摘要:

Abstract1H and19F spectra of methoxypentafluorophenyltitanocene complexes have been analysed. They show the possibility of coupling between the methyl protons of the methoxy group and the twoorthofluorine atoms of the pentfluorophenyl ligand. Furthermore, anisochrony of the twoorthoand the twometafluorine atoms is detected in some cases. The analysis of conformational factors is presented.

ISSN:0030-4921    

DOI:10.1002/mrc.1270140302

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR chemical shifts and1J(CH),2J(CH) and3J(CH) coupling constants of selected saturated nitrogen heterocyclic molecules containing the acetylenic moiety have been determined. These NMR parameters have also been determined for the correspondingN‐oxides and the Meisenheimer rearrangement products, the O‐allenylhydroxylamines. The effect of theN‐oxidation on the chemical shifts of the ring and the acetylenic carbon atoms is di

ISSN:0030-4921    

DOI:10.1002/mrc.1270140303

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe barriers to rotation of RCH2groups (R  Me, Et and Isopr) as 3‐substituents in 4‐Me‐δ4‐thiazoline‐2‐thiones, their 4‐t‐Bu analogues, and the methiodides of the latter compounds have been studied by1H DNMR and by molecular mechanics calculations. The barriers in the 4‐t‐Bu compounds are rather insensitive to the size of R, which is shown to be caused by strain in the ground state. More generally, it is shown that when δG‡values are used in various methods for estimating the apparent spatial requirements of substituents, such ground‐state strain may lead to erroneous results in

ISSN:0030-4921    

DOI:10.1002/mrc.1270140304

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractFrom a series of antioxidants comprising 2,2′‐biphenyldiols, 2,2′‐thiobisphenols and 2,2′‐dithiobisphenol, free phenoxyls were prepared by oxidation withtert‐butylperoxyls co‐ordinated to Co(III) in non‐polar media at ambient temperature. Both the effect of extended conjugation as a consequence of the direct bond between the two aromatic nuclei and, also, the steric effect of alkyl substituents could be observed. In the presence of freetert‐butylperoxyls in excess, primary phenoxyls are transformed into cyclohexadienonyloxyls, which form stable radical complexes with Co(III). A mechanism for the formation of the cyclohexadienony

ISSN:0030-4921    

DOI:10.1002/mrc.1270140305

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractA mixture of stereoisomers of 2,4‐dimethoxybicyclo[3.3.1]nonan‐9‐one was prepared, separated by column chromatography and characterized by 60 MHz1H NMR spectroscopy using Eu(fod)3. A double chair conformation with axial methoxyl groups is established for (1R,2S,4R,5S)‐2,4‐dimethoxybicyclo[3.3.1]‐nonan‐9‐one on the basis of theJ(12),J(2,H‐3exo) andJ(2,3endo) values and the chemical shifts for H‐2(4). The conformation of some related compounds is su

ISSN:0030-4921    

DOI:10.1002/mrc.1270140306

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe transmission of electronic effects across the ferrocene analogues of chalcones [3‐aryl‐1‐ferrocenyl‐2‐propene‐1‐ones (series 1) and 1‐aryl‐3‐ferrocenyl‐2‐propene‐1‐ones (series 2)], as well as the conformations of both types of ferrocene analogues have been studied. The ferrocene analogues of chalcones of series 1 were found to be in a non‐planar conformation. Their H‐α and C‐α chemical shifts are more sensitive to the resonance than to the inductive effects of substituents. The C‐α chemical shifts of the ferrocene analogues of chalcones of series 2 are more sensitive to the inductive than to the resonance effects of substituents. The transmission of the substituent effects to the ferr

ISSN:0030-4921    

DOI:10.1002/mrc.1270140307

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe19F substituent chemical shifts (SCS) ofmeta‐ andpara‐benzoyl fluorides are found to correlate well with substituent parameters using the dual substituent parameter (DSP) equation, indicating that they reflect electronic perturbations induced by the substituent. The direction of the SCS values is such that donating substituents cause upfield shifts whilst acceptors cause downfield shifts. STO‐3G calculations indicate that substituents induce only very small changes in π‐electron density about the fluorine atom, but that these changes correlate reasonably well with the observed SCS values. For theparaseries, the slope of the relationship between δq πFand19F SCS is 5000 ppm/electron, indicating the great sensitivity of the flourine atom to small changes in elec

ISSN:0030-4921    

DOI:10.1002/mrc.1270140308

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe proton spectra ofexo‐ andendo‐3‐thiatricyclo[4.2.1.02,5]non‐7‐ene 3,3‐dioxide have been analysed and completely assigned. Considerations of coupling constants indicate that the thietane ring is nonplanar and that the norbornene residue is significantly distorted from the geometry of norbornene itself. The sulfone group induces significant changes in the shielding of the proximate olefinic proton in theendoisomer and the bridge protons in theexoisomer. These shifts appear to be the result of the electrostatic effects and effects associated with the diagmagnetic anisotropy of the su

ISSN:0030-4921    

DOI:10.1002/mrc.1270140309

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe chemical shifts of amino acidN‐carboxyanhydrides (NCAs) and cyclic or linear urethanes are less sensitive to solvent effects than those of amides and lactams. The values of the one‐bond15N1H coupling constants depend on the solvent and are 5‐8 Hz larger than those of ureas and amides. The15N13C coupling constant of the NCO group is also unusually high, while that of the N—CH group lies within the range known forN‐acylated aliphatic amines. The one‐bond15N13C coupling constant was found to be insensitive to con

ISSN:0030-4921    

DOI:10.1002/mrc.1270140310

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY

摘要:

AbstractThe configuration and conformation ofZ‐ andE‐N‐methyl‐ and ‐N‐benzyl‐2‐p‐nitrophenyl‐4,5‐, and ‐5,6‐tetramethylenetetrahydro‐1,3‐oxazines were determined by1H and13C NMR spectroscopy. TheZisomers were proved to be conformationally homogeneous, having the heteroatom in axial and equatorial position, respectively, in the case of the 5,6‐ and 4,5‐tetramethylene compounds. Consequently, thep‐nitrophenyl group and the anellated cyclohexyl ring are all‐cisarranged in theZ‐5,6‐tetramethylene compounds while in the case of theZ‐4,5‐tetramethylene isomers thep‐nitrophenyl group and the cycl

ISSN:0030-4921    

DOI:10.1002/mrc.1270140311

出版商:John Wiley&Sons Limited    

年代:1980

数据来源: WILEY