bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multinuclear NMR and infrared spectroscopic study of a series of cis‐Mo(CO)4(py‐R)2 (Py‐R = 3‐ or 4‐substituted pyridine) complexes: Relationship between chemical shifts and infrared force constants and the Taft electron donor/acceptor parameters of the pyridine substituents
Authors: Box James W. , Gray Gary M. 
Published: May 2005

AbstractPoor correlations are normally observed between the chemical shifts of the various NMR‐active nuclei in Mo carbonyl complexes of group 15 ligands as the group 15 atom substituents are varied. It is possible to observe good chemical shift correlations and to develop relationships between chemical shift and changes in electron density due to variations in the group 15 atom substituents, provided that this variation does not change the cone angles of these ligands. This is the case for complexes of the type cis‐Mo(CO)4(py‐R)2 (py‐R = 3‐ or 4‐substituted pyridine). Good to excellent linear correlations are observed between the chemical shifts of the cis and trans CO 13C and 17O resonances and the 95Mo resonances in these complexes, and between these chemical shifts and the CO infrared stretching force constants of the complexes. Good to excellent correlations also occur between either the chemical shifts or the CO infrared stretching force constants and either the Taft σm/σp or σR and σ1 parameters. These correlations provide significant insights into the relationship between the electron donor/acceptor abilities of the pyridine ligands and the NMR and infrared spectra exhibited by the cis‐Mo(CO)4(py‐R)2 complexes.
Identification of guayule triterpenes by two‐dimensional and multipulse NMR techniques
Authors: Komoroski Richard A. , Gregg Earl C. , Shockcor John P. , Geckle J. Michael 
Published: May 2005

AbstractFive triterpene natural products have been isolated from the resin of the guayule bush (Parthenium argentatum) and four of these identified using two‐dimensional (2D) and multipulse NMR techniques. Of the five structures, two have been reported previously. Two of the structures contain an uncommon seven‐membered ring incorporating an ether linkage. The 2D carbon–carbon chemical shift correlation (2D INADEQUATE) and DEPT multiplicity experiments are used as the primary techniques for determining the molecular skeleton. Supporting evidence is provided by the carbon–proton and proton–proton (COSY) chemical shift correlation experiments, and by preparation of simple derivatives. The merits and problems of the various techniques are discussed. We reverse the previous assignments of C‐27 and C‐29 of cycloartanone.
Use of lanthanide shift reagents to probe the conformation of fatty acids in solution by 13C NMR
Authors: Pons Miquel , Chapman Dennis 
Published: May 2005

AbstractThe conformational analysis of short polymer chains involves the use of statistical models, and their predictions must be checked against experimental information. Ytterbium‐induced shifts in the 13C NMR spectra of fatty acids provide a non‐perturbing, straightforward method of simultaneously obtaining positional information about all the carbon atoms up to nine bonds away from the comuplexation point. Experimental results for saturated and unsaturated C‐18 fatty acids are compared with the predictions of a restricted isomeric states (RIS) model.
Stereochemical investigations on (E)‐homoeburnane derivatives by 1H and 13C NMR spectroscopy
Authors: Tóth Gábor , Szántay Csaba , Kardos Zsuzsa , Incze Mária , Sóti Ferenc , Szántay Csaba , Kotovych George 
Published: May 2005

AbstractSeveral 14‐hydroxy‐14a‐methyl‐(E)‐homoeburnane diastereoisomers have been synthesized and studied by 1H and 13C NMR spectroscopy. ID NOE difference experiments, together with proton‐proton correlation and decoupling measurements, have allowed the complete assignment of the 1H and 13C NMR spectra. The relative configurations and predominant conformations have been established.
Dinuclear tungsten and molybdenum complexes with fulvalene ligands: Assignment of their 1H and 13C NMR spectra by one‐dimensional heteronuclear noe difference spectroscopy
Authors: Meyerhoff Dieter J. , Nunlist Rudi , Tilset Mats , Vollhardt K. Peter C. 
Published: May 2005

AbstractOne‐dimensional heteronuclear NOE difference spectroscopy was used to assign 1H and 13C NMR spectra of dinuclear fulvalene complexes with tungsten and molybdenum. It was found that metal‐metal bonded complexes show 1H chemical shifts which are the inverse of those in non‐metal—metal bonded complexes, whereas the relative 13C chemical shifts are not affected by the metal—metal bond.
A caveat concerning ‘ultra‐high‐resolution nmr.’ effects of magnetic field induced alignment
Authors: Bastiaan E. W. , Bulthuis J. , MacLean C. 
Published: May 2005

AbstractLine positions in high‐resolution NMR spectra may be affected by dipolar couplings and anisotropic shift contributions, which arise from the partial orientation of the molecules by the magnetic field of the spectrometer. It is shown that, depending on the system studied, these effects can be larger than 0.01 Hz at moderate fields (ca 7 × 104 G), and should therefore be considered when claiming accuracies of 10mHz or better.
Carbon‐13 NMR spectra of nineteen (1R)‐(+)‐camphor derivatives
Authors: Crull George B. , Garber Albert R. , Kennington John W. , Prosser Christina M. , Stone Phillip W. , Fant James W. , Dawson John H. 
Published: May 2005

AbstractNineteen derivatives of (1R)‐( + )‐camphor with deutero, fluoro, bromo, iodo, keto, and hydroxyl functionalities at carbons 3, 5, 8, or 9 have been examined using 13C NMR. The chemical shifts for each carbon of these substituted camphor derivatives have been assigned using broad band decoupling and the refocused INEPT pulse sequence.
Heterocyclic β‐enamino esters 43—easy 13C NMR distinction between aryl‐substituted dimroth isomers of the 1,2,3‐triazole series
Authors: Wamhoff H. , Bohlen J. , Yang S. Y. 
Published: May 2005

Abstract5‐Amino‐1‐aryl‐1,2,3‐triazoles and 5‐anilino‐1,2,3‐triazoles can be easily distinguished by their 13C NMR spectra. Thus, C‐4 and C‐5 of some studied 5‐anilino isomers are deshielded by 2–5 ppm in comparison with the corresponding 5‐amino‐1‐aryl isomers. From the 13C NMR signals of the aryl carbons in the same 5‐anilino isomers, C‐6 is shifted downfield (ca 9 ppm; –I effect), whereas C‐7 and C‐9 are shifted upfield (ca 7 and 10 ppm, respectively; +M effect). This allows a fast and easy assignment of both Dimroth isomers.
13C NMR spectroscopy of naphtho‐γ‐pyrones
Authors: Priestap Horacio A. 
Published: May 2005

AbstractThe 13C NMR spectra of three naphtho‐γ‐pyrones produced by Aspergillus fonsecaeus (NRRL 67, 0 16–1), viz. 5‐hydroxy‐6,8‐dimethoxy‐2‐methyl‐4H‐naphtho[2,3‐b]pyran‐4‐one (rubrofusarin B), 2,3‐dihydro‐2,5‐dihydroxy‐6,8‐dimethoxy‐2‐mehtyl‐4H‐naphtho[2,3‐b]pyran‐4‐one (fonsecin B) and 2,3‐dihydro‐2,5,8‐trihydroxy‐6‐methoxy‐2methyl‐4H‐naptho[2,3‐b]pyran‐4‐one (fonsecin), have been determined. Assignments of the carbon resonances were carried out from chemical shifts, long‐range carbon‐hydrogen couplings and hydrogen–deuterium exchange information. Carbon shift assignments previously reported for fonsecin have been revised. The C‐4 and C‐5 signals show that the angle of twist of the carbonyl group with the aryl ring system is larger in fonsecin than in fonsecin B, indicating the occurrence of different preferred conformations in the dihydropyrone ring of these compounds.
Selenium‐77 NMR spectral analysis of selected substituted selenanes, selenanones and 3‐selena‐7‐azabicyclo[3.3.1]nonanes and derivatives
Authors: Thompson M. Daniel , Smith Gary S. , Ramalingam K. , Berlin K. Darrell 
Published: May 2005

AbstractA series of selenanes and selenanones have been examined using 77Se NMR analysis. Sharp resonances were found in all cases whether recorded at 47.7, 51.4 or 57.22 MHz or in DCCI3 or DMSO‐d6. Diphenyl diselenide was used as the external reference, but all resonances were subsequently referred to dimethyl selenide (0°C, O ppm). It was observed that in the selenanone family any substituent at the α‐, β‐ or γ‐positions exerted a significant effect on the 77Se resonances. The same was true in the selenanes. Moreover, the presence of a chair‐chair or chair‐boat form in certain 3‐selena‐7‐azabicyclo[3.3.1]nonan‐9‐ones and related 3‐selena‐7‐azabicyclo[3.3.1]nonanes (and hydroperchlorates) induced remarkable differences in 77Se shifts. Some general observations and conclusions are delineated in terms of the influence of various groups on the 77Se resonances in these cyclic systems.
NMR spectra of betaines from marine algae
Authors: Blunden Gerald , Gordon Sally M. , Crabb Trevor A. , Roch Olive G. , Rowan Michael G. , Wood Brian 
Published: May 2005

AbstractThe 1H and 13C NMR spectroscopic characteristics of a range of behines, most of which are found in marine algae, are described. The spectral features are an important aid to the identification of these compounds. In the 13C NMR spectra, some (14N, 13C) couplings are clearly observed. The FAB mass spectral characteristics of some of these compounds are also described.
Carbon‐13 NMR of solid phenylazo‐2‐naphthols: Tautomerism and (13C, 14N) residual dipolar coupling
Authors: Harris Robin K. , Jonsen Paul , Packer Kenneth J. , Campbell Colin D. 
Published: May 2005

AbstractThe use of 13C CP/MAS NMR is illustrated by the determination of the tautomeric structures of some phenylazo‐2‐naphthols in the solid state. The effects of (13C, 14N) residual dipolar coupling for such systems are discussed.
17O NMR spectroscopy: Referencing in diamagnetic and paramagnetic solutions
Authors: Gerothanassis Ioannis P. , Lauterwein Jürgen 
Published: May 2005

AbstractSeveral referencing techniques for measuring 17O NMR chemical shifts in diamagnetic and paramagnetic solutions have been examined. 1,4‐Dioxane is recommended as an external reference standard for diamagnetic solutions because the 17O resonance position is independent of temperature between 27 and 90°C. At 40°C the 17O chemical shift, within experimental error, corresponds to that of doubly distilled water. Nitromethane cannot be considered as a suitable internal reference because of large solvent effects on the 17O chemical shift. Further, in organic solutions its lanthanide‐induced chemical shifts are not negligible. For the study of paramagnetic solutions the combined use of a cylindrical and a spherical cell is proposed: the 17O resonance of either the magnetically active solvent or a convenient compound added to the solution is recorded in both cells; the chemical shift difference between the two measurements is the bulk magnetic susceptibility shift.
Deuterium isotope effects in propylene and ethylene ozonide
Authors: Choe Jong‐In , Choi Hyung‐Soo , Kuczkowski Robert L. 
Published: May 2005

AbstractThe proton NMR spectra of four deuteriated species of propylene ozonide and five of ethylene ozonide were analysed. The deuterium isotope shifts were 0.0140 ppm (H gem to D), 0.0034 ppm (H trans to D) and 0.0015 ppm (H cis to D) for propylene ozonide. The same trends were observed in ethylene ozonide. The isotope shifts were not additive when two geminal protons were substituted by deuterium. The relative intensities of microwave rotational and proton NMR transitions were compared for propylen ozonide‐d1 prepared stereoselectively in order to assign unambiguously its chemical shifts and spin–spin splittings.
Interactions between protonated retinal schiff base and various counter ions: A study by two‐dimensional NOE NMR spectroscopy
Authors: Ghirlando Rodolfo , Berman Elisha , Baasov Timor , Sheves Mordechai 
Published: May 2005

AbstractUsing two‐dimensional NMR spectroscopy, the spatial location of various carboxylate anions relative to the polyene chain of the protonated Schiff base of all‐trans‐retinal was determined. The observed intermolecular NOE cross‐peaks between a proton on the counter ion and a proton near the nitrogen atom indicate the existence of ion‐pair formation between the protonated retinal Schiff base and various counter ions in chloroform. The results suggest that the most likely site of the carboxylate group of the counter ion is in the immediate vicinity of the positively charged nitrogen atom of the retinal Schiff base.
Assignment of carbon‐13 nuclear magnetic resonance spectra of some friedelanes
Authors: Patra Amarendra , Chaudhuri Swapan Kumar 
Published: May 2005

AbstractCarbon‐13 resonance assignments of cerin acetate, 2α‐pyridine‐N‐oxyfriedelan‐3‐one, epi‐cerin and its acetate, 3α‐hydroxyfriedelan‐2‐one and its acetate, 3‐hydroxyfriedel‐3‐en‐2‐one and its acetate, friedelane‐3,7‐dione, 3β‐hydroxyfriedelan‐7‐one, canophyllol, friedelolactone and friedelolactone‐2α‐yl acetate, friedelane‐2α,3β‐diol and its diacetate, friedelane‐2β,3α‐diyl diacetate, pachysandiyl‐A diacetate and friedelane‐2β‐3β‐diyl diacetate have been made. The carbon signals of 3‐oxofriedelan‐29‐ol and its acetate, methyl 3‐oxofriedelan‐29‐oate, 3‐oxofriedelan‐30‐ol, maytenfoliol, maytensifolin‐A, maytensifolin‐B, pachysonol and pristimerin reported in the literature have also been considered for their specific resonance assignments. A few signal assignments of some friedelanes, viz. friedelan‐28‐ol, friedelan‐29‐ol, friedelan‐30‐ol, friedelan‐29‐al, 3‐oxofriedelane‐21α,26‐diol and zeylasterone, reported recently by others, are unusual and have been reviewed.
1H NMR chemical shifts of gaseous amines
Authors: Chauvel J. Paul , Folkendt Michael M. , True Nancy S. 
Published: May 2005

AbstractGas‐phase 200 MHz 1H NMR spectra of nineteen primary and nine secondary aliphatic amines were obtained at total densities below 0.15 amagat at 148.6 °C. Theoretical predictions of 1H chemical shifts of ammonia and methylamine are compared with the gas‐phase experimental values. The amino proton chemical shifts move downfield with increasing alkyl group size. For series of amines with similar structural geometry about the amino nitrogen, the 1H amino proton chemical shifts correlate reasonably well with gas‐phase basicities as measured via ion cyclotron resonance spectroscopy (r = 0.95 for a linear fit of chemical shift to the gas‐phase basicity for the primary amines and r = 0.93 for the secondary amines). Gas‐phase 1H NMR spectra for linear diamines, hydroxyamines, cyclic amines and substituted anilines were also obtained.
Carbon‐13 NMR Studies. 127—13C and 2H NMR investigations of 1H/2H exchange in isomeric tricyclic [5.2.1.0] and [5.3.1.0] ketones
Authors: Jurlina Jeffrey L. , Patel Hemant A. , Peiris Sriyawathie , Stothers J. B. 
Published: May 2005

AbstractUnder strongly basic conditions (t‐BuO−/t‐BuOD at 185 °C), the 9,9‐dimethyltricyclo[5.2.1.02,6]‐ and ‐[5.2.1.01,5]decan. 8‐ones and the homologous [5.3.1.0]undecanones undergo multi‐site 1H/2H exchange. The total 2H uptake was monitored by mass spectrometry, while the individual sites of exchange were established by 13C NMR spectroscopy. The relative rates and stereoselectivity of incorporation at each site were determined by 2H NMR. These results extend our knowledge on the activating effect of the carbonyl group for proton abstraction at remote centres and are compared with earlier data for several related bi‐ and tricyclic systems. In addition, the 13C spectra provide several examples of geminal and vicinal 2H‐induced isotope shifts in tricyclic carbon skeletons.
Triterpenoids. Part II—Carbon‐13 NMR spectra of 18β‐ and 18α‐11‐oxooleanolic acid derivatives
Authors: Wrzeciono U. , Zaprutko L. , Budzianowski J. , Wojtowicz H. , Dubowska D. 
Published: May 2005

AbstractThe 13C NMR spectra of five pairs of 18β‐ and 18°‐11‐oxooleanolic acid derivatives have been assigned. The chemical shifts of C‐12, C‐13, C‐17, C‐18 and C‐28 are of diagnostic value for the determination of the D/E junction stereochemistry.
Carbon‐13 and proton nuclear magnetic resonance studies of (E)‐ and (Z)‐ azetidinones
Authors: Hinz W. , Just G. , Sacripante G. 
Published: May 2005

AbstractCarbon‐13 and proton NMR spectra of a variety of E and Z pairs of mono‐ and bi‐cyclic polysubstituted azetidinones have been measured. The effect of E/Z isomerism on the chemical shift values of ring carbon atoms and of proton substituents attached to the azetidinone nucleus is discussed.
Influence of the 1,1,3,3‐tetramethylguanidinyl substituent on the charge distribution in chlorobenzenes, studied by 35Cl NQR
Authors: Nogaj Boleslaw , Pruszyński Przemyslaw 
Published: May 2005

Abstract35Cl NQR measurements were carried out on a series of chlorobenzenes with the 1,1,3,3‐tetramethylguanidinyl substituent {TMG = –N=C[N(CH3)2]2}. The substituent constants σp, σm, σaI, and σR for the TMG group were estimated from the relationships between the NQR resonance frequencies, νQ, and substituent constant values, σ. The νQ value for 2‐(4‐chlorophenyl)‐1,1,3,3‐tetramethylguanidine is the lowest observed for all chlorobenzenes, and arises from the strong positive conjugative effect of the TMG group. This effect is attributed to the possible resonance stabilization of the positive charge. Steric inhibition of resonance is observed for the ortho‐substituted isomers.
13C NMR spectroscopy of indole derivatives
Authors: Morales‐Ríos M. S. , Espiñeira J. , Joseph‐Nathan P. 
Published: May 2005

AbstractThe chemical shifts of 298 naturally occurring and synthetic compounds containing the indole chromophoric group are listed. Substituent effects on 13C chemical shifts (SCS) induced by substitution on the heteroaromatic five‐membered ring are discussed. The data provide a reference set for future 13C NMR investigations and highlight the need for unambiguous experimental evidence to resolve controversial assignments for differently substituted representative indole derivatives. Many original assignments have been changed, and values not considered to be unambiguously assinged are delineated. The 1 J(CH) values for the parent indole were measured.
13C and 1H NMR study of N‐5′‐methylsalicylideneanilines
Authors: Kishore K. , Sathyanarayana D. N. , Bhanu V. A. 
Published: May 2005

AbstractThe 13C and 1H NMR spectra of six N‐5′ ‐methylsalicylideneanilines have been studied. Correlations of the chemical shifts of C‐α (azomethine carbon) and C‐4′ with the σ, F, R, σ1 and σ parameters have been examined for N‐5′‐methylsalicylideneanilines, and also for N‐benzylideneanilines and N‐salicylideneanilines. The results suggest that the first compounds have a nearly planar conformation whereas the second and third type of derivatives have a twisted conformation.
Use of NOE difference spectra to determine configurations and conformations of imidate esters
Authors: Gallis David E. , Crist Delanson R. 
Published: May 2005

AbstractA new method for determining conformations and configurations of imidate esters was developed based on NOE difference spectra in CDCI3. As a test of the method, methyl N‐methylacetimidate was determined to exist in the E configuration, ap conformation, in agreement with assignments by homoallylic coupling and dipole moment data. Methyl N‐tert‐butylformimidate, for which existing methods were not suitable, was also determined to exist as E‐ap. Two methyl benzimidates were investigated, the N‐methyl derivative 2, which was E‐ap, and the N‐tert‐butyl derivative 6, which exhibited an unusually easy E/Z isomerization at room temperature (Tc = 24°C). At ‐58 °C, resolved spectra showed the E/Z isomers of 6 in a 40:60 ratio. From NOE data (E)‐6 was determined to exist mostly as the ap conformer and (Z)‐6 as the sp conformer. These results, in agreement with chemical shift data, can be interpreted in terms of the unusual steric requirements of the tert‐butyl group.
NMR study of substituent effects in platinum(II) intercalating agents
Authors: Brownlee Robert T. C. , McFadyen W. David , O'Connor Maxwell J. , Rook Trevor J. , Roos Ian A. G. , Wakelin Laurence P. G. 
Published: May 2005

AbstractA series of (4‐X‐thiophenolato) (2,2′:6′,2″‐terpyridine)platinum(H) complexes [X = H, F, Cl, Br, CH3, OCH3, NH2, N(CH3)2, NO2, COOCH3, CN, NH], which have potential as DNA intercalators, have been synthesized. 13C and 195Pt NMR spectra of these complexes have been obtained in both D2O and DMSO‐d6. The 195Pt shifts are highly sensitive to both solvent and distant substituent effects and span a chemical shift range of 72 ppm. The propagation and transmission of substituent effects within the complexes have been studied, and the 195Pt and thiophenolato C‐1 13C chemical shifts correlated with Hammett substituent constants, using the dual substituent approach. The results show that the (terpy)Pt—S— group is an effective π‐donor to the aromatic ring. Further, a normal substituent chemical shift effect is seen with the thiophenol C‐1, whereby electron‐withdrawing groups cause a decrease in electron density, whereas the platinum centre shows the reverse effect, i.e. electron‐withdrawing groups cause an increase in electron density. The latter effect has been explained in terms of a π‐polarization effect, with electron density from the terpyridine ligand being supplied to the platinum centre in response to demand by the thiophenol substituent.
Carbon‐13 NMR study of some triterpene hydrocarbons of the hopane group
Authors: Wilkins Alistair L. , Bird Peter W. , Jager Peter M. 
Published: May 2005

AbstractThe 13C NMR assignments of ten triterpene hydrocarbons of the hopane group are presented. Assignments for eight of the hydrocarbons are reported for the first time, whilst revisions to the published assignments of hopane and 17 α‐hopane are described.
NMR structural investigation of cellobiose and glucose
Authors: Lepri A. , Marchettini N. , Pogliani L. , Rossi C. , Ulgiati S. 
Published: May 2005

AbstractT1(13C) NMR measurements on cellobiose and glucose in aqueous solutions at pH 5 at 276° and 296° K suggest that cellobiose molecules assume a nearly spherical shape in solution. NOE‐2D HETCOR and HOMCOR proton spectra of cellobiose confirm that cellobiose assumes a folded structure in aqueous solutions.
17O NMR spectra of methyl‐substituted 2‐oxo‐1,3,2‐dioxathianes
Authors: Mattinen Jorma , Pihlaja Kalevi 
Published: May 2005

Abstract17O NMR chemical shifts of 2‐oxo‐1,3,2‐dioxathiane and 13 of its methyl‐substituted derivatives are reported. The chemical shifts depend strongly on temperature and to a much smaller extent on concentration. As a whole, however, they strongly support the predominance of chair conformations in these compounds and indicate some misinterpretations in a previous report.
Complexation of lanthanide(III) ions with a β‐diphosphorylated ligand: Nonamethylimidodiphosphoramide (NIPA). A 1H and 31P NMR study
Authors: Rubini P. , Nasr C. Ben , Rodehüser L. , Delpuech J.‐J. 
Published: May 2005

AbstractTrivalent lanthanide ions form complexes of different stoichiometries with the bidentate ligand nonamethyl‐imidodiphosphoramide (NIPA). Depending on the method of preparation, compounds with two or three NIPA molecules may be obtained, which can be distinguished and characterized on the basis of their NMR spectra. The method of preparation for the tris‐chelates and an analysis of the isotropic paramagnetic shifts for these compounds are reported; the results allow the conclusion that the complexes in solution are isostructural along the lanthanide series. The same conclusion is drawn for the bis‐chelates. In both cases the contact and pseudo‐contact contributions to 31P shifts are important, whereas for the 1H nuclei the dipolar contribution is largely predominant.