bluuebunny/crossref_metadata_2025_split huggingface dataset:
Paramagnetic products formed in the reactions of organometallic compounds. XII ESR study of oxido anion substituted diaryl ketyl radicals
Authors: Malik Ľ. , Staško A. , Mat'ašová E. , Tkáč A. 
Published: May 2005

AbstractIn the reactions of alkyl‐substituted‐benzenecarboxylic and ‐2‐hydroxybenzenecarboxylic acids (ArCOOH) with alkyl‐substituted phenyl Grignard reagents (RMgX) in the presence of nickel, ketyl radicals ArCO−R are formed. The para substituents (H, Me, Et, Isopr and t‐Bu) of R increase the non‐equivalence of its ortho protons (a change of a2H = 0.43 mT, a6H = 0.422 mT to 0.435 mT, 0.395mT respectively, on substituting t‐butyl for H at position 4). The oxido anion group originating from 2‐hydroxybenzenecarboxylic acid has a strong push effect and nearly doubles the unpaired spin density on the phenyl ring R.
The 15N NMR spectra of macrocyclic compounds containing the ferrocene unit
Authors: Hall C. Dennis , Bell Alan P. , Denney Dorthy Z. 
Published: May 2005

AbstractThe synthesis of a 15N enriched macrocycle containing the ferrocene unit is descibed, and the 15N NMR spectra of the macrocycle and those of its complexes with some metallic cations are reported.
Carbon‐13 NMR spectra of DDT, its analogues and related compounds
Authors: Freidlina R. Kh. , Dostovalova V. I. , Kuz'mina N. A. , Chukovskaya E. C. 
Published: May 2005

AbstractCarbon‐13 NMR spectra of mono‐ and disubstituted aromatic compounds including DDT, its analogues, homologues, derivatives and certain model compounds have been studied. The Savitsky scheme of carbon chemical shifts in disubstituted benzenes is applicable to these compounds. The data obtained show that in mono‐ and disubstituted aromatic compounds containing two different substituents in the α‐ and β‐positions of the side chain, the substituted ring carbon atom shifts follow the additivity rule and can be calculated from substituent increments. Mutual effects of substituents in the ring and in the side chains are analysed. The chlorine atoms in α‐position to the phenyl ring give rise to an additive α‐effect of about 25 ppm, as in perchloroalkanes. The influence of a β‐chlorine atom in the side chain on the substituted carbon atom in the ring is, however, only 3 ppm as against the usual value of about 10 ppm for the β‐effect in alkyl chains. Moreover, the first β‐chlorine substituent has no noticeable influence on the substituted ring carbon chemical shift: the effect of 3 ppm is transferred to the para‐carbon atom almost without attenuation. The ring substituted carbon atom signal shifts caused by the γ‐effect of chlorine in the side chain are similar to those observed in aliphatic chains. The ortho‐chlorine substituents shift the side chain α‐carbon atom signal by 3.6‐5.2 ppm to high field compared to para‐chlorophenyl compounds. This is similar to the chlorine γ‐effect in aliphatic chains.
Carbon‐13 nuclear magnetic resonance of mono‐ and di‐chloro‐hexanes and mono‐ and di‐chloro‐heptanes. Assignment of configurations
Authors: Nouguier R. , Surzur J.‐M. , Virgili A. 
Published: May 2005

AbstractCarbon‐13 NMR spectra of mono‐ and dichloro‐hexanes and mono‐ and dichloro‐heptanes are reported. Substituent effects for α, β and γ positions are presented. Differences between the 13C chemical shifts of diastereoisomers are observed in the cases of 2,4‐ and 2,5‐dicholohexanes and 2,4‐, 2,5‐ and 3,5‐dichloroheptanes.
15N NMR spectroscopy. 30—structure/shift relationships of oligopeptides and copolypeptides, including gramicidin S
Authors: Kricheldorf Hans R. 
Published: May 2005

AbstractThe 15N NMR spectra of various oligopeptide derivatives of the ZXYYOMe structure, where X and Y are variable amino acids and Z is the benzyloxycarbonyl group, were measured in several protic and aprotic solvents. The shift difference of the 15N of the YY and XY bond (neighbouring residue effect) is discussed with respect to the nature of X and Y with respect to the solvent. Oligopeptides of the ZXYYOH and n̊H3XYYOMe structures were compared with the Z‐pëptide esters to investigate the spectroscopic influence of the protecting groups. The methyl ester hydrochlorides of the 25 most common amino acids were measured in water and DMSO to elucidate the solvent dependence of the substituent effects. Moreover, the methyl ester hydrochlorides were compared with Z‐amino acids and N‐acetyl‐amino acid methyl esters in DMSO to establish whether the substituent effects depend on the nature of the amino acid derivatives. In this connection the assignments of the serine, threonine and glycine signals are discussed with respect to silk proteins. Furthermore, the assignments of the signals of copolypeptides by comparison with oligo‐ and homo‐polypeptides are discussed. Finally, it was demonstrated that intramolecular H bonds cause downfied shifts of 7–10 ppm of the acceptor amide groups.
Transmission of the substituent effects in 2‐substituted benzimidazoles studied by 1H and 13C nuclear magnetic resonance
Authors: Lopyrev V. A. , Larina L. I. , Vakul'skaya T. I. , Larin M. F. , Nefedova O. B. , Shibanova E. F. , Voronkov M. G. 
Published: May 2005

AbstractThe substituent influence on the 1H and 13C NMR chemical shifts in 2‐substituted benzimidazoles and their anions and cations has been investigated. The transmission of the electronic effects of substituents from C‐2 to C‐5 (6) is approximately 20% less effective than that in the opposite direction. The solvent influence on the chemical shifts of protons and transmission effects in the charged forms of 2‐substituted benzimidazoles has been studied.
NMR spectra of tricyclic compounds oriented in the nematic phase: The spectrum of phenazine
Authors: Khetrapal C. L. 
Published: May 2005

AbstractThe NMR spectrum of phenazine, the tricyclic diazine, oriented in a nematic phase is investigated. The ratios of the interproton distances are determined. They do not deviate significantly from the corresponding values in quinoxaline oriented in a thermotropic solvent.
14N NMR studies on some N‐sulphinylamines
Authors: Sicińska W. , Stefaniak L. , Witanowski M. , Webb G. A. 
Published: May 2005

AbstractHigh precision 14N nuclear screening data are presented for some alkyl‐ and aryl‐N‐sulphinylamines. For the alkyl compounds the β effect is seen to produce a decrease in screening and the opposite influence from the γ effect is also observed. An exception to the general tendency for the β effect is noted for (CH3)3CNSO. CNDO/S parameterized nitrogen screening calculations show that for this molecule the distorted cis form, with all of the methyl carbons rotated out of the CNSO plane, is the most probable structure. A similar effect is observed upon substituting the bulky tert‐butyl group in the 2 position of the aryl compounds studied. Nitrogen screening calculations again indicate the presence of the distorted cis form.
Fourier transform NMR studies of organometallic compounds. II—synthesis and NMR spectroscopy of propenyl and isopropenyl derivatives of silicon and lead
Authors: Mitchell T. N. , Marsmann H. C. 
Published: May 2005

AbstractIsomeric mixtures of compounds MenM(CHCHMe)4−n (M=Si, Pb; n=0−3) have been prepared and studied, as well as pure Me3M(CMeCH2) and mixtures containing propenyl isopropenyl residues bonded to silicon and lead. 1H, 13C, 29Si and 207Pb NMR data are presented; as previously observed for the corresponding tin compounds, the 29Si and 207Pb shifts for the Me3MC3H5 isomers can be used to calculate the shifts expected for the other isomers; while for lead the agreement is good, calculated and observed values for silicon diverge with decreasing n due, at least in part, to steric factors.
Signs of 1H, 19F spin—spin couplings in pentafluorobenzaldehyde
Authors: Schaefer Ted , Marat Kirk 
Published: May 2005

AbstractThe signs of the spin–spin coupling constants between the aldehydic proton and the fluorine nuclei in pentafluorobenzaldehyde are negative over four and six formal bonds and positive over five bonds. The opposite signs had been assumed in previous studies of this molecule. The correct signs are necessary for the determination of the conformational and substituent dependence of these coupling parameters.
Selenium‐77 nuclear magnetic resonance in mono‐ and disubstituted benzo[b]selenophenes
Authors: Baiwir Marcel , Llabrès Gabriel , Christiaens Léon , Piette Jean‐Louis 
Published: May 2005

AbstractThe 77Se chemical shifts of 79 mono‐ or disubstituted benzo[b]selenophenes are reported. The results in the 2‐ and 3‐substituted derivatives closely parallel those previously obtained in the corresponding selenophenes. The measured parameters also correlate well with those measured in benzo[b]tellurophenes. The 125Te and 77Se chalcogen nuclei appear to be much more sensitive to substituent effects than the more classical nuclei. The effects of Cr(acac)3, Eu(dpm)3 and concentration on the 77Se NMR spectra are briefly discussed.
1H and 13C NMR studies of two monosubstituted [2.2]paracyclophanes
Authors: Solladié‐Cavallo Arlette , Hibert Marcel 
Published: May 2005

Abstract250 MHz 1H NMR of two monosubstituted [2.2]paracyclophanes shows that whether the substituent is an electron releasing group, OMe, or a withdrawing group, CO2Me, the transannular effect is deshielding. 62.86 MHz 13C NMR shows that among the six transannular effects, only one has a sign which changes with the nature of the substituent (–4.6 ppm for OMe but +3.3 ppm for CO2Me).
A 13C NMR study of pyridine in the presence of aqueous solutions of carbohydrates
Authors: Hall Laurance D. , Yalpani Mansur 
Published: May 2005

AbstractSpin‐lattice relaxation rates of the 13C responses of pyridine were measured in the presence of aqueous sucrose and sodium alginate solutions and calcium alginate gels. In each case the results indicated a reduction in the overall tumbling rate of pyridine compared with that in aqueous media due to molecular association with the carbohydrate. Although anisotropic motion about the C‐4:N axis of pyridine was apparent in the sucrose solutions no consistent trends were observed for the alginate samples.
Interbenzylic 19F,19F spin‐spin coupling constants in bis(fluoromethyl) arenes
Authors: Ernst Ludger , Pulmann Sabine 
Published: May 2005

AbstractFive‐ to eleven‐bond F,F spin coupling is observed in bis(fluoromethyl)arenes. According to INDO MO calculations, these couplings are transmitted mainly via the aromatic π‐system. The low preference of 1,4‐(CH2F)2‐benzene for the conformation in which the CF bonds are perpendicular to the aromatic ring is
shown by the strong increase of7J(FF) upon double ortho‐substitution.
1H NMR utilization of through‐space effects. II—conformation of dienic ketones
Authors: Rouillard Michel , Geribaldi Serge , Azzaro Marcel 
Published: May 2005

AbstractThe configurational and conformational assignments of the carbonyl group in the Z‐ and E‐1‐(3‐substituted‐5,5‐dimethyl‐2‐cyclohexen‐1‐ylidene)‐2‐butanones are carried out using only the through‐space effects of the carbonyl group. It is demonstrated that, regardless of the Z‐ or E‐configuration or the nature of the substituent in position 3, the conformation of the carbonyl group is always s‐cis.
1H NMR study of partially oriented 1‐phenylpropyne
Authors: Khetrapal C. L. , Highet R. 
Published: May 2005

AbstractThe proton magnetic resonance spectrum of partially oriented 1‐phenylpropyne has been studied and the values of the chemical shifts, the direct and the indirect coupling constants determined from the analysis of the spectrum. The ratios of the interproton distances have been derived. No significant deviations have been observed between the relative proton positions on the aromatic ring in 1‐phenylpropyne and those expected for the regular hexagonal geometry of the benzene ring. The results are insensitive to the mode of internal rotation of the methyl group about the CC bond.
Carbon‐13 and aluminium‐27 nuclear spin relaxation in triethylaluminum
Authors: Vestin U. , Kowalewski J. , Henriksson U. 
Published: May 2005

AbstractCarbon‐13 spin–lattice relaxation times and nuclear Overhauser enhancement factors are reported for triethylaluminium in toluene‐d8 solution in the temperature interval 208–318 K. Aluminium‐27 linewidths are reported for the same solution in the temperature range 212–334 K. The effective correlation times at different positions in the molecule are determined and used for qualitative discussion of internal motions.
NQR investigations of 35Cl in crystalline 2,5‐dichloro‐4‐nitroaniline
Authors: Ramanamurti D. V. , Srihari D. , Venkatacharyulu P. , Premaswarup D. 
Published: May 2005

AbstractTwo NQR lines were observed for 35Cl in 2,5‐dichloro‐4‐nitroaniline at room temperature, using a self‐quenched super‐regenerative spectrometer. Analysis of the Zeeman effect on the two lines using a cylindrical single crystal reveals that the crystal belongs to the monoclinic system. The principal field gradient Z axes enclose an angle of 35° and 28° in the cases of the low and high frequency resonance lines, respectively. The b axis is parallel to 81°, 280°. The unit cell contains either two or a multiple of two molecules. The molecules in the crystal can be arranged into two sets, with the molecular planes in each set being parallel among each other. The angle subtended between the two planes is 159° and each of the planes is inclined to the b axis at an angle of 79.5°. There is an in‐plane bending of the two CCl bonds by 5.5°. The ionic, single bond and double bond characters of the CCl bonds for both chlorines are almost equal, and are in the ratio 24:73:3.
19F and 1H NMR of aldimines of fluoroamino acids with pyridoxal‐5′‐phosphate
Authors: Beguin Claude , Hamman Sylvain 
Published: May 2005

Abstract1H and 19F NMR spectra were obtained for six Schiff bases (aldimines) formed by pyridoxal‐5′‐phosphate (PLP) with four fluorinated or their two parent non‐fluorinated α‐amino acids (phenylalanine and α‐aminobutyric acid). pKA Values were derived from 1H and 19F titration curves. The imine nitrogen of the aldimines is very basic (∼13) and sensitive to the electron withdrawing effect of fluorine. The pyridine nitrogen is less basic in the aldimines (∼7) than in PLP (8.12) and is less sensitive to the electron withdrawing effect of the fluorine than is the imine nitrogen. The phosphate group has a pK in the same range (∼6) and the chemical shifts of some nuclei are sensitive to both pK values. Protonation of the aldimine causes the 1H signal to shift downfield at the methyl protons of the pyridine ring and at the aldehydic proton of the aldimine for the high pK value (except for the aldimines prepared from the β‐fluorophenylalanine), but upfield at the aromatic proton and at the aldehydic proton of the aldimine for the low pK. Protonation of the aldimine causes the 19F signal of an aryl fluorine to shift downfield but gives an upfield shift at a β‐fluorine. These data are related to the highly conjugated electronic structure of the Schiff bases.
Carbon‐13 nuclear magnetic resonance spectra of juvenile hormone III, some of its derivatives, and of analogous compounds
Authors: Kuhnz W. , Rembold H. 
Published: May 2005

AbstractThe 13C NMR spectra of methyl farnesoate and related compounds, including juvenile hormone III, are presented, as well as those of analogous compounds derived from methyl geranate. Correlations between the homologous derivatives are discussed in terms of substituent influences.
Compounds with bridgehead nitrogen. 40—Stereochemistry of perhydronaphthaleno[3,4‐e]pyrido[1,2c]‐[1,3]oxazines
Authors: Crabb Trevor A. , Mitchell Jacqueline S. , Turner Christopher H. 
Published: May 2005

AbstractSeven of the possible diastereoisomeric perhydronaphthaleno[3,4‐e]pyrido[1,2‐c][1,3]oxazines have been synthesized and the configurations and preferred conformations of these assigned on the basis of IR and 1H NMR spectroscopy and the application of conformational principles.
High resolution NMR spectroscopy of heteroaromatic cations. II—pyrylium, thiapyrylium and seleninium cations
Authors: Sándor P. , Radics L. 
Published: May 2005

AbstractHigh resolution 1H, proton coupled 13C and broad‐band decoupled 13C{1H} spectra have been recorded for pyrylium, thiapyrylium and seleninium tetrafluoroborates in CD3CN. Analysis of these spectra has provided accurate values and relative signs of all 1H,1H and 13C,1H coupling constants, as well as the magnitudes of all one‐ and three‐bond 13C,13C couplings observable in naturally occurring doubly‐labelled isotopomers. For the seleninium cation, the magnitudes and relative signs of all 77Se,1H and 77Se,13C coupling constants were also obtained. The chemical shifts and coupling data are compared, on a qualitative basis, with existing theoretical predictions.
NMR study of the complexation of boric acid with catechol (1,2‐dihydroxybenzene)
Authors: Pasdeloup Maurice , Brisson Colette 
Published: May 2005

AbstractThe boric acid–catechol system in aqueous solutions has been studied by means of 11B, 1H and 13C NMR over wide ranges of concentration and pH. 11B spectra show a striking difference between the complexation possibilities of dilute and more concentrated solutions of boric acid. Both the 1:1 and 1:2 complexes can be simultaneously observed by 13C NMR.
On the structure of dithizone
Authors: Rashidi‐Ranjbar Parviz , Yavari Issa 
Published: May 2005

AbstractThe 13C NMR spectrum of dithizone, unlike that of its oxygen analogue, shows only five different types of carbon atom. The 13C chemical shift of the CS group in dithizone is only 7 ppm to lower field of that of the CO moiety in its analogous compound. The results can be rationalized by consideration of tautomeric equilibria which lead to C2v time‐averaged symmetry.
15N,1H coupling constants in pyridines and pyrimidines An application of the INEPT pulse sequence
Authors: Städeli W. , Bigler P. , Von Philipsborn W. 
Published: May 2005

AbstractApplication of a modified INEPT pulse sequence to obtain fully proton‐coupled and selectively decoupled 15N NMR spectra of pyridines and pyrimidines with natural isotope abundance is demonstrated. The spectra are analysed for 2J, 3J and 4J(NH) coupling constants.
Carbon‐13 spectral analysis, tautomeric structures and conformations of four two‐ring methylene‐bridged phloroglucinol derivatives
Authors: Äyräs Pertti , Lötjönen Simo , Widén Carl‐Johan 
Published: May 2005

AbstractThe 13C NMR spectra of phloropyron BB, desaspidin BB, albaspidin BB and margaspidin BB were recorded and the structures of the compounds investigated with the aid of chemical shifts and CH coupling constants. The filicinic acid ring of the first three compounds appeared to have a monoketonic structure with the carbonyl group in position 2 (acyl group in position 3). The pyronone ring of phloropyron BB also has a monoketonic structure, with the carbonyl function adjacent to the ring oxygen. The two rings of the first three compounds attain a conformation where a stabilizing hydrogen bond(s) is (are) formed between the two rings, as shown by the observed CH couplings to some of the hydroxyl protons. The spectrum of margaspidin BB, whichconsists of two aromatic acyl phloroglucinol rings, indicates less inter‐ring hydrogen bonding interactions.
The anisotropic effect of 4‐substituents on the 1H NMR chemical shift of H‐5 in phenanthrenes
Authors: Letcher R. M. 
Published: May 2005

AbstractChloro‐, methoxy‐ and methyl‐substituents in the 4‐position of phenanthrenes exert a profound and diagnostic influence on the 1H chemicalshift of H‐5, and from 13C measurements it is considered to be dueto an anisotropic effect.
Carbon‐13 NMR spectra of polybromoalkanes and polychlorobromoalkanes. Structural increments of halogens in polyhalogenated groups
Authors: Dostovalova V. I. , Velichko F. K. , Vasil'eva T. T. , Kruglova N. V. , Freidlina R. Kh. 
Published: May 2005

AbstractThe 13C NMR spectra of 48 polychlorobromoalkanes have been studied. Unlike the 13C signals of chlorine‐containing groups (38–105 ppm), those of bromine‐containing fragments, with the exception of CBr2 (60–70 ppm), appear in a rather narrow range (25–50 ppm) and are shifted to higher field in relation to similar chlorine‐containing groups. The spin–spin coupling constants in similar bromine‐ and chlorine‐containing groups practically coinciEN. Calculation of the chemical shifts for the polyhaloalkanes under study according to the additivity scheme, as previously observed for polychloroalkanes, renders values which are in considerable discord with experimental values (up to –32 ppm for CBr3). These discrepancies may be compensated for by corrections for the binary interaction of halogen atoms by grouping the halogen‐containing fragments according to the geminal, vicinal, 1,3‐, 1,3,5‐ and 1,2,3‐arrangement of halogen atoms, and by introducing an increment for the position of the halogen at the secondary atom. It is established that as compared to 1‐monohaloalkanes: (a) in the case of the geminal arrangement of halogen atoms the α‐ and γ‐effects diminish (Δ α from –3.2 to –8 ppm; Δγ = 2.6 ppm), while the β‐effect increases slightly (from 0 to 1.2 ppm); (b) in the case of a vicinal arrangement both the α‐ and β‐effects diminish (by about –3.5 ppm) and the γ‐effect remains constant, as if the vicinal system of the halogens was topologically insulated; (c) for the 1,3‐ and 1,3,5‐arrangement of halogens their mutual influence is weak (about –0.5 ppm for each halogen atom in the α‐ and γ‐positions); (d) the 1,2,3 system (serial arrangement of halogen atoms) is the sum of two vicinal fragments and hardly deviates from the additivity scheme; (e) the arrangement of a halogen at the secondary C atom enhances the α‐effect (Δα = 2.8 and 1.0 for methyl and methylene, respectively, in the case of Cl, and 3.5 and 3.7 ppm in the case of Br); the variation of the β‐effect has a different sign in relation to CH3 and CH2 groups (+1.2 and –1.7 for Cl, and +2.5 and –1.0 for Br). More distant effects of halogens (δ and ϵ) were not considered. The determined increments (Δα, Δβ and Δγ) for the α‐, β‐ and γ‐effects of chlorine and bromine atoms allow the prediction of the 13C chemical shifts in polyhaloalkanes with an accuracy up to ±1.5 ppm. Some deviations of up to ±5 ppm may be connected with the influence of a three particle interaction of halogen atoms, which was taken into account only in the case of a geminal arrangement of halogen atoms.
Conformational equilibrium in 8‐methyl‐cis‐2‐thiahydrindane and 8‐methyl‐cis‐2‐oxahydrindane by 13C NMR spectroscopy
Authors: Willer Rodney L. 
Published: May 2005

AbstractThe preferred conformation of 8‐methyl‐cis‐thiahydrindane has been both estimated by 13C NMR chemical shifts and determined by low temperature 13C NMR spectroscopy to be the conformer with the methyl group equatorial with respect to the cyclohexane ring. This result is in disagreement with the interpretation of the temperature dependence of the CD spectra of (+) and (−) 8‐methyl‐cis‐2‐thiahydrindane, whereby the conformation with the methyl group axial with respect to the cyclohexane ring was claimed to be the preferred conformation. The preferred conformation of the related oxygen heterocycle, 8‐methyl‐cis‐2‐oxahydrindane, has been estimated by 13C NMR chemical shifts to be the conformer with the methyl group axial with respect to the cyclohexane ring. Possible reasons for these observations are discussed.
Enriched 13C NMR of a metallated α‐sulphinyl ester; temperature effect
Authors: Solladié‐Cavallo Arlette , Mioskowski Charles 
Published: May 2005

AbstractLithium and magnesium enolates of an α‐sulphinyl ester 83% 13C enriched at C‐1 and C‐2 are studied by 13C NMR at different temperatures. It is shown that two metaliated species are present in the case of lithium which exchange at −60°C, ΔG≠ −60° = 37.8 KJ mol−1 (9.05 Kcal mol−1) and that there is no rapid exchange between the non‐metallated ester and the metallated species (on the NMR time scale). In the case of magnesium, two or three metallated species are formed, according to the temperature which do not exchange up to 0 °C.