bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radical reactions in the co‐ordination sphere of transition metals IX—phenoxy and cyclohexadienonyloxy radicals derived from 2,2′‐biphenyldiols and 2,2′‐thiobisphenols
Authors: Tkáč A. , Omelka L. , Jiráčková L. , Pospišil J. 
Published: May 2005

AbstractFrom a series of antioxidants comprising 2,2′‐biphenyldiols, 2,2′‐thiobisphenols and 2,2′‐dithiobisphenol, free phenoxyls were prepared by oxidation with tert‐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 free tert‐butylperoxyls in excess, primary phenoxyls are transformed into cyclohexadienonyloxyls, which form stable radical complexes with Co(III). A mechanism for the formation of the cyclohexadienonyloxyls is suggested.
The rα‐structures of partially oriented 1,2,4,5‐and 1,2,3,4‐tetrachlorobenzene determined from their proton magnetic resonance spectra with natural abundance 13C‐satellites
Authors: Diehl P. , Dombi G. , Boesiger H. 
Published: May 2005

AbstractBy recording two spectra of the same molecule in different nematic liquid crystals, and analysing the data simultaneously, information has been obtained on the molecular structures of 1,2,4,5‐ (1) and 1,2,3,4‐tetrachlorobenzene (2). Carbon–hydrogen and carbon–carbon internuclear distance ratios, as well as bond lengths and bond angles, were computed and corrected for harmonic vibrations. Only part of the molecular structure of 2 could be derived with reasonable precision; the reasons for this limitation are discussed. The spectra of the two isomers were also analysed in isotropic solvents in order to determine the indirect coupling constants. One‐ and two‐bond 13C isotope effects on the chemical shifts of the protons were observed. The solvent effects of the different nematic liquid crystals on the structure were found to be small compared with the experimental error.
15N NMR spectroscopy 28—solvent effects on the 15N13C coupling constants of amides, imides, ureas and polypeptides
Authors: Kricheldorf Hans R. 
Published: May 2005

AbstractThe 15N13C coupling constants of 15N‐enriched acetamide, N‐acetylglycine anilide, phthalimide, α,α′‐bisphthalimido‐p‐xylene, N‐methyl‐N′‐phenylurea, poly‐L‐alanine and poly‐L‐valine were measured in various solvents. It was found that the 15N13C coupling constants depend largely on the nature of the solvent. Increasing acidity leads to higher one‐bond and lower two‐bond coupling constants. A change of concentration does not have any influence on the 15N13C couplings while a large increase in temperature leads to a slightly lower 1J(NC). It is concluded that solvent effects may limit the use of 15N13C coupling constants for the elucidation of solvent‐induced conformational changes.
13C NMR spectra of 1,3,4‐thiadiazole/thiadiazoline isomeric pairs
Authors: Rackham David M. , Morgan Sarah E. , Williamson W. R. Nigel 
Published: May 2005

AbstractThe 13C NMR spectra of four pairs of 1,3,4‐thiadiazole/thiadiazoline isomers have been recorded using broad band and off‐resonance proton decoupling techniques and in the coupled mode. Differences in the chemical shifts of the heterocyclic ring and the carbonyl carbons allow identification of the isomer present. Their IR and UV spectra are in agreement with literature reports for azole/azoline analogues.
ENDOR study on the anion radical of benzo[c]cinnoline
Authors: Fujita Hideo , Deguchi Yasuo , Ohya‐Nishiguchi Hiroaki , Ishizu Kazuhiko 
Published: May 2005

AbstractThe ENDOR spectrum was obtained for the benzo[c]cinnoline anion radicalin 1,2‐dimethoxyethane. The hfs constants of the protons correspond with those found by EPR spectroscopy, and also agree well with the qualitative tendency of the reported spin density distributions by HMO calculation.
Carbon‐13 NMR studies of monohydroxylated and monochlorinated derivatives of Z‐ and E‐p‐menthanes
Authors: Dauzonne D. , Goasdoue N. , Platzer N. 
Published: May 2005

AbstractCarbon‐13 NMR spectra of the 18 monohydroxylated‐ and of the 18 monochlorinated‐p‐menthanes have been recorded. The data of these complete sets of isomeric compounds allow a comparison of the efficiency of the various empirical methods for the calculation of chemical shifts. The application to conformational analysis is proposed.
13C,13C coupling constants of conjugated dienes
Authors: Stöcker Michael , Klessinger Martin , Wilhelm Konrad 
Published: May 2005

AbstractOne bond 13C,13C‐ and 13C,1H‐coupling constants have been measured for some 1,2‐dimethylene‐cycloalkanes, as well as for 2,3‐dimethylbuta‐1,3‐diene and methylenecyclobutane. The results for 2,3‐dimethylbuta‐1,3‐diene confirm the findings for buta‐1,3‐diene, i.e. that J(C‐1, C‐2) is smaller for the diene than for the correspondingly substituted monoene. No differences have been found between the 1J(CC) exocyclic coupling constants of the dimethylene and monomethylene cycloalkanes.
Half‐chair conformations of unsaturated heterocyclic compounds
Authors: Fatheree D. M. , Deeg G. L. , Matthews D. B. , Russell J. G. 
Published: May 2005

AbstractThe vicinal proton coupling constants were obtained for some 6‐membered ring unsaturated heterocyclic compounds. The R values and ring dihedral angles were determined and found to be consistent with half‐chair conformations. Relative to saturated heterocyclic compounds, the effect of the sulfur atom on ring puckering was attenuated. However, an increase in ring puckering resulted from the sulfone group and was attributed to torsional energy.
Structural assignment of isomeric chain demethylated retinals by 1H NMR spectroscopy
Authors: Broek A. D. , Courtin J. M. L. , Mellema J. R. , Lugtenburg J. , Nicolay K. , Dijkstra K. , Kaptein R. 
Published: May 2005

AbstractGeometric isomers of all‐trans‐9‐demethyl‐, −13‐demethyl‐ and −9,13‐bisdemethylretinal were prepared. The 360 MHz 1H NMR spectra of 13 geometric isomers of these three demethylated retinal systems have been measured. The chemical shift and coupling constant values in each case allowed an unambiguous assignment of the structure of each compound.
Carbon‐13 NMR studies. 96—carbon‐13 spectra of several polyhydroxylated 9,10‐dihydrophenanthrene and phenanthrene derivatives
Authors: Stoessl Albert , Stothers J. B. 
Published: May 2005

AbstractThe 13C spectra of eleven 9,10‐dihydrophenanthrene and twelve phenanthrene derivatives were recorded in order to examine the effects of hydroxy and methoxy substitution on the skeletal carbon shieldings. For each series, the parent compounds were the 2,4‐disubstituted derivatives with the others bearing 5‐, 6‐ and/or 7‐substituents, including the naturally occurring orchinol and loroglossol. The data should be helpful for examinations of related compounds. Some examples of particularly facile hydrogen‐deuterium exchange at aryl positions were encountered. Since these occur under apparently neutral conditions, suitable caution may be required in examinations of related compounds.
14N and 35Cl nuclear quadrupole resonance data for nitrogen mustards: Attempted correlations with chemical and biological activities
Authors: Buess M. L. , Bray P. J. , Sheppard D. W. 
Published: May 2005

AbstractThe 14N nuclear quadrupole resonance (NQR) spectra of several nitrogen mustard compounds are reported and analyzed in the framework of the Townes and Dailey theory. For the aniline derivatives, a correlation exists between l–σ (where l is the nitrogen lone pair electron density and σ the average NC sigma‐bond electron density) and the enhanced Hammett sigma constant σ−. An improved correlation is obtained between l–σ and σR−, which emphasizes the importance of resonance effects in determining l–σ. The increase of hydrolysis and alkylation rates with increasing values of l–σ is in agreement with the identification of the aziridinium ion as the intermediate in aromatic nitrogen mustard hydrolysis and alkylation. A possible correlation is noted between the 35Cl NQR spectra for some of the mustards and measures of toxic and antitumor activity.
1H NMR long‐range coupling in the assignment of stereochemistry to 4‐imidazolidinones
Authors: Połoński T. 
Published: May 2005

AbstractLong‐range couplings were observed between protons attached to C‐2 and C‐5 of the 4‐imidazolidinone ring. Since 4J(25) has a measurable value only for a trans arrangement of H‐2 and H‐5, this coupling can be utilized as an easy method of identification of 4‐imidazolidinone stereoisomers.
15N NMR spectroscopy of some azines
Authors: Stefaniak L. , Roberts John D. , Witanowski M. , Webb G. A. 
Published: May 2005

Abstract15N NMR shielding data are presented for 56 cyclic azines in 0.5 M dimethyl sulfoxide solutions with 0.01 M increments of Cr(acac)3 added for each nitrogen atom in the molecules. For the polyazines, the 15N signal assignments were based on 2J(NH) interactions and some INDO/S‐SOS shielding calculations. The effects of α‐, β‐ and γ‐methyl and conjugated ring substitution on nitrogen shielding are presented and discussed, as are the influences arising from fusion with alicyclic and aromatic rings at various positions. The effects of a second nitrogen atom on the shielding of the first one are shown to be critically dependent on both their relative positions and on the position of fusion of conjugated ring systems.
A 15N NMR study of some azoles
Authors: Stefaniak L. , Roberts John D. , Witanowski M. , Webb G. A. 
Published: May 2005

Abstract15N NMR data are reported for 42 azoles, taken mostly at a standard concentration and in a common solvent (0.5 M dimethyl sulfoxide with a 0.01 M increment of Cr(acac)3 for each nitrogen atom present). Signal assignments were assisted by comparison with 14N line widths, the use of 2J(15N1H) couplings, and shielding calculations obtained by the INDO/S–SOS approach. The generally large differences in nitrogen‐shielding changes permitted rather facile shift assignments.
Application of NMR spectroscopy of chiral association complexes. 14—chiral recognition of terpene and cyclohexene hydrocarbons by 1H and 13C NMR
Authors: Offermann Werner , Mannschreck Albrecht 
Published: May 2005

AbstractChiral NMR recognition of terpenic and similar hydrocarbons by Ag(fod) and optically active lanthanide shift reagents is described. Twenty‐four 1H signals of eight compounds and, as a first report in the literature, eleven 13C signals of three compounds were split into signal pairs due to the respective enantiomers. Although the magnitudes of the splittings are not connected to the structure of the substrate molecules in an obvious manner, the configurations of the similar compounds camphene and epi‐β‐santalene were related empirically. All spectra were sufficiently resolved to allow separate integration of enantiomer signals; from the integrals the enantiomeric purities of seven non‐racemic mixtures were determined with good accuracy. The shift curves made several hitherto unknown assignments feasible.
Conformational studies by nuclear magnetic resonance in nematic phases: Benzyl chloride
Authors: Longeri Marcello , Chidichimo Giuseppe , Bucci Pietro 
Published: May 2005

AbstractSpectra of benzyl chloride were analysed in two nematic phases (PCH and ZLI). The existence of the molecule as conformer with the CCl bond perpendicular or parallel to the benzene plane can be safely excluded. The data are consistent with a conformer with the CCl bond forming an angle of 60° with the benzene plane. A full discussion of the conformational problem was not possible owing to the small number of independent Dij couplings related to the internal motion. In addition, when dealing with low potential barriers, the LCNMR technique does not give rigorous answers.
Calculation of 13C NMR chemical shifts for aromatic carbons in polyalkylated benzenes
Authors: Sudmeijer O. , Wilson A. E. , Hays G. R. 
Published: May 2005

Abstract13C NMR spectra of a large number of polyalkylated benzenes with branched and linear aliphatic chains have been studied. This resulted in the development of a general procedure that can be used for the calculation of the aromatic chemical shifts in any polyalkylated benzene.
Precise values of the 13C component vicinal coupling constants for calculating side‐chain conformations in amino acids
Authors: Reddy M. C. , Reddy B. P. Nagi , Sridharan K. R. , Ramakrishna J. 
Published: May 2005

AbstractFrom consideration of 1H–1H vicinal coupling constants and 13C1H long‐range coupling constants in a series of amino acid derivatives, the precise values of 13C component vicinal coupling constants have been calculated for the three minimum energy staggered rotamers for the C(α)HC(β)H2 side‐chains of amino acids.
13C NMR study of some polychloro‐isobutane and ‐isobutene compounds
Authors: Pitkänen Maija , Laihia Katri , Schulze Klaus 
Published: May 2005

AbstractThe 13C chemical shifts and the carbon–proton coupling constants have been determined for some chlorinated isobutane and isobutene compounds. The one‐bond coupling constants in isobutane derivatives showed a regular increase with an increasing number of γ‐chlorine substituents. The three‐bond coupling constant of the methyl carbon decreased from 4.2 to 2.0 Hz as the number of chlorine substituents in the γ‐position increased. In the isobutene compounds, the vicinal coupling of C‐1 was larger to protons in a group that is trans with respect to a chlorine substituent on C‐1 than to those in the corresponding group cis to the chlorine. The vicinal coupling constants between atoms in geminal groups (on C‐2) seem to be affected by the orientation of the chlorine substituent on C‐1.
1H, 13C and 29Si NMR spectra of allylic trimethylsilanes
Authors: Alberts Vincent , Cuthbertson Matthew J. , Hawker Darryl W. , Wells Peter R. 
Published: May 2005

AbstractChemical shift and scalar coupling constant data have been obtained for the 1H, 13C and 29Si nuclei in allyl, methally, cis‐ and trans‐crotyl, cis‐2‐methyl‐2‐butenyl and 3‐methyl‐2‐butenyl derivatives of trimethylsilane.
Use of 13C isotope shifts for assignment of deuterium labelling sites in 1,3‐diphenylpropan‐1‐one
Authors: Bar Raphael , Sasson Yoel , Blum Jochanan 
Published: May 2005

Abstract13C NMR spectroscopy was used for the unequivocal analysis of the mixture of products of RuCl2[P(C6H5)3]3‐catalysed transfer deuteriation of benzylideneacetophenone by (a) DCOONa/H2O, (b) HCOONa/D2O and (c) DCOONa/D2O. Signal assignments in the 13C spectra were obtained mainly from the deuterium‐induced 13C isotope shifts. The geminal 13C2H shift of the β‐carbon of deuteriated 1,3‐diphenylpropan‐1‐one is almost twice that for the α‐carbon.
Investigation of substituent effects on the 1H and 13C NMR spectra of (Z)‐N‐(arylmethylene)‐arylamine N‐oxides (α,N‐diaryl nitrones)
Authors: Arumugam N. , Manisankar P. , Sivasubramanian S. , Wilson D. A. 
Published: May 2005

AbstractSubstituent effects on the 1H and 13C chemical shifts of 18 differently substituted (Z)‐α,N‐diaryl nitrones [N‐(p‐X‐benzylidene)phenylamine N‐oxides (Series I) and N‐(benzylidene)‐p‐Y‐phenylamine N‐oxides (Series II)] have been obtained. A correlation has been found between the chemical shifts of the azomethine proton (H‐α) and the Hammett σ parameters and the Swain and Lupton F and R parameters. Correlations of the chemical shifts of C‐1 and C‐4′ in Series I, and of C‐α and C‐1′ in Series II, with the same parameters have been investigated. In addition, the chemical shifts of the aromatic protons and carbons of the p‐disubstituted (m‐disubstituted in one case) benzene rings correlated with the appropriate substituent increments (Zi). These correlations confirm the dual behaviour of the nitrone group and the presence of through‐resonance in these nitrones.
Electronic delocalization in NC and NN bonds
Authors: Brémond M. , Martin G. J. , Webb G. A. , Reynolds D. J. 
Published: May 2005

AbstractFor a series of compounds with NC or NN bonds, the CNDO/S parameterized calculations for Qπ, the electronic charge density on the nitrogen atom, and π bond orders Pπ provide evidence for the simultaneous dependence of the 15N chemical shift on both of these parameters. The multilinear regressions obtained produce high values for the regression coefficients. The results throw some light on the nitrogen lone pair delocalization mechanism.
13C NMR examination of some N‐thioaroylmorpholine–bromine adducts
Authors: Chiacchio Ugo , Corsaro Antonino , Bottino Francesco A. 
Published: May 2005

AbstractThe 13C NMR chemical shifts of three N‐thioaroylmorpholine–bromine adducts, previously used as synthetic intermediates, are compared and discussed in the light of the corresponding shifts of the parent thioamides and suitable model compounds. Chemical shift changes are interpreted in terms of the electronic perturbation resulting from bromine coordination at sulphur.
17O NMR spectroscopy: Effect of substituents on chemical shifts for p‐substituted benzoic acids, methyl benzoates, cinnamic acids and methyl cinnamates
Authors: Balakrishnan P. , Baumstark A. L. , Boykin D. W. 
Published: May 2005

AbstractThe 17O NMR spectra for a series of 17O‐enriched p‐substituted benzoic acids, methyl benzoates, cinnamic acids and methyl cinnamates in acetone at 40°C are reported. The carboxylic acids showed one signal (benzoic 250.5 ppm, SCS range p‐MeO to p‐NO2 = 10.5 ppm; cinnamic 254.1 ppm, SCS range p‐MeO to p‐NO2 = 5.4 ppm). The esters showed two signals [methyl benzoate (CO) 341.3 ppm and (OCH3) 128.0 ppm; methyl cinnamate (CO) 339.9 ppm and (OCH3) 134.2 ppm]. The SCS ranges for the carbonyls of the esters were larger than those for the corresponding acids, while those for the OCH3 groups of the esters were slightly smaller. The carbonyl data gave good correlations with σ+ constants, while the OCH3 data gave at best only a poor correlation with σ constants. Dual substituent parameter treatment improved the correlations for all the data using σR+ constants. The ratios of ρI to ρR+ were similar for all the sets of data.
Electric field effects in 13C NMR of some quaternary morphinan derivatives
Authors: Theuns Hubert G. , Janssen Richard H. A. M. , Biessels Hubertus W. A. , Salemink Cornelis A. 
Published: May 2005

Abstract13C NMR chemical shifts are assigned for some quaternary morphinan derivatives, including the ‘minor isomer’ of the thebaine N‐oxides. In quaternary morphinan alkaloids having an 8.14‐double bond, electric field effects cause unusual 13C NMR shifts.
Advertising for the introduction of an age‐sensitive product
Authors: Grosset Luca , Viscolani Bruno 
Published: May 2005

AbstractAn age‐dependent market segmentation is often observed for real life products. We introduce a simple age‐structured model for the advertising process of a firm and the consequent goodwill evolution. The model formal structure is characterized by a first order linear partial differential equation. We formulate the advertising problem for a new product introduction as a distributed parameter optimal control problem and solve it using the suitable maximum principle conditions. Then, we discuss and solve the same problem under the assumption that a finite set of boundedly age‐selective advertising channels are available, instead of one infinitely age‐selective channel. Copyright © 2005 John Wiley & Sons, Ltd.
DNMR investigations on 3,3‐Dihalo‐2,2,4,4‐tetramethylpentanes
Authors: Kalinowski Hans‐Otto , Röcker Erwin , Maier Günther 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of 3,3,‐diiodotetramethylpentane (2), 3,3‐dibromotetramethylpentane (3), and 3,3‐dichlorotetramethylpentane (4) are temperature dependent. The activation parameters for the tert‐butyl group rotation in 2–4 have been determined. The 13C NMR chemical shifts are discussed.
13C NMR spectral analysis of dihydrobenzofuran lignans
Authors: Agrawal P. K. , Rastogi R. P. , Osterdahl B.‐G. 
Published: May 2005

AbstractThe assignments of the 13C NMR shift values of the dihydrobenzofuranoid lignans cedrusin and dihydrodehydrodiconiferyl alcohol, their respective 4‐O‐β‐D‐glucosides and their acetates have been made. The furanoid stereochemistry in 8,3′‐lignans could be deduced from comparative 13C NMR data.
Stereochemistry of alkyl 3‐substituted 4‐halotetrahydro‐2‐oxo‐3‐furancarboxylates: 2—1H and 13C NMR spectra
Authors: Gryff‐Keller A. , Kołodziejek W. , Prejzner J. 
Published: May 2005

AbstractThe 1H NMR parameters of methyl 3‐substituted cis‐4‐halotetrahydro‐2‐oxo‐3‐furancarboxylates are reported, with assignments of the ring protons based on solvent‐induced changes in the vicinal trans coupling constants, 3J(H‐4, H‐5). Preferred conformations, ce with a pseudo‐equatorial halogen for the cis isomers and ta with a pseudo‐axial halogen for the trans isomers, have been suggested on comparison of the magnitudes of J(trans) and J(gem) in both series. The 3J(13CH3, H‐4) values measured for methyl cis‐4‐bromotetrahydro‐3‐methyl‐3‐furancarboxylate, methyl trans‐4‐bromotetrahydro‐3‐methyl‐3‐furancarboxylate and trans‐3,4‐dibromodihydro‐3‐methyl‐2(3H)‐furanone have confirmed the stereochemical assignments.
Combined 35Cl and 79Br NQR Zeeman effect study in α‐bromo‐p‐chloroacetophenone
Authors: Ramakrishna V. , Rao D. Krishna , Satyanandam G. , Murty C. R. K. 
Published: May 2005

AbstractA combined nuclear quadrupole Zeeman effect study on a single crystal of α‐bromo‐p‐chloroacetophenone was carried out for 35Cl and 79Br resonances using recording and oscilloscope displays, respectively. The orientations of the principal field gradient directions, the values of the asymmetry parameter, the crystal class (orthorhombic) and the bond characters were determined and the results are discussed.
Assignment of relative configuration in cyclopentenes from proton chemical shift increments
Authors: Hunter G. , Miller J. A. , Moore M. , Ullah G. M. 
Published: May 2005

AbstractThe ‘syn‐upfield’ rule for vicinal shielding by methyl and chlorine substituents has been confirmed for a series of 4‐chlorocyclopentenes, and used to make configurational assignments in cases where conclusions based on vicinal proton coupling are not reliable. The methoxymethyl group should be added to those substituents whose effect on vicinal protons can be deshielding, irrespective of geometry.
13C NMR study on the methoxy carbon chemical shifts in chloro‐substituted anisoles and guaiacols
Authors: Kolehmainen E. , Knuutinen J. 
Published: May 2005

AbstractThe 13C NMR chemical shifts of methoxy carbons in chlorinated anisoles and guaiacols have been measured for acetone‐d6 solutions. Multiple linear regression analysis, and also ‘simple sum rule’ calculations, have been used to estimate the effects of the chlorine atoms (the position and degree of substitution) on the chemical shifts. The most important effects have shown to be due to the chlorine atoms adjacent to the methoxy and hydroxy substituents. For chlorinated guaiacols, the greatest effect is due to the chlorine atom adjacent to the methoxy group. For chlorinated anisoles, the substituents adjacent to the methoxy group (2,6‐disubstitution) cause large effects. For both groups of compounds, the chemical shifts are also greatly influenced by the number of chlorine substituents. Using the three most important independent variables, the average differences between the observed and calculated chemical shifts are ca 0.2 ppm for anisoles and 0.1 ppm for guaiacols. For chloroguaiacols, the corresponding difference was only 0.1 ppm when calculations were performed using single substituent effects.