bluuebunny/crossref_metadata_2025 huggingface dataset:
Täuschend einfache 1H‐NMR‐Spektren bei symmetrisch aufgebauten, zwei Phosphoratome enthaltenden organischen Verbindungen
Authors: Metzinger H. G.
Published: May 2005

Es wurden 1H‐NMR Spektren symmetrisch aufgebauter, zwei Phosphorkerne enthaltender Verbindungen vom Typ RXPYPXR, R = CH3, C2H5, X = —, O, NCH3, NCH2, Y = NCH3, gemessen. Die Spektren der Protonen aus den Resten R ergaben (nach Elimination etwaiger Kopplungen zwischen den R‐Protonen) im Falle dreiwertigen Phosphors stets Triplett‐Signale, im Falle fünfwertigen Phosphors Dublett‐Signale. Da gleiche Kopplungen von R zu beiden Phosphorkernen ausgeschlossen werden konnten, muß eine entartete, täuschend einfache Kopplung vorliegen, die in der vorliegenden Arbeit geklärt wird:

Auch in den bisher vermessenen symmetrischen Diorgano‐diphosphinen dürfte dieses Kopplungs‐system vorliegen. Die Berechnungen dieses Systems werden mitgeteilt.
Temperature dependence of the NQR frequencies and relaxation times in Menshutkin's complexes on the basis of arsenic trichloride and tribromide
Authors: Yusupov M. Z. , Grechishkin V. S. , Kosulin A. T. , Anferov V. P. , Versilov V. S.
Published: May 2005

The temperature dependence of NQR frequencies and spin‐lattice relaxation times in Menshutkin's complexes, prepared on the basis of AsCl3 and AsBr3 have been investigated.

The rotational oscillation frequencies νt and the average life times τa of rotational oscillation quanta have been calculated by both the Bayer and Woessner‐Gutowsky theories.
Nuclear magnetic resonance spectra of carbanions—VI. Cumyl‐, α‐methylbenzyl‐ and benzyl carbanions
Authors: Takahashi Kensuke , Takaki Mikio , Asami Ryuzo
Published: May 2005

The proton magnetic resonance spectra of the three title carbanions have been observed in THF with potassium as a counter ion. The ortho‐protons in the α‐methylbenzyl carbanion are nonequivalent at room temperature. This shows that the α‐carbon in this carbanion is in the near‐sp2 configuration. The aromatic proton chemical shifts of the benzylpotassium obtained here are at higher shielding than those of benzyllithium reported previously by Sandel and Freedman. This seems to arise from the different ionic nature of the bonds between carbon and metal in the carbanions.
Spectroscopic studies on N,N‐dimethylamides—III Amide‐rotational barriers of N,N‐dimethylbenzamides and ‐cinnamamides. A comparison of the NMR intensity ratio‐ and iterative total line shape method
Authors: Spaargaren K. , Korver P. K. , Van Haak P. J. Der , de Boer Th. J.
Published: May 2005

Amide‐rotational barriers of a series of para‐substituted N,N‐dimethylbenzamides and ‐cinnamamides have been obtained by both the intensity ratio method, according to Rogers and Woodbrey,2 and an iterative total line shape analysis.

From a comparison of the results, it is concluded that a discussion of rotational barriers obtained with the intensity ratio method should preferably be based on ΔG values, which are nearly equal for both methods, rather than on ΔG‡ at other temperatures.
Solvent effects on internal rotation about the BN bond in aminoboranes as studied by proton magnetic resonance spectroscopy
Authors: Totani Tetsushi , Tori Kazuo , Murakami Junko , Watanabe Haruyuki
Published: May 2005

Proton magnetic resonance spectra of two series of aminoboranes, Me2N BRPh (R = Cl, Me, Et, i‐Pr, i‐Bu, t‐Bu and CCMe) and PhRN BMe2 (R = Me, Et and i‐Pr), have been examined in various solvents to show that the potential barrier to internal rotation about their BN bond is lowered in some electron‐pair donor solvents. The barrier in an aminoborane decreases with increasing electron‐donating power of the solvent. The barrier in alkylaminoboranes in an electronpair donor solvent was found to increase with increasing size of the substituent alkyl group, owing to the steric repulsion between the alkyl and the solvent molecule. The solvent effects of benzene resulted in downfield shifts of the proton signals due to B‐substituents and in upfield shifts of the signals due to N‐substituents, as expected. The formation of a 1:1 adduct of Me2N BPh(t‐Bu) with carbon disulphide was found.
Spectroscopic studies on N,N‐dimethylamides—V Amide‐rotational barriers from iterative total line shape analysis of N,N‐dimethylcyclopropanecarboxamides
Authors: Spaargaren K. , Korver P. K. , van der Haak P. J. , de Boer Th. J.
Published: May 2005

Amide‐rotational barriers in some 2‐substituted N,N‐dimethylcyclopropanecarboxamides in CDCl3 as a solvent (0·25 M) were obtained with an iterative total line shape analysis.

N,N‐dimethylcyclopropanecarboxamide shows a barrier ΔG = 16·72 ± 0·01 kcal/mole. Para‐nitro substitution in (trans)‐2‐phenyl‐N,N‐dimethylcyclopropanecarboxamide raises the barrier ΔG from 17·08 ± 0·01 to 17·40 ± 0·02 kcal/mole.
Configurational and conformational insights on exo‐ and en do‐1, 4:3, 6‐dianhydroglucitol mononitrate
Authors: Anteunis M. , Verhegghe G. , Rosseel T.
Published: May 2005

A PMR study of the 1,4:3,6‐dianhydroglucitol mononitrates allows the easy attribution of the 2‐exo‐ or 5‐endo nitrate configuration to each of the isomers. Coupling data obtained in chloroform and in pyridine provide insight into their conformations. The solvent shifts indicate a hydrogen bridged solute‐solvent complex in the exo‐compound, but a random solvation for the endo‐nitrate.
The proton magnetic resonance spectra of d‐aldosterone and its acetylated derivatives
Authors: Genard P.
Published: May 2005

PMR spectra of d‐aldosterone, its acetylated derivatives and related compounds were studied using 60 and 100 MHz spectrometers at various temperatures, in CDCI3, DMSO‐d6, CD3OD and D2O.

The aldehyde form (1) was not found. The solutions of d‐aldosterone and aldosterone‐21 acetate contain a mixture of the cyclic forms with one (11–18) hemi‐ketal bridge (2) and two (11–18, 18–20) hemi‐ketal bridges (3).

Preliminary results concerning modifications of the relative concentration of 2 and 3 obtained by varying solvents and temperature are given. Aldosterone‐diacetate exists in only one form, most likely form 2.

There is restricted rotation of the group at C‐21 in d‐aldosterone and in form 3 of aldosterone 21‐acetate.

One molecule of water is probably bound to d‐aldosterone.
13C NMR spectra of adamantane derivatives
Authors: Pehk T. , Lippmaa E. , Sevostjanova V. V. , Krayuschkin M. M. , Tarasova A. I.
Published: May 2005

The carbon‐13 chemical shifts of mono‐ and 1,3‐disubstituted adamantanes are reported. The effects caused by the substituents are compared with those met in aliphatic and alicyclic compounds. It is shown that the 1,4‐interactions have only minor importance in l‐substituted adamantanes. The influence of polar groups on the chemical shifts of γ‐ and δ‐carbon atoms is a typical ‘through‐the‐bonds’ interaction and correlates with inductive parameters of the substituents.
13C NMR spectra of cyclopropane derivatives. Stereoisomeric substituted 2‐phenylcyclopropanes
Authors: Subbotin O. A. , Kozmin A. S. , Grishin Yu K. , Sergeyev N. M. , Bolesov I. G.
Published: May 2005

Proton‐decoupled carbon‐13 magnetic resonance spectra of a series of cyclopropane derivatives have been studied. For stereoisomeric substituted 2‐phenylcyclopropanes a difference between the isomers has been found in the shieldings of the three‐membered cyclic carbons as well as in the shieldings of the carbons of the substituents. The chemical shifts have been interpreted on the basis of an additive approach worked out in a study of the spectra of monosubstituted cyclopropanes and substituted 2,2‐diphenylcyclopropanes. Some simple rules have been proposed, which are useful in distinguishing stereoisomeric 1,2‐disubstiuted cyclopropanes.
Enol‐enolic equilibrium of nuclear‐substituted formylbenzoylmethanes
Authors: Gindin V. A. , Chripun I. A. , Ershov B. A. , Koltsov A. I.
Published: May 2005

The enol‐enolic equilibrium position of nuclear‐substituted formylbenzoylmethanes [p‐X = H, CH3, CH3O, Br, N(CH3)2, NO2] is estimated. With an increase in the electron‐donating property of the substituent X the equilibrium shifts to the hydroxymethyleneketone from. These results support the previous conclusions1 about the existence of the same dependence for nuclear‐substituted benzoylacetones and throw serious doubts on the idea of dominant enolization of benzoylacetones at the benzoyl group.
A proton magnetic resonance study of the conformation of the seven‐membered ring in benzocycloheptene
Authors: St‐Jacques Maurice , Vaziri Cambyse
Published: May 2005

The computer analysis of the PMR spectra of several partially deuterated benzocycloheptene derivatives at −120° provides values for all the coupling constants about the C3C4 bond. An interpretaion using the Karplus equation shows unambiguously that the seven‐membered ring exists as a chair conformation. The relationship between the coupling constants determined shows that the form of the Karplus equation established empirically for cyclohexane is applicable to this seven‐membered ring. A comparison of coupling constants shows that the benzocycloheptene chair is more puckered than the cyclohexane chair.
High resolution 13C spectroscopy by Fourier transform NMR. Thiete sulfone
Authors: Levy George C. , Dittmer Donald C.
Published: May 2005

The high resolution 13C NMR spectrum of thiete sulfone (obtained without wide‐band 1H decoupling) indicates that ring strain and re‐hybridization in this small ring compound are significant. Pulsed‐Fourier operation allows rapid determination of spectral parameters. Experimental acquisition time by pulsed NMR without 1H decoupling is comparable to the experimental time required for swept 13C NMR with complete 1H decoupling.
Solvent effects in NMR spectra induced by benzene in amidoximes—V
Authors: Alexandrou N. E. , Nicolaides D. N.
Published: May 2005

Proton chemical shifts as well as solvent shifts induced by benzene in several amidoximes are examined with respect to their configuration and are compared to the solvent shifts induced in benzalanilines. The geometry of the benzene‐solute ‘collision‐complex’ is also discussed.
The NMR spectra of fluoroaromatics—IV:1H and 19F spectra of some fluorinated benzofurans
Authors: Abraham R. J. , Wileman D. F. , Bedford G. R. , Greatbanks D.
Published: May 2005

The complete analyses of the 19F spectra of some fluorinated benzofurans are given. These provide an unambiguous determination of the substituent position in these compounds. Comparison of the 19F SCS and coupling constants in the benzofuran, benzothiophene and benzene series shows that 19F spectral parameters can be transposed from the benzene series with caution.

A large increase in the para FF coupling with ring closure of the hetero‐ring is noteworthy. A long‐range through‐space 8JH is reported which arises from the proximity of the 3 carboethoxy methyl group and the C4 fluorine in these molecules.
13C NMR spectra of metal σ‐cyclopentadienyls
Authors: Grishin Yu. K. , Sergeyev N. M. , Ustynyuk Yu. A.
Published: May 2005

Proton decoupled 13C NMR spectra have been measured for the cyclopentadienyl compounds C5H5Si(CH3)nCl3−n(n = 1, 2, 3), C5H5Ge(CH3)3, CH3C5H4Ge(CH3)3, C5H5Sn(CH3)3, σ‐C5H5Fe(CO)2‐π‐C5H5 and C5H5HgCH3. A fast metallotropic rearrangement occurring in the compounds causes the spectra to be temperature dependent for the Si, Ge, Sn and Fe derivatives. For the derivatives of silicon or germanium, the olefinic signals are unsymmetrically broadened by the 1,2‐shift at lower migration rates. Line widths of the ring carbon signals have been measured to give an estimate for the activation parameters of the rearrangement in C5H5Ge(CH3)3 (Ea = 10·7 ± 0·9 kcal/mole, ΔG‡ = 13·4 ± 0·9 kcal/mole) and C5H5Sn(CH3)3 (Ea = 6·8 ± 0·7 kcal/mole, ΔG‡ = 7·1 ± 0·7 kcal/mole). At room temperature, the spectrum of C5H5HgCH3 displays just one narrow signal responsible for the cyclopentadienyl ligand. The spectrum of CH3C5H4Ge(CH3)3 at –30° demonstrates that two isomers containing methyl in the vinylic position are present, the ratio being ca. 2:1. The 13C spectra of the vinylic isomers have been analysed in the case of C5H5Si(CH3)nCl3−n.
NMR spectra and structure elucidation by indor of the pepper acids derived from the pungent components of piper nigrum
Authors: Anteunis M. , De Cleyn R. , Verzele M.
Published: May 2005

1H‐{1H} INDOR studies on the PMR spectra of the acids derived from the pungent principles of piper nigrum nl. piperinic acid (1), isopiperinic acid (2), chavicinic acid (3) and isochavicinic acid (4) were undertaken. The spectral parameters as well as most of the relative signs of the coupling constants were obtained (Tables 1 to 3). The data are consistent with s‐trans conformations around C3C4 for all isomers.
The NMR spectra of 1,4‐dioxin and 1,4‐dithiin partially oriented in a nematic phase
Authors: Russell J.
Published: May 2005

The PMR spectra of 1,4‐dioxin and 1,4‐dithiin have been studied in nematic phase liquid crystalline solvents. The ratio of the interproton distances r12 and r13 and the CCH angles have been determined.
Electrical and magnetic properties of some organic charge transfer complexes
Authors: Bazhina I. N. , Versilov V. S. , Grechishkin V. S. , Grechishkina R. V. , Gusarov V. M. , Petrova L. S.
Published: May 2005

Two 7,7,8,8‐tetracyanoquinodimethane (TCNQ) complexes with cystein and guanine have been investigated. EPR spin signals of these charge transfer complexes were recorded and the electron spin lattice relaxation time (T1) temperature dependence was investigated. The electron scattering time, calculated from T1, agreed reasonably well with that from the current carrier effective mass (as determined through the Hall mobility measurements).
Boron‐sulphur compounds—II: A proton magnetic resonance study of complexes of pyridine and γ‐picoline with trialkylthioboranes
Authors: Cragg R. H. , Husband J. P. N. , Mitchell P. R.
Published: May 2005

Proton magnetic resonance studies of the pyridine and γ‐picoline complexes of trimethyl‐and triethylthioboranes provide strong evidence that the pπ—dπ bonding in the boron‐sulphur bond is much weaker than the pπpπ bonding in the boron‐oxygen bond.
Long range phenomena—XIV: 1H‐{1H} indor spectra and relative signs of coupling constants of some oxirane derivatives with adjacent methylene groups
Authors: Anteunis M. , Borremans F. , Van Den Bossche R. , Verhegge G.
Published: May 2005

PMR parameters of some methylene substituted oxiranes are obtained from INDOR experiments on the ABXMN spin systems. Compounds investigated include safrol‐ and bromosafrol epoxide and β‐phenoxypropylene oxide. For the latter compound all the relative signs (except for some long range couplings) were obtained and certain of these are in contradiction with those reported 2 in β‐chloropropylene oxide. ‘Non‐classical’ long range coupling
equation image
is also noted and differs in pathway from that reported previously.2.
Proton magnetic resonance studies of compounds with bridgehead nitrogen atoms—XX: The NMR spectra and stereochemistry of some hexahydropyrido[2, 1‐c] [1, 4] oxazin‐3(4H)‐ones and related compounds
Authors: Cahill R. , Crabb T. A.
Published: May 2005

A series of substituted hexahydropyrido [2,1‐c] [1,4] oxazin‐3(4H)‐ones has been synthesised, and the configurations of these bicyclic lactones assigned utilising chemical and spectral data. All the compounds adopttrans‐fused conformations and the conformation of the lactone ring is discussed with reference to the magnitude of the geminal coupling constant of the NCH2C(O)O protons, and the vicinal couplings between the angular proton and the methylene protons adjacent to the ring oxygen atom. The lactone ring conformation is shown to differ slightly from the half chair conformation described for some monocyclic δ ‐lactones. The synthesis and NMR spectra of some related compounds possessing the bridgehead NCH2C(O)O system are discussed and these compounds are also shown to adopt atrans‐fused ring conformation.
Phosphorus nuclear magnetic resonance studies of the pyrophosphate backbone of pyridine coenzymes
Authors: Sarma Ramaswamy H. , Mynott Richard J.
Published: May 2005

Phosphorus nuclear magnetic resonance spectra of pyridine coenzymes show that the reduced and the oxidized coenzymes exhibit different spectral patterns and chemical shifts. The 31P{1H} NMR spectrum of β‐TPN taken as a function pH indicates that the pKa value for the 2′ phosphate group is 6·0. It was further found that in β‐TPN, the protonation of the 2′ phosphate group selectively perturbs one 31P resonance of the pyrophosphate backbone.
Nuclear quadrupole resonance of bromothiophenes
Authors: Dormidontov Yu. P. , Grechishkin V. S. , Gushchin S. I.
Published: May 2005

Br79 NQR frequencies of a number of bromothiophene derivatives have been measured at 77°K. The frequencies correlate with Hammett δ values and this correlation demonstrates the importance of the inductive effect. The influences of more than one substituent on the thiophene ring are additive.
Fluorine NMR spectra of pentafluorophenyl derivatives
Authors: Pushkina L. N. , Stepanov A. P. , Zhukov V. S. , Naumov A. D.
Published: May 2005

The fluorine chemical shifts and spin‐spin coupling constants of 65 pentafluorophenyl derivatives with widely varying organic substituents were examined. Useful correlations of the three meta coupling constants with the chemical shifts of the para fluorine were found. It is suggested that these relationships be extended to all compounds of the type considered in order to determine the signs and approximate values of meta coupling constants.

Equations for correlation of the fluorine chemical shifts with the Taft constants are presented. The possibility of calculating the Taft constants from the 19F NMR spectra of pentafluorophenyl compounds is being discussed.
Transferts Protoniques de Sels d'Ammonium Substitues—VII: Deprotonation de Sels de N‐Methylpiperidinium en Solution Aqueuse
Authors: Delpuech J. J. , Siriex F. , Deschamps M. N.
Published: May 2005

La déprotonation de sels de N‐méthylpipéridinium BHa⊕, observé par la coalescence du doublet N‐méthylique en RMN, s'effecute soit par OH⊖ (k1 ∼ 1010 M−1 s−1), soit par la base conjugée B (k2 ∼ 108 M−1 s−1). L'action de OH⊖ est prédominante lorsque croi' l'encombrement stérique autour de Ha, et a lieu 2 fois plus facilement en direction axiale.
Thermodynamic data for hydrogen bonding of thiols with Lewis bases in carbon tetrachloride. Weak association by the PMR method
Authors: Hu Siung J. , Goldberg Edward , Miller Sidney I.
Published: May 2005

Data for 30 hydrogen bonding pairs taken from the alkanethiols, i‐C3H7SH, nC3H9SH and t‐C4H9SH, and 16 bases have been obtained by a PMR method. Representative data for i‐C3H7SH at 304 ± 2°K are (base, 102K in M−1, –ΔH° in kcal/mole): (CH2)4S, 3·1, 0·8; (CH3)2S, 3·0, 0·9; (CH3)2S2, 3·7, 0·5; (CH3)2CO, 4·7, 0·9; CH3COOC2H5, 5·7, 1·1; (CH2)4O, 6·1, 1·0; HCON(CH3)2, 12, 0·9; (CH3 O)2 SO, 12, 0·9; (C2 H5O)3PO, 6·5, 1·0; CH3 (CH3 O)2PO, 18, 1·0; ((CH3)2N)2 CO, 5·9, 1·1; CH3 CN, 13, 0·6. In essence, the problems and errors involved in obtaining equilibrium data for weak complexes stem from the limited concentration rangethat is accessible. This leads to large uncertainties in the quantities K, ΔH° and ΔS°. Structural effects on hydrogen bonding at the sulfur site, both as Lewis acid or base, are discussed. Two erroneous PMR methods in the literature used for assessing the strength of hydrogen bonds are pointed out.
(Pentafluorophenyl)sulfur fluorides, 19F NMR
Authors: Sheppard William A. , Ovenall Derick W.
Published: May 2005

The low‐temperature 19F NMR spectra of (pentafluorophenyl)sulfur trifluoride are explained by the trigonal bipyramid structure (1a) with the pentafluorophenyl ring in the basal plane and a relatively high barrier to rotation about the CS bond. In the presence of a hydrogen fluoride scavenger, there is a high barrier to intramolecular rearrangement of the sulfur fluorines about the sulfur atom. The single basal fluorine couples strongly with one ortho fluorine and weakly with the other, but the two apical fluorines couple equally with both ortho fluorines. A six‐bond coupling between SF and pF is found in (pentafluorophenyl)sulfur trifluoride and in (pentafluorophenyl)‐sulfinyl fluoride, but not in (pentafluorophenyl)sulfonyl fluoride.
Stereochimie en Serie Aziridine—III Etude de l'Isomérie de Rotation d'un Aldéhyde Aziridinique
Authors: Pierre Jean‐Louis , Handel Henri , Baret Paul
Published: May 2005

L'étude de l'isomérie de rotation de la tertiobutyl‐1 formyl‐2 aziridine est abordée en RMN par examen de l'effet ASIS sur les déplacements chimiques, par examen de l'effet de solvant sur la constante de couplage du proton aldéhydique, enfin par étude de l'effet de la température sur ce couplage. L'isomère s‐trans qui est le moins polaire est largement privilégié.
NMR analysis of benzotrifluoride partially oriented in a nematic phase
Authors: Degelaen J. , Diehl P. , Niederberger W.
Published: May 2005

The NMR spectrum of benzotrifluoride dissolved in the nematic phase of n‐(p‐ethoxybenzylidene)‐p'‐n‐butylaniline has been analysed, and the structure of the proton and fluorine skeleton has been determined. The height of the hindering potential to trifluoromethyl rotation cannot be measured. Due to the low accuracy of the determined FF distance, no precise information about the anisotropy of the indirect coupling can be given.
Strukturuntersuchungen an Mannanderivaten
Authors: Frank N. , Friebolin H. , Keilich G. , Merle J. P. , Siefert E.
Published: May 2005

Die PR‐Spektren einiger Methyl‐, Acetyl‐ und Benzoylderivate von Mannan aus Steinnuß und Tubera salep sowie der d‐Mannopyranose wurden analysiert. Durch einen Vergleich der Kopplungskonstanten und der Signallagen von entsprechend substituierten Polymeren und Monomeren wird, mit Ausnahme der Konfiguration an C(1), die Struktur dieser Polysaccharide bestimmt. Es wird auf charakteristische Unterschiede der Resonanzlagen von H(1) in Polysacchariden mit α‐bzw. β‐glycosidischen Bindungen hingewiesen. Dieser Befund eröffnet die Möglichkeit, auch in solchen Fällen eine Entscheidung über die Art der glycosidischen Bindung zu treffen, in denen, wie im Falle der Mannoside mit äquatorialständigem H(2), der Wert der KopplungskonstanteJ12keine Aussage erlaubt.

Die auffallend große Breite der Signale in den Spektren der nieder‐ und hochmolekularen Acetyl‐ und Benzoylmannane wird auf eine geringe Beweglichkeit der Kette oder einzelner Kettensegmente bei Mannanderivaten in Lösung zurückgeführt.
Etude par RMN des 2‐2′ ‐Dihalogeno‐diethylethers—II: Effet de Solvant
Authors: Haloui Ezzeddine , Canet Daniel , Granger Pierre
Published: May 2005

L'effet de solvant sur les éthers disubstitués de formule (XCH2CH2)2O avec X  Cl, Br, I a été étudié. Les pourcentages des différentes formes stables ont été déterminés pour chaque solvant suivant la méthode de Lin et il est montré que ces trois halogénures évoluent vers les formes gauches quand la constante diélectrique de la solution augmente.

De plus, il est montré que les couplages géminés dans le cas du dérivé iodé diminuent algébriquement quand la polarité du solvant augmente. Les auteurs pésentent une tentative de corrélation des variations des couplages géminés avec l'évolution conformationnelle.
Carbon‐13 nuclear magnetic resonance spectroscopy—VII:para‐substituted fluorobenzenes
Authors: Miyajima Goh , Akiyama Hiromichi , Nishimoto Kichisuke
Published: May 2005

C‐13 and F‐19 NMR spectra of seventeen para‐substituted fluorobenzenes were measured and the chemical shifts as well as coupling constants with respect to substituents were analysed. The chemical shifts of the fluorine, the C1 and the C2 atoms were found to depend on the total electron densities. In the case of the C3 atom, the chemical shifts seem to depend on π‐electron densities rather than the total electron densities. The present calculations also indicate that the chemical shift of the C4 atom depends mainly on σ‐electron densities due to the inductive effects of substituents. The strongest factor influencing the coupling constant, nJ(CF), is also considered to be the π‐electron densities on the carbon atoms. In the case of the direct couplings, 1J(CF), the π‐bond orders are important.
Proton exchange and protonation of substituted oxadiazoles in trifluoroacetic acid
Authors: Puar Mohindar S. , Cohen Allen I.
Published: May 2005

The rates of NHCOOH proton exchange between 5‐amino‐(1a) and 5‐N‐methylamino‐(1b)3‐[2‐(5′‐nitro‐2′‐furyl)vinyl]‐1,2,4‐oxadiazoles and trifluoroacetic acid (TFA) have been measured by NMR spectroscopy. The values of the first‐order rate constant and thermodynamic parameters for 1a and 1b, respectively, are: kapp (sec−1) = 820 and 40 (50°C), ΔF (kcal/mole) = 14·7 and 16·5, ΔH# (kcal/mole) = 17·3 and 24·3 and ΔS# (e.u.) = 17 and 34. The comparison of rate constants indicates that after correction for proton equivalency proton exchange in 1a is faster than in 1b by a factor of ten. The presence of an NH2 proton resonance (1a) and an N‐methyl doublet (J = 5·0 Hz) between 0 and 30° (1b) suggests that 1a and 1b are present as amines and not as imines in TFA.
13CMR‐Tieftemperatur‐Untersuchungen an Cyclooctan‐Konformeren
Authors: Schneider Hans‐Jörg , Keller Toni , Price Roger
Published: May 2005

Die Konformerengleichgewichte verschiedener monosubstituierter Cyclooctane werden durch 13CMR‐Tieftemperatur‐Spektroskopie bestimmt. Aus den 13C‐Verschiebungen kann auf die Geometrie der Konformeren geschlossen werden. Durch Vergleich berechneter und experimenteller Spektren werden für die Konformerenumwandlungen einige ΔG#‐Werte erhalten.
14N, 1H spin couplings in diethylmethylvinylammonium bromide
Authors: Ueyama (nee Ohtsuru) Masako , Tori Kazuo
Published: May 2005

The proton magnetic resonance spectrum of diethylmethylvinylammonium bromide, in which splittings due to 14N, 1H spin couplings are clearly observed as strongly perturbed second‐order patterns, has been analysed and the difference in the substituent effect between a methyl and an ethyl group upon 1H, 1H and 14N, 1H spin couplings are summarised.
Steric effects in 31P NMR spectra: ‘Gamma’ shielding in aliphatic phosphorus compounds
Authors: Quin Louis D. , Breen Joseph J.
Published: May 2005

An examination of published 31P NMR spectral data for aliphatic phosphorus compounds has revealed that chain lengthening and branching effects on the chemical shift can be interpreted in terms similar to those used for 13C and 15N shifts. For six families of phosphorus compounds, a β‐carbon substituent was shown to deshield phosphorus, while a γ‐carbon caused shielding. The effects are additive, and good agreement was obtained between 31P shifts calculated with the appropriate constants and the experimental values. Shielding by γ‐carbon is indicative of the operation of a steric influence on 31P chemical shifts, not heretofore articulated. The γ‐effect is also useful in explaining the unusually large shielding found in six‐membered cyclic phosphines.
Lanthanide‐induced shifts in proton NMR spectra of cyclohexanones
Authors: Shapiro B. L. , Johnston M. D. , Shapiro M. J.
Published: May 2005

The lanthanide‐induced shifts (LIS) of the lanthanide shift reagent (LSR) Eu(FOD)3 are reported for a large number of cyclohexanones, especially those which are highly substituted. The following compounds were synthesized and characterized: 3‐(aryl)‐3,5,5‐trimethylcyclohexanones, in which aryl = 1‐naphthyl, phenyl, o‐anisyl, m‐anisyl, p‐anisyl and p‐chlorophenyl. Some analogous compounds were also studied: 3,5,5‐trimethylcyclohexanone, 4‐tert‐butyl‐cyclohexanone, 3,3,5,5‐tetramethylcyclohexanone 3‐(1‐naphthyl)5,5‐dimethylcyclohexanone and para‐tert‐butyl‐anisole. A method for the regression analysis of the concentration dependence of the LIS of these substrates is developed and reported, and used to derive the limiting incremental LIS (Δ2) for the LS2 complex and to evaluate the proton chemical shifts (δ0) in the absence of LSR. An ‘incremental dilution’ technique was found to be most appropriate to insure constant substrate concentrations, needed to extract both Δ2 and δ0. The conformations of the 3‐(aryl)‐type systems and analogous compounds were studied via LIS and found to conform to:—(i) an axially disposed aryl substituent in the 3,3,5,5‐tetra‐substituted cyclohexanones and (ii) a flattened chair form of the cyclohexanone ring with distortions in this chair form being an increase in the syn‐diaxial (C‐3, C‐5) substituent distance (C‐3 and C‐5 substituents still eclipsed). The LIS were fully compatible with these structural assumptions.
Détermination des Axes Propres et des Valeurs Principales du Tenseur ḡ dans deux Radicaux Libres Nitroxydes par Étude de Monocristaux
Authors: Bordeaux D. , Lajzerowicz‐Bonneteau J. , Briere R. , Lemaire H. , Rassat A.
Published: May 2005

La structure de la phase basse température du radical nitroxyde tétraméthyl‐2,2,6,6 pipéridine oxyle‐1 (Tanane) a été déterminée. Ce radical libre est isomorphe du tétraméthyl‐2,2,6,6 pipéridinol‐4 oxyle‐1 (Tanol). Une étude en résonance paramagnétique électronique de monocristaux a permis de déterminer les valeurs principales et l'orientation des axes propres du tenseur ḡ pour ces deux radicaux. Pour le Tanane, la liaison NO est une direction propre du tenseur ḡ. Pour le Tanol, il existe un angle de 8° ± 2° entre cette direction propre et la liaison NO. Il est vraisemblable que, dans le cas du Tanol, la liaison hydrogène intermoléculaire est responsable de la déviation observée pour les axes propres situés dans le plan miroir , ainsi que des plus faibles valeurs mesurées pour gxx, gyy et gzz.
Conformations of highly hindered aryl ethers—VIII Interannular HF coupling in diphenyl ethers
Authors: Lehmann F. Pedro A. , Johnson LeRoy F.
Published: May 2005

A novel type of interannular coupling (6JH,F = 1.0 to 1.3 Hz) has been observed in some fluorodinitrodiphenyl ethers between the fluorine(s) on one ring ortho to the ether linkage and a proton ortho to it on the other ring. 1H and 19F chemical shift and coupling constant data support the previous conclusion that these ethers preferentially adopt a twist (propeller) conformation. On account of the geometrical disposition of the six bonds between the interacting nuclei and the latter's spatial proximity in this conformation, direct coupling through‐space is indicated. Concerted libration around the ether bonds brings about magnetic equivalence of the o‐fluoro substituents on one ring and causes equal coupling to be observed to the o‐proton on the other ring. The possiblity that the coupling is mediated by an intervening π‐cloud is suggested as an alternate mechanism for indirect coupling. The observed interannular transmission of spin information provides evidence in favor of a recent proposal made concerning the mode of action of the thyroid hormones.
NMR long‐range coupling and shift effects in the assignment of stereochemistry to 3‐substituted 5,6‐dehydroisoquinuclidines
Authors: Krow Grant , Rodebaugh Ronald
Published: May 2005

The complementary NMR techniques of long‐range W‐plan coupling and substituent shift effects on nearby olefinic hydrogens have been used to assign the stereochemistry of 3‐phenyl‐ and 3‐acetyl‐dehydroisoquinuclidines (2 to 5).
Magnetic nonequivalence in NMR spectroscopy—II. The role of hydrogen bonding in 2,2,4‐trimethylpentane‐1,3‐diol and its monoisobutyrates
Authors: Fantazier Richard M.
Published: May 2005

The methylene protons in 2,2,4‐trimethylpentane‐1,3‐diol (1), its 1‐isobutyrate (2) and 3‐isobutyrate (3) monoesters, are magnetically nonequivalent with respect to chemical shift. Under the same experimental conditions, the chemical shift differences are 14·4 Hz, 46·2 Hz and 18·2 Hz for 1, 2 and 3, respectively. These nonequivalences were examined as a function of temperature and concentration. The large nonequivalence in 2 is attributed to a highly restricted conformation resulting from intramolecular hydrogen bonding. Less favorable steric interactions result in a substantially smaller contribution of intramolecular hydrogen bonding in 3, while in 1 intermolecular hydrogen bonding occurs exclusively. Infrared data were obtained in support of these conclusions.
Correlation of molecular orbital indices of reactivity and proton chemical shifts: Acenaphtho[1,2‐b]‐ and ‐[1,2‐c]thiophens
Authors: Bartle K. D.
Published: May 2005

Nuclear magnetic resonance proton chemical shifts may be correlated with free valence, a representative reactivity index, for fluoranthene and two novel sulphur heterocyclic analogues, acenaphtho[1,2‐b]‐ and ‐[1,2‐c]thiophens. Such correlations arise fortuitously, however, and an attempt to explain them in terms of intrinsic properties of the Hückel‐McWeeny theory of proton shielding is proved to be fallacious.
The sign of four‐bond couplings in cyclobutanes: NMR spectra ofvic‐dihalo‐2,3‐oxazabicyclo[3.2.0]hept‐3‐enes
Authors: Mondelli R. , Gamba A.
Published: May 2005

The spectra ofvic‐dihalo‐2,3‐oxazabicyclo[3.2.0]‐hept‐3‐enes were analysed and the sign of all the coupling constants determined by tickling experiments. Stereochemical assignments, and three and four‐bond coupling are discussed in particular.
Etude de nitrophénylhydrazones α‐carbonylées—I. RMN des molécules modèles acycliques
Authors: Venien Frédéric , Lefeuvre Mme M.
Published: May 2005

L'étude par RMN des nitrophénylhydrazones α‐carbonylées nécessite une bonne connaissance du groupe hydrazono et des effets qu'il provoque, comparativement au carbonyle, sur les protons de la chaîne carbonée. L'étude RMN de cétones aliphatiques et aromatiques et de leurs arylhydrazones (ortho,para et dinitrés) permet d'atteindre cet objectif. Les valeurs de déplacement chimique des protons de la cétone servent de référence à partir desquelles les influences suivantes sont mises en évidence: l'identité du proton étudié (méthyle, méthylène ou méthyne); la position de ce proton par rapport au groupe hydrazono (en α, β ou γ); la configuration syn ou anti du reste hydrazono; la substitution de ce groupe.

L'anisotropie du groupe nitrophényl hydrazono ainsi mise en évidence semble principalement attachée à la paire libre de l'azote doublement lié et secondairement au groupe nitro et à sa polarisation.

Les effets provoqués par les chaînes carbonée et azotée l'une sur l'autre, laissent prévoir que l'azote porteur de l'hydrogène doit posséder une hybridation proche de sp2.

Enfin, le déplacement chimique du proton lié à l'azote est trés sensible aux diverses substitutions de la molécule, ce qui laisse présager un rôle ‘antenne’ dans les hydrazones α‐carbonylées.
Chemische Verschiebungen von Methylprotonen in 1H‐NMR‐Spektren von Alkylcyclohexanen
Authors: Werner H. , Köhler H. J. , Mühlstädt M. , Zschunke A. , Mann G.
Published: May 2005

Die chemischen Verschiebungen der Alkylprotonen von 51 methyl‐ und tert‐butyl‐substituierten Cyclohexanen wurden bestimmt. Der Resonanzbereich axialer Methyl‐gruppen erstreckt sich von δ = 0,63 bis 0,98 ppm, der von äquatorialen von δ = 0,81 bis 1,02 ppm. Die chemischen Verschiebungen axialer Methylgruppen werden durch Nachbargruppen stärker beeinflusst als die der äquatorialen Methylgruppen. Die Shifteffekte von Alkylgruppen auf Methylprotonen werden mit denen auf Ringprotonen verglichen.
An NMR study of cis‐2‐butene partially oriented in a nematic phase
Authors: Burnell E. E. , Diehl P.
Published: May 2005

The NMR spectrum of cis‐2‐butene partially oriented in a nematic phase has been analysed, and information about the geometry and the indirect spin‐spin coupling constants has been obtained. Assuming the barrier of rotation of the methyl groups and other geometrical information from microwave studies, we obtained = 126 ± 2° and = 116.8 ± 0·6°. The angle that the CH3 rotation axis makes with the double bond was calculated to be 127·5 ± 0.4°; this value is closely linked with the assumed value of = 109°28′.
An abnormal spin‐spin coupling of vinylic‐allylic protons generated by a constraint of configuration
Authors: Chow Y. L. , Streith J. , Taurand G.
Published: May 2005

In a system where a rigid or frozen conformation constrains an allylic proton to orient nearly perpendicular to the plane of the olefinic bond, the allylic spin coupling may become comparable to, or greater than, the vicinal spin coupling. This anomalous situation is demonstrated in three series of compounds: the adducts of diazoalkanes to 1,2‐diazepines, 4‐piperidinocycloalk‐2‐en‐1‐one oximes and heterobicyclo[3,2,0]hept‐3,6‐dienes, where the NMR spectra have been well established by decoupling experiments.
Position specificity of 13C31P coupling constants for methyl substituents in phospholes and 2—Phospholenes
Authors: Quin L. D. , Borleske S. G. , Stocks R. C.
Published: May 2005

The 13C—31P coupling constant is much larger for a 2‐methyl substituent (about 20 Hz) than for a 3‐methyl substituent (about 5 Hz) in phospholes and 2‐phospholenes, and appears useful for assigning structures in these compounds.
Self‐association of thiols. The baggy fit problem in weak complexes
Authors: Hu Siung J. , Miller Sidney I.
Published: May 2005

The PMR technique has been used to obtain thermodynamic data for hydrogen bonding of alkanethiols (RSH) in 1:1 dimers in carbon tetrachloride. At ca. 303°K these are (R, 104K(M−1), −ΔH°(kcal/mole), −ΔS°(eu)): n‐C3H7, 51 ± 5, 0.9 ± 0.15, 13 ± 1; i‐C3H7, 50 ± 10, 0.8 ± 0.3, 13 ± 1; n‐C4H9, 35 ± 2, 0.8 ± 0.15, 14 ± 1; t‐C4H9, 14 ± 4, 1.1 ± 0.7, 16 ± 2; C6H11, 1.3 ± 2, 0.7 ± 0.3, 15 ± 1. Alkanethiol self‐association is weak, and although an exact expression [Eqn. (5)] reproduces spectral data precisely, the fit is sufficiently ‘loose’ or ‘baggy’ so that values of K, ΔH° and ΔS° are uncertain. The methodology of the treatment of self‐association data and their errors is examined and Deranleau's useful approach is extended. The impossibility of obtaining reliable data for very weak (< 10 %) or very strong (> 90 %) associations by techniques equivalent to ours is emphasized. The possibility of cyclic thiol dimers is discussed. It is suggested that the PMR method cannot give trustworthy self‐association data for aryl or arylalkylthiols because of the relatively large anisotropy effects introduced into the dilution shift.
Interactions Intramolécularies—XVII Calcul des constantes de couplage en RMN du cyclohexane et de cyclohexanes substitués. Comparaison des méthodes de Pople et Santry et des perturbations finies
Authors: Pouzard Guy , Rajzmann Michel , Bodot Hubert , Pujol Louis
Published: May 2005

Les constantes de couplage RMN 3J, 4J et 5J entre protons ont été calculées par les deux méthodes citées, pour le cyclohexane et pour les conformères de ses dérivés monosubstitués (substituants: Li, CH3, OH, F). La comparaison des deux méthodes sur la base de la théorie des groupes met en évidence la nécessité d'utiliser la méthode des perturbations finies dont les résultats sont confrontés avec les données expérimentales de la littérature.
Déplacements Chimiques Induits par Complexation à l'Europium en Série Δ1‐Pyrazoline
Authors: Franck‐Neumann Michel , Sedrati Madjid
Published: May 2005

Le complexe Eu (FOD)3 constitue un bon réactif de déplacement en spectroscopie de RMN de Δ1‐pyrazolines. Les 5 exemples décrits ici ont été choisis en série polycyclique pour mettre en évidence l'utilité de cette technique en vue de l'attribution des stéréochimies.
Proton magnetic resonance studies of actinomycin‐related peptides containing N‐methyl groups
Authors: Mauger A. B. , Rzeszotarski W. J. , Ford R. A.
Published: May 2005

The PMR spectra of several cyclic and acyclic dipeptide derivatives representing portions of the actinomycin structure have been studied. In the spectra of the acyclic compounds temperature‐dependent duplicity resulted from the equilibration of conformers possessing cis and trans peptide bonds. The lanthanide shift reagent Eu(FOD)3 was utilized to distinguish N‐methyl groups in the two conformations and observations were made on the steric dependence of the observed shifts. The origin of the wide variation in chemical shift of N‐methylvalyl α‐protons is discussed in relation to the conformation of actinomycin.
Long‐range 4J coupling constants and conformation of the four‐membered heterocycles
Authors: Fomichov A. A. , Zon I. A. , Gella I. M. , Kostyanovsky R. G. , Saprin A. N. , Markov V. I.
Published: May 2005

The correlation between the puckering angle of the four‐membered cycle and 4J has been obtained from analysis of the PMR spectra of some 2‐substituted azetidines and oxetanes. The absolute values of 4Jcis and 4Jtrans were found to decrease with decreasing of the puckering angle.
The use of DSS as an internal standard in PMR studies of nucleic acid interactions
Authors: Live David. H. , Chan Sunney I.
Published: May 2005

Two commonly used PMR internal reference compounds, 3‐(trimethyl silyl) propane sulfonic acid sodium salt (DSS) and 3‐(trimethyl silyl) sodium propionate (TSP), have been shown to interact with purine in aqueous solution, causing significant shifts in the resonance position of their reference protons. Tetramethyl ammonium chloride (TMACl) appears to be a more suitable reference compound for such studies.
NMR stereotopic induced shifts in epimeric mixtures
Authors: Enríquez R. , Taboada J. , Salazar I. , Díaz E.
Published: May 2005

The proton NMR spectra of epimeric mixtures of menthone (1), carvomenthone (2), carquejone (3), 2,5‐dimethyl‐1,4‐cyclohexanedione (4) and piqueridione (5) were studied using the chemical shift reagent Eu(DPM)3. The results allow quantifications of the epimers and some conformational assignments to be made.
Proton magnetic resonance studies of compounds with bridgehead nitrogen atoms—XXIII: Deformation of the piperidine ring in some bicyclic compounds possessing a bridgehead amide nitrogen atom
Authors: Cahill R. , Crabb T. A.
Published: May 2005

Some bridgehead nitrogen compounds possessing the CH(Me)‐bridgehead NC(O) system have been synthesised and their configurations assigned. The chemical shifts of the proton geminal to the methyl group provides evidence for the existence of a deformed chair conformation for the methyl substituted ring.
CIDNP of 13C and 1H nuclei in the reactions of cyclohexadienone carbenes
Authors: Nikiforov G. A. , Markaryan Sh. A. , Plekhanova L. G. , Sviridov B. D. , Rykov S. V. , Ershov V. V. , Buchachenko A. L. , Pehk T. , Saluvere T. , Lippmaa E.
Published: May 2005

Thermal decomposition of 4‐diazo‐2,6‐di‐tert‐butyl‐2, 5‐cyclohexadien‐1‐one in perhalogenated solvents has been investigated. The decomposition reaction proceeds via a carbene intermediate first to a singlet and then to an effectively triplet free encounter radical pair formed in a halogen abstraction reaction. The polarisation of the stable reaction product is determined by competing processes in the primary cage, intersystem crossing and escape from the cage.
Tris‐(4,4,4‐trifluoro‐1‐(‐2‐thienyl)‐1,3‐butandiono)‐europium(III) als NMR‐Verschiebungsreagens
Authors: Beyer Klaus
Published: May 2005

Die Eigenschaften von Europium thenoytrifluoroacetonat als Verschiebungsreagens werden an verschiedenen Substraten untersucht. Auf Grund seiner guten Löslichkeit ist der Komplex bei schwach komplexierenden Substraten dem Eu(DPM)3überlegen.—Im13C‐NMR–Spektrum von D(+)‐Campher werden die Signale von C9und C10zugeordnet.
Identification of 4,5‐asymmetrically substituted 1‐(N‐isoimido)‐1,2,3‐triazoles by benzene induced shifts in NMR spectra—VII
Authors: Alexandrou N. E. , Rodios N. A. , Hadjiantoniou‐Louizou C. P.
Published: May 2005

Proton chemical shifts, as well as solvent shifts induced by benzene, can be used for the structure determination of 4,5‐asymmetrically substituted 1‐(N‐isoimido)‐1,2,3‐triazoles, derived from the oxidation of α‐diketone bisaroylhydrazones. The geometry of the postulated ‘collision complex’ is discussed and an attempt is made to estimate theoretically the induced shifts of some of the protons.
Etude comparative des méthyl‐borazines par RMN
Authors: Beaumelou G. , Pasdeloup M. , Laurent J.‐P.
Published: May 2005

Une étude comparée du borazine (0) et de six méthyl‐borazines (1 à 6) a été effectuée par RMN. Il apparaǐt nettement que le déplacement chimique des protons NCH3 varie peu entre les mono‐, di‐ et triméthyl‐N borazines alors que ce měme paramètre subit une modification importante (au total 0,21 ppm vers les champs forts) quand on passe du triméthyl‐N borazine (HBNCH3)3 à l'hexaméthylborazine (CH3BNCH3)3 par substitution progressive sur les trois atomes de bore (cycles 3,4, 5 et 6). En outre, une variation systématique du paramètre δ a pu ětre décelée entre les composés 3, 4 et 5 pour les protons qui conservent strictement le měme environnement immédiat. Une interprétation qualitative de ce résultat expérimental est proposée en termes d'effets électroniques généralisés au cycle hexagonal plan bore–azote qui caractérise ces molécules.
cis‐trans‐and Intramolecular enol‐enolic equilibrium of β‐ketoaldehydes
Authors: Noy R. S. , Gindin V. A. , Ershov B. A. , Kol'tsov A. I. , Zubkov V. A.
Published: May 2005

Tautomerism of aromatic β‐ketoaldehydes p‐XPhCOCH2CHO (1, X = NMe2, OMe, Me, H, Br, NO2), aliphatic β‐ketoaldehydes and benzoylacetaldehyde RCOCH2CHO (2, R = Me, i‐Bu, t‐Bu, Ph), RCOCH(Me)CHO (3, R = Me, Et, i‐Pr) and methyl 2‐formylpropionate MeOCOCH(Me)CHO (4) has been studied by the 1H NMR technique. In basic solvents both cis‐ and trans‐enol forms of these compounds co‐exist. trans‐Enolisation, which occurs exclusively at the formyl group, is most favoured in compound (4) and least favoured in compounds (1) and (2). The increasing electron‐attracting property of the substituent X in the aromatic β‐ketoaldehydes (1), as well as increasing solvent basicity in the series propanediol‐1, 2‐carbonate, acetone < dimethylformamide < dimethylacetamide < pyridine, also shifts the equilibrium towards the trans‐enol form. The trans‐enol form is absent in aprotic solvents of low basicity such as CCl4, C2HCl3 and toluene. The thermodynamic parameters of the cis‐trans‐enol (C ⇌ T) and cis‐enol‐enolic (C ⇌ C') equilibria have been estimated from the temperature dependences. The transition from the cis‐to the trans‐enol form is accompanied by an entropy decrease of about 10 cal mol−1 degree−1. Nevertheless the trans‐enol form is stabilised due to its lower enthalpy. The cis‐trans‐enol equilibrium is determined by the relative strength of the intramolecular hydrogen bond in the cis‐enol form and the intermolecular hydrogen bonds with basic solvent molecules of the trans‐enol form.

The enthalpy difference of the two cis‐enolic forms does not exceed 1.0 kcal/mol, in rough agreement with the data calculated by the CNDO/2 approximation. Polar solvents favour the hydroxymethyleneketone form (C) for both groups of compounds 2 and 3. The content of the hydroxymethyleneketone form is about the same within series 2 where R = Me, i‐Bu, Ph and is a little higher for the t‐Bu derivative. A decrease of temperature only slightly shifts the equilibrium of compounds 1 and 2 to the hydroxymethyleneketone form, while in the case of 2‐methyl‐β‐ketoaldehydes (3) this effect is markedly pronounced.
Carbon‐13 NMR spectra of fusicoccin and its derivatives
Authors: Radics L. , Kajtár‐Peredy M. , Casinovi C. G. , Grandolini G. , Rossi C.
Published: May 2005

The 13C NMR spectra of fusicoccin, some of its cometabolites and derivatives were studied. Using standard Fourier transform techniques, T1 relaxation time measurements and lanthanide shift reagents, the resonances of individual carbon‐13 nuclei were assigned.
Carbon‐13 nuclear magnetic resonance spectra. I—Monosubstituted adamantanes and adamantanones
Authors: Duddeck Helmut
Published: May 2005

The chemical shifts of 4ax and 4eq substituted adamantanones are compared with those calculated with the aid of a given additivity rule. It is found that both δ carbons are shielded with respect to the substituent. In contract to the situation for the y‐atoms, however, the δsyn atom is less shielded than the δanti atom. In most cases the additivity rule predicts the chemical shifts with an accuracy of approximately 1 ppm. Exceptions are carbon atoms 4 and 9 of the 4eq substituted adamantanones. In both cases the measured values are 4 to 6 ppm upfield. This can possibly be explained by an electronic interaction between the carbonyl group and the substituent.