bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron spin resonance of some nitro‐ and fluoro‐substituted triphenylmethyl radicals
Authors: Kulkarni Shrikant V. , Trapp Charles
Published: May 2005

The electron spin resonance spectra of the tris(4‐nitrophenyl)methyl and tris(2,3,5,6‐tetrafluoro‐4‐nitrophenyl)methyl radicals in toluene solution have been obtained and their 14N, 19F and 1H hyperfine splitting constants have been determined. Analysis of the data indicates that fluorine substituents in this system are appreciably electron attracting. This is in contrast to the fluorinated nitrobenzene radical ions, where the data suggest that fluorine may be weakly electron donating. The present results on the fluoro‐ and nitro‐substituted radical also lead to the conclusion that no steric interaction between the NO2 group and ortho‐fluorine atoms occurs, and that the group remains coplanar with the aromatic rings. The nitro group in these radicals is less electron attracting than in the nitrobenzene anions and their protonated analogs.
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

13C 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

The 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

The 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

The 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

The 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

Carbon‐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

The 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

1H 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

13C 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

15N 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

The 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

1H 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.
13C NMR phenol substituent effect in acyclic alkanes
Authors: Hearmon R. Angus , Chippendale A. Margaret
Published: May 2005

Literature and unpublished data on phenols have been analysed to give phenol substituent effects for acyclic alkanes. The results are analysed in terms of the α‐branching of the alkyl phenol side chain.
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

13C 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

13C 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

Lanthanide‐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

Rate 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

COSY 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

The 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

Three‐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

Extensive 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

17O 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

The 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

Three 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

Electrophilic 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

ESR 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

Natural 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

Sixteen 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

The 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

Recent 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

The 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

2D 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

The 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.
Carbon‐13 NMR data of some 4H‐imidazo[2,1‐c][1,4]benzoxazines
Authors: Rao K. Vara Prasad , Reddy P. S. N. , Sundaramurthy V.
Published: May 2005

Carbon‐13 chemical shifts of twelve 4H‐imidazo[2,1‐c][1,4]‐benzoxazine derivatives and three 4‐alkyl‐2H‐1,4‐benzoxazin‐3‐ones are reported.
The 1H and 13C NMR spectra of some furanoid norditerpenes
Authors: Lentini A. , Webster J. , Ternai B. , Komori T.
Published: May 2005

The 1H and 13C NMR spectra of Diosbulbin A, B, D and G have been studied. The proton spectra were analysed with the aid of nuclear, magnetic double resonance and comparison with reference compounds. The assignments of the carbon shifts have been obtained by means of proton noise decoupling, single frequency off‐resonance decoupling, the attached proton test and by comparison with reference compounds.
13C NMR determination of the configuration of methyl‐substituted double bonds in medium‐ and large‐ring terpenoids
Authors: Lange Gordon L. , Lee Moses
Published: May 2005

13C NMR spectroscopy can be used to determine the configuration of methyl‐substituted double bonds in medium‐ and large‐ring terpenoid natural products. A number of examples from our investigations in the germacranolide field are presented, and clearly show that if the resonance for the vinylic methyl group appears at a value greater than 20 ppm the double bond has a (Z)‐configuration whereas if the value is less than 20 ppm an (E)‐configuration is present. Literature examples of other classes of compounds are also cited to illustrate the generality of this method.
Deuterium isotope effects on silicon‐29 chemical shifts
Authors: Berchier Fabienne , Pai Yi‐Ming , Weber William P. , Servis Kenneth L.
Published: May 2005

The deuterium isotope effects on the 29Si chemical shifts in several organosilanes and siloxanes have been determined. For silanes, the one‐bond effects are approximately −0.2 ppm per deuterium and follow an additivity relationship. The two‐bond effect is small.
Characterization of P—AU—N bonds in the solid state by 15N NMR
Authors: Berners‐Price S. J. , Morden K. , Opella S. J. , Sadler P. J.
Published: May 2005

The high‐resolution solid‐state and solution 15N NMR spectrum of Et3PAu(phthalimide‐15N) are compared. Both spectra exhibit a remarkably well resolved doublet attributable to the scalar two‐bond31P–15N coupling (41 Hz). The absence of substantial quadrupolar effects due to 197Au is discussed.
NMR studies of methylenebispyridinium derivatives
Authors: Munavalli S. , Szafraniec L. L. , Beaudry W. , Poziomek E. J.
Published: May 2005

The methylene proton chemical shifts of the magnified image system appear to be affected by the synergistic interactions of a combination of various effects. Although it is difficult to single out the origin, transmission and magnitude of these effects, the synergistic interactions pervade the molecule, causing a net displacement of the chemical shifts. The substituent‐produced chemical shifts show a clear trend in their dependence on the nature of the substituents and the Hammett parameters. Strong through‐conjugation between the aromatic nitrogen and resonance donor substituents in the para‐position is observed.
Carbon–carbon coupling constants of 1‐phenylazo‐2‐naphthol and 2‐phenylazo‐1‐naphthol obtained by the SEMINA‐1 technique
Authors: Hansen Poul Erik , Lyčka Antonín
Published: May 2005

Carbon‐carbon coupling constants of 1‐phenylazo‐2‐naphthol and 2‐phenylazo‐1‐naphthol have been measured with the SEMINA‐1 pulse sequence. The carbon–carbon couplings provide an unambiguous assignment of the 13C spectra. The magnitudes of the carbon–carbon coupling constants are discussed in relation to the tautomeric nature of the compound. Substituent effects on couplings are also considered.
1H and 13C NMR spectra of tetrahydroquinoxalines condensed with six‐membered heterocycles
Authors: Charushin V. N. , Sorokin N. N. , Chernyshev A. I. , Baklykov V. G. , Ponizovsky M. G. , Chupakhin O. N.
Published: May 2005

The 1H and 13C NMR spectra of tetrahydroquinoxalines condensed with pyridazine, pyrazine, oxazine, oxadiazine, thiadiazine or triazine rings have been measured in DMSO‐d6 solution. The effects of six‐membered heterocycles on 1H and 13C chemical shifts and the values of one‐bond 1J(CH) and vicinal 3J(HH) coupling constants for the ring junction fragment are considered. The differences between the 1H and 13C spectral parameters of tetrahydroquinoxalines annelated with five‐ or six‐membered heterocycles with the same set of heteroatoms attached to the ring junction carbons are also discussed.
13C NMR chemical shift assignments for some 1H‐pyrrole‐2‐carboxylic acid derivatives
Authors: Sammes Michael P. , Katritzky Alan R. , Law Kam Wah
Published: May 2005

Complete 13C NMR chemical shift assignments are reported for 32 1H‐pyrrole‐2‐carboxylic acid esters and amides, bearing in addition alkyl, phenyl, acetyl, alkoxycarbonyl and diethylamino substituents. The substituent chemical shift effect for the 2‐Ph group on the pyrrole ring carbon atoms is also reported.
13C NMR spectra of substituted indoles
Authors: Burton Gerardo , Ghini Alberto A. , Gros Eduardo G.
Published: May 2005

13C chemical shifts for indole and ten indoles substituted at positions 1, 3 and/or 6 are reported. Previous assignments have been revised using specific deuterium labelling and selective proton decoupling.
1H NMR spectra of carbohydrate‐derived polyhydroxycarboxylates
Authors: Van Duin M. , Peters J. A. , Kieboom A. P. G. , Van Bekkum H.
Published: May 2005

An analysis of the 1H NMR spectra of polyhydroxycarboxylates is presented. Conclusions with regard to the configuration and the conformation are drawn from chemical shifts and vicinal coupling constants.
1H, 13C and 31P NMR studies of the stereochemistry of chiral (4R, 6R)‐2‐substituted‐1,3,2‐dioxaphosphorinanes
Authors: Szalontai G. , Bakos J. , Tóth I. , Heil B. , Pelczer I. , Sohár P.
Published: May 2005

13C, 1H and 31P NMR investigations have been carried out to determine the ring stereochemistry and phosphorus configuration for four chiral (4R, 6R)‐2‐substituted‐1,3,2‐dioxaphosphorinane derivatives 1–4 (2‐substituent = Cl, Ph, OMe and O‐t‐Bu, respectively). 1H NMR spectra, double resonance, 2D‐J experiments and spin simulation proved the chair character of the ring. Depending on the position of R, two diastereomers may exist, but in most cases only one predominating form was detected. Dynamic processes were observed for 1 and 2. Saturation transfer experiments proved the existence of ring and/or phosphorus inversions.
Synthesis and high‐resolution 1H NMR spectra of four dimethylaminated dipyridyl ketones
Authors: Jones D. W. , Pakdel H. , Hallas G. , Hepworth J. D.
Published: May 2005

Four new dimethylaminated pyridoylpyridine intermediates, bis(3‐dimethylamino‐2‐pyridyl) ketone (1), 6‐dimethylamino‐3‐pyridyl 4‐pyridyl ketone (2), 6‐dimethylamino‐3‐pyridyl 3‐pyridyl ketone (3) and 6‐dimethylamino‐3‐pyridyl 2‐pyridyl ketone (4), have been synthesized and their 100 MHz 1H NMR spectra analysed iteratively as ABC, ABCX and ABXY spin systems. In 2–4 the H‐5 shift ortho to the dimethylamino substituent is unaffected by the orientation of the pyridyl substituent, but H‐4 and H‐2 are increasingly deshielded in the sequence 2–4. In 3, when benzene‐d6 replaces chloroform‐d1 as solvent, H‐5′ and H‐4′ in the unsubstituted pyridyl ring suffer appreciable upfield shifts.
13C NMR studies of the triterpene 3α‐hydroxylup‐20(29)‐en‐23,28‐dioic acid and some derivatives
Authors: Preiss A. , Lischewski M. , Adam G. , Budéšínský M.
Published: May 2005

The 13C NMR assignment of the triterpene 3α‐hydroxylup‐20(29)‐en‐23,28‐dioic acid and some of its derivatives has been carried out. In addition to conventional methods, 2D 1H13C chemical shift correlation, nuclear Overhauser enhancement difference and decoupling difference techniques were used for the assignment.
Heteronuclear Overhauser effect measured with selective proton irradiation. Application of a new method
Authors: Bigler P. , Kamber M.
Published: May 2005

A new method for the measurement of partial heteronuclear NOE effects is proposed, and its application to the elucidation of unknown structures is demonstrated. In contrast to the basic experiment with simultaneous irradiation of all proton multiplet lines with a relatively high decoupler power, the individual lines are irradiated successively several times using a very low decoupler power. An improved selectivity in the proton domain combined with higher sensitivity in the carbon domain are the main attributes of this powerful technique.
Line widths, sensitivity and artifacts in 33S NMR Spectra: The case of aqueous sulphides
Authors: Belton P. S. , Cox I. J. , Harris R. K.
Published: May 2005

The factors giving rise to artifacts in the NMR spectra of 33S and other quadrupolar nuclei of low magnetogyric ratio are examined and some tests for their detection are proposed. The effects of line width and probe ring‐down time on the observed signal intensity are considered and a quantitative relationship is described. Sulphur‐33 NMR spectra of sodium sulphide solutions are reported which differ substantially from those recently published. The reasons for these and other differences between reported spectra are explained in terms of experimental artifacts of the types described.
Complete assignment of the 13C NMR spectra of the ring forms of digitoxose by DEPT spectrum editing and two‐dimensional proton chemical shift correlation spectroscopy
Authors: Coxon Bruce
Published: May 2005

The 13C chemical shifts of the four isomeric ring forms of D‐digitoxose in dimethyl sulfoxide‐d6 solution have been assigned completely by DEPT 13C NMR spectrum editing and two‐dimensional carbon–proton chemical shift correlation spectroscopy. The 13C chemical shifts are discussed in terms of their dependence on ring size and on anomeric configuration. The equilibrated mixture of four ring forms of D‐digitoxose in dimethyl sulfoxide‐d6 solution has been analysed quantitatively by 13C NMR spectroscopy, and the results compared with those obtained previously by 1H NMR.
13C chemical shifts of chlorinated biphenyls
Authors: Yanagisawa Masaru , Hayamizu Kikuko , Yamamoto Osamu
Published: May 2005

The 13C NMR spectra of 48 chlorinated biphenyls are presented. The 13C shifts of the individual carbons are interpreted by the additive contributions from the substituent effect of a chlorine atom, and by the repulsive interaction of chlorine atoms substituted in a crowded relationship on the biphenyl ring.
Compounds with bridgehead nitrogen. 50—1H NMR spectra and structures of the products derived from the reaction between trans‐3‐aminotetralin‐2‐ol and formaldehyde
Authors: Crabb Trevor A. , Roch Olive G. , Robinson Paul
Published: May 2005

In contrast to the reported reaction between trans‐1‐aminotetralin‐2‐ol and formaldehyde, which gives r‐6a, c‐9a,t‐15a,t‐18a‐5,6,6a,9a,14,15,15a,18a‐octahydro‐9,18‐methanodinaphtho[1,2‐d:1′,2′‐i][1,6,3,8]dioxadiazecine, an examination of the δ 4.0–5.0 region of the 1H NMR spectra of the products of the reaction between trans‐3‐aminotetralin‐2‐ol and formaldehyde showed these to be a 50:50 mixture of r‐5a,t‐8a,c‐14a,t‐17a‐ and r‐5a,c‐8a,t‐14a,t‐17a‐5,5a,8a,9,14,14a,17a,18‐octahydro‐8,17‐methanodinaphtho[2,3‐d:2′,3′‐i] [1,6,3,8]dioxa‐diazecine. In a similar way, the reaction between trans‐2‐aminocyclohexanol and formaldehyde was re‐examined and found to produce initially a ca 80:20 mixture of r‐4a,t‐7a,c‐11a,t‐14a‐ and r‐4a,c‐7a,t‐11a,t‐14a‐7,14‐methanoperhydrodibenzo[d,i][1,6,3,8]dioxandiazecines.
Sulphur‐33 nuclear magnetic resonance of oxidized petroleum asphaltene
Authors: McIntyre Deane D. , Strausz Otto P.
Published: May 2005

A 33S NMR spectrum has been obtained from an asphaltene sample for the first time. Asphaltene from the Athabasca tar sands bitumen, Alberta, Canada, was oxidized with RuVIII, which selectively converts sulphide sulphur into the corresponding sulphone. The 33S NMR spectrum of this sample at 30.7 MHz featured a broad signal centred at 320 ppm downfield from CS2. The width of this signal was too broad, owing to the quadrupole relaxation of the nuclei in the solution and/or the many types of sulphone molecules, to permit the assignment to any particular sulphone types. This situation was not improved by the use of proton broad band decoupling at elevated temperatures. Nevertheless, the mere presence of the aliphatic sulphones provides the first unambiguous evidence for the presence of aliphatic sulphides in a petroleum asphaltene. Similar results were obtained from sulphones prepared by peroxide oxidation of high molecular weight sulphides isolated from bitumen from the Wabasca, Alberta deposit.
1H NMR additive shielding coefficients (Z) for organoseleno groups in vinyl selenides
Authors: Ferraz Helena M. C. , Comasseto Jaão V. , Brandt Carlos A.
Published: May 2005

Additive shielding parameters for the phenylseleno group (ZPhSe‐gem = 1.36; ZPhSe‐cis = 0.31; ZPhSe‐trans = 0.29) have been estimated. Examples of the calculation of chemical shifts for olefinic protons in vinylic selenides by means of these increments are given. A comparison with 2‐pyridylseleno and methylseleno substituents has been made. The standard deviations of the Z values are 0.06 for ZPhSe‐gem, 0.10 for ZPhSe‐cis and 0.05 for ZPhSe‐trans.
Complete 13C NMR spectra of the axial forms of methyl‐, ethyl‐ and isopropylcyclohexane
Authors: Squillacote Michael E. , Neth Joann M.
Published: May 2005

Low‐temperature 13C NMR spectral data have been obtained for equatorial and axial methyl‐, ethyl‐ and isopropylcyclohexane using a high‐temperature cryogenic trapping technique. 13C chemical shift differences between major and minor conformations of each compound are discussed in terms of chemical shift theories. A convenient synthesis of deuteriated dichlorofluoro‐ and difluorochloromethane, which are excellent low‐temperature NMR solvents, is also presented.
14N nuclear quadrupole resonance study of the protonation of thiourea
Authors: Murgich Juan , Magaly Santana R. , Abanero Jose A.
Published: May 2005

14N NQR frequencies of thiourea complexes with HCIO4, HCI and H2SO4 obtained at 77 K are reported. Comparison of NQR data previously obtained in hexamethylenetetramine‐2thiourea showed that the perchloric acid complex was a hydrogen‐bonded complex. A similar comparison with uronium salts showed that the other complexes were thiouronium salts. The protonation site in thiouronium salts was shown to be the S atom. S protonation produced decreases of the N non‐bonding orbital occupation number and increases in those of the NN and NC sigma bonds. Changes in the N non‐bonding orbital produced by protonation were larger in thiourea than in urea.
High‐resolution 13C NMR studies of proanthocyanidin polymers (condensed tannins)
Authors: Newman Roger H. , Porter Lawrence J. , Foo L. Yeap , Johns Stanley R. , Willing Richard I.
Published: May 2005

High‐resolution 13C NMR spectra of some proanthocyanidin polymers are presented. They were measured in acetone‐d6‐water (1:1, v/v) solution at 30 °C and at 62.5 MHz. The chemical shifts of selected resonances in these spectra were compared with those of structurally related monomers and oligomers. These comparisons enable certain deductions to be made regarding the stereochemistry and mode of linkage of the constituent flavanoid monomer units of these polymers.
Optimized detection of small spin–spin couplings in two‐dimensional chemical shift correlation experimentsCOSY and DEPT
Authors: Batta Gy. , Kövér Katalin E.
Published: May 2005

Two‐dimensional chemical shift correlation experiments (COSY and DEPT) may be applied to the detection of small spin‐spin couplings. To increase the sensitivity of these techniques, careful optimization of the experimental parameters is required. Equations applicable to AX spin systems are given for the optimal choice of delay periods in the pulse sequences. Practical applications have been demonstrated for oligosaccharide sequencing.
Conformational analysis part. 8—A lanthanide‐induced shift NMR investigation of the conformation of amiodarone derivatives
Authors: Abraham Raymond J. , Smith Paul E. , Deleuze Colette , Gatto Vincent Lo
Published: May 2005

A LIS investigation of analogues of amiodarone containing the 3‐benzoyl‐2‐butylbenzofuran system has been performed, utilizing the pseudo‐contact shifts of all the proton and carbon nuclei in the molecules. The 13C diamagnetic shifts were removed by use of La(fod)3 and the pseudo‐contact shifts were analysed to obtain the conformations in solution of these molecules.

In 3‐(2,6‐dibromobenzoyl)‐2‐butylbenzofuran (1), the ortho bromo substituents produce sufficient steric hindrance so as to enable the separate O‐trans and O‐cis conformers to be observed at room temperature.

Thus the LIS analysis was performed on both conformers separately. In each case good solutions (Rx <5%) were obtained for the conformations in which the benzofuran and carbonyl groups are coplanar and the phenyl group orthogonal to this plane. This was achieved using an unsymmetrical model of the lanthanide complexation to the carbonyl group in which the different spatial environment of the oxygen lone pairs is allowed for in the refinement procedure.

In 3‐(3,5‐diiodobenzoyl)‐2‐butylbenzofuran (2), in which there is no evidence of conformation isomerism in the NMR spectrum down to ‐100 °C, the analysis of the LIS data on the basis of a rapidly interconverting mixture of conformers analogous to those of 1 did not produce a satisfactory result. In contrast, analysis on the basis of a single conformation in which the phenyl group is coplanar with the carbonyl group and the benzofuran moiety is twisted out of this plane gave a satisfactory solution for an angle of twist of ca 90°. Owing to the long time scale of the NMR experiment, the LIS results are also consistent with a rapidly interconverting equilibrium between two non‐planar conformations in which the average angle of twist of the benzofuran group is ca 90°. This intriguing result can be rationalized by steric considerations and molecular mechanics calculations which indicate that, in the absence of any abutting ortho substituents on the phenyl group, coplanarity of the carbonyl group and the 2‐alkylbenzofuran moiety is less favoured energetically than coplanarity of the carbonyl and the phenyl groups. The slightly greater intrinsic torsional barrier of the carbonyl and benzofuran parts is more than compensated for by the increased steric interactions of the carbonyl with the 2‐alkyl and 4‐hydrogen groups of the benzofuran in the planar form.
Cyclodextrins as chiral complexing agents in water, and their application to optical purity measurements
Authors: Greatbanks David , Pickford Roderick
Published: May 2005

The interaction of β‐cyclodextrin with propanolol hydrochloride was shown by NMR to produce diastereomeric pairs observable in D2O solution at 400 MHz. By addition of racemate to pure (–)‐isomer, the usefulness of this novel technique in being able to measure optical purity in water down to the 1% level was demonstrated. Using changes in chemical shifts and NOE effects, a possible structure for the inclusion complex is proposed. γ‐Cyclodextrin induced larger shifts in the spectrum than the β‐equivalent, whereas α‐cyclodextrin had no effect.
Chiral phenyl‐substituted chalcone epoxides. I—Correlative determination of absolute configuration by 1H NMR lanthanide‐induced shifts
Authors: Langin‐Lantéri Marie‐Thérèse , Fonbonne Catherine , Huet Jean , Petit‐Ramel Michèle
Published: May 2005

The absolute configuration of an unknown 2′‐ or 4‐ and (or) 4′ phenyl‐substituted chalcone oxide can be predicted from the chemical shift behaviour of the 1H NMR spectrum of the substrate in the presence of the lanthanide chiral complex Eu(hfbc)3.
Interactions between 2,2‐dimethyl‐2‐silapentane‐5‐sulfonate and nucleoside 5′‐monophosphates in aqueous solution
Authors: Sagan Barbara L. , Walmsley Judith A.
Published: May 2005

Hydrophobic binding of 2,2‐dimethyl‐2‐silapentane‐5‐sulfonate (DSS) to guanosine 5′‐monophosphate (5′‐GMP) and cytidine 5′‐monophosphate (5′‐CMP) results in an upfield shift of the 1H NMR trimethylsilyl resonances with respect to an internal reference tetramethy lammonium ion. The nature of the nucleotide‐DSS interaction and the stability of the resulting complexes have been studied. The magntiude of the effect is dependent on the nature and extent of the self‐association of the nucleotide and the nucleotide concentration. For nucleotides which self‐associate non‐cooperatively to form disordered base stacks, such as Li2(5′‐GMP) and M2(5′‐CMP), where M = Li+, Na+, K+ and Rb+, the formation of 2 : 1 complexes (nucleotide to DSS molar ratio) has been proposed. Apparent equilibrium constants for the 2 : 1 complexes are 0.44 M−2 for Li2(5′‐GMP) at 2 °C and an average value of 0.30 M‐2 for M2(5′‐CMP) at 1 °C. For the Na+ and Rb+ salts of 5′‐GMP, which form strongly associated, ordered self‐aggregates, the interaction between DSS and 5′‐GMP is considerably reduced owing to the inability of DSS to compete effectively with the self‐aggregation process.
1H and 13C NMR investigation of conformational isomerism in amiodarone and derivatives
Authors: Deleuze C. , Nisato D. , Gatto V. Lo , Chatelain P. , Gubin J.
Published: May 2005

The 1H and 13C NMR spectra of amiodarone and several derivatives are reported and assigned. The hypothesis of an O‐trans to O‐cis conformational equilibrium in most of these molecules has been investigated by examining the 1H and 13C chemical shifts, and by NOE and LIS experiments, variable‐temperature NMR and IR spectroscopy.

The assumed O‐trans/O‐cis equilibrium would be fast on the NMR time scale for amiodarone, which has no ortho substituents on the C‐3 benzoyl substituent. However, in the 2′,6′‐dibromobenzoyl derivatives, separate O‐trans and O‐cis conformers are observed at room temperature in the NMR spectrum in the ratio of ca 60:40, favouring the O‐trans conformer. The coalescence temperatures and activation energies (ΔG) of the 2′,6′‐disubstituted compounds are obtained; the activation energy increases with the size of the ortho substituents but the conformer ratio remains unchanged. In contrast, removal of the C‐2 butyl substituent on the benzofuran ring gives 100% of the O‐trans conformation.
NMR and theoretical (MNDO and Ab Initio) studies of lone‐pair electron‐π‐electron interactions: The conformation of 9‐methoxyfluorene
Authors: Bakke Jan M. , Rønneberg Hanne , Chadwick Derek J.
Published: May 2005

The results of NMR investigations based on the heteronuclear 3J(CH3, H‐9) coupling constant, the methyl group chemical shift, lanthanide‐induced shifts and MNDO calculations indicate that 9‐methoxyfluorene exists predominantly in the trans conformation in which the methyl group is oriented in an antiperiplanar relationship with respect to H‐9. Previous experimental work on the 9‐hydroxy analogue demonstrated a similar conformational preference, which is also indicated by the results of MNDO and ab initio calculations presented here. The origin of the preference probably lies in a repulsive interaction between the electrons of the aromatic π‐systems and the lone‐pair electrons of the hydroxyl or methoxyl oxygen.