摘要:

AbstractThe title compound has been synthesized and its crystal structure determined by X‐ray crystallographic method. The crystal is monoclinic, space groupC2/c, with unit cell dimensionsa=19.260 (3),b=11.217 (1),c=15.997 (1) Å; β=92.08 (2)° andZ=8.This is the first crystal structure determined in the series of bicyclo[10.3.0]pentadec‐1(12)‐en‐13‐one derivatives. The structure and the conformation of thecis‐cyclododecene moiety in this compound is demonstrated to be closely similar to the lowest energy conform

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080502

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe banding and electronic structures of a series of long‐chain macromolecules of cellulose, 2‐, 3‐, 6‐mononitrocellulose, 2,3‐,2,6‐, 3,6‐dinitrocellulose and trinitrocellulose as well as their structural units (i.e.single‐, double‐ or three‐ring systems) have been calculated by both the EH and CNDO/2 methods. The increase of molecular total energies is consistent with the decrease of their stabilities at the three conformations of gg, gt and tg. The Mulliken bond order of O—NO2bond is the smallest in each molecule at any of the three conformations, which indicates that this bond is the weakest, and supports the view of initial homolytic cleavage of O—NO2bond on slow thermal decomposition. The band gap at the edge of the first Brillouin zone far surpasses 5 eV for cellulose, and is less than 3 eV for mono‐, di‐, and trinitrocellulose. The results show that cellulose is a typical insulator, as we know, and it can be predicted that nitrocellulose has electric conductivity simil

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080503

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe semiconducting properties of anodic film formed on Pb in 4.5mol·dm−3H2SO4solution (30°C) at 0.9 V (vs. Hg/Hg2SO4) for 2 h were studied using AC impedance method. The phase composition of the film is PbSO4and PbO·PbSO4. The semiconducting properties are due to the latter. The Mott‐Schottky plots show that the said film is ann‐type semiconductor with flat‐band potential of −0.9 V (vs. Hg/Hg2SO4) and donor density of 1×1016cm−3. The surface density measured at 410–2500 Hz is (

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080504

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe unimolecular reactions of ammonia oxide H3NO, isomerization and dehydrogenation, are investigated byab initioMO calculations with the 4‐31G basis set. The geometries and energies of the reactant, transition states and products have been determined on the singlet potential energy surface. The reaction ergodography along the intrinsic reaction coordinate (IRC) for the two reactions have been performed. The vibrational frequency correlation diagram of the two reactions are analyzed along the IR

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080505

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractExperimental data of hydrolytic polymerization of lanthanide ions in aqueous solution were treated by graphic method, computer fitting andpqanalysis, species present were ascertained and hydrolysis constants obtained. Ln (OH)2+and Ln2(OH)24+predominated in the species of all hydrolysis products. When the first and the second hydrolysis constants were plotted against radii and effective nuclear charge of lanthanide ions, the curves obtained conformed with the “three‐division groups” rule. Correlation between hydrolysis constants of Ln2(OH)24+and other hydrolysis constants is linear.Using the above empirical correlations we calculated hydrolysis constants of all lanthanide ions and obtained satisfactory results which showed good regularity for hydrolysis of lanthanide ions and thus systematized all data of the rea

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080506

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractConformation of L‐lysine in aqueous solution was investigated by lanthanide shift probes (Dy, Ho, Er, Tm and Yb). Reilley's method was employed to separate the contact and dipolar components of the13C paramagnetic shifts. This study reveals that Cα shift has the largest contact contribution while the other carbon shifts are dominated by the dipolar contribution. The average overall conformation ofL‐lysine in aqueous solution is extended with the molecular backbone in trans form. In the complex, lanthanide ion coordinates to the carboxyl group with Ln—O bond length 2.2 Å and the whole ligand is located outside the zero‐dipolar shift cone of the lanthanide ion. The electronic spin density distribution on the ligand nuclei shows that the spin polarization is the predominant mechanism of the contact interaction for nuclei in close proximity to the bound lanth

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080507

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractRing inversion of eight substituted 2‐phenyl‐4, 4‐dimethyloxazolidines ino‐dichlorobenzene‐d4was studied by1H DNMR. Very high inversion barriers (ΔGo≠= 86.7–93.4 kJ·mol−1) were found for these oxazolidine rings. The magnitude of the inversion barrier is dependent on the polarity of the substituent on the phenyl group. A linear correlation is present between the ΔGo≠of the inversion and the substituent constant, σ

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080508

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractBoth direct and sensitized irradiations of theendotitle compound lead to a decarbonylation product, 4‐isopropylbiphenyl, via Norrish Type 1 reaction, while theexoisomer gives a carbene intermediate and subsequently formaldehyde 2‐biphenylyl isopropyl hemiacetal, which in turn gradually decomposes to dimethyl phenylbenzyl alcohol at room temperature. The triplet pathway dominates the photoreaction of theexoisomer. The singlet and triplet lifetimes of the reactant are found to be 0.29 ns and 5.4 μs, respectively,3(n,x*),1(n,x*),3(x,x*) electronic configurations of theexoisomer and3(x,x*) of theendoisomer are photochemically active, but1(x,x*) of theendoisomer shows indirect photoreacti

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080509

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe 2‐C, methylene group of 1‐aroyl‐1,2‐dihydro‐3H‐naphtho[2,1‐b]pyran‐3‐ones (2) have been showed to possess a superior reactivity towards many of organic reagents. The naphthopyrones (2) condensed with aromatic aldehydes to give the 2‐arylidine derivatives (3). Bromination of 2 gave 1,2‐dibromo (4) or 5‐bromo (5) derivatives depending on the reaction conditions. The base catalyzed addition or cycloaddition of naphthopyrones (2) to 4‐methoxy benzalacetophenone gave the expected Michael adduct (6) or the cyclic adducts (7–9) depending on the type of catalytic base and reaction conditions. Structures of the products have been established by elemental analyses, IR and1

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080510

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe palladium‐catalyzed cross‐coupling reaction of phenyl fluoroalkanesulfonates with organozinc, organotin and organoaluminum reagents in the presence of lithium chloride takes place to afford alkylbenzenes in good yields. However, the coupling reaction with organolithium and Grignard reagents proceeds unsatisfactorily with poor regioselectivity. On the basis of the isolation of an oxidative addition product of phenyl fluoroalkanesulfonate to palladium, a catalytic cycle in the reaction is sugges

ISSN:1001-604X    

DOI:10.1002/cjoc.19900080511

出版商:WILEY‐VCH Verlag    

年代:1990

数据来源: WILEY