Structure assignments in polysubstituted ethylenes by nuclear magnetic resonance

Tobey, Stephen W.

doi:10.1021/jo01257a019

Cited by 97 publications

(20 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Tobey calculated Z-factors for the phenyl group itself by examining vinylic proton shifts in a number of di-and trisubstituted ethenes and arrived at Z gem (1.43), Z cis (0.39) and Z trans 0.06 values. 6 These data are close to those attributed to an aromatic group in all other tabulations.…”

Section: Introductionsupporting

confidence: 84%

“…8 The rule that an aromatic group would deshield a cisrelated more than a trans-related proton arises from the concept that the aromatic group is coplanar with the double bond, causing the cis-related proton (and the gem proton) to lie in the plane of the ring and thus experience the aromatic's deshielding magnetic field. That concept was outlined explicitly by Tobey,6 who wrote: 'protons near the plane of a phenyl group experience a downfield shift which decreases quite rapidly with increasing distance of the proton from the ring center, but which is relatively insensitive to the angular location of the proton relative to the ring plane as long as this angle is less than about 20°.' The greater deshielding of a cis compared with a trans proton is attributable, then, to the greater proximity of the cis proton to the phenyl group's plane.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The role of aromatic groups in the Tobey–Simon additivity rule for vinylic protons

Shine

Rangappa

2007

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

The Tobey-Simon (additivity) rule for aromatic groups which was devised about 40 years ago has been found to need revision. The rule shows an aromatic group attached to a C==C double bond as causing a downfield chemical shift of a cis-related vinylic proton and a small upfield shift of a trans-related proton. A search of data in the recent literature has shown that this rule should apply mainly to monosubstituted phenyl groups and some polynuclear aromatics. In contrast with them, 2,6-disubstituted phenyl, 2,4,6-trisubstituted phenyl and 9-anthracenyl groups cause cis-related vinylic protons to resonate upfield of comparable trans-related protons. Further, the current rule for o-substituted phenyl groups has been found to be inaccurate. In writing a rule for aromatic groups, therefore, greater attention needs to be given to the diversity of effects that these groups have on chemical shifts of vinylic protons.

show abstract

Section: Introductionsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

The role of aromatic groups in the Tobey–Simon additivity rule for vinylic protons

Shine

Rangappa

2007

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

show abstract

“…Borowitz er al. (2) se heurtent B certaines difficultCs en utilisant la mCthode de Tobey (5) et Pascual el al. (6) pour identifier les isom2res E et 2.…”

Section: Introductionunclassified

Phosphates d'énols-X. Détermination des isomères géométriques diversement substitués par résonance magnétique nucléaire

Gaydou¹

1973

Can. J. Chem.

View full text Add to dashboard Cite

R e~u le 28 marsLa configuration des phosphates tnoliques E et Z , substituts sur le premier atome de carbone de la double liaison, a t t t dtterminte dans 27 cas, en utilisant les constantes de couplage 4Jp~c=c-H et les constantes d'tcran selon la mtthode de Tobey-Pascual. Les facteurs qui influencent les constantes de couplage 4 J~~~=~-~ et 5 J~~~=~-~~, sont discutts.The E and Z configuration of en01 phosphates substituted on the first carbon of the double bond are determined, in 27 cases, using4JpoC=C-H coupling constants and the Tobey-Pascual substituent shielding constants method. The factors influencing 4Jp0C=C-H and 5Jpoc=c-c,i, coupling constants are discussed.

show abstract

“…The E configuration of these products was established by comparing the chemical shifts of the vinylic protons in their 'H NMR spectra to the related derivatives (9,13,14). Furthermore, the calculated chemical shift values of the vinylic protons, obtained by applying the NMR rules of additivity (15,16), for E-and Z-P-(N,N-dialkylamino) cinnamate esters (6c,1c. = 4.72 and 5.20 ppm, respectively) indicated the E configuration for the isolated products 2-4a-e (60bs = 4.72-5.00 ppm).…”

Section: Configuration Of the Productsmentioning

confidence: 99%

Stereochemistry and kinetics of amines addition to acetylenic esters

Sharaf¹,

El‐Sadany²,

Hamed³

et al. 1991

Can. J. Chem.

View full text Add to dashboard Cite

The reactions of a series of methyl para-substituted phenylpropiolates la-e with piperidine, morpholine, and diethylamine in methanol and dirnethylformamide (DMF) have been studied and their rates measured. The products were methyl P-(N,Ndialky1amino)-p-substituted cinnamates 2-4a-e. 'H NMR spectra were used to determine the configuration of the products. The p values in methanol ranged between 0.34 and 1.24 whereas in DMF they were between 0.85 and 1.88. The values of AS* favor a bimolecular rate-limiting step mechanism.

show abstract

Structure assignments in polysubstituted ethylenes by nuclear magnetic resonance

Cited by 97 publications

References 1 publication

The role of aromatic groups in the Tobey–Simon additivity rule for vinylic protons

The role of aromatic groups in the Tobey–Simon additivity rule for vinylic protons

Phosphates d'énols-X. Détermination des isomères géométriques diversement substitués par résonance magnétique nucléaire

Stereochemistry and kinetics of amines addition to acetylenic esters

Contact Info

Product

Resources

About