bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon‐13 NMR spectra of some polychloro hydrocarbons and related compounds
Authors: Velichko F. K. , Chukovskaya E. C. , Dostovalova V. I. , Kuzmina N. A. , Freidlina R. Kh. 
Published: May 2005

AbstractData derived from the carbon‐13 NMR spectra of 37 organic polychloro compounds allow one to identify readily the CHCl2, CCl2 and CH2Cl groups, the 13C signals of which are registered in the shift ranges of 67 to 78 (80), 85 to 96 and 38 to 55 (59) ppm (from TMS), respectively, and have the distinctive one bond spin‐spin coupling constants 1J(CH) 170 to 184 Hz (for the CHCl2 groups) and 147 to 158 Hz (for the CH2Cl groups). The CCl2CH2CH2Cl fragment features characteristic diamagnetic shieldings of the CCl2 and CH2Cl that may be related to increased electron density on both of these groups.
Etudes configurationnelles et conformationnelles de quelques chlorures de désoxy‐6 β‐L‐héxopyrannosyle chlorosulfonyles et de leurs glycosides de méthyle
Authors: Hajdukovic G. , Martin M. L. , Sinaÿ P. , Pougny J. R. 
Published: May 2005

AbstractUne analyse complète des spectres RMN de désoxy‐6 L‐hexopyrannoses de configuration α et des anomères β correspondants est réalisée. L'ensemble des paramètres obtenus confirme l'existence d'une structure chaise 1C (L) présentant une disposition axiale du substituant anomère dans le cas des α‐fuco‐, α‐rhamno‐ et α‐chinovopyrannosides de méthyle et des chlorures de α‐fuco‐ et α‐rhamnopyrannosyle. La structure reste de type chaise 1C (L) dans le cas des β‐fuco‐ et β‐chinovopyrannosides de méthyle. Il en est de même en dépit de I'effect anomère dû à I'atome de chlore, pour les chlorures de β‐fuco‐et β‐rhamnopyrannosyle. Par contre les paramètres RMN du chlorure de β‐chinovopyrannosyle ne semblent interprétables ni sur la base d'une géométrie chaise à chlore équatorial ni par une structure bateau.
Carbon‐13 NMR spectroscopy of hop bitter substances
Authors: Borremans F. , De Potter M. , De Keukeleire D. 
Published: May 2005

AbstractThe 13C NMR spectra of the most important hop bitter substances are analysed. All individual carbon atoms are assigned, except the oxygen bonded sp2 carbon atoms. Most assignments are made partly by comparison with analogous compounds and partly by reference to literature data. Cross‐correlations with the 1H NMR shifts are made for two main products and confirm the correctness of the assignments. All data are in agreement with the known structures.
Azolides. VII—Restricted rotation in N‐acylindoles and carbazoles. Anisotropy effect of the carbonyl group
Authors: Elguero José , Marzin Claude , Peek Michael E. 
Published: May 2005

AbstractThe barrier to internal rotation about the NC bond and the E/Z configuration of some N‐acetyl and N‐formylindole derivatives have been determined and discussed in terms of electronic and steric effects. The barriers to internal rotation have been determined for certain N‐acetylcarbazoles and some new N‐formyl derivatives of carbazole. Experimental proof is also given, showing that contrary to the provisions of the classical model of carbonyl anisotropy, the protons (α and peri positions) next to the oxygen of the acyl group are displaced to high frequencies. This result allows one to determine the preferred configuration of N‐acetyl derivatives of perimidine and 1H‐naphtho[1,8‐de]triazine.
Influence of chemical exchange on the temperature dependence of Eu(fod)3‐induced shifts
Authors: Samitov Yu. Yu. , Bikeev Sh. S. 
Published: May 2005

AbstractTemperature dependences of the paramagnetic shifts induced by Eu(fod)3 in 1H NMR spectra of ethylene oxide in carbon disulphide solution are obtained in the temperature range from +40 to − 100°C at 100 MHz and from +30 to −60°C at 60 MHz. The influence of chemical exchange leads to a decrease of the observed paramagnetic shifts with decreasing temperature. It is shown that a modified Swift and Connick equation can be used to describe the observed dependences. Upper limits of the mean lifetimes of the Eu(fod)3‐ethylene oxide adduct are τp < 1·7 × 10−8 s at 14 °C and τp < 1 × 10−8 s at 20 °C, respectively. The corresponding activation energy is equal to Va = 13·7 kcal/mol.
1H‐NMR‐Spektroskopische Untersuchungen zur Konformation von Cyclohexandicarbonsäure‐(1,2)‐anhydriden
Authors: Werner H. , Zschunke A. , Mann G. , Kleinpeter E. 
Published: May 2005

AbstractDie chemischen Verschiebungen der 1H‐NMR‐Spektren von 18 methylsubstituierten Cyclohexandicarbonsäure‐(1,2)‐anhydriden wurden bestimmt. Von den unsymmetrisch sub‐stituierten Verbindungen wurden die vicinalen Kopplungskonstanten ermittelt. Bei den trans‐Anhydriden lässtsich aus den NMR‐Daten ableiten, dass der Sechsring in einer sesselähnlichen Form vorliegt. Auch bei den cis‐Anhydriden sind in den meisten Fällen Konformationen mit verdrillter Sesselanordnung des Cyclohexans bevorzugt.
The 250 MHz 1H NMR spectrum of cinnoline
Authors: Pappalardo Giuseppe C. , Gruttadauria Salvatore , Le Bail Henri 
Published: May 2005

AbstractThe proton NMR spectrum of cinnoline has been measured at high field (250 MHz) and analysed as an H‐8‐de‐coupled ABCXY and H‐4‐decoupled ABCX system. Inter‐ring HH couplings have been determined and discussed in relation to theoretical values obtained using INDO calculations.
Synthesis and structure assignments of cis‐ and trans‐2‐(diethylaminomethyl)cyclohexanols
Authors: Puar Mohindar S. , Cohen Allen I. , Krapcho John 
Published: May 2005

AbstractThe synthesis of cis‐ and trans‐2‐(diethylaminomethyl)‐cyclohexanols and their structural assignments by NMR using the shift reagent Eu(dpm)3 are described. The correlation of the induced shifts with the equation Δν = K(3 cos2θ – 1)r−3, assuming an EuO distance of 2·4 Å and θ less than 30°, suggests that the interactions are pseudocontact. The values of K are 452 and 420 for the two cyclohexanols, respectively.
On the mechanism of reaction of tert‐butoxyl radicals with dialkylphosphites
Authors: Brunton G. , Ingold K. U. 
Published: May 2005

AbstractIt has been shown by ESR spectroscopy that the title reaction involves abstraction of hydrogen from the phosphite, since at −10°C the reaction has a kinetic deuterium isotope effect, kH/kD, or ∼3. The rate constant for hydrogen abstraction is c. 2 × 104 M−1 s−1. There is no significant addition of alkoxyl radicals to the phosphite.
19F NMR analysis of the fluorides of perfluorocyclohexane‐sulphonic acid and of 3‐trifluoromethylperfluorocyclopentane‐1‐sulphonic acid
Authors: Gurato Giorgio , Cavalli Luciano , Troilo G. Giorgio 
Published: May 2005

AbstractFrom the electrochemical fluorination of the chloride and the fluoride of benzenesulphonic acid, in addition to the main product C6F11SO2F, the side products C5F8(CF3)SO2F, a structural isomer of the main product and C6F10ClSO2F are also obtained.The NMR analysis of these products was performed. Chemical shift and coupling constant values were obtained for all the compounds. The NMR parameters of the main product are compared with those of perfluoromethylcyclohexane according to the data of Jolley, Sutcliffe and Walker. From the NMR parameters of C5F8(CF3)SO2F it was possible to demonstrate that substitution on the ring for —SO2F and CF3— is of the 1,3 and not the 1,2 type.
Conformationally dependent influence of 3‐substituents on the observable magnetic non‐equivalence of benzylic methylene protons in N‐benzylpiperidines
Authors: Iorio M. A. , Casy A. F. 
Published: May 2005

AbstractExamples are given of the conformationally dependent influence of 3‐substituents (methyl, n‐propyl, allyl, aryl, hydroxy and acyloxy) on the magnetic non‐equivalence of the benzylic methylene protons (NCH2Ph) of N‐benzylpiperidine as observable by 1H NMR. The results, together with data already reported, emphasise the value of 1H NMR studies of N‐benzyl derivatives in stereochemical investigations of substituted piperidines.
Additive NMR shielding parameters for some substituted cyclohexanols
Authors: Ceccarelli G. , Macchia B. , Macchia F. , Monti L. 
Published: May 2005

AbstractThe shielding effects of some substituents on the chemical shifts of the methine proton of axial and equatorial cyclohexanols have been calculated and rationalised. The remarkable downfield shift observed for the phenyl substituent has been discussed on the basis of Johnson‐Bovey and Haigh‐Mallion theories. The chemical shift of methine protons of some cyclohexanols have been calculated using additive shielding increments. Agreement between calculated and experimental values substantiates the use of the additivity principle in cyclohexyl systems and justifies the origin of certain marked inversions of the accepted rule that the axial protons resonate at lower fields than the corresponding equatorial ones.
NMR studies of the configuration of the isomeric 2,3‐dimethyloxetanes
Authors: Ewing D. F. , Holbrook K. A. , Scott R. A. 
Published: May 2005

AbstractThe 1H and 13C NMR spectra of cis‐ and trans‐2,3‐dimethyloxetane have been re‐examined and the published NMR assignments shown to be in error.
An NMR study of the conformations of certain alcohol derivatives of tricarbonyl(diene)iron compounds: A critique
Authors: Willcott M. R. , Bearden W. H. , Davis Raymond E. , Pettit R. 
Published: May 2005

AbstractThe initial assignments by Mahler and Pettit of relative configurations of the two racemic diastereomeric tricarbonyl‐(trans,trans‐3,5‐heptadien‐2‐ol)iron complexes and to the two racemic diastereomeric tricarbonyl‐(trans‐3,5‐hexadien‐2‐ol)iron complexes are consistent with NMR coupling constants, conformational analysis, previously reported Eu(fod)3 lanthanide‐induced shift data and new Yb(dpm)3 lanthanide‐induced shift data. A detailed discussion shows that, contrary to the claim by Foreman, the lanthanide‐induced shift data alone provide no new information regarding the relative configurations of these alcohols.
Semi‐empirical MO calculations of nuclear spin coupling constants
Authors: Barbieri Giorgio , Benassi Rois , Lazzeretti Paolo , Taddei Ferdinando 
Published: May 2005

AbstractThe results obtained using different semi‐empirical approaches, namely EHMO, IEHMO, CNDO/2 and INDO, in the calculation of spin–spin coupling constants within the framework of the one‐electron MO approximation are systematically compared in the case of several classes of organic molecules. While, at a semi‐empirical level SCF methods normally provide satisfactory wave function, the use of the simple EHMO seems better able to satisfy the problem connected with the calculation of spin–spin coupling constants, expecially when an appropriate set of AO's is chosen, in order to avoid parametrisation of Dirac monocentric integrals. Charge iteration (IEHMO) seems to improve the results slightly only when heteroatoms are present, but the complexity introduced into the calculations and the greatly increased computer time do not justify the slight improvement achieved, particularly as the method is applied to large molecules and organometallic compounds.
The proton magnetic resonance of heterocyclic diketones
Authors: Galasso V. , Pellizer G. , Lisini A. , Bigotto A. 
Published: May 2005

AbstractA full analysis of the 60 MHz 1H NMR spectra of heterocyclic analogues of 1,3‐indandione [N‐(2‐bromoethyl)‐phthalimide, phthalic anhydride and thiophthalic anhydride] and of 1,2‐indandione (N‐methylisatin, coumarandione and 2,3‐dihydrothionapthene‐2,3‐dione) has been carried out. The protons of the symmetric compounds resonate at lower fields than those of the asymmetric ones and the proton ortho to the CO function is more deshielded than the proton ortho to the heteroatom. Coupled Hartree‐Fock perturbation theory has been applied to estimate the ring current contributions to the proton chemical shifts and to the magnetic susceptibilities. MO calculations based on the finite perturbation theory at the CNINDO levels provide information on the relative importance of σ and π pathways for the various coupling constants.
13C Fourier transform NMR and partially relaxed Fourier transform NMR relaxation study on the ethanol–manganese(II) system
Authors: Tiezzi E. , Valensin G. 
Published: May 2005

AbstractThe paramagnetic contribution to the 13C and 1H nuclear relaxation rates in the ethanol‐Mn(II) system has been calculated. Both T1 and T2 experiments have been performed by means of Fourier transform and partially relaxed Fourier transform NMR spectroscopy. The correlation times for the dipolar and scalar parts have been discussed and evaluated. Calculations of distances and of hyperfine coupling constants have been carried out.
29Si and 13C NMR studies of organosilicon chemistry. V—Sugar derivatives
Authors: Gale D. J. , Haines A. H. , Harris R. K. 
Published: May 2005

Abstract29Si spectra have been obtained for four trimethylsilylated hexopyranoside sugars, and the resonance due to the CH2OSiMe3 group at position 5 has been assigned by experiments involving gated decoupling at a single 1H frequency.
Carbon‐13 chemical shifts and conformations of dimethylcyclohexanols
Authors: Pehk T. , Kooskora H. , Lippmaa E. 
Published: May 2005

AbstractCarbon‐13 chemical shifts of all twenty‐two dimethylcyclohexanols, formed by the hydrogenation of isomeric xylenols, have been measured and assigned. Conformational peculiarities of dimethylcyclohexanols are discussed on the basis of their carbon‐13 chemical shifts.
13C NMR spectra of pyridinium betaines and related compounds
Authors: Takeuchi Yoshito , Dennis Nicholas 
Published: May 2005

Abstract13C NMR spectra of 1‐methyl‐, 1‐phenyl‐ and 1, 6‐dimethyl‐pyridinium‐3‐oxide, 3‐methylphthalazinium 1‐oxide and anhydro‐3‐methanesulphonamido‐1‐methylpyridinium hydroxide, together with the corresponding amines and quaternary salts, were determined with and without proton noise‐decoupling. The assignment of resonances was based on the analysis of the fine splitting pattern caused by long range couplings whenever appropriate. A procedure for the estimation of chemical shifts of the salts and betaines is proposed.
Substituent chemical shifts of the organotin moiety in compounds of the type RSnMenCl3 − n (n = 0 to 3; R = n‐alkyl)
Authors: Mitchell Terence N. 
Published: May 2005

AbstractThe 13C and 119Sn NMR spectra of 33 organotin compounds of the type RSnMenCl3 − n and related types are discussed. The substituent effects of the groups SnMe3, SnMe2Cl, SnMeCl2 and SnCl3 (and of some related groups) on the carbon chemical shifts in the alkyl group R have been determined; the SnMe3 group causes a small upfield shift of the carbon attached to it, while the other groups cause downfield shifts. The shifts show a monotonic change on replacing methyl groups in Me3Sn by chlorine atoms. The effects on carbons further removed from the tin atom are discussed. Variation in R causes little change in nJ(SnC) or δ(119Sn).
A NMR identification of isomeric Meisenheimer adducts from 4‐nitrobenzofurazan and 4‐nitrobenzofuroxan
Authors: Terrier François , Millot François , Chatrousse Alain‐Pierre , Pouet Marie‐José , Simonnin Marie‐Paule 
Published: May 2005

AbstractIt has been shown by NMR spectroscopy that both 4‐nitrobenzofurazan and 4‐nitrobenzofuroxan give isomeric σ‐adducts, which result from methoxide addition at the non‐substituted 5‐and 7‐carbons.
The assignment of the 1H NMR signals to the methine bridge H‐atoms in chlorophyll derivatives
Authors: Trowitzsch Wolfram 
Published: May 2005

AbstractExperiments are described which prove the assignments of the α‐ and β‐protons in the 1H NMR spectra of methyl phaeophorbide a (1) and methyl pyrophaeophorbide a (2). Because of the structural relationship between derivatives of the bacteriochlorophylls d (5) and 2, dehydration of 5 results in a homologue mixture [2‐(des‐α‐hydroxyethyl)‐2‐vinyl‐bacteriomethyl phaeophorbide] d (6) of 2. Since the homologue substituents in 6 are located at C‐4 and C‐5 surrounding the β‐H position, and since only one broad signal appears in its 1H NMR spectrum, this is assigned to the β‐proton. This experiment proves that the sequence of increasing shielding is β, α and δ in 6; and, therefore, the same sequence applies to the 1H NMR spectra of 1 and 2. This knowledge reveals that the product of electrochemical reduction of 1 in deuteromethanol is exclusively an α‐chlorin‐phlorin (8). In addition, the 1H NMR spectrum of the 2‐vinyl derivatives of the bacteriomethyl phaeophorbides c (7) shows the same broad signal at lowest field as does that of 6. The sequence of increasing shielding is therefore, β, α. The influence of the additional δ‐methyl group in 7 on the ring current is explained.
Etude RMN 13C d'aziridines non substituées sur l'azote II—Aza‐7 bicyclo[4.1.0]heptanes, configurations relatives et conformations privilégiées
Authors: Mison P. , Chaabouni R. , Diab Y. , Laurent A. , Martino R. , Lopez A. , Wehrli F. W. , Wirthlin T. 
Published: May 2005

AbstractL'étude des spectres RMN 13C de dialkyl‐1,2 (ou alkylphényl) aza‐7 bicyclo[4.1.0]heptane diastéréoisomères nous a permis de déterminer leur configuration et leurs conformations priviligiées. Dans les isomères de configuration cis le substituant en position 2 est ‘pseudoaxial’ alors qu'il est ‘pseudo‐équatorial’ pour ceux de configuration trans.
Interactions intramoléculaires: XXIII—Constantes de couplage et interactions gauches avec un groupement t‐butyle (cyclohexanones disubstituées 3, 4)
Authors: Lafrance Ronald , Aycard Jean‐Pierre , Berger Jeanne , Bodot Hubert 
Published: May 2005

AbstractLes spectres RMN du proton d'une série de R‐3 X‐4 cyclohexanone (d4‐2,2,6,6), cis et trans sons analysés. La comparaison des constantes de couplage vicinales avec celles des homologues cyclohexaniques conduit à préciser les équilibres conformationnels chaise‐chaise pour R = CH3, X = CN, la structure chaise des isomères cis avec un groupement t‐butyl équatorial et l'existence d'un équilibre conformationnel lorque les groupements (CH3)3C et CN sont trans. Cette dernière situation est analysée au moyen d'une relation de Karplus simplifiée, mais controlée, et dans l'hypothèse d'un mélange de deux conformères. Dans ces conditions, seuls peuvent être impliqués les conformères chaise diéquatorial et bateau (angle dièdre Φ34 de l'ordre de −6°C).
Structural studies on some 1,3,5,7‐tetraaza‐ and 1,3,5‐triazaadamantane derivatives
Authors: Farminer A. R. , Webb G. A. 
Published: May 2005

Abstract1H and 13C NMR data are reported for hexamethylenetetramine (hexamine), 7‐nitro‐1,3,5‐triazaadamantane and some of their quaternary derivatives. INDO molecular orbital calculations have been performed on these molecules to aid the interpretation of their spectra.
Azobilirubin isomers: NMR structure determination using a shift reagent
Authors: Salmón Manuel , Díaz E. , Rock M. C. , Fenselau Catherine 
Published: May 2005

AbstractThe isomeric benzeneazodipyrromethene derivatives, obtained from the reaction of bilirubin and a phenyldiazonium salt were separated as their corresponding methyl esters. The lanthanide‐induced chemical shifts, coupling constants and double irradiation experiments permit direct assignment of methyl and vinyl substituent positions in these bilirubin‐derived isomers.
NMR spectral studies: XIII—titanium tetrachloride‐induced and lanthanide‐induced shifts in the proton NMR spectra of β‐lactams
Authors: Bose Ajay K. , Manhas M. S. , Srinivasan P. R. , Chawla H. P. S. , Dayal B. , Foley D. A. 
Published: May 2005

Abstract2‐Azetidinones which carry a proton each on C‐3 and C‐4 often pose a problem in the correct assignment of the resonances due to these protons; titanium tetrachloride has been shown to be an effective and reliable n.m.r. shift reagent to differentiate between these two protons on the basis of their different sensitivities to this reagent. A few compounds were also studied with Eu(fod)3 and Pr(fod)3 for the sake of confirmation.
The enol‐imine to keto‐enamine tautomerization involved in the formation of 3‐benzylamino‐5,5‐dimethylcyclohex‐2‐enone
Authors: Kikta E. J. , Bieron J. F. 
Published: May 2005

AbstractThe formation of 3‐benzylamino‐5,5‐dimethylcyclohex‐2‐enone has been found to proceed through the initial formation of its enol‐imine tautomer. The enol‐imine has been isolated by a novel synthesis. It involves suspending dimedone in hexane for one hour at 67 °C with the amine in solution. Nuclear magnetic resonance spectroscopy has confirmed the tautomerization by observing the changing spectra as the enol‐imine tautomerizes to 3‐benzylamino‐5,5‐dimethylcyclohex‐2‐enone. The change in the nuclear magnetic resonance spectra is highlighted by a moving peak, which proceeds upfield with decreasing intensity as the tautomerization reaches completion. This moving peak involves chelated water formed in the initial condensation of dimedone and benzylamine. The chelated water acts as an active exchange agent which enhances the tautomerization rate. Similar results are obtained for the Schiff base derived from dimedone and aniline. This is the first isolation of the pure enol‐imine tautomeric form of 3‐benzylamino‐5,5‐dimethylcyclohex‐2‐enone. Under refrigeration the enol‐imine is found to be stable for over six months.
The 13C NMR spectra of nine ortho‐substituted phenols
Authors: Smith William B. , Proulx Thomas W. 
Published: May 2005

AbstractThe 13C chemical shifts of nine ortho‐substituted phenols have been determined in cyclohexane and in dimethyl sulfoxide. All data were acquired in duplicate upon c.w. and FT instrumentation and both sets of data are presented.The chemical shifts at carbons 1, 2 and 3 are correlated with the parameter Q. Q has been defined as P/Ir3 where P is the polarizability of the adjacent CX bond, I is the first ionization potential of the elements F, Cl, Br, I and H, and r is the CX bond length. Experimental values of Q are available for other substituents. The field and resonance parameters of Swain and Lupton may be combined with Q to form a three part multiple regression correlation which is more exact than that with Q alone and which applies to all carbons in the aromatic ring.The results of this study suggest that only one value of the Q parameter is needed to characterize the behavior of the nitro group in these solvent systems. This conclusion is contrasted with earlier results of the effect of substituents on proton chemical shifts in these systems.
The reactions of transition metal chelates with organometallic compounds and their paramagnetic products: IV—the anion radical of acetylacetonate
Authors: Staško A. , Tkáč A. , Laurinc V. , Malík L. 
Published: May 2005

AbstractThe anion radical of acetylacetonate is formed by the reaction of nickel (II) acetylacetonate with Grignard reagents. From the two coupling constants found in the e.s.r. spectrum, the one of 2·6 G was assigned to the methine proton and the one of 12·5 G to the six equivalent methyl protons of acetylacetonate. The calculations of spin densities for the anion radical of acetylacetonate by the INDO method are in relatively good agreement with experiment.
Proton magnetic resonance studies of compounds with bridgehead nitrogen atoms: XXXII—The 1H n.m.r. spectra and stereochemistry of 4‐aryl‐1,6,7,11b‐tetrahydro‐2H,4H‐[1,3]oxazino[4,3‐a]isoquinoline, 4‐aryl‐1,2,6,7,12,12b‐hexahydro‐4H‐[1,3]oxazino[3′,4′:1,2]pyrido[3,4‐b]indole and of related systems
Authors: Crabb Trevor A. , Mitchell Jacqueline S. 
Published: May 2005

Abstractcis(4‐H,11b‐H)‐4‐Aryl‐1,6,7,11b‐tetrahydro‐2H,4H‐[1,3]oxazino [4,3‐a]isoquinoline and the related thiazino compound preferentially adopt in solution the O (or S) inside cis‐conformation in contrast to cis(1‐H,4a‐H)‐1‐arylperhydropyrido[1,2‐c][1,3]oxazine which adopts the trans fused conformation. 1‐(β‐Hydroxy‐ethyl)‐1,2,3,4‐tetrahydro‐β‐carboline condenses with benzaldehyde to give the 1,3‐oxazine derivative rather than the dimeric structure reported in the literature.