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Three Isomers (three + isomer)
Selected AbstractsStereoselective Synthesis of Three Isomers of tert -Butyl 5-Hydroxy-4-methyl-3-oxohexanoate through Alcohol Dehydrogenase-Catalyzed Dynamic Kinetic ResolutionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Steffen Lüdeke Abstract Regioselective reduction of the 5-keto group of tert -butyl 4-methyl-3,5-dioxohexanoate (1) leads to a stereodiad of tert -butyl 5-hydroxy-4-methyl-3-oxohexanoate (2). Alcohol dehydrogenases from Lactobacillus brevis (LBADH), Rhodococcus sp. (RS 1-ADH) and Saccharomyces cerevisiae (YGL157w) reduce 1 under dynamic kinetic resolution conditions, thereby establishing two chiral carbons with a single reduction step. While it had been shown previously that LBADH reduction of 1 stereoselectively leads to syn -(4S,5R)- 2, alcohol dehydrogenase-mediated dynamic kinetic resolution now allows easy access to syn -(4R,5S)- 2 (RS 1-ADH; 97.6% ee, syn:anti=92:8, 66% conversion, 37% isolated yield) and anti -(4S,5S)- 2 (YGL157w; 90% ee, anti:syn=93:7, 64% conversion, 42% isolated yield), as well. Thus three out of four possible stereoisomers were formed selectively upon reduction of 1. [source] The Kinetic Modeling of Strong Diffusion-Limited Reaction with Cyclization for Three Isomers , Diallyl Ortho-, Iso- and Tere - Phthalate in a BulkMACROMOLECULAR REACTION ENGINEERING, Issue 3 2007Iztok Hace Abstract Free radical polymerization kinetic in a bulk for three diallyl phthalate isomers , diallyl orthophthalate, diallyl isophthalate and diallyl terephthalate was investigated in a temperature range from 50 to 70,°C initiated with dicyclohexan peroxydicarbonate as initiator at three different initiator concentrations. Conversion points were measured using Fourier Transform Raman measurements. A new kinetic model for polymerization of three diallyl phthalate isomers was developed. It demands the inclusion of only two new kinetic parameters kDegC and kpc which were obtained as a ratio kDegC/kpc from an additional set of experiments conducted. Computed conversions from the proposed kinetic model show good agreement with the conversion and molecular weight measured data for all three investigated diallyl phthalate isomers. [source] cis-Enhanced Cyclopropanation Catalysts: Reaction Chemistry of Three Isomers of Rh2[N(C6H5)COCH3]4.CHEMINFORM, Issue 26 2003Cassandra T. Eagle Abstract For Abstract see ChemInform Abstract in Full Text. [source] Theoretical Investigation on the Absorption and Emission Properties of the Three Isomers of Bis(thiocyanato)(2,2,-bipyridyl)platinum(II)CHINESE JOURNAL OF CHEMISTRY, Issue 9 2007Xiao-Ying Hu Abstract This paper presents a Density Functional or Time Dependent Density Functional (DFT/TDDFT) study of the molecular and electronic structures, optical absorption and emission spectra of three linkage isomers:bis(isothiocyanato-S)(2,2,-bipyridyl) platinum(II) ([Pt(SCN)2(bpy)]), (isothiocyanato-S)(thiocyanato-N)-(2,2,-bipy- ridyl) platinum(II) ([Pt(SCN)(NCS)(bpy)]), and bis(thiocyanato-N)(2,2,)-bipyridyl)platinum(II) ([Pt(NCS)2(bpy)]), in which different coordination ligands based on the N- and S-coordination of the thiocyanato ligands control the luminescent color. The electronic structures were studied using the B3LYP functional. Optimized geometries were compared to the experimentally observed structures. TDDFT calculation was carried out to investigate the excited singlet and triplet states. Calculations have been performed both in vacuo and in solvents, using a polarized continuum model (PCM) to account for solute-solvent interactions. Inclusion of the solvent led to a significant energy change, and as a consequence, the computed spectrum calculated in the presence of the solvent was in good agreement with the experimental determinations. The first two absorptions were found to originate from mixed platinum-SCN (or NSC) to bipyridyl-,* transitions rather than pure metal-to-ligand-charge-transfer (MLCT) transitions, whereas the higher-energy bands arose from intraligand ,,,* transitions. The stretching frequencies of C,N have been calculated both in the ground and excited states, which are relative to the charge transition during the excitation. In addition, different sizes of basis sets were also discussed in this paper. [source] | ||||||||||