilane show a very rapid kinetic equilibrium giving aryl-SiMe₂Cl groups in place of the aryl-SiMe₂OH of the BHB and OH groups in place of Cl in the dichlorosilane. This is followed by a slow condensation polymerization of the 1,4-bis(chlorodimethylsilyl)benzene with the hydroxy terminated disilane groups. The very rapid initial rates could be followed with ²⁹Si NMR using the INEPT pulse sequence despite the very long ²⁹Si relaxation times. Condensation polymerization is complete within minutes for BHB + SiMe₂Cl₂, but hours and days are required for the SiMePhCl₂ and SiPh₂Cl₂, respectively, at +22°C. Initial reaction kinetics in the presence of Cr(acac)₃ are not identical to those obtained using the INEPT pulse sequence and no relaxation reagent.     

Growth and characterization of l-prolinium picrate single crystal: A promising NLO crystal

l-Prolinium picrate was synthesized and its solubility in the mixed solvent of acetone and water was estimated. Employing temperature reduction method crystals of size 22×4×3 mm³ were grown. The cell dimensions were obtained by single-crystal X-ray diffraction study. FT-IR, UV–vis–NIR and fluorescence spectral analyses were carried out for the grown crystals. The optical band gap estimated for this crystal is about 2.4 eV. Thermogravimetric study was carried out to determine the thermal properties of the grown crystal. Kurtz powder second harmonic generation (SHG) efficiency measurement revealed that the SHG efficiency is about 52 times that of potassium dihydrogen orthophosphate. Mechanical strength was tested by Vicker's microhardness test.     

Three-dimensional numerical study of jet-in-crossflow characteristics at low Reynolds number

A numerical study of a square jet in a cross flow is carried out at a Reynolds number of 100. The flow field and heat transfer characteristic downstream of the jet have been explored by solving three-dimensional unsteady Navier–Stokes equations and energy equation using higher order spatial and temporal discretization. The projection of vortical structure on a plane is seen to give the component of vortex normal to the plane. Four combinations of velocity profile namely (1) uniform crossflow and uniform jet, (2) laminar boundary layer crossflow and uniform jet, (3) uniform crossflow and parabolic jet profile, and (4) laminar boundary layer crossflow and parabolic jet are compared at same phase to see their effect on the flow field and heat transfer characteristic. All the four cases are seen to exhibit unsteadiness but the jet with parabolic profile is seen to show stronger unsteadiness. The instantaneous vortical structures of all the cases at the same phase show that the structures are more complex for the jet with parabolic velocity profile. The temperature field is seen to be correlated with the vortical structures. Comparison of the time averaged flow field reveals that the jet penetration is the highest for the jet having parabolic profile and boundary layer crossflow. The adiabatic effectiveness is observed to be more for the jet with uniform velocity profile and uniform crossflow and was least for the jet with parabolic velocity profile and boundary layer crossflow.     

Effect of Gravity on Collective Excitations of a Quasi Two-Dimensional Bose Einstein Condensate in an Anharmonic Trap

Using variational method, the wave function of a quasi two-dimensionalBose-Einstein Condensate in an anharmonic trap is analyzed and the influence of gravity on the collective excitations is studied. It is found that the effect of gravity on the condensate has got crucial dependence on the anharmonicity of the trap.     

XtalFluor‐E: An Efficient Reagent for Synthesis of Oxazolines from Carboxylic Acids and O‐Silylated Amino Alcohols

An efficient protocol has been developed for the synthesis of 2‐oxazolines from carboxylic acids and silylated amino alcohols. The advantage of this method was demonstrated by preparing O‐silylated amino alcohols. The reaction proceeds via in situ desilylation of O‐silylated amide followed by cyclization. Studies on silyl deprotection were carried out to explain yield for 2‐oxazolines.     

Metal free synthesis of 1‐azaspiro[4.4]nonane‐3‐one system via reactions of nitrones with 1,1‐disubstituted allenes

In the cycloaddition reaction between fluorenone N‐aryl nitrones and 1,1‐disubstituted allenes, the initially formed cycloadduct underwent facile [1,3] shift to give 1′‐phenylspiro[fluorene‐9,2′‐pyrrolidin]‐4′‐ones. Although 1′‐phenylspiro[fluorene‐9,2′‐pyrrolidin]‐4′‐ones are stable in solid state, a few of them underwent facile aerial oxidation in solution to give the corresponding 1′‐phenylspiro[fluorene‐9,2′‐pyrrolidine]‐4′,5′‐diones in excellent overall yields.     

Microwave assisted one pot synthesis of 2-ethylamino benzimidazole,benzoxazole and benzothiazole derivatives

A rapid and efficient one-pot method for the synthesis of 2-ethylamino benzimidazole, benzoxazole, and benzothiazole derivatives has been described. The reaction of o-phenylenediamines or o-aminophenols or 2-mercaptoanilines with EDC.HCl under microwave irradiation afforded the corresponding 2-ethylamino benzimidazole, benzoxazole and benzothiazole derivatives in excellent yields.     

An alternative total synthesis of Patulolide A

A new total synthesis of [R]‐Patulolide A from readily available (R)‐propylene epoxide obtained using the asymmetric synthetic approach is reported. The key reactions involved are ozonolysis and Yamaguchi macrolactonization, resulting in the ring system.