bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solvent effect on chemical shift non‐equivalence of methylene protons in dibenzyl‐, diphenacyl‐ and benzyl phenacyl sulphoxides
Authors: Sataty Ishai 
Published: May 2005

AbstractThe methylene protons of dibenzyl sulphoxide are magnetically equivalent in low dielectric and non‐equivalent in high dielectric constant solvents, while for diphenacyl sulphoxide this behaviour is reversed. In both cases, the variation in the magnitude of the non‐equivalence reflects a greater downfield shift of one methylene proton than the other on passing from non‐polar to polar solvents. By contrast, the chemical shift difference between the benzyl methylene protons or between the phenacyl methylene protons of benzyl phenacyl sulphoxide varies only slightly with solvent polarity.
Täuschend einfache 1H‐NMR‐Spektren bei symmetrisch aufgebauten, zwei Phosphoratome enthaltenden organischen Verbindungen
Authors: Metzinger H. G. 
Published: May 2005

AbstractEs 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

AbstractThe 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

AbstractThe 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

AbstractAmide‐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

AbstractProton 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

AbstractAmide‐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

AbstractA 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

AbstractPMR 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

AbstractThe 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

AbstractProton‐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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractProton 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

AbstractThe 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

AbstractProton 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

Abstract1H‐{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

AbstractThe 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

AbstractTwo 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

AbstractProton 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

AbstractPMR 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

AbstractA 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

AbstractPhosphorus 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

AbstractBr79 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

AbstractThe 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

AbstractLa 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

AbstractData 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

AbstractThe 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

AbstractL'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

AbstractThe 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

AbstractDie 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.