bluuebunny/crossref_metadata_2025_split huggingface dataset:
1H and 31P nuclear magnetic resonance spectra of compounds containing the PIIINPV skeleton
Authors: Bulloch Gordon , Keat Rodney , Rycroft David S. , Thompson David G. 
Published: May 2005

AbstractThe 1H and 31P NMR spectra of a series of compounds containing the PIII‐N‐PV skeleton including Cl2PNMeP(Z)Cl2 (ZO or S), Cl2P·NMe·P(O)CINMe2, P4(NMe)6Zn (ZS, n = 1−3; ZSe, n = 1), XP(NBut)2P(Z)X (XCl, ZO or S; XOMe, ZS or Se; XNMe2, ZS or Se; XNEt2, ZSe), (XO or S), and Ph2PNRP(S)Ph2 (RMe, Et) have been obtained. 1H‐{31P} double resonance, and in selected cases, 31P‐{1H, 77Se} and 31P‐{1H, 31P} triple resonance experiments, indicate that 2J(PIII NPV) is positive in acyclic compounds, negative in most cyclic or cage compounds, and furthermore, is related to the conformation adopted by the PIII‐N bond.
Carbon‐13 NMR spectra of some tetra‐ and pentacyclic triterpene methyl ethers
Authors: Blunt J. W. , Munro M. H. G. 
Published: May 2005

AbstractThe carbon‐13 NMR spectra have been recorded for representatives of three previously unexamined classes of pentacyclic triterpenes—lupanes, fernanes and arboranes. In addition to the spectra of lupeol methyl ether, cylindrin and arundoin, the spectra of a number of other triterpene methyl ethers are also recorded. The effect of methyl ether formation on the shilding values for carbons in the 3β‐hydroxy‐4,4‐dimethyl‐ ring A system is defined.
The determination of the COOH substiuent effect for branched carboxylic acids from carbon‐13 chemical shifts
Authors: Marr David H. 
Published: May 2005

AbstractThe carboxyl substituent effects for branched carboxylic acids have been determined by carbon‐13 Fourier ransform nuclear magnetic resonance of eighteen measured and reported branched acids. For α‐branched systems the substituent effects are α = 15.3 ppm, β = 2.6 ppm, γ = −1.9 ppm, δ = 0.9 ppm and ϵ = 0.5 ppm. For other branched acids, the determined carboxyl substituent effects are α = 19.2 ppm, β = 2.1 ppm, γ = −1.4 ppm, δ = 0.6 ppm, and ϵ = 0.6 ppm.
15N NMR spectroscopy. 19—spectroscopic characterization of cyclodipeptides (2,5‐dioxopiperazines)
Authors: Kricheldorf Hans R. 
Published: May 2005

AbstractVarious cyclodipeptides containing glycine, alanine, leucine, valine, phenylalanine, phenylglycine and sarcosine units were synthesized by cyclization of dipeptide pentachlorophenyl esters. The 13C and natural abundance 15N NMR spectra of these heterocycles were measured in trifluoroacetic acid and compared with the spectra of the corresponding amino acids and polypeptides. The 13C NMR carbonyl signals of all cyclodipeptides show a 1.5–4.0 ppm upfield shift relative to the corresponding polypeptides. The 15N NMR signals show no such consistent relationship. The substituent effects and the neighbouring residue effects observed in the 15N NMR spectra of the cyclodipeptides are different from those of polypeptides, while the one bond NH coupling constant of cis and trans amide groups was almost identical. The nitrogen and the carbonyl signal of the Gly units in cyclo‐Gly‐Phe show an extraordinary downfield shift, reflecting the interaction of the phenyl group with the 2,5‐dioxopiperazine ring.
Substituent effects on carbon‐13 chemical shifts of para‐substituted benzylbenzenes
Authors: Nakai Yoshimi , Takabayashi Tetsuo , Yamada Fukiko 
Published: May 2005

AbstractCarbon‐13 chemical shifts of fourteen para‐substituted benzylbenzenes have been determined. The relative substituent chemical shifts (SCS) of the methylene carbons and the aromatic ring carbons (C‐4, C‐1′ and C‐4′) correlated well with the Hammett substituent effects using the dual substituent parameter method. The transmission of substituent effects through the benzylbenzene system is briefly discussed.
Application of rank correlation to lanthanide induced shift data
Authors: Li Wai‐Kee , Lee Sik‐Yum 
Published: May 2005

AbstractSpearman's rank correlation method is suggested as an alternative procedure for the treatment of lanthanide induced shift data. When this method is applied to Sullivan's data [J. Am. Chem. Soc. 98, 7162 (1976)], the results are similar to those obtained by the jack‐knife and Kendall techniques, which were introduced in a previous article. All three methods are able to distinguish between closely related structures. Among these three non‐parametric methods, the Spearman procedure is probably the simplest.
Carbon‐13 nuclear magnetic resonance spectroscopy of cephalotaxus alkaloids
Authors: Weisleder David , Powell Richard G. , Smith Cecil R. 
Published: May 2005

AbstractCarbon‐13 chemical shift assignments have been obtained for the naturally occurring Cephalotaxus alkaloids, cephalotaxine, acetylcephalotaxine, harringtonine, isoharringtonine, drupacine and cephalotaxinone.
Applications of 15N NMR spectroscopy to the study of unsymmetrically N‐substituted amides and model peptide compounds
Authors: Dorie J. , Gouesnard J. P. , Mechin B. , Naulet N. , Martin G. J. 
Published: May 2005

Abstract13C and 15N spectra of unsymmetrically N‐substituted formamides and alkyl‐, substituted alkyl‐, and arylcarboxamides, which can be considered as model peptide compounds, were determined and discussed in terms of nitrogen lone pair delocalization. Differential solvent shifts and through‐space steric effects are considered as a tentative explanation of the difference in screening between geometrical diastereoisomers. Z‐E assignment and the thermodynamic stability of diastereoisomers can also be predicted in some circumstances from a consideration of the 15N chemical shifts. Data concerning small peptides are discussed in the light of the results obtained using the model compounds.
13C chemical shifts of phenol derivatives. A correlation with electronic structure
Authors: Ilczyszyn Marek , Latajka Zdzisław , Ratajczak Henryk 
Published: May 2005

AbstractThe 13C chemical shifts of twenty chloro‐ and nitro‐substituted phenols have been measured in d‐chloroform. The influence of substituents on the screening at C‐1, on the total charge at this position and on the dipole moments is reported and analysed. The results of this study suggest that variations of the chemical shifts at C‐1 for meta‐methyl‐, meta‐chloro‐, meta‐nitro‐, ortho‐ and para‐methyl‐, ortho‐ and para‐chlorosubstituents mainly reflect charge density changes. The influence of ortho‐nitro groups on the screening of C‐1 is more complex.
Carbon‐13, 1H spin‐spin coupling. V—π‐benzenechromium tricarbonyl and the π‐tropyliumchromium tricarbonyl cation
Authors: Aydin Rafet , Günther Harald , Runsink Jan , Schmickler Hans , Seel Horst 
Published: May 2005

AbstractThe 13C, 1H spin‐spin coupling constants have been determined for π‐benzenechromium tricarbonyl (3) and the π‐tropyliumchromium tricarbonyl cation using the 13C{2H}double resonance technique described in a previous paper. In addition, conventional analysis of the 1H‐coupled 13C NMR spectrum of 3 was carried out and the 1H NMR spectrum of 3 partially oriented in the nematic phase was analysed. Both treatments also allowed the determination of the 1H, 1H coupling constants for this compound. The nJ(CH) results are discussed on the basis of structural data and the theoretical results available. The complexation effects for 1J(CH) are found to correlate with the CH overlap population and hybridization changes, and those for 3J(CH) with the CC bond lengths and π‐bond orders. The dependence of 2J(CH) on CC bond length as well as on the CCH bond angle is indicated. The liquid crystal results are compared with those of related studies.
Nuclear spin magnetization transfer by doubly selective irradiation
Authors: Craig Robert A. , Harris Robin K. , Morrow Robert J. 
Published: May 2005

AbstractA procedure for doubly selective irradiation of an AX NMR spin system so as to achieve complete magnetization transfer from X to A is described. In combination with suitably gated decoupling this sequence will give substantial savings of time in determinations of T1 for low‐sensitivity spin‐½ nuclei, particularly those with negative magnetogyric ratios.
The temperature dependence of 13C NMR shifts in polar compounds and its role for the determination of conformational equilibria
Authors: Schneider Hans‐Jörg , Freitag Wolfgang , Hoppen Volker 
Published: May 2005

AbstractIntrinsic temperature dependencies of 13C NMR shifts in alkanes bearing one polar C‐αX bond are determined with neopentyl and 4‐tert‐butylcyclohexyl derivatives as conformationally homogeneous model compounds. The increased shiedling for C‐α at higher temperatures can be related to a C‐α—X bond length increase and, for less polarizable CX bonds, essentially to a decrease of solvent polarity on raising the temperature. The use of temperature dependent 13C shifts in conformationally mixed compounds for the determination of the equilibrium constants, K, is evaluated with n‐propyl halides; the computer fit of the unknown conformer shifts and the conformational enthalphy difference, δH° to the time averaged shifts yields δH° values which, although converging rather broadly, are in general agreement with literature data. In compounds with higher conformational barriers, such as methoxy‐ and bromocyclohexane, low temperature signal integration yields accurate δG° values; inclusion of shifts above coalescence, however, yields unreliable δH° and δS° parameters. This can only partially be remedied by application of temperature shift corrections obtained from parent t‐butylcyclohexyl compounds.
On the convergence of iterative computation in the LAOCOON 3 program
Authors: Attimonelli M. , Sciacovelli O. 
Published: May 2005

AbstractThe reasons which sometimes cause failure of convergence in the iteration of NMR spectra by LAOCOON 3 are discussed. The problem can be avoided by retaining the sequence of the eigenfunctions throughout the iterative process. In addition, assignment of the lines to start the iterative analysis can be facilitated by considering the dependence of the transitions on the NMR parameters in the simulation stage. LAOCOON 3, modified and extended to handle eight spin systems, has been successfully tested in the iterative analysis of the 1H NMR spectrum of naphthalene.
1H NMR assignments for t‐2‐deuterio‐r‐1‐methyl‐1‐phenylcyclopropane and c‐2‐deuterio‐r‐1‐methyl‐1‐phenylcylclopropane. A literature correction
Authors: McKinney Michael A. , Nagarajan Sridhar C. 
Published: May 2005

AbstractThe synthesis and 1H NMR spectra of the cis and trans monodeuterated isomers of 2‐deuterio‐1‐methyl‐1‐phenylcyclopropane have been previously reported. We have prepared one of the isomers, c‐2‐deuterio‐r‐1‐methyl‐1‐phenylcyclopropane, by a different, stereospecific, route. We now wish to correct the original 1H NMR assignments which were in error.
Evidence for an important 13C NMR shielding effect for carbon atoms bearing a heavy chalcogen substituent
Authors: Laitem Leopold , Christiaens Leon , Renson Marcel 
Published: May 2005

AbstractAn important 13C NMR shielding effect on carbons bearing a heavy chalcogen is demonstrated. This effect is parallel to that induced by iodine, but to a lesser extent. For acyclic compounds and for partially saturated heterocycles, there is an excellent linear correlation between the 13C chemical shifts of carbons bearing a chalcogen and carbons bearing a halogen atom in the corresponding compound. The linearity of the relationship is less satisfactory with heteroaromatic compounds.
1H NMR utilization of through‐space effects in configurational assignments. I—application to nitriles; determination of the separate effects of the electric field and anisotropy of the CN group
Authors: Rouillard Michel , Geribaldi Serge , Khazarian Jean , Azzaro Marcel 
Published: May 2005

AbstractThe changes in chemical shift induced by isomerization for all the ring protons of the Z‐ and E‐5,5‐dimethyl‐2‐cyclohexenylidene acetonitriles depend only on the through‐space effects of the cyano group. The configurational assignments were made taking into consideration the anisotropic and electric field effects, either separately or together. In the first case, the total effects are ΔXCNT=−14.7×10−6cm3 mol−1 and bμCNT=14.7×10−30 cm3, respectively. The second approach allows the estimation of the values ΔXCN=−4.9 × 10−6 cm3 mol−1 and bμCN=9.8 × 10−3 cm3, reflecting the combined contributions of magnetic anisotropy and electric field to the total effect.
The rα‐structure and the 1H and 199Hg shielding anisotropies of dimethylmercury as determined in nematic and smectic liquid crystal solvents
Authors: Jokisaari J. , Diehl P. 
Published: May 2005

AbstractThe complete rα‐structure of dimethylmercury in the nematic ZLI 1167 liquid crystal was determined. This study confirms the earlier results, indicating that the structure is practically independent of the liquid crystal solvent, although some minor deviations exist. The HgC distance was found to be 207.97±0.05 pm, when the vibration corrections in the dipole‐dipole coupling constants were taken into account. This is rather similar to the distances obtained with other spectroscopic methods. The anisotropies of the 1H and 199Hg chemical shifts were obtained by using a smectic liquid crystal and recording the corresponding spectra, the optical axis being parallel with or perpendicular to the external field direction. The experimental ratio‐2.007±0.017 of the D∥ (HgH) and D⟂ (HgH) coupling constants proves that the indirect contributions in these coupling constants are negligible. Shielding anisotropies of 3.70±0.3 ppm and 7325±55 ppm for 1H and 199Hg, respectively, were obtained.
Carbon‐13 nuclear magnetic resonance spectroscopy. Substituent‐induced chemical shift effects on cyclopropyl carbons of 4‐substituted cyclopropylbenzenes
Authors: Kusuyama Yoshiaki , Dyllick‐Brenzinger Christina , Roberts John D. 
Published: May 2005

AbstractCarbon‐13 chemical shifts of the cyclopropyl carbons of eleven 4‐substituted cyclopropylbenzenes have been measured under conditions effectively corresponding to infinite dilution in DCCI3. The substituent‐induced chemical shifts (SCS) of both the α and β carbons of the cyclopropane ring were found to be downfield with electron‐attracting groups and upfield for electron‐donating groups. The trends for the β carbons correspond to those observed for the β carbons of 4‐substituted phenylethenes, while the trends of the α carbons are similar to those found for the α carbons of 4‐substituted isopropyl benzenes. The results for the β carbons can be rationalized by postulating a substantial contribution from a hyperconjugative resonance effect involving the σ system of the benzene ring (and its 4‐substituent) and the C‐α—Cβ bonds of the cyclopropane ring. The effects on the α carbons are in accord with a very reasonable smaller inductive polarization of the C‐αC‐β bonds than encountered for the carbons of corresponding ethenyl‐ or ethynylbenzenes.
Configurational assignment and 1H NMR spectral parameters of isomeric 1,2‐diacetoxy‐4‐alkyl‐3‐methylcyclopentanes
Authors: Hanselaer R. , De Clercq P. 
Published: May 2005

AbstractThe 1H NMR spectral parameters of all eight 1,2‐diacetoxy‐3,4‐dimethylcyclopentanes and 1,2‐diacetoxy‐4‐t‐butyl‐3‐methylcyclopentanes are discussed.
The structure and intramolecular motion of benzaldehyde as studied on the basis of proton spectra with 13C satellites of the oriented molecule
Authors: Diehl P. , Jokisaari J. , Amrein J. 
Published: May 2005

AbstractThe proton spectrum with 13C satellites of benzaldehyde oriented in a liquid crystal solvent has been analysed and the structure of the proton and carbon skeleton has been determined. The large number of observed direct couplings also allows the study of the intramolecular rotation. The depth of the hindering potential is extremely model dependent, however, so that no unique result has been obtained.
35Cl NQR spectra and 13C NMR spectra of polycyclic chlorinated hydrocarbons with 10 and 12 carbon atoms
Authors: Fitzky Hans Georg , Gäb Siegmar 
Published: May 2005

AbstractThe structure of cyclic chlorinated hydrocarbons can be elucidated by the use of combined 13C nuclear magnetic resonance and 35Cl nuclear quadrupole resonance. The advantages obtained and the techniques employed with respect to some new and already investigated compounds, and typical shift values aiding studies of similar derivatives, are reported.
Downfield 1H NMR shifts induced by electron‐rich substituents
Authors: Hand E. Smakula , Paudler W. W. 
Published: May 2005

AbstractThe 1H NMR signal due to the peri proton H‐5 in imidazo[1,2‐a]pyridines exhibits large downfield shifts when the 3‐position bears a substituent (−XY) containing an electron‐rich atom (Y) two bonds removed from C‐3. Such shifts are observed not only when the ring electron density can be decreased by resonance interaction [from −1.29 to −1.87 ppm for 3‐COR, 3‐(2′‐quinoxalyl) and 3‐No in CDCl3], but also when electron withdrawal must be minimal: −1.10 ppm when X is an sp3 center [3‐CH(OH)CCl3 in CDCl3], −1.0 ppm when the 3‐substituent is negatively charged (3‐CO2 −Na+ in D2O), and −1.32 to −1.46 ppm when the ring system is protonated (3‐COR and 3‐NO2 in TFAA). The effect is largest in those compounds for which orientation of lone‐pair electrons on atom Y toward H‐5 can be invoked. The desielding is attributed primarily to a through‐space electric field effect.
The 1H NMR spectra of exo‐ and endo‐3‐thiatricylo[4.2.1.02,5]non‐7‐ene 3,3‐dioxide. The shielding effect of the sulfone group
Authors: Martin H.‐D. , Iden R. , Scheutzow D. , Jackman L. M. 
Published: May 2005

AbstractThe proton spectra of exo‐ and endo‐3‐thiatricyclo[4.2.1.02,5]non‐7‐ene 3,3‐dioxide have been analysed and completely assigned. Considerations of coupling constants indicate that the thietane ring is nonplanar and that the norbornene residue is significantly distorted from the geometry of norbornene itself. The sulfone group induces significant changes in the shielding of the proximate olefinic proton in the endo isomer and the bridge protons in the exo isomer. These shifts appear to be the result of the electrostatic effects and effects associated with the diagmagnetic anisotropy of the sulfone group.
13C and15N NMR study of acyclic vicinal diastereoisomers. Conformational effects
Authors: Levy George C. , Pehk T. , Lippmaa E. 
Published: May 2005

AbstractConformations of aliphatic diastereoisomers with vicinal asymmetric centers (2,3‐disubstituted butanes and 5,6‐disubstitutedn‐decanes) are discussed in terms of their13C and, in some cases,15N chemical shifts and spin‐lattice relaxation times. Solvent and protonation effects are explained by conformational changes in the isomers.
Analysis of the 19F and 1H NMR spectra of a number of polyfluoroindenes
Authors: Matthews R. S. , Preston W. E. 
Published: May 2005

Abstract19F and 1H NMR spectra of the products of nucleophilic attack on octafluoroindene are analysed and structures assigned. The major product in the reaction of butyllithium with octafluoroindene is 3‐methylheptafluoroindene, with sodium borohydride it is 2‐hydroheptafluoroindene and with sodium methoxide it is 3‐methoxyheptafluoroindene. Vacuum pyrolysis of undecafluorotricyclo[5.2.2.02,6]undeca‐ 2,5,8‐triene, with elimination of C2F4, gives 6‐hydroheptafluoroindene as the major product. The NMR assignments are based on the unambiguous synthesis via vacuum pyrolysis of 5,6‐dihydrohexafluoroindene, 3‐hydro‐ and 3‐methyl‐heptafluoroindene and the large long‐range coupling of 15 Hz assigned to the F‐2, F‐6 interaction.
Investigation of phenyl derivatives of group IV elements using carbon‐13 NMR spectroscopy
Authors: Vaickus M. J. , Anderson D. G. 
Published: May 2005

AbstractThe tetraphenyl–metal, hexaphenyl–dimetal, and triphenylchloro–metal derivatives of the Group IV elements were examined using 13C NMR methods. Chemical shifts and metal–carbon coupling constants were obtained for all compounds studied.
Carbon‐13 NMR and conformational analysis of meso‐ and dl‐α,α′‐disubstituted succinic acids
Authors: Hasan Misbah Ul 
Published: May 2005

Abstractmeso‐and dl‐Diastereomers of a number of α,α′‐disubstituted succinic acids have been shown to give different 13C NMR chemical shifts. The results can be satisfactorily explained on the basis of their conformational analyses. A discussion of the observed chemical shifts is presented, and the preferred conformation for each of several compounds is predicted on the basis of these chemical shifts.
1H NMR spectral properties and conformational preferences of some 1,2,9,10,17,18,25,26‐octathia[2.2.2.2]‐metacyclophanes
Authors: Ronsisvalle Giuseppe , Bottino Francesco , Pappalardo Sebastiano 
Published: May 2005

AbstractThe stereochemistry in solution of three octathia[2.2.2.2]metacyclophanes has been investigated by means of 1H NMR spectroscopy. The results lead to the conclusion that the saddle or crown conformation is preferred for these compounds, depending on the substitution pattern of the constituent aromatic rings.
Detection of partially resolved carbon‐13–proton couplings with selective population inversion (SPI)
Authors: Pachter Ruth , Wessels Philippus L. 
Published: May 2005

AbstractIn a heteronuclear 13C{1H} selective population inversion 13C NMR spectrum a splitting, resulting from a (CH) coupling over more than one bond, can be detected even when no splitting is observed in the single‐frequency 13C NMR spectrum. The relationship between the observed splitting, coupling constant and line width is discussed. A method is proposed from which the value of the coupling constant can be estimated, and its application illustrated by the splittings observed in the 13C NMR spectra of the mycotoxin, ochratoxin A.
13C13C coupling constants in diacetylene (1,3‐butadiyne) and its bis(triethylsilyl) derivative
Authors: Kamieńska‐Trela Krystyna 
Published: May 2005

AbstractCompletely 13C‐labelled diacetylene and its bis(triethylsilyl) derivative have been synthesized and all the possible spin–spin couplings between the acetylenic carbon nuclei have been determined from their Fourier transform 13C NMR spectra. J(CC) values in diacetylene have been also computed by means of the finite perturbation INDO method. Carbon–proton coupling constants in diacetylene have been determined from the spectrum at natural abundance. It has been established that J(CC) values across the triple bond in diacetylene and bis(triethylsilyl)diacetylene are greater than in acetylene and triethylsilylacetylene, respectively. The increase is interpreted in terms of σ‐ and π‐electronic changes which occur with the coupling of two isolated triple bonds into a dimer‐like system. All CC coupling constants are greater in diacetylene than in bis(triethylsilyl)diacetylene, which indicates that strong (p→d)π interaction takes place in the latter compound.
Proton spin‐lattice relaxation rate studies. 1‐Aryl‐4,4‐dimethyl‐2‐methylthio‐2‐imidazolin‐5‐ones
Authors: Navarre Jean‐Marie , Colebrook Lawrence D. , Hall Laurance D. 
Published: May 2005

AbstractProton spin‐lattice relaxation rates (R1 values) have been measured, at 270 MHz, for a series of 1‐aryl‐4,4‐dimethyl‐2‐methylthio‐2‐imidazolin‐5‐ones, using both null‐point and non‐linear regression methods; the two procedures give the same rates. A normalization procedure has been used to enable comparisons to be made between the R1 values of different compounds; this is necessary because the experimental values are affected by changes in motional correlation times associated with changes in molecular structure. A substantial (five‐fold) dynamic range of R1 values has been observed for the protons of individual compounds, and the values have been correlated with the molecular environments of the nuclei. Evidence for anisotropic molecular motion and inter‐ring proton relaxation in these compounds has been considered.