摘要:

AbstractDual laser ionization (DLI) is a technique which can be used to detect trace elements in a flame by ionizing the analyte via a dual‐laser stepwise excitation. As a powerful method for flame diagnostics, DLI can detect trace amount of Na at a concentration of ppb (ng/mL), more sensitive by two orders of magnitude than laser‐enhanced ionization (LEI), in which only single laser is used. To demonstrate its potential in trace analysis, we compare the detection limit of DLI for Na with other methods utilizing LEI, atomic emission and laser atomic absorpt

ISSN:0009-4536    

DOI:10.1002/jccs.198800026

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThermolysis of (H2CPz′2)M(CO)4(H2CPz′2= bis(3,5‐dimethylpyrazol‐1‐yl)methane; M=Mo, W) in 1,2‐dimethoxyethane did not give the expected 16‐electron complexes, (H2CPz′2)M(CO)3, but gave dinuclear compounds, [(H2CPz′2)M(CO)3]2, probably containing two linear carbonyl bridges and no metal‐metal interactions. The dimers reacted with CH3CN to give mononuclear compounds, (H2CPz′2)M(CO)3(NCCH3), identical to the substitution products between (H2

ISSN:0009-4536    

DOI:10.1002/jccs.198800027

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractBy refluxing the anatase form of TiO2powder in phosphoric acid, the surface acidity was observed to increase. The amount of acid was determined by n‐butylamine titration in n‐heptane media, and was found to be proportional to the reflux period in phosphoric acid. XRD patterns and IR spectra revealed that the products contained a mixture of the anatase form of TiO2and titanium phosphate phases. Based on the calculated acid density on the surface, part of the titrant, n‐butylamine penetrated into the titanium phosphate layers. Further investigations using TGA, FT‐IR and TEM techniques along with surface area measurements indicated that the titanium phosphate phase was coated over the TiO2phase. The surface acidity of the phosphoric acid treated anatase increased due to the substitution of Ti‐OH groups by phosphate groups. Nevertheless, the chemical properties of the resultant surfaces were found to be influenced by the internal anatase phase. The kinetic data on the 2‐propanol dehydration reaction, where the activation energies were found to decrease gradually with an increase in phosphate content, also support these

ISSN:0009-4536    

DOI:10.1002/jccs.198800028

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractMetal substituted aluminum phosphate molecular sieves, MeAPO‐5 (Me = Co, Mn, Fe(II), Fe(III), and Mg) were synthesized and characterized with X‐ray diffraction and scanning electron microscopy. The acidity was determined by temperature programmed desorption of ammonia, Desorption peaks at around 200°C were observed for all the MeAPO samples studied. Additional desorption peaks at around 300°C were found in MnAPO‐5, CoAPO‐5, and MAPO‐5. MnAPO‐5, CoAPO‐5, and MAPO‐5 also show good activities toward the cracking reaction of cumene at 350°C, while Fe(II)APO‐5 and Fe(III)APO‐5 show some activity at 500°C. The order of the cracking activity correlates with the presence of strong acidic sites in MnAPO‐5, CoAPO‐5, and MAPO‐5 as in

ISSN:0009-4536    

DOI:10.1002/jccs.198800029

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractProcedures have been developed for the preparation of aspartyl containing dipeptides P‐L‐Asp‐AA2(P=Boc, Cbz and Moz; AA2=Phe‐R or Ala‐R; R=OH, OBzl and OTMB) using papain as a catalyst. The pH dependent of esterase activity by papain catalyzed hydrolysis have been studied. The papain catalyzing reaction can be reacted in aqueous solution, buffer solution or cosolvent system in a thermodynamically controlled approach. A procedure for the conversion of the artificial sweetner precursor P‐Asp‐Phe‐OH to the aspartame

ISSN:0009-4536    

DOI:10.1002/jccs.198800030

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA systematic racemization study of the coupling of Z‐Phe with Phe‐OBzl has been carried in order to determine the optimal conditions. It is found that the L,D diastereomer is the favored product in the coupling of Z‐L‐Phe with D,L‐Phe‐OBzl. A possible mechanism is proposed and elucidated by

ISSN:0009-4536    

DOI:10.1002/jccs.198800031

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe hydroxyl group in polyvinyl alcohol (PVA) membranes had been partially reacted with diisocyanates such as 4,4′‐diphenylmethane diisocyanate (MDI) or the prepolymers containing different functional groups. The transport properties toward water and salt and the stress‐strain properties of these modified membranes were investigated.The results showed an improvement in salt rejection and a considerable increase in the wet strength of the modified membrane. The water absorption and permeabilities of these modified membranes depended largely upon the functional groups introduced into

ISSN:0009-4536    

DOI:10.1002/jccs.198800032

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractOxidation of the furan cyclopentadienes (2) and (4) with pyridinium chlorochromate gave the cyclopentenones (5) and (6) respectively. Oxidation of the alkyl cyclopentadienes (7a and 7b) also gave the corresponding cyclopentenones (8a and 8b) as the major products.

ISSN:0009-4536    

DOI:10.1002/jccs.198800033

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA new synthesis of amrinone, 1, from 5‐(4‐pyridinyl) −2(1H)‐pyridone,5, is reported. Nitration at C‐3 of the pyridone ring of5followed by reduction afforded amrinone. Another synthetic route was also carried out by bromination at C‐3 of the pyridone ring of5followed by substitution with sodium azide to give the corresponding azide compounds8which was reduced

ISSN:0009-4536    

DOI:10.1002/jccs.198800034

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA new method to prepare 3,3′‐ethylenebissydnone (40%), 3,3′‐tetramethylenebissydnone (37%) and 3,3′‐hexamethylenebissydnone (43%) from the corresponding alkylene diamine with paraformaldehyde and potassium cyanide were investigated.Some new bissydone: −3,3′‐trimethylenebissydnone (6%), 3,3′‐(4,4′‐diphenyl)bissydnonylmethane (9%) and 3,3′‐(4,4′‐diphenyi)bissydnonyl ether (28%) were synthesized from the corresponding diamine, paraformaldehyde, sodium bisulfite and potassium cyanide.Biological test of 3,3′‐(4,4′‐diphenyl)bissydnonylmethane shows significant response for coronary dilgtion test, inhibition of collagen induced platelet aggregation and moderate carditropic response. 3,3′‐(4,4′‐Diphenyl)bissydnonyl ether also shows inhibition of collagen induced plate

ISSN:0009-4536    

DOI:10.1002/jccs.198800035

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY