bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of phenyl derivatives of group IV elements using carbon‐13 NMR spectroscopy
Authors: Vaickus M. J. , Anderson D. G.
Published: May 2005

The 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

meso‐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

The 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

In 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

Completely 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

Proton 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.
The NMR spectra of the porphyrins 16—zinc(II) meso‐tetraphenylporphyrin (Zn TPP) as a diamagnetic shift reagent. A quantitative ring current model
Authors: Abraham Raymond J. , Bedford Geoffrey R. , McNeillie David , Wright Brian
Published: May 2005

The facile preparation of zinc(II) meso‐tetraphenylporphyrin (Zn TPP) and derivatives from substituted benzaldehydes and pyrrole, combined with the calculation of ring current shifts in these molecules, provides a useful series of selective diamagnetic shift reagents. The porphyrin‐ligand equilibrium is examined for some nitrogenous bases and the complexation shifts (δP values) are obtained in precisely the same manner as LIS. The parameterization of the double‐dipole model of the porphyrin ring current is given, with the inclusion of the phenyl ring currents and free rotation about the substrate‐Zn bond. Precise agreement with the porphyrin proton chemical shifts and the complexation shifts of the geometrically rigid substrates of pyridine, 4‐picoline and quinuclidine is obtained. In contrast, the 13C complexation shifts in these molecules are subject to additional effects other than the ring current shift.
1H NMR structural increments for alkyl substituted η3‐allyl transition metal complexes
Authors: Benn Reinhard , Schroth Gerhard
Published: May 2005

The 1H NMR spectra of various alkyl substituted η3‐allyl transition metal complexes (MNi, Ru) have been analysed. The chemical shifts of the η3‐allyl protons can be calculated using additive increments; the values of the syn and anti vicinal proton‐proton coupling constants approach each other on alkyl substitution of the η3‐allyl group.
A Study of the behaviour of an analogous series of 2H‐thiopyrans, 6H‐1,3‐thiazines and their derivatives by carbon‐13 and nitrogen‐15 nuclear magnetic resonance
Authors: Rabiller C. , Martin G. J. , Pradere J. P. , Meslin J. C. , Quiniou H.
Published: May 2005

The influence of substituents in a new series of 2H‐thiopyrans, 2H‐thiopyran‐2‐ones (thiones) and their thiazine analogues is examined by means of carbon (13C) and nitrogen (15N) NMR. A linear relationship is shown to exist between the chemical shifts (δ13C or δ15N) of the thiopyrans and the thiazines. This relationship is a good indication of the structural similarity which exists between the two series.
Linear solvation energy relationships VIII—solvent effects on NMR spectral shifts and coupling constants
Authors: Taft R. W. , Kamlet Mortimer J.
Published: May 2005

The solvatochromic comparison method is used to unravel solvent polarity and hydrogen bonding effects on a variety of NMR spectral shifts and coupling constants. Solvent effects are rationalized in terms of the solvatochromic parameters π*, δ, α and β. Properties analyzed include 19F shifts of 5‐fluoroindole, 1H shifts of fluorodinitromethane, tert‐butanol, phenol, 2‐methylbut‐1‐en‐3‐yne, and thioacetamide, 1H and 13C shifts and J(13C1H) coupling constants of chloroform, 13C shifts of acetone, 15N shifts of pyridine, 15N and 29Si shifts of 1‐methylsilatrane, and some J(119Sn,C,19F) coupling constants of polyalkyltin compounds.
Electronic and steric effects in arylphosphoramidates and phosphorimidates as monitored by carbon‐13 nuclear magnetic resonance
Authors: Buchanan G. W. , Morin F. G.
Published: May 2005

13C NMR chemical shifts and 13C31P couplings are reported for ten arylphosphoramidates and five arylphoshorimidates. The para‐carbon chemical shifts in the phosphoramidates are interpreted in terms of substantial nitrogen lone pair delocalization into the aromatic ring, a phenomenon which is subject to steric inhibition of resonance. By contrast, in the phosphorimidates the electron release into the phenyl ring is not attenuated by steric congestion. Conformational changes about the arylN bond in all compounds have been monitored by vicinal 31PNC13C couplings.
The diphenyliodonium‐2‐carboxylates: An NMR structure investigation
Authors: Mazza Dario Del , Reinecke Manfred G. , Smith William B.
Published: May 2005

Diphenyliodonium‐2‐carboxylate, phenyl 4‐methylphenyliodonium‐2‐carboxylate and phenyl 5‐methyl‐phenyliodonium‐2‐carboxylate have been examined by 1H and 13C NMR spectroscopy. Each compound showed one proton considerably upfield from the others. From the two substituted compounds this was deduced to be H‐6 on the ring containing the carboxylate group. Shift reagents and relaxation measurements were used to make the 13C chemical shift assignments. These data are most consistent with a cyclic, neutral structure for these iodonium carboxylates. The iodine is in the center of a trigonal bipyramid with the unsubstituted phenyl and carboxylate group apical, which places the C‐6 proton in the shielding region of the adjacent phenyl group.
Proton NMR studies of reduced porphyrin compounds
Authors: Harel Yaacov , Manassen Joost
Published: May 2005

Detailed 1H NMR studies of ms tetraphenylchlorins (H2TPC), new amino‐ and hydroxypyrroline substituted ms tetraphenylchlorins and ms tetraphenylisobacteriochlorins (H2TPisoB) are presented and discussed. The results obtained are consistent with the general aspects of the ring current models as applied to the parent porphyrins. According to proton chemical shifts a gradual reduction in the magnitude of the ring current is observed in the order ms tetraphenylporphyrin (H2TPP) > H2TPC> ms tetraphenylbacteriochlorin (H2TPB) > H2TPisoB. The 1H NMR spectra show chemical non‐equivalence of the pyrroline ring protons due to adjacent substituents, and effects of steric constraints on the aminoalkyl substituents due to the close vicinity to the meso phenyl rings. The non‐equivalence of the methylene protons of the pyrroline ring produces geminal coupling between the two methylene protons and vicinal coupling with the adjacent pyrroline proton, more pronounced in H2TPCOH and in . Restricted configuration of the methylene groups in the ethyl groups of H2TPCC(H)(CH3)N(CH2CH3)2 produces observable geminal coupling between the methylene protons. 1H NMR reveals the difference between two types of meso phenyls in the chlorins, and three types of meso phenyls in isobacteriochlorins, as reflected in the chemical shifts of the o‐phenyl protons.
The 1H, 13C and 31P NMR spectra of EZ pairs of some phosphorus substituted alkenes
Authors: Duncan Mark , Gallagher Michael J.
Published: May 2005

The olefins Ph2P(X)CHCHR [X=lone pair, O, S, Ch3I; RCh3, ph, P(X)ph2] have been prepared and their 1H, 13C and 31P NMR spectra measured. trans 3J[P(IV)C] (range 18.3–25.7 Hz) is greater than cis 3J[P(IV)C] (range 6.9–11 Hz) but this relationship does not hold for P(III) compounds. In the 31P spectra the E isomer absorbs to higher field than the Z isomer for P(III) and P(IV) compounds. The 1H data are in accord with previous results; average substituent shielding coefficients for ph2P(X) substituted alkenes are reported.
Carbon‐13 nuclear magnetic resonance spectra of aminocyclohexanecarbonitriles and comparison with phencyclidine analogues
Authors: Bailey Keith , Legault Donald
Published: May 2005

The 13C NMR spectra of 20 aminocycloalkanecarbonitriles were determined in CDCl3. The signals were assigned by a self‐consistent analysis of chemical shift data and comparison with results from phencyclidine analogues. The results were interpreted in terms of changes in the amine (primary, secondary, tertiary) and the cycloakane (cyclohexane vs cyclopentane) moieties and their bulk. Changes in the conformational equilibria of the cyclohexane series are suggested by comparisons between data from the carbonitrile and phencyclidine series. The spectra are suitable for corroborative authentication of reference materials and the identification of unknowns.
1H NMR studies of solvent and substituent effects on strong intramolecular hydrogen bonds
Authors: Brzezinski Bogumił , Szafran Miroslaw
Published: May 2005

Chemical shifts of H‐bonded protons in tetrabutylammonium hydrogen maleate and 14‐substituted picolinic acid N‐oxides have been measured in a number of dry solvents, of different activity, in order to distinguish between symmetrical single minimum and asymmetrical hydrogen bonds. In tetrabutylammonium hydrogen maleate the resonance was observed at 20.70 ppm and its was independent of the nature of the solvent used. The chemical shift value of picolinic acid N‐oxide varies with the solvent. These observations suggest that the hydrogen bond is symmetrical in tetrabutylammonium hydrogen maleate but that it is asymmetrical in picolinic acid N‐oxide. The chemical shifts of substituted picolinic acid N‐oxides were correlated with σp, σm and ΔpKa. The substituent and solvent effects are compared and the position of the intramolecular H‐bonded protons in picolinic acid N‐oxides are estimated and discussed.
Carbon‐13 NMR signals of some benzodiazepine drugs
Authors: Patra Amarendra , Mukhopadhyay Apurba K. , Mitra Alok K. , Acharyya Aditi K.
Published: May 2005

Some carbon‐13 NMR signal assignments of diazepam, flurazepam, clonazepam and chlordiazepoxide have been revised and the assignments of nitrazepam are reported. The assignments of the various resonances were made by considering the changes in chemical shifts produced by the change of substituents and also by comparison with the chemical shifts of model compounds.
One‐bond carbon–carbon spin–spin coupling constants: A data summary
Authors: Hansen Poul E. , Wray Victor
Published: May 2005

A summary of all the one‐bond carbon–carbon spin–spin coupling constants, Known up to the beginning of 1980, is given in diagrammatic form.
A practical paramagnetic relaxation reagent for aqueous solutions
Authors: Bearden William H. , Cargin Valorie M. , Roberson Willie R.
Published: May 2005

While there is a useable paramagnetic relaxation reagent (PARR) for use in nonpolar or low polarity solvents, there has not been a practical PARR for use in highly polar solvents. A reagent, Gd(NO3)3‐inositol, is described which appears to satisfy this need. The performance of the reagent is given in terms of its effect on the T1, NOE and line width values of N,N‐dimethylformamide. In addition, the application of this reagent to adenosine is also reported.
Derivatives of cis‐NPCl2(NSOCl)2 and (NPCl2)2NSOCl. Part XIV—synthesis and nuclear magnetic resonance study of dimethylamino derivatives of NPCl2(NSOPh)2 and (NPCl2)2NSOPh
Authors: de Ruiter B. , van de Grampel J. C.
Published: May 2005

The compounds trans‐NPCl2−n(NMe2)n(NSOPh)2(n=0‐2iNPCl2−n NMe2)n (NSOPh)2 (n=0‐2) and N2P2Cl4−nl4−n(NMe2)nNSOP2P2Cl4−n(NMe2)nNSOPh(n=0‐4), were prepared from their chloro‐precursors. The substitution follows a completely non‐geminal pathway, and all possible isomers are formed. The observed relative abundance of these isomers shows that the phenyl group exhibits a strong directing effect on the incoming amine. The 1H, 31P and 13C NMR spectra of the most abundant isomers are reported. 2J(CP) couplings within the PNMe2 grouping are affected by the number of substituents at the phosphorus atom. Almost linear relationships exist between the degree of substitution and the chemical shift of C‐1 and C‐4 of the phenyl groups. The effect of substitution on the 13C chemical shifts of these groups is ascribed to inductive effects.
77Se, 13C and 1H NMR investigations on ortho‐carbonyl benzeneselenenyl derivatives
Authors: Llabrès Gabriel , Baiwir Marcel , Piette Jean‐Louis , Christiaens Léon
Published: May 2005

o‐Carbonyl benzeneselenenyl compounds with COCH3, CHO and COOCH3 as carbonyl functions and SeCl, SeBr, SeSCN, SeSeCN, SeCN and SeCH3 as selenium‐containing groups, have been studied by 1H, 13C and 77Se NMR spectroscopy. The IR CO stretching frequencies of these compounds are also reported. If the SeCH3 derivatives are excluded, the compounds mainly adopt a planar ‘cis’ conformation, due to an interaction between the CO group and the selenium atom. The range of over 800 ppm for the observed 77Se chemical shifts makes 77Se NMR spectroscopy a powerful tool for physical organic chemists.
Carbon‐13 chemical shift assignments of the nitration products of pyrene
Authors: Kaplan Samuel
Published: May 2005

13C and 1H nuclear magnetic resonance (NMR) spectra have been obtained in order to identify the six nitration products of pyrene—1‐nitropyrene, 1,3‐dinitropyrene, 1,6‐dinitropyrene, 1,8‐dinitropyrene, 1,3,6‐trinitropyrene and 1,3,6,8‐tetranitropyrene. 13C chemical shifts in DMSO‐d6 were assigned using empirical rules, with particular emphasis on the additivity of the substituent effects. Carbon spectra of separated dinitromixtures enabled identification of the previously unreported 1,3‐isomer, and proton spectra differentiated the 1,6‐ and 1,8‐ isomers.
Carbon‐13 nuclear magnetic resonance studies of anthraquinones. Part III—correlation of substituent effects for 2‐substituted anthraquinones
Authors: Berger Y. , Berger‐Deguée M. , Castonguay A.
Published: May 2005

The 13C chemical shifts of 2‐substituted and 2,6‐disubstituted anthraquinones have been determined and assigned. The C‐1, 2, 3, 4, 13 and C‐14 chemical shifts of 2‐substituted anthraquinones are correlated with the chemical shifts of monosubstituted benzenes. A three‐parameter correlation with Swain and Lupton's ℱ and ℛ parameters and Schaefer's Q parameter provides relationships for the prediction of all chemical shifts of 2‐substituted anthraquinones from the substituent parameters. Q values for the SCH3, OCOCH3, C2H5 and C(CH3)3 groups are proposed. The two types of correlations are compared for predicting chemical shifts.
Iterative analysis of the 1H NMR spectra of naphthalene (AA′ A″ A‴ BB′ B″ B‴ system) and two of its derivatives
Authors: Cassidei Luigi , Sciacovelli Oronzo
Published: May 2005

The 1H NMR spectra of naphthalene as an eight spin system, and two of its derivatives, 2,4‐dichloro‐ and 2,4‐dinitro‐1‐naphthol, have been completely analysed. The Indor technique has been very useful in the determination of the signs and magnitudes of very small coupling constants. An improved version of the Laocoon 3 program has greatly facilitated the spectral analysis through, first, the knowledge of the dependence of each transition upon the spectral parameters; second, some modifications in the iterative loop which avoid failure of convergence, and, third, the use of a slightly modified diagonalization subroutine which saves 20% CPU computer time. Our data suggest a rather small substituent effect on intra‐ring couplings of the unsubstituted ring. The inter‐ring coupling constants display a negative or positive sign according to an even or odd number of intervening bound, except the all‐trans 6J which is positive. No substituent effect on the inter‐ring couplings has been observed, except a small effect for the all‐trans 6J.
13C NMR studies of isomeric piperidine derivatives with opiate properties and related compounds
Authors: Casy A. F. , Iorio M. A. , Podo F.
Published: May 2005

The 13C NMR spectra of a series of methyl substituted 3‐arylpiperidines and 4‐aryl‐4‐piperidinols and related compounds are reported, and chemical shift data analysed in terms of the configuration and conformation of isomeric pairs. Special attention is given to the γ chemical shift parameter of axial methyl, and the effects of a nitrogen lone pair orbital and hydroxyl or acyloxy group on the chemical shifts of ring and methyl carbons.
CH, CD, CC and HH coupling constants in isotopically enriched cyclobutene
Authors: Hansen Poul Erik , Led Jens J.
Published: May 2005

1H, 2H and 13C NMR studies of cyclobutene and a series of isotopically enriched species have led to a determination of the 1H1H, 13C1H, 13C2H and 13C13C coupling constants in these compounds. In agreement with general observations, 1J(CH) is found to depend on the hybridization of the carbon atoms. Likewise, 2J(HH), 2J(CC), 3J(HH) and 3J(CH), but not 2J(CH), depend on the angles between the bonds connecting the coupled nuclei. When comparing cyclobutene with thiete 1,1‐dioxide (thiete sulphone) an increase of almost 20 Hz is observed for 1J(C‐2, H‐2) in the latter compound. All but one of the observed deuterium isotope effects on chemical shifts are negative. In the case of isotope effects upon the one‐bond coupling constants, the obtained values support the results of the theoretical calculations of Sergeev and Solkan.
13C NMR study of ortho‐, meta‐ and para‐ substituted phenyldiphenylamines: Substituent effect correlations
Authors: Grimley Eugene , Collum David H. , Alley Earl G. , the late Layton Bobby
Published: May 2005

The 13C chemical shifts of 11 substituted triphenylamines have been determined and the assignment of these resonances made using intensities, 1H and 19F couplings and predictions from bond additivity relationships. 13C chemical shifts at carbons bearing the substituent and at carbons ortho to the substituent correlated reasonably well with the Q parameter. A multiple regression analysis of chemical shifts with the field and resonance parameters of Swain and Lupton and the Q parameter produced significantly better correlations than those obtained when Q was omitted for these positions. 13C chemical shift correlations for carbons meta and para to the substituent were not significantly better than when Q was omitted. Significant correlations were obtained between field and resonance parameters and 13C chemical shifts of C‐o and C‐p, and C‐i, C‐o, C‐m and C‐p of the non‐substituent bearing phenyl rings in ortho‐ and para‐substituted phenyldiphenylamines, respectively.
Carbon‐13 NMR studies of benzoquinones
Authors: Joseph‐Nathan P. , Abramo‐Bruno D. , Ortega D. A.
Published: May 2005

The assignment of all ring carbons of p‐benzoquinones derived from perezone and from thymoquinone was completed using gated decoupled spectra. The long range proton‐carbon couplings are discussed in terms of the degree of substitution of the quinone ring. The tautomeric interconversion of the two energetically equivalent forms of 2,5‐dihydroxy‐1,4‐benzoquinones has been studied in various solvents and at several temperatures.
Conformational changes in cyclodecanone due to 2H substitution
Authors: Andrews G. C. , Chmurny G. N. , Whipple E. B.
Published: May 2005

Recently reported long‐range deuterium isotope shifts of 13C NMR lines in [2‐2H1]cyclodecanones are simply explained on the basis of changes in the averaging of otherwise equivalent conformations.
19F chemical shifts of bridgehead fluorides
Authors: Bradshaw Tony K. , Hine Philip T. , Della Ernest W.
Published: May 2005

The 19F chemical shifts of a series of bridgehead fluorides are reported. It is found that, contrary to earlier conclusions based on a limited number of substrates, the fluorine shifts occur randomly.
Effect of the orientation of substituents on the chemical shifts of 13C. IV—13C NMR spectra of N,N‐diisopropylamides and ‐thioamides
Authors: Fritz Hans , Hug Paul , Sauter Hanspeter , Winkler Tammo , Lawesson Sven‐Olov , Pedersen Bjarne Skindhoj , Scheibye Sten
Published: May 2005

N,N‐diisopropylamides and ‐thioamides show hindered rotation around the NCH bonds, and the presence of mixtures of conformational isomers can be demonstrated at temperatures below 273 K in solution. 1H and 13C NMR spectra of these conformers are measured and assigned. The 13C data serve to study through‐space effects on 13C chemical shifts, which strongly depend on the conformations of the isopropyl groups. For amides, a through‐space shielding of the N‐methine carbons is found to exist only for conformers in which the methine hydrogen atom is spatially close to the oxygen atom. Chemical shift differences between amides and thioamides can be rationalized in terms of through‐bond and through‐space contributions, and serve for a better understanding of the shift differences in N,N‐dialkylamides and ‐thioamides.
Carbon‐13 NMR spectra of tembamide, aegeline and related amides
Authors: Patra Amarendra , Mitra Alok K. , Ghosh Arundhati , Mukhopadhyay Prabir K.
Published: May 2005

Carbon‐13 NMR spectral studies of tembamide (1) and aegeline (2), constituents of Fagara hyemalis and Aegle marmelos respectively, and a series of their structurally related amides (3–13) have been carried out. The assignment of the resonances of two related dimers are also reported. The assignment of the various resonances were made by considering the changes in chemical shifts produced by the change of substituents and also by using 1, 13 and a related compound as model compounds.
Configuration and 13C NMR spectra of alkylcyclopropane derivatives
Authors: Touillaux R. , Van Meerssche M. , Dereppe J. M. , Leroy G. , Weiler J. , Wilante C.
Published: May 2005

Eight alkylcyclopropane derivatives were prepared in a conventional manner and analysed by 13C NMR spectroscopy. Additivity parameters were calculated from the chemical shifts of the endocyclic carbons, and the configurational structures derived for these compounds are confirmed by the internal coherence found for this set of parameters.
The differentiation of diastereomers by 13C NMR spectroscopy
Authors: Schneider Hans‐Jörg , Lonsdorfer Michael
Published: May 2005

13C shifts are reported for diastereomers with halogen, oxygen and amino substituents which are mainly at vicinal chiral centres. The conformer populations underlying the 13C shift analysis can be verified by chemical means, such as change of temperature, solvent polarity (with dihalides), solvent hydrogen bonding capacity (with diols), deprotonation (with diacids) and by molecular mechanics calculations. The latter provide the basis for configurational and conformational assignments with a series of ephedrine derivatives. In accordance with the 13C shift observations, it is found that ephedrine derivatives predominate in conformations with a gauche O and N substituent arrangement, even in cases where hydrogen bonds are absent.
Remote polar substituent effects on 13C NMR spectra of olefinic and aromatic carbons
Authors: Hill E. Alexander , Guenther Howard E.
Published: May 2005

Chemical shifts of the olefinic carbons of ω‐substituted 1‐pentenes and 1‐butenes and the aromatic carbons of phenylethanes and phenylpropanes have been measured. Correlations with various substitutent constants, electronegativities, NMR data from related chemical systems and calculated electrical fields were evaluated. Although the pattern of results is quite consistent with expectations for a field‐induced shift of π‐electron density, simple correlations of high statistical precision are not found. The general problem of correlating substitutent effects with reactivity and NMR shifts is discussed.
Deuterium nuclear magnetic resonance spectroscopy. 1—Larmor frequency ratio, referencing and chemical shift
Authors: Al‐Rawi Jasim M. A. , Behnam George Q. , Taha Nihad I.
Published: May 2005

Precise values for the ratio of the Larmor frequencies, w1H/w2H, were measured at constant field for various organic compounds. The values of the Larmor frequency ratio depend on carbon‐hydrogen bond hybridization. The best ratio for the ghost referencing of 2H NMR spectra was then determined (6.514399862). This value enables an accurate ghost reference for any 2H NMR spectrum to be derived from the observed 1H NMR frequency of the normal internal reference. Deuterium and proton chemical shifts measured from internal, partially deuteriated TMS under the same conditions are shown to be the same.
Carbon‐13 nuclear magnetic resonance spectra of D‐homoandrostane derivatives
Authors: Marcano Deanna , Rojas Anibal , Méndez Bernardo , De Méndez Jeannette
Published: May 2005

The 13C chemical shift data of a series of ketone, alcohol and ester derivatives of D‐homoandrostane are reported. Homologation effects are discussed, as well as substituent effects on the homologated structures.
Anisochrony of the O‐methylene protons of the C‐2‐ethyl ester function in triethyl meso, cis‐1,3‐dimethylcyclohexane‐1,2,3‐tricarboxylate—Atropisomerism of an ester group
Authors: Balasubrahmanyam S. N. , Bharati S. Narasimha
Published: May 2005

The methylene protons of the ethyl ester function at C‐2 in triethyl meso, cis‐1,3‐dimethylcyclohexane‐1,2,3‐tricarboxylate (A) are anisochronous, despite the apparent symmetry of structure A. The necessary diastereotopy is thought to be engendered by the central ester being stabilized in a rotamerization in which the O:C·O plane is held parallel to the general plane of the 6‐membered ring while fast exchanges take place among rotamers about the alkyl–oxygen bond; other rotamers about the ester axis are thought to encounter high order repulsive steric/polar interactions with the flanking ester functions and C‐methyl groups. Evidence for the axial orientation of the C‐1 and C‐2 ester functions in A, based on comparisons of its 1H NMR spectral characteristics with those of its RS‐cis, trans and meso, trans analogues, is presented. The role of ion‐pairing in the stereoselectivity of methylation of precursor enolates, leading to the formation of these three systems, is briefly discussed. A comment on the appropriateness, or otherwise, of drawing conformational conclusions from the magnitudes of the anisochrony in comparable systems is included. Triester A is thought to be the first instance where atropisomerism about an sp3sp2 bond involving an ordinary ester function has been detected employing a prochiral sensor group.
Automatic assignment of 13C NMR spectra based on the chemical shift/charge density relationship
Authors: Bangov Ivan P.
Published: May 2005

An approach for the automatic assignment of 13C spectra, based on the chemical shift/charge density relationship, is suggested. All permutations of spectral signals are computer‐generated, and for every permutation a least squares adjustment is carried out. The permutation presenting the highest correlation coefficient, or the lowest Hamilton's agreement factor, is considered to be correct. The application is exemplified by the 13C chemical shifts of a series of aromatic compounds. It is shown that more reliable assignment is achieved if the considered permutations are restricted by taking intoaccount the signal multiplicity.
Rapid injection NMR: A simple technique for the observation of reactive intermediates
Authors: McGarrity John F. , Prodolliet Jacques , Smyth Timothy
Published: May 2005

A system has been designed for the NMR observation (at 60 MHz) of unstable intermediates, with half‐lives of 100 ms, at concentration levels above 10−2 M. Rapid mixing can be achieved in less than 40 ms and a series of eight spectra acquired in less than 1.08 s. Low temperature operation is straightforward. Reactive intermediates involved in the reaction of methylamine with 2,4,6,‐trinitroanisole and the acid‐catalysed hydrolysis of 1,1‐diethoxy‐2,3‐diphenylcycloprop‐2‐ene were identified, and in a kinetic application, the rate of hydrolysis of trimethyloxonium tetrafluoroborate was measured.
The paramagnetic species produced in the reactions of organometallic compounds XIII—the anion radicals of carboxylates
Authors: Staško A. , Malik Ľ. , Mat'ašova E. , Tkáč A.
Published: May 2005

In the reactions of meta‐ and para‐alkyl substituted benzoic acids with aryl Grignard reagents, in tetrahydrofuran solutions and in the presence of nickel salts, the ESR spectra of the anion radicals of carboxylates derived from the benzoic acids were observed which represent the intermediates in the formation of ketyl radicals.
New triterpenes from Swietenia mahagoni. IV—the 13C NMR spectra of cycloswietenol, 30‐norcycloswietenol and isocycloswietenol
Authors: Lakshminarayana V. , Murty Y. L. N. , Row L. R.
Published: May 2005

13C NMR spectral data of cycloswietenol and 30‐norcycloswietenol from Swietenia mahagoni and the rearranged product, isocycloswietenol, are presented and their specific structural features discussed.
Application of principal component analysis to 13C NMR shifts of chalcones and their thiophene and furan analogues: A useful tool for the shift assignment and for the study of substituent effects
Authors: Musumarra Giuseppe , Wold Svante , Gronowitz Salo
Published: May 2005

13C NMR shifts of 54 chalcones and their thiophene and furan analogues are analyzed by principal component analysis. Thus, a mathematical model is derived for the variation of the carbon shifts in each of seven classes. Two component models are found to be adequate by cross‐validation. The first component corresponds to ordinary σpara values, while the second one differentiates benzenes, thiophenes and furans. This type of data analysis is a useful tool for checking the consistencies of spectral parameters. The model parameters, which describe systematic variations within each class, are also used for the study of substituent effects and discussed in relation to substituent constants in linear free energy relationships.
Nitrogen‐15 nuclear magnetic resonance spectroscopy. Chemical shifts of methyl substituted cis‐decahydroquinolines
Authors: Vierhapper Friedrich W. , Furst George T. , Lichter Robert L.
Published: May 2005

15N Chemical shifts of cis‐decahydroquinoline, N‐methyl‐cis‐decahydroquinoline, and of 19 methyl substituted NH‐ and NCH3‐cis‐decahydroquinolines are reported. Shift values of conformationally homogeneous compounds can be used to determine the chemical shifts of the possible conformations of the mobile compounds. Equilibrium constants derived from the shifts of the contributing conformations agree with results of low temperature 13C NMR spectroscopy.
Carbon‐13 NMR spectra of some novel migrated hopanes and 21α‐H hopanes
Authors: Patra Amarendra , Mitra Alok K. , Chatterjee Tapan K. , Barua A. K.
Published: May 2005

The carbon‐13 NMR spectra of the novel rearranged hopanes, spergulagenin‐A and related triterpenoids, and 21α‐Hopanes, mollugogenol‐A, mollugogenol‐G diacetate and related compounds, were recorded. Their analyses were aided by the chemical shifts of some model compounds and by the change in chemical shifts produced on change of substituents/s.
1H and 31P NMR studies of rotational isomerism in phosphorus analogues of aspartic acid, 3‐amino‐3‐phosphonatopropionic and 3‐amino‐3‐(methylphosphinato) propionic acids
Authors: Siatecki Zdzisław , Kozłowski Henryk
Published: May 2005

By the use of the 1H1H and 1H31P coupling constants in two analogues of aspartic acid i.e. 3‐amino‐3‐phosphonatopropionic and 3‐amino‐3‐(methylphosphinato) propionic acids, it was shown that the six parameter formulation for the evaluation of mole fractions of three staggered ethanic rotamers is not necessarily better than the two parameter formulation in this system. The results allowed the recommendation of the following values for the two vicinal proton parameters i.e. J(HH)g=2.3, J(HH)t=13.9 and for the two vicinal proton‐phosphorus parameters i.e. J(HP)g=4.2, J(HP)t=33.0 Hz.
14N nuclear quadrupole resonance in N‐acetyl amino acids
Authors: Sadiq G. F. , Greenbaum S. G. , Bray P. J.
Published: May 2005

14N Nuclear quadrupole resonance (NQR) spectra of several N‐acetyl amino acids and related compounds are reported and analyzed within the framework of the Townes and Dailey theory. The inductive effect of the chloroacetyl group on the nitrogen is discussed. A positive correlation between the π‐σNC electron density at the nitrogen and the Taft inductive parameter σ* is observed, suggesting that the nitrogen π‐charge density in the N‐acetyl amino acids does not vary appreciably. NQR data for hippuric acid are compared to the 14N quadrupole parameters extracted from ENDOR data reported for X‐irradiated hippuric acid.
14N nuclear quadrupole resonance in carbazoles
Authors: Kim N. S. , Bray P. J.
Published: May 2005

Nitrogen‐14 nuclear quadrupole resonance frequencies at 77 K are reported for a series of carbazole compounds including N‐vinylcarbazole. Differences in charge distribution between pyrrole and carbazole are explained on the basis of delocalization of pi electrons. Effects of the aldehyde and vinyl groups on charge distribution are discussed. Sigma bond polarization between the pyrrole nitrogen and the nitroso nitrogen toward the pyrrole nitrogen exists in N‐nitrosocarbazole.
Values and signs of 13C, 1H spin‐spin coupling constants in 1,6,6aλ4‐trithiapentalene and 1,6‐dioxa‐6aλ 4‐thiapentalene
Authors: Bjorholm T. , Jacobsen J. P.
Published: May 2005

The values and signs of 13C, 1H spin‐spin coupling constants in 1,6,6aλ4‐trithiapentalene and 1,6‐dioxa‐6aλ4‐thiapentalene have been re‐investigated. The contributions from second order effects in the spectra have been included in an iterative spectral analysis. The values found deviate significantly from the values found earlier by first order analysis. The signs of the spin‐spin coupling constants have been established by the use of the SPT technique.
The isotropic hyperfine interaction in some aliphatic polyamine copper II complexes
Authors: Pisipati V. G. K. M. , Satyanandam G. , Rao N. V. S.
Published: May 2005

ESR and optical absorption studies have been carried out on bis[N‐(2‐hydroxyethyl)ethylenediamine] copper II‐chloride, ‐bromide, ‐nitrate, ‐sulphate, bis(N‐methylethylenediamine) copper II thiocyanate and bis(N,N′‐dimethylethylenediamine) copper II thiocyanate, in non‐interacting solvents at room and liquid nitrogen temperatures. The molecular orbital coefficients are estimated assuming axial symmetry and indicate that the in‐plane π bond is as strong as the σ bond. The consistency in the value of the χ parameter, which is proportional to the hyperfine constants, indicates that it is quite independent of the ligand substitution and depends upon the immediate environment of the copper II ion.
13C NMR investigation of some hetero‐ring substituted 2‐ and 4‐quinolone systems
Authors: Coppola G. M. , Kahle A. D. , Shapiro M. J.
Published: May 2005

A series of 2‐ and 4‐quinolones substituted in the hetero‐ring have been evaluated using 13C NMR techniques. Substituent effects are discussed as an aid to evaluation of potential tautomerization in the 2‐quinolone systems. The observed substituent shifts for systems having a hydroxy function at the 4‐position in the 2‐quinolones can be explained without implementing the tautomerism to a 4‐quinolone.
Conformational analysis XX—13C NMR studies of saturated heterocycles 5—substituent effects on the 13C chemical shifts of methyl substituted 1,3‐dithiolanes
Authors: Pihlaja Kalevi , Eskonmaa Mauri , Keskinen Raimo , Nikkilä Alpo , Nurmi Timo
Published: May 2005

The 13C NMR chemical shifts for 1,3‐dithiolane and 13 methyl substituted derivatives are reported. Substituent effects are derived and compared with those for cyclopentanes and 1,3‐dioxolanes. The magnitude and variety of the substituent effects are best explained with the aid of a half‐chair conformation where the S‐1C‐2S‐3 plane passes between C‐4 and C‐5.
The reaction between trans‐2‐alkylaminocycloalkanols and formaldehyde
Authors: Barkworth Peter M. R. , Crabb Trevor A.
Published: May 2005

trans‐2‐Alkylaminocyclohexanols and trans‐2‐alkylaminocycloheptanols condense with formaldehyde to give perhydrocycloalkano[d][1,3]oxazoles, whereas trans‐2‐alkylaminocyclopentanols give rise to perhydrocyclopentano[f][1,3,5]dioxazepines. The two types of ring systems are characterized by differing proton‐proton geminal coupling constants and 13C NMR parameters.
15N chemical shifts as a conformational probe in enaminones A variable temperature study at natural isotope abundance
Authors: Kozerski L. , von Philipsborn W.
Published: May 2005

The high sensitivity of 15N shielding to the displacement of the lone pair electrons makes it a useful conformational probe for remote parts of a conjugated molecule. Thus, the chemical shifts are observed for different rotamers of enaminones in the slow exchange limit. The interpretation of the 15N chemical shifts in terms of the non‐planarity of the E, s‐E rotamers is in accord with 13C chemical shifts and 1J(CH) coupling constants.
Correlation of para substituent carbon‐13 chemical shifts in aromatic compounds using polar (inductive) and resonance constants which are identical for aliphatic and aromatic compounds
Authors: Afanas'ev I. B. , Trojanker V. L.
Published: May 2005

A correlation of para substituted 13C chemical shifts in aromatic compounds with substituent polar (inductive) and resonance constants σ* and σr of aliphatic compounds has been studied. It has been shown that the precision of the correlations obtained corresponds to that of the Swain‐Lupton and Taft two‐parameter equations, but the correlation equation used in this work seems to permit a more exact separation of the substituent effects of aromatic compounds into inductive and resonance contributions. Thus, σ* and σr substituent constants are universal parameters which can be used in a correlation analysis of the properties of both aliphatic and aromatic compounds.
The NMR spectra of the porphyrins. 17—Metalloporphyrins as diamagnetic shift reagents, structural and specificity studies
Authors: Abraham Raymond J. , Bedford Geoffrey R. , Wright Brian
Published: May 2005

The nature of the metalloporphyrin‐ligand complexes produced by zinc, magnesium and cobalt porphyrins with basic ligands has been investigated using the diamagnetic ring current shifts of the porphyrin on the ligand protons. The metal to nitrogen bond lengths in some metallo‐meso‐tetraphenylporphyrin (pyridine) complexes have been determined and compared with the data of the crystalline complexes. The geometry of the Zn meso‐tetraphenylporphyrin complexes with 2‐picoline, quinoline and isoquinoline has been investigated. Steric interactions between the ligand and the porphyrin in 2‐picoline and quinoline produce a dramatic increase in the ZnN bond length when compared to the unstrained analogues pyridine and isoquinoline. This large increase is associated with comparatively minor angle distortions in the complex. The specificity of the Zn meso‐tetraphenylporphyrin complexation shifts has been determined for a range of benzyl and butyl compounds. The complexation shift is linearly related to the basicity of the ligand for a wide range of basicities.
15N chemical shifts of a number of polyazaindenes: Correlation with charge separated resonance contributing structures
Authors: Paudler William W. , Sheets Roger M. , Goodson B.
Published: May 2005

The 15N chemical shifts of a number of polyazaindenes have been determined, and have been correlated with the degree of contribution to the ground state of those resonance structures which place a partial positive charge on the bridge‐head nitrogen.
17O nuclear magnetic resonance studies of some enriched amino acids
Authors: Hunston Roger , Gerothanassis Ioannis P. , Lauterwein Jürgen
Published: May 2005

The 17O NMR chemical shifts of five enriched amino acids have been measured under strictly controlled conditions of concentration, ionic strength, pH and temperature. The α, β and α, γ carboxyl resonances of aspartic and glutamic acid, respectively, have been resolved. Line widths were examined as a function of solution viscosity.
13C NMR spectra of wedeloside and related kaurenoid derivatives
Authors: Lewis I. A. S. , MacLeod J. K.
Published: May 2005

The 13C NMR spectra of the diterpenoid aminoglycoside wedeloside and certain of its derivatives, representatives of a new kaurenoid series, have been assigned. Shift calculations and labelling experiments have established a general substituent additivity relationship for chemical shifts in kaur‐16‐enes which allowed the reassignment of certain 13C resonances in the previously reported spectra of other kaur‐16‐enes.
DNA fragment conformations. I—methods for the assignment of DNA fragment proton resonances. 1H NMR spectra of dApTpGpT and dApCpApTpGpT
Authors: Tran‐Dinh S. , Neumann J. M. , Huynh‐Dinh T. , Igolen J. , Kan S. K.
Published: May 2005

A general method for the assignment of DNA fragment proton resonances, especially for the sugar protons, has been presented and used to interpret the 400 MHz proton spectra of dApTpGpT and dApCpApTpGpT in neutral aqueous solution. Only fine splittings of about 3 Hz are observed in the H‐2″ resonances, and the total splitting is larger for the H‐2′ (≈29 Hz) than for the H‐2″ (22–23 Hz) multiplets. The purine and pyrimidine resonances can be distinguished on the basis of the H‐2″ and H‐2″ chemical shifts. The resonances of the H‐2′ and H‐2″ protons (above and below the sugar plane, respectively) of dA and dG exhibit chemical shifts of 2.65—2.80 ppm, while those of dC and dT residues are located at higher fields between 1.95 and 2.40 ppm. At high temperature (≥60°C), δH‐2′>YδH‐2″ for the purine family, while δH‐2′ « δH‐2″ in the case of the pyrimidine family. Except for the terminal residue, the H‐3′ resonances of dA and dG are located at lower fields compared with those of the dC and dT residues. The same is true for the H‐4′ resonances. In general δA1′>δG1′ and in the case of self complementary duplexes the H‐1′ and H‐2′ chemical shift variations versus temperature are found to be larger for the dC than for the dT residues.
NMR study on trapping techniques to deduce the conformations of 1‐alkyl‐3‐ hydroxypiperidines
Authors: Van Luppen J. J. , Lepoivre J. A. , Dommisse R. A. , Alderweireldt F. C.
Published: May 2005

The conformational equilibrium of 1‐alkyl‐3‐hydroxypiperidines in n‐heptane and aqueous solution is investigated. Several methods, e.g. IR and NMR spectroscopy, are discussed. The conformation trapping in D2SO4‐D2O mixtures, and subsequent analysis of the 1H and 13C NMR spectra, is proven to be the most reliable method. In an apolar solvent the conformation with an axial hydroxyl group is always dominant (69%). In aqueous solution the same conformation predominates in the protonated form (56%, pH<5), while only 43% of this conformation is present in the free base (pH∼11). A detailed 13C NMR study is described of 1‐isopropyl‐3‐hydroxypiperidine in aqueous solution at pH between 2 and 11.
Studies in sulphur heterocyles. 2—The 13C NMR spectra of thienocoumarins
Authors: Brown Norman M. D. , De Asish , Brunskill John S. A. , Jeffrey Howard
Published: May 2005

13C NMR spectra of 3‐ substituted thieno[2,3‐h][1]benzopyran‐2‐ones and 8‐substituted thieno[3,2‐f]‐[1]benzopyran‐7‐ones are reported and the substituent dependence of certain 13C chemical shifts is noted.
19F NMR of five polyfluoronaphthalenes. Inter‐ring FF coupling constants
Authors: Matthews R. S.
Published: May 2005

Analyses of the 19F and 1H spectra of 1,2,3,4,5‐pentafluoro‐, 1‐bromo‐4,5,6,7,8‐pentafluoro‐, 1,2,3,4,5,6‐hexafluoro‐, and 1‐bromo‐3,4,5,6,7,8‐hexafluoro‐naphthalene are presented, and it is observed that the Fermi contact mechanism does not, simply, account for the long range couplings. Calculations of the carbon‐carbon polarizability part of the Fermi contact term do, however, imply that inter‐ring F,F couplings should be almost constant from difluoro‐ to heptafluoro‐naphthalene. Within the limits of this study, the inter‐ring F,F couplings, excluding peri F,F couplings, do not vary substantially. The steric effect of substituting an α‐hydrogen with bromine, at a peri position and adjacent to fluorine, is to increase the F,F coupling at the opposed peri position by 20 Hz, an unusually high increase in J(FF)peri.
Carbon‐13 spectral studies of some chalcones and flavanones
Authors: Patra Amarendra , Mitra Alok K. , Bhattacharyya Anjan , Adityachaudhury N.
Published: May 2005

Carbon‐13 signal assignments of 2′,4′‐dihydroxychalcone, flemichapparin, pashanone, isodidymocarpin, pedicellin, pedicinin, methylpedicinin, didymocarpin‐A and the corresponding quinoflavanone dehydrodidymocarpin‐A are reported.
13C NMR spectra of thieno[2,3‐b][1,5]benzodiazepine neuroleptics
Authors: Rackham David M. , Morgan Sarah E.
Published: May 2005

The 13C NMR spectra of five thieno[2,3‐b][1,5]benzodiazepines and two related benzodiazepinones have been recorded at 22.64 MHz using broad band and off‐resonance proton decoupling techniques. Spectral interpretation is facilitated by the presence of one (or more) fluorine substituents in the benzo‐ring.