Diastereomers of N-alpha-phenylethyl-t-butylsulfinamide: absolute configurations and predominant conformations

N-alpha-Phenylethyl-t-butylsulfinamide is a complicated system for determining molecular stereochemistry because of numerous possibilities for assigning the absolute configuration and a predominant conformation. Two diastereomers of N-alpha-phenylethyl-t-butylsulfinamide derived from (-)-(S)-alpha-phenylethyl amine, a (+)-diastereomer and a (-)-diastereomer, have been synthesized and their experimental chiroptical spectroscopic properties have been measured. These properties include vibrational circular dichroism, electronic circular dichroism and optical rotatory dispersion. Using these experimental data, in conjunction with corresponding density functional theoretical predictions, the absolute configuration and predominant conformations of these two diastereomers have been determined. Also, the absolute configuration of (-)-diastereomer has been independently confirmed by determining its structure from X-ray diffraction data.     

Dynamic correlation for MCSCF wave functions: An effective potential method

A method is suggested which allows the inclusion of dynamic correlation into CASSCF calculations. An effective Coulomb hole potential is added to the Hamiltonian. The potential has a simple form, which allows its implementation into existing LCAO programs using Gaussian integral packages. The parameters appearing in the potential are determined by fitting to empirical valence correlation energies for first row atoms. Calculations of ionization energies and electron affinities show considerable improvement compared to the MCSCF values. Test calculations on three molecules give the following results, H₂ r _e=0.745 (0.741) Å, D _e=4.62 (4.75) eV; N₂ r _e=1.099 (1.098) Å, D _e= 10.42 (9.91) eV; O₂ r _e=1.198 (1.207) Å, D _e=4.73 (5.21) eV. Experimental values within parenthesis. On leave from: Institute of Organic Chemistry, Polish Academy of Sciences, PL-01-224 Warszawa 42, ul. Kasprzaka 44, Poland.     

Enzymatic Apporoach to the Synthesis of Non-Racemic,P-Chiral Hydroxymethylphosphonates and Phosphinates

Abstract

α-Hydroxyalkanephosphonates and phosphinates exhibit interesting biologd achvlty whch IS highly dependent on theu absolute configumon Therefore, a search for efficient and general methods of the synthesis of enantlopure htle compounds continues As part of our studies on the use of enzymes in preparahon of non-racemic heteroorganic compounds,2 we have developed a hpasemediated lunebc resoluhon of racemic hydroxy- methylphosphonates and phosphinates, which is based on ather acetylatlon of the substrates 1, or hydrolysis of thar O-acetyl denvatlves 2 The absolute configurahon of the products has been determined by means of CD and chemical conelatlon     

Effect of processing consitions on the development of morphology in clay nanoparticle filled nylon 6 fibers

The effect of melt temperature on the phase behavior and preferential orientation development in Nylon 6/montmorillonite nanocomposites were investigated at melt spinning temperatures ranging from 230° to 250°C. The fibers were found to exhibit mostly γ crystalline form that is typical of Nylon 6 filled with montmorillonite nanoparticles. At higher take-up speeds α-crystals begin to appear in the crystalline phase. The presence of nanoparticles was found to impart substantial chain orientation levels even at low to moderate take up speeds reaching a plateau at moderate take up speeds. This was attributed to the increased spin line stress in the presence of nanoparticles that increase the overall viscosity due to their large contact areas with the polymer chains. This increased spinline tension was found to cause fiber breakup at moderate speeds. Increasing melt temperature from 230° to 250°C alleviated this problem.