Transmission of electronic effects. Proton magnetic resonance chemical shifts for benzyl halides in several solvents

Yokoyama, Takehito; Wiley, Gary R.; Miller, Sidney I.

doi:10.1021/jo01258a073

Cited by 39 publications

(8 citation statements)

References 5 publications

(6 reference statements)

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“…However, S.C.S. for phenolic and amino protons are enhanced by a factor of 2-3 on going f r o m non-polar t o polar solvents (1). A similar enhancement could occur for TMA derivatives since the N(CH3),+ hydrogens bear considerable positive charge and should be susceptible t o hydrogen bonding (the larger f and r values in D 2 0 than in CH3CN support this).…”

mentioning

confidence: 83%

“…for N(CH,),+ Miller and co-workers summarized the results P'OtonS of 3-and 4-substituted N,N,N-triof nearly one hundred correlations of substituent-m e t h~l~h e n~l a m m o n i u m derivatives (henceforth induced 1~ chemical shifts (s.c.s.) in aromatic referred to as trimethylanilinium o r TMA derivatives against H~~~~~~ constants (1) derivatives) should reflect resonance effects since R = 0 for the N(CH,),+ group (3). They also [I] 6 = p o + 6, found it inexplicable that 3-and 4-substituted Many of the correlations were poor and they detected no pattern of slopes, p, which could be related to mechanisms of transmission of substituent effects.…”

Section: Introductionmentioning

confidence: 99%

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A Reconsideration of the Validity of Correlating Substituent-induced Proton Chemical Shifts in Aromatic Derivatives with Reactivity Parameters

Dawson¹,

Hamer²,

Reynolds³

1974

Can. J. Chem.

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Comparisons of 'H chemical shifts and charge densities (determined by C N D 0 / 2 MO calculations) for 4-substituted derivatives of styrene, toluene, benzylchloride, and N,N,N-trimethylphenylammonium ion indicate that the chemical shifts primarily reflect intramolecular electronic effects. These effects are reflected by correlations of 'H chemical shifts with the F and R reactivity parameters of Swain and Lupton. It is concluded that it is valid to correlate substituent-induced chemical shifts for aromatic derivatives with divided reactivity parameters provided that ( I ) chemical shifts are measured at infinite dilution in a non-polar medium and'(2) at least ten derivatives of each family are investigated.Calculations for 4-substituted toluenes indicate that there will be a small conformational dependence for substituent-induced benzylic proton chemical shifts.La comparaison des deplacements chimiques ' H et des densites de charge (dktermintes par la mkthode CNDO/2 MO) pour des derives substitues en position 4 du styrene, du toluene, du chlorure de benzyle et de I'ion N,N,N-trimkthylphinyl ammonium indiquent que les deplacements chimiques refletent principalement les effets Clectroniques intramolCculaires. Ces effets apparaissent sous forme de correlation entre les deplacements chimiques 'H avec les parametres de rkactivite F e t R de Swain et Lupton. On en conclut qu'il est valide de faire une correlation entre le substituant et les diplacements chimiques induits dans les derives aromatiques possedant des parametres de reactivite divises pourvu (I) q u e les deplacements chimiques soient mesurks dilution infinie dans un solvant non-polaire et (2) qu'au moins dix derives de la famille soient etudits.Les calculs pour les toluenes substituCs en position 4 indiquent qu'il y a une petite dependance conformationnelle pour les dkplacements chi~niques des protons benzyliques qui ont ett induits p a r les substituants.[ (1) derivatives) should reflect resonance effects since R = 0 for the N(CH,),+ group (3). They also [I]

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mentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

A Reconsideration of the Validity of Correlating Substituent-induced Proton Chemical Shifts in Aromatic Derivatives with Reactivity Parameters

Dawson¹,

Hamer²,

Reynolds³

1974

Can. J. Chem.

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“…Concurrent with the appearance of our complete paper (I) on this topic a comprehensive review and assessment of the same subject was published by Yokoyama et al (2). These authors showed that several literature discrepancies regarding the substituent chemical shifts (s.c.s.)…”

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confidence: 83%

Effect of Substituents on the Chemical Shift of Benzylic Protons. III

Fraser¹,

Renaud²

1971

Can. J. Chem.

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The effects of para substituents on the chemical shifts of the diastereotopic benzylic protons in three series of chiral molecules have been determined from a study of the 100 MHz spectra of these molecules in deuterochloroform. The results show that the slope, p, obtained from a plot of 7 vs. Hammett o constant, is influenced by a number of factors and that the conformational disposition of the benzylic proton with respect to the aromatic ring is not a dominant factor.

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“…[21] The dibromides 4 and 7 were prepared by modification of literature procedure [22] through the addition of bromine to ethyl trans-cinnamate and the chalcone 8, respectively. The alkyl bromide 12 was prepared through modification of literature procedure, [20] from the corresponding alcohol 12 and phosphorus tribromide and identified using the key resonance in the 13 C NMR spectrum at δ C 74.6.…”

Section: Methodsmentioning

confidence: 99%

⁷⁹Br NMR spectroscopy as a practical tool for kinetic analysis

Chan

Howe

Hook

et al. 2009

Magnetic Reson in Chemistry

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(79)Br NMR spectroscopy has been used to monitor a series of reactions in which the bromide ion is produced, including the Menschutkin reaction of pyridine with a range of substituted benzyl bromides and a Heck coupling process. In cases where the process could also be monitored using (1)H NMR spectroscopy, the kinetic analyses using heteronuclear magnetic resonance spectroscopy were shown to be completely consistent. Both the utility of the process in following reactions which may be difficult to analyse using other techniques and the practical limitations associated with solvent choice are discussed.

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Transmission of electronic effects. Proton magnetic resonance chemical shifts for benzyl halides in several solvents

Cited by 39 publications

References 5 publications

A Reconsideration of the Validity of Correlating Substituent-induced Proton Chemical Shifts in Aromatic Derivatives with Reactivity Parameters

A Reconsideration of the Validity of Correlating Substituent-induced Proton Chemical Shifts in Aromatic Derivatives with Reactivity Parameters

Effect of Substituents on the Chemical Shift of Benzylic Protons. III

⁷⁹Br NMR spectroscopy as a practical tool for kinetic analysis

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Transmission of electronic effects. Proton magnetic resonance chemical shifts for benzyl halides in several solvents

Cited by 39 publications

References 5 publications

A Reconsideration of the Validity of Correlating Substituent-induced Proton Chemical Shifts in Aromatic Derivatives with Reactivity Parameters

A Reconsideration of the Validity of Correlating Substituent-induced Proton Chemical Shifts in Aromatic Derivatives with Reactivity Parameters

Effect of Substituents on the Chemical Shift of Benzylic Protons. III

79Br NMR spectroscopy as a practical tool for kinetic analysis

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Product

Resources

About

⁷⁹Br NMR spectroscopy as a practical tool for kinetic analysis