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Average Deviation (average + deviation)
Selected AbstractsAn efficient synthesis and crystal structure of novel 1-oxo-2-propyl-4-(substituted)phenylimino-1,2,3,4,5,6,7,8-octahydro[1,4,3]thiazaphosphorino[4,3- a][1,3,2]benzodiazaphosphorine 3-oxides,HETEROATOM CHEMISTRY, Issue 7 2002Junmin Huang A series of 1-oxo-2-propyl-4-(substituted)phenylimino-1,2,3,4,5,6,7,8-octahydro-[1,4,3]thiazaphosphorino[4,3-a][1,3,2]benzodiazaphosphorine 3-oxides (5a,g) has been synthesized in excellent yields via the reaction of 1-(2-bromoethyl)-2,3-dihydro-3-propyl-1,3,2-benzodiazaphosphorin-4(1H)-one 2-oxide with (substituted) phenyl isothiocyanates, which contain the proximate imino and phosphoryl groups in the fused heterocycle. The structures of all of the new compounds were confirmed by spectroscopic methods and microanalyses. The results from X-ray crystallography analysis of 5a showed that the proximate imino and phosphoryl groups are not coplanar due to their being jointly located in the fused heterocycle, thus having ring tension, and this then destroys the conjugation between the CN and the PO moieties. As a result, the length of the PC bond, measured as 1.8285(18) Å, is just the same as that of a PC bond not involved in conjugation (1.80,1.85 Å). Also, the C(1), C(2), S(1), C(3), P(1), and N(2) atoms of the [1,4,3]thiazaphosphorino moiety exist preferably in the boat conformation. The coplanar C(1), N(2), C(3), and S(1) atoms, within an average deviation of 0.0564 Å, form the ground floor of the boat conformation, whereas, the P(1) and C(2) atoms are on the same side of the coplanar structure with the distance of 0.7729 Å and 0.7621 Å, respectively. On the other hand, around the CN double bond, the P(1)C(3) bond and the N(1)C(11) bond are in a trans relationship because of the repulsive action of the n-propyl group in the 2-position of the title compound. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:599,610, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10041 [source] Comprehensive theoretical study towards the accurate proton affinity values of naturally occurring amino acidsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2006T. C. Dinadayalane Abstract Systematic quantum chemical studies of Hartree,Fock (HF) and second-order Møller,Plesset (MP2) methods, and B3LYP functional, with a range of basis sets were employed to evaluate proton affinity values of all naturally occurring amino acids. The B3LYP and MP2 in conjunction with 6-311+G(d,p) basis set provide the proton affinity values that are in very good agreement with the experimental results, with an average deviation of ,1 kcal/mol. The number and the relative strength of intramolecular hydrogen bonding play a key role in the proton affinities of amino acids. The computational exploration of the conformers reveals that the global minima conformations of the neutral and protonated amino acids are different in eight cases. The present study reveals that B3LYP/6-311+G(d,p) is a very good choice of technique to evaluate the proton affinities of amino acids and the compounds derived from them reliably and economically. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Quality control of protein standards for molecular mass determinations by small-angle X-ray scatteringJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2010Shuji Akiyama Small-angle X-ray scattering (SAXS) is a powerful technique with which to evaluate the size and shape of biological macromolecules in solution. Forward scattering intensity normalized relative to the particle concentration, I(0)/c, is useful as a good measure of molecular mass. A general method for deducing the molecular mass from SAXS data is to determine the ratio of I(0)/c of a target protein to that of a standard protein with known molecular mass. The accuracy of this interprotein calibration is affected considerably by the monodispersity of the prepared standard, as well as by the precision in estimating its concentration. In the present study, chromatographic fractionation followed by hydrodynamic characterization is proposed as an effective procedure by which to prepare a series of monodispersed protein standards. The estimation of molecular mass within an average deviation of 8% is demonstrated using monodispersed bovine serum albumin as a standard. The present results demonstrate the importance of protein standard quality control in order to take full advantage of interprotein calibration. [source] Ab initio energy calculations and macroscopic rate modeling of hydroformylation of higher alkenes by Rh-based catalystAICHE JOURNAL, Issue 12 2009Maizatul S. Shaharun Abstract Ab initio quantum chemical computations have been done to determine the energetics and reaction pathways of hydroformylation of higher alkenes using a rhodium complex homogeneous catalyst. Calculation of fragments of the potential energy surfaces of the HRh(CO)(PPh3)3 -catalyzed hydroformylation of 1-decene, 1-dodecene, and styrene were performed by the restricted Hartree-Fock method at the second-order MØller-Plesset (MP2) level of perturbation theory and basis set of 6-31++G(d,p). Geometrically optimized structures of the intermediates and transition states were identified. Three generalized rate models were developed on the basis of above reaction path analysis as well as experimental findings reported in the literature. The kinetic and equilibrium parameters of the models were estimated by nonlinear least square regression of available literature data. The model based on H2 -oxidative addition fitted the data best; it predicts the conversion of all the alkenes quite satisfactorily with an average deviation of 7.6% and a maximum deviation of 13%. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Experimental validation of a rigorous absorber model for CO2 postcombustion captureAICHE JOURNAL, Issue 4 2007Finn Andrew Tobiesen Abstract A rigorous rate-based model for acid gas absorption was developed and validated against mass-transfer data obtained from a 3-month campaign in a laboratory pilot-plant absorber in which the experimental gas,liquid material balance was within an average of 6%. The mass-transfer model is based on the penetration theory where the liquid film is discretized using an adaptive grid. The model was validated against all data and the deviation between simulated and averaged gas and liquid side experimental mass-transfer rates yielded a total variability of 6.26%, while the total average deviation was 6.16%. Simpler enhancement factor mass-transfer models were also tested, but showed slight over-prediction of mass-transfer rates. A sensitivity analysis shows that the accuracy of the equilibrium model is the single most important source of deviation between experiments and model, in particular at high loadings. Experimental data for the absorber in the integrated pilot plant are included. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Solubility of terephthalic acid in the reaction system oligomeric bishydroxybutyl terephthalates,1,4-butanediolPOLYMER ENGINEERING & SCIENCE, Issue 4 2009Hainan Huang The physical solubilities of terephthalic acid (TPA) in the reaction system oligomeric bishydroxybutyl terephthalates,1,4-butanediol (BD) are measured using an analytic method from 449 to 507 K. The reaction system is obtained by transesterification of dimethyl terephthalate and excess BD. These results are fitted with the solubility model based on the Margules equation, and the average deviation of the model is 1.20%; the fusion enthalpies ,Hfus of TPA and infinite-dilution activity coefficients ,,2 in the system are obtained by regressing of the experimental data. In addition, synthetic method is chosen to determine the total solubility which is complicated by chemical reaction, the results indicate that the chemical reaction start at 452,472 K. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] | ||||||||||