首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
Corsini A  Louch WJ  Thompson M 《Talanta》1974,21(3):252-255
The PMR spectra of 8-hydroxyquinoline and eighteen derivatives have been obtained at 220 MHz. For several of the compounds, PMR spectra have not been reported previously. The use of 220-MHz frequency considerably facilitates the interpretation of spectra from such complex derivatives as 2-(2'-pyridyl) and 2-(2'-thienyl)-8-hydroxyquinoline.  相似文献   

4.
5.
6.
7.
The PMR spectra of several cyclic and acyclic dipeptide derivatives representing portions of the actinomycin structure have been studied. In the spectra of the acyclic compounds temperature-dependent duplicity resulted from the equilibration of conformers possessing cis and trans peptide bonds. The lanthanide shift reagent Eu(FOD)3 was utilized to distinguish N-methyl groups in the two conformations and observations were made on the steric dependence of the observed shifts. The origin of the wide variation in chemical shift of N-methylvalyl α-protons is discussed in relation to the conformation of actinomycin.  相似文献   

8.
9.
Proton and boron-11 magnetic resonance spectra for several potassium para-substituted tetraarylborate compounds [KB(C6H4-pX)4, where X is H, OCH3, CH3, Br, Cl, F, CF3] have been obtained. The chemical shift between the centers of the AA′ and XX′ multiplets for the ring proton multiplets, relative to a reference chemical shift of 0·39 ppm for potassium tetraphenylborate, correlated with the corresponding Hammett σ values for the para-substituent. Additionally, the boron-11 chemical shifts gave a good correlation with corresponding σ values for the substituents. Electronegativities of para-substituted phenyl rings were calculated and found to be approximately 2·70 for all compounds studied. It was shown that electronic substituent effects do not greatly influence the electron density surrounding the central boron atom in the tetraarylborate ions.  相似文献   

10.
13C n.m.r. spectra of some substituted isoxazoles have been examined to ascertain the reactive site in the metallation of 4-substituted 3,5-dimethylisoxazoles. The results obtained indicate that metallation occurred exclusively at the C-5 methyl.  相似文献   

11.
12.
13.
The broad-line proton NMR spectra of melt-crystallized samples of polyethylene covering a very wide range in molecular weight have been analyzed in terms of contributions from three components: (1) a crystalline region with crystals of orthorhombic form; (2) a noncrystalline region with liquid-like character which produces a Lorentzian contribution to the spectrum; and (3) an intermediate region in which the rotation of methylene groups about C—C bonds is partly hindered. The relative mass fractions as well as the character of these components depend greatly on the molecular weight. Samples of low molecular weight (e.g., ?30,000) are predominantly composed of lamellar crystalline regions with a minor amount of interfacial regions and no liquid-like interzonal regions. As the molecular weight increases beyond 45,000, an interzonal region with a liquid-like character associated with a higher molecular mobility is produced. Above a molecular weight of 100,000, this liquid-like character becomes pronounced with an increase in molecular mobility in the interfacial region.  相似文献   

14.
The 1H NMR spectra of cinnoline and some 8-substituted derivatives 1 in DMSO-d6 are reported. A previous assignment of the chemical shifts of the heterocyclic ring protons H-3 and H-4 is confirmed by deuteration studies. The variations in the chemical shifts of H-3 to H-7 are discussed in terms of (a) solvent effects, (b) the perturbation effect of the heterocyclic ring, and (c) the electronic and proximity effects of the 8-substituents, using single-parameter (SCSo, SCSm, SCSp, σo, σm, σp, σp+, σ4,1, σ5,1, σ6,1Q) and dual-parameter (F, R; σ1R) treatments to correlate the data. Marked proximity effects on H-7 are noted for the nitro and acetamido groups, and are correlated with conformational changes due to interaction of the groups with the N-1 lone pair. Variations in the coupling constants are attributed to partial double-bond fixation.  相似文献   

15.
16.
13C NMR spectra of thiophenol, 4-nitrothiophenol, 4-X-thioanisole (X = NO2, NH2, SH, H) were examined in CDCl3 solution. Substituent chemical shift values (additivity parameters) for the −SH and −SCH3 groups are reported.In para-substituted thioanisoles, while the −NH2 group caused a deshielding and −NO2 a shielding of SCH3 carbon resonance, −SH appeared to have had no effect on the carbon resonance.  相似文献   

17.
18.
19.
The chemical shifts and coupling constants for the ring protons of fourteen monosubstituted naphthalenes in carbon tetrachloride solution have been obtained by analysis and computer simulation of their 100 MHz magnetic resonance spectra. Studies at several concentrations have enabled shifts extrapolated to infinite dilution to be obtained and concentration effects arising from solute–solute interactions to be determined.  相似文献   

20.
The reaction of -(N-tert-butylhydrazino)alcohols with acetone and acetaldehyde leads to the formation of 4-tert-butylperhydro-1,3,4-oxadiazines. The tautomeric equilibrium between the latter and the corresponding N-tert-butyl-N-(-hydroxyalkyl)hydrazones is displaced strongly in the direction of the cyclic form. The PMR spectra of the majority of the perhydrooxadiazines obtained show that they exist in the chair conformation with practically no deformation in the N-C-C-O region. However, for the 2,2,6,6-tetramethyl derivative two nonchair (probably twist) conformations are preferred.For Communication VI, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1461–1468, November, 1973.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号