bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amidines. XVII—substituent‐induced chemical shifts in 13C NMR spectra of N2‐phenyl‐formamidines, ‐acetamidines and ‐guanidines
Authors: Oszczapowicz Janusz , Raczyńska Ewa , Osek Jerzy 
Published: May 2005

Abstract13C chemical shifts in CDCI3 of 65 compounds, divided into several series, containing a substituted phenyl ring at the imino (N2) nitrogen atom of the amidine group magnified image are reported. Additivity parameters (SCS) of the substituted aminomethyleneamino group [R2NC(R′)N‐] for the prediction of the chemical shifts of the N2‐phenyl carbon atoms in formamidines, acetamidines and guanidines are derived. The SCS obtained can be used for the determination of the configuration at the CN bond, and for the assignments of the chemical shifts in tautomeric forms of N‐phenyl‐formamidines, ‐acetamidines and ‐guanidines. The chemical shifts of the amidine carbon atom depend on the substitutents on the phenyl rings of both nitrogen atoms.
13C substituent‐induced chemical shifts in 1‐amino‐4‐phenyl‐ and 4‐phenyl‐1H‐1,2,3‐triazoles
Authors: Kleinpeter E. , Wilde H. , Hauptmann S. 
Published: May 2005

AbstractThe 13C NMR spectra of several 3′‐ and 4′‐substituted 4‐phenyl‐1,2,3‐triazoles have been recorded, and the observed chemical shifts analysed in terms of (i) the influence of this heteroaromatic system on the phenyl carbons and (ii) the transmission of the electronic effects of the meta and para substituents on the phenyl ring to the triazole carbon atoms.
13C NMR spectra of 1,4‐oxathian‐2‐ones: The conformational implications
Authors: Koskimies Jorma 
Published: May 2005

AbstractThe 13C NMR chemical shifts of fifteen 1,4‐oxathian‐2‐ones were obtained and analysed by multiple linear regression. The results are in agreement with those of an earlier 1H NMR study, indicating the boat conformation for the heterocyclic ring. The observed unexplained variation of the C‐3 shift was interpreted as being due to the conformational mobility of the ring.
The use of high‐field carbon‐13 NMR spectroscopy to characterize chiral centers in isopranes
Authors: Dalling Don K. , Pugmire Ronald J. , Grant David M. , Hull William E. 
Published: May 2005

AbstractThe 13C nuclear magnetic resonance spectra of four diastereomeric, acyclic isoprenoids [farnesane (C15), pristane (C19), phytane (C20), and squalane (C30)] have been obtained as a means for interpreting hydrocarbon mixtures common in some fossil fuels and biosynthesized organic compounds. Multiple resonance environments were detected for carbons influenced by two or three chiral centers. Samples of farnesane and squalane were found to exhibit random stereochemistry, whereas the phytane sample was demonstrated to be a mixture of two isomers, probably the 6(R), 10(S), 14(R,S) compound. The sample of pristane consisted of a single diastereomer and was probably obtained from a natural product. It is shown that general chemical shift assignments can be made in this class of molecules by considering the number of carbons located at positions one, two and three bonds distant, while assignment of closely spaced lines may be made on the basis of diastereomerically induced chemical shifts. Using these principles, the structural features of two fossil fuels were analysed.
Studies of substituent effects by carbon‐13 NMR spectroscopy. VI—Application of multivariate data analysis to 13C NMR chemical shifts of protonated chalcones and thiophene chalcone analogues
Authors: Musumarra Giuseppe , Carbone Domenica , Johnels Dan , Edlund Ulf 
Published: May 2005

AbstractThe 13C NMR chemical shifts of protonated chalcones and thiophene chalcone analogues were analysed by two multivariate data analysis methods, principal components analysis and partial least squares analysis. A general relaying effect of the carbenium centre was manifested by an increased sensitivity to substituent changes at positions conjugated to the charged position. The shift data in both series could be satisfactorily described by the 13C NMR shifts of monosubstituted benzenes, as shown by partial least squares data analysis. This indicates a grouping of substituent effects into those of donors, acceptors, alkyls and halogens.
Transmission of polar substituent effects through the bicyclo[2.2.2]octane ring system as monitored by NMR shifts: A 13C NMR study of 4‐substituted‐1‐methylbicyclo[2.2.2]octanes
Authors: Adcock William , Abeywickrema Anil N. , Iyer V. Sankar , Kok Gaik B. 
Published: May 2005

AbstractCarbon‐13 substituent chemical shifts (SCS) are reported for the methyl group of a series of 4‐substituted 1‐methylbicyclo[2.2.2]octanes covering a wide range of electronic substituent effects. Unlike the 13C SCS of the α‐carbon centre in various unsaturated side‐chain probes attached to the bicyclo[2.2.2]octane ring, which are mainly proportional to substituent field effects (σF), the 13CH3, SCS are found to display a definitive statistical dependence on substituent electronegativity effects as well as the field parameter. Compelling support for the validity of the statistical dissection by multivariate analysis is provided by an independent measure of polar susceptibility parameters (ρF; CDCl3, and CCl4). The coefficient (A) of the Buckingham equation for linear electric field effects on the CH3, group is calculated for CCl4 as the solvent. The origin of the reverse substituent electronegativity effect is discussed, and compared with the similar phenomenon displayed by the resonance contribution to the 13C SCS of the β‐carbon of p‐substituted ethylbenzenes.
Carbon‐13 nuclear magnetic resonance spectra of isoflavones
Authors: Murthy M. Sree Rama , Rao E. Venkata , Ward R. S. 
Published: May 2005

AbstractThe 13C chemical shifts of a series of isoflavones having hydroxy, acetoxy, methoxy and methylenedioxy substituents are compared. Some general relationships between substitution patterns and chemical shifts, useful for the identification of naturally occurring isoflavones, are outlined.
Carbon‐13 NMR spectra of pyrrolo[1,2‐a]quinoxaline, pyrrolo[1,2‐a]pyrazine and imidazo [1,2‐a ] quinoxaline
Authors: Cobb J. , Cheeseman G. W. H. 
Published: May 2005

Abstract1H and 13C NMR spectra of pyrrolo[1,2‐a]quinoxaline and seven of its derivatives have been measured. Assignments of the carbon resonances have been made by correlation of chemical shift and coupling constant data for the pyrroloquinoxalines with those of structurally related pyrrolo[1,2‐a]pyrazines and imidazo[1,2‐a]quinoxaline. Spin‐lattice relaxation times for the carbons of pyrrolo[1,2‐a]quinoxaline are also reported.
13C NMR studies of epimeric 20(R,S)‐hydroxy‐23‐norcholanoic acid derivatives
Authors: Seldes Alicia M. , Maier Marta S. , Gros Eduardo G. 
Published: May 2005

Abstract13C NMR spectra for sixteen 20‐hydroxy‐23‐norcholanoic acid derivatives have been obtained and individual resonances assigned. The different chemical shifts due to preferred conformers depending on the C‐20 configuration are rationalized in terms of steric interactions using model compounds.
15N NMR studies on cyclopalladated Schiff's base complexes
Authors: Pregosin P. S. , Rüedi R. , Anklin C. 
Published: May 2005

Abstract15N NMR spectra for a series of cyclopalladated m‐ and p‐substituted benzylidene Schiff's base complexes have been measured. The dominant factor affecting the nitrogen chemical shift is the ligand in the trans position to the coordinated nitrogen, and not the aryl ring substituent. Tertiary phosphine ligands trans to the 15NCH moiety weaken the Pd‐N bond more than oxygen, chlorine or nitrogen donors, thereby reducing the coordination chemical shift. The values for δ(15N) in the free and complexed ligands correlate linearly with one another.1H and 15N spectra of the geometric isomers [Pd(2a)Cl(pyridine)] and [Pd(2a)Cl(NHEt2)], where 2a = the 2′‐cyclopalladated Schiff's base (5′‐OCH3C6H3)CHN(4‐CH3C6H4), were assigned based on the local anisotropic effects of the Cl and nitrogen ligand. For the pyridine complex the assignment is supported by difference NOE, NOESY and COSY measurements.
Waltz‐16 decoupling on JEOL FX series NMR spectrometers
Authors: Hearmon R. Angus , Goodacre John 
Published: May 2005

AbstractThe interfacing of a circuit to generate WALTZ‐16 decoupling pulse trains with a JEOL FX series NMR spectrometer is possible for any instrument which has a 0°/180° phase shifter control line. The use of the decoupler gives a reduction in sample heating and line width improvements.
1H NMR data for methyl trans‐β‐(2‐, 4‐, and 5‐Substituted‐3‐thienyl)acrylates
Authors: Satonaka H. 
Published: May 2005

Abstract1H NMR data are reported for methyl trans‐β‐(2‐, 4‐ and 5‐substituted‐3‐thienyl)acrylates. The assignments of the proton resonances are based on spin‐spin coupling constants and substituent chemical shifts.
Substituent effects on 13C–15N spin couplings and 13C chemical shifts in benzylideneanilines
Authors: Axenrod T. , Huang X. H. , Wieder M. J. , Watnick C. M. 
Published: May 2005

Abstract13C NMR chemical shifts and 13C‐15N spin couplings over one, two and three bonds are reported for a series of 15N‐labeled benzylideneanilines bearing a variety of substituents in both the benzaldehyde and aniline rings.
Carbon‐13 NMR spectra of five sesquiterpenes isolated from Ylang Ylang essential oil
Authors: Randriamiharisoa R. , Gaydou E. M. , Faure R. , Bianchini J. P. 
Published: May 2005

Abstract13C NMR chemical shifts are given for germacrene‐D, α‐humulene, δ‐cadinene, ε‐cadinene and γ‐muurolene isolated from Ylang Ylang (Cananga odorata, forma genuina) essential oil.
Binuclear shift reagents. Structure and mode of interaction of Ag(fod)–Ln(fod)3 with benzene
Authors: Raber Douglas J. , Hájek Milan 
Published: May 2005

AbstractLanthanide‐tris(fod) reagents interact reversibly in solution with Ag(fod) to form binuclear adducts having the formula AgLn(fod)4. The formation constant (K) for AgYb(fod)4 in CDCl3 is 500 M−1, and this equilibrium is in the slow exchange region below 20°C. Slow exchange is also found for AgDy(fod)4. The NMR data support a structure for the binuclear adduct consisting of an ion pair with a silver cation and a lanthanide‐tetrakis(fod) anion. The binuclear reagent associates weakly with benzene (K = 3M−1). The primary interaction involves coordination of the silver cation to the aromatic ring, and the tetrakis(fod) anion is situated in close proximity to the silver cation. Induced shifts for the aromatic moiety are primarily pseudo‐contact in origin.
Comparison of rate constants determined by two‐dimensional NMR spectroscopy with rate constants determined by other NMR techniques
Authors: Baine Peter 
Published: May 2005

AbstractRate constants for the interconversion of N‐trifluoroacetyl‐N‐methylbenzylamine between its conformers were measured over a temperature range by two‐dimensional NMR spectroscopy. These rate constants were compared with those obtained by line shape analysis, saturation transfer and selective pulse transfer. The rate constants measured by the two‐dimensional method were, over the temperature range of the experiments, about 40% higher than those from line shape analysis. At lower temperatures, the agreement between the two‐dimensional data and the rate constants obtained by saturation transfer and selective pulse transfer studies were much closer. The two‐dimensional NMR method for measuring rate constants gives good agreement with rate constants obtained by other NMR methods, particularly in the slow rate region.
Application of 2D NMR spectroscopy to the complete analysis of the 1H NMR spectra of 1‐ and 3‐nitrobenzo[e]pyrene
Authors: Sydnes Leiv K. , Skjetne Tore 
Published: May 2005

AbstractCOSY and NOESY spectra (400 MHz) have been used to complete the assignment of the 1H NMR spectra of 1‐ and 3‐nitrobenzo[e]pyrene. Both compounds show strong bay region nuclear Overhauser enhancement and significant coupling across bay regions. Both compounds also exhibit extensive long‐range couplings. For 1‐nitrobenzo[e]pyrene the most spectacular couplings are between H‐4 and H‐6 and between H‐4 and H‐8. The most unusual long‐range couplings in 3‐nitrobenzo[e]pyrene are between H‐1 and H‐5, H‐2 and H‐7 and H‐4 and H‐8. Simulation of the spectra reveals that all short‐range coupling constants are normal, and confirms the presence of the long‐range couplings.
Effects of substitution on nitrogen on barriers to rotation of amides. III—effect of the variation of ring size of cyclic substituents
Authors: Pinto B. Mario , Grindley T. Bruce , Szarek Walter A. 
Published: May 2005

AbstractThe magnitudes of the rotational barriers about the amide bond in the p‐nitrobenzoyl and acetyl derivatives of azacyclohexane and azacyclopentane have been measured by variable‐temperature 13C NMR spectroscopy. The barriers in both acyl derivatives of azacyclohexane are significantly lower than those in the corresponding azacyclopentane derivatives (differences 6.9–8.3 kJ mol−1 for the p‐nitrobenzoyl derivatives in various solvents and 9.3 kJ mol−1 for the acetyl derivatives in dimethyl sulfoxide‐d6). The difference is rationalized in terms of a dominant contribution from steric effects in the transition states of the latter compounds and in the ground states of the former compounds. The rotational barrier in N‐(p‐nitrobenzoyl)azacyclopent‐3‐ene has also been measured and is of a similar magnitude to that in its saturated counterpart. It is argued that both the ground state and transition state of the unsaturated compound are destabilized relative to those in the saturated compound.
Three‐bond carbon–fluorine coupling constants in substituted 3‐fluoropropanes and 3‐fluoropropanoates
Authors: Dahbi Abderrahman , Hamman Sylvain , Béguin Claude G. 
Published: May 2005

AbstractThree‐bond carbon‐fluorine coupling constants of 32 substituted 3‐fluoropropanes and 3‐fluoropropanoates were measured. From these values and from those of other alicyclic compounds already known in the literature, it can be established that the influence of molecular parameters on 3J(FC) depends on the nature of the coupled carbon. When this carbon belongs to an alkyl group, the main molecular parameter is the dihedral angle [J(FC)g = 1.2 Hz and J(FC)t = 11.2 Hz]. When the carbon belongs to a carbethoxy group, more complex effects are observed: for one series the main parameter is the dihedral angle [J(FC)g = 0 Hz and J(FC)t = 20 Hz], and for other series the electronegativity and orientation of substituents particularly influence J(FC)g. Conversely, the diastereoisomers can be unambiguously identified from the 3J(HH), 3J(FH) and 3J(FC) values of both diastereoisomers.
Measurement of coupling constants in broad multiplets
Authors: Chevalier Yves 
Published: May 2005

AbstractExtensive broadening of the lines of an NMR multiplet induces errors in the measurement of the coupling constants. In order to make corrections to the measured splittings in these cases, analytical expressions for doublets and triplets and correction curves are given. The practical example of 3J(POCC) in alkyl phosphate micelles shows the necessity for such corrections when slow molecular motions occur.
17O NMR spectroscopy (natural abundance) of heterocycles: Anhydrides
Authors: Vasquez P. C. , Boykin D. W. , Baumstark A. L. 
Published: May 2005

Abstract17O NMR spectra were recorded for several series of anhydrides (⩽0.5 M) in dried acetonoitrile at 75°C. The 17O NMR data for simple anhydrides were found to be highly sensitive [acetic anhydride, δ 411 ppm (CO), δ 273; glutaric anhydride (2), δ 396 ppm (CO), δ 288 ppm; succinic anhydride δ 376 (CO), δ 301; maleic anhydride, δ 401 (CO), δ 252; phthalic anhydride (27), δ 374 (CO), δ 263]. The 17O NMR data were found to be sensitive to ring size and conformation. Substitutent effects on a series of maleic anhydrides could be rationalized in terms of electronic effects. In contrast, the 17O NMR data for polycyclic succinic anhydrides showed that the chemical shifts of the carbonyl oxygens were roughly constant, while those of the central oxygens were sensitive to structure. The 17O NMR data for homophthalic anhydride [δ 397 (CO), δ 372 (CO), δ 273] were consistent with those for 2 and 27; the data for pyridine‐2,3‐dicar‐boxylic anhydride [δ 383 (CO), δ 380 (CO), δ 263] could be rationalized in terms of electronic effects, and those for 3,4‐dihydronaphthalene‐1,2‐dicarboxylic anhydride [δ 392 (CO), δ 387 (CO), δ 252] were explained by compressional and electronic effects.
Study of the effect of N‐protonation and N‐methylation on the 1H and 13C chemical shifts of the six‐membered ring in benzazoles and 2‐substituted N,N‐dimethylamino derivatives
Authors: Benassi Rois , Grandi Romano , Pagnoni Ugo M. , Taddei Ferdinando 
Published: May 2005

AbstractThe 1H and 13C NMR spectral data of benzimidazole, benzoxazole, benzothiazole and N‐methylbenzimida‐zole and of their 2‐N,N‐dimethylamino derivatives are reported. The spectra were recorded in acetone‐water solution. The chemical shifts of these molecules are compared with those of the corresponding cations obtained by N‐protonation and N‐methylation of the neutral molecules. The carbon atoms C‐4, C‐5, C‐6 and C‐4a show a qualitatively identical behaviour, moving to higher field when the cations are formed from the benzazoles examined, but a different behaviour is found for C‐2, C‐7 and C‐7a, which depends on the heterocyclic ring, on the presence of the substituent in position 2 and on the type of cation formed (N‐protonation and N‐methylation cause different effects). The conversion of benzazoles into the corresponding cations causes all 1H chemical shifts to move to lower field.
3H1H shift correlation NMR spectroscopy
Authors: Funke Carel W. , Wagenaars Gerard N. , Kaspersen Frans M. 
Published: May 2005

AbstractThree two‐dimensional 3H1H chemical shift correlation experiments are described, all using familiar pulse sequences. The experiments reveal the chemical shifts of the 1H spins which are coupled scalarly to a 3H spin and, thus, assist in the unambiguous location of this 3H spin within the molecule. The limitations for molecules involving a 3H spin which is coupled differently to various 1H spins are indicated. In practice, the detection limit is of the order of 100 MBq per 3H‐labelling site.
NMR structure proofs for a series of substituted benzobicyclooctanes
Authors: Smith William B. 
Published: May 2005

AbstractElectrophilic additions to 5,8‐dimethoxy‐1,4‐dihydro‐1,4‐ethanonaphthalene have produced a series of new products resulting from Wagner–Meerwein rearrangements. Proton and 13C NMR have been used to provide structure proofs for these molecules, which fall into two series of substituted benzobicyclooctanes. The full range of NMR techniques, i.e. lanthanide‐induced shifts (LIS), difference NOEs and 2D NMR, have been employed. Proton and carbon chemical shifts are reported, and also a brief description is given of the more complex experimental results.
ESR bonding parameters and hyperfine line width studies of ternary copper(II) complexes
Authors: Pisipati V. G. K. M. , Rao N. V. S. , Muralikrishna V. , Premchand  
Published: May 2005

AbstractESR and optical absorption studies are described for a number of ternary copper(II) compounds formed with substituted amino acids and different aliphatic polyamines, giving rise to two different immediate environments around copper(II), [3N, O] and [2N, 2O]. The ESR measurements were carried out in different solvents such as dimethyl sulphoxide, dimethylformamide and pyridine at room and liquid nitrogen temperatures. Molecular orbital coefficients were estimated assuming an axial symmetry. The parameter χ, proportional to the hyperfine constants, was estimated and shows a variation with solvent. The χ values in a solvent were found to be lower than the corresponding average values reported in the solid state for a particular type of environment. The solvent effect and the influence of the 4s character in the ground state are discussed. The hyperfine line widths in solution are estimated using Kivelson's theory. The disagreement between theoretical and experimental line widths are discussed.
15N INEPT spectra of some perfluoroazines
Authors: Costa A. , Tato M. , Matthews R. S. 
Published: May 2005

AbstractNatural abundance 15N NMR spectra were measured for pentafluoropyridine and five other perfluorodiazines. The spectra were obtained using the INEPT pulse sequence with 19F as the source of polarization. The nitrogen nuclei are shielded by approximately 56–97 ppm with respect to the hydrocarbon analogues, and the 2J(NF) values appear to be approximately 52 Hz.
13C NMR study of N2‐alkyl or aryl pyrazolinium salts
Authors: Faure R. , Llinares J. , Elguero J. 
Published: May 2005

AbstractSixteen 1‐methyl‐2‐alkyl(or aryl)‐Δ2‐pyrazolinium salts, one 1,1,2‐trimethyl‐Δ3‐pyrazolinium salts were studied by 13C NMR spectroscopy and their chemical shifts are reported.
The chemistry of santonene. XIII—13C NMR spectra of some santonene derivatives
Authors: Kelly Paul K. , McMurry T. Brian H. 
Published: May 2005

AbstractThe 13C NMR spectra of a series of 3,5,7(11)‐eudesmatrien‐6,12‐olides and of 1,3,5,7(11)‐eudesmatetraen‐6,12‐olides have been assigned. The spectra of some model compounds containing the 5,7(11)‐eudesmadien‐6,12‐olide chromophore have also been recorded.
Some aspects of high‐pressure NMR
Authors: Ando I. , Webb G. A. 
Published: May 2005

AbstractRecent advances in the field of high‐resolution NMR spectroscopy in both pure liquids and solutions, under high pressure, are reviewed. Experimental techniques employed for making the NMR measurements at high pressures are discussed. An overview of high‐pressure NMR studies as applied to intramolecular dynamics, structures of liquids, molecular conformations and intermolecular interactions is presented.
ESR analysis of the complexing equilibria of Mn(II) with nucleo bases in solution
Authors: Laschi Franco , Rossi Claudio 
Published: May 2005

AbstractThe X‐band ESR spectra of manganese(II) complexes with nucleobase constituents such as pyridine, imidazole and purine have been analysed at various metal to ligand molar ratios and pH values. Mixed complexing Mn(II)H2ON base, together with the direct N base coordination of the metal ion, have been characterized on the basis of the ESR parameters a, ΔH, intensity and line shape. The ESR evidence for a direct interaction of pyridine and imidazole with Mn(II) is reported.
NMR studies of bile acid salts: 2D NMR studies of aqueous and methanolic solutions of sodium cholate and deoxycholate
Authors: Campredon M. , Quiroa V. , Thevand A. , Allouche A. , Pouzard G. 
Published: May 2005

Abstract2D NMR methods have been applied to the complete assignment of the proton and carbon signals of aqueous solutions of sodium cholate and deoxycholate. Comparative studies of the 13C chemical shifts, in terms of concentration in D2O and CD3OD solutions, show a dependence of the carbons bearing a hydroxy group, exhibiting hydrophilic face activity during the premicellization processes. The behaviour of the methyl carbons at low concentration is an indication of the involvement of the hydrophobic face in the association processes.
One‐ and two‐dimensional NMR data processing on external computers. The PRONMR 1 and 2 software system
Authors: Benn Reinhard , Klein Jochen 
Published: May 2005

AbstractThe computer program PRONMR 1 and 2 has been developed for the reduction of data from one‐ and two‐dimensional Fourier transform NMR experiments. This software system is written in FORTRAN 77 and is largely machine‐independent. Hardware requirements are a device for NMR data transfer, a graphic display, a plotter and a computer. Implemented PRONMR software features are various types of apodization of FIDs, routines for one‐ and two‐dimensional Fourier transformations, phase corrections and algorithms for rapid quantisation of NMR spectral features, including the presentation of data originating from 2D spectra. The versatility of this software system is illustrated by extracting 1H and 13C NMR data stemming from various one‐ and two‐dimensional pulse experiments for structure elucidation of a sesquiterpene.