Tritium nuclear magnetic resonance spectroscopy. Part 11. Further consideration of referencing, isotope effects and coupling constants: Preparation of [<sup>3</sup>H]tetramethylsilane

Bloxsidge, James P.; Elvidge, J. A.; Jones, John R.; Mane, Ramachandra B.; Saljoughian, Manouchehr

doi:10.1002/mrc.1270121006

Cited by 44 publications

(15 citation statements)

References 18 publications

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“…It may be noted that the respective ZJH,H values in the sidechain (Table 1) are apparently equal to those in toluene (18) and in methyl bromide (19). A similar comparison holds for phenylethane (20), toluene, and methane. Because the conformational averages of the H-H vector in the alpha methylene group with respect to the benzene n system must be quite different in the three phenyl compounds, doubt arises about the use of ZJH,H in conformational deductions for benzyl derivatives.…”

Section: I-bromo-(35-dibromophenyl) Ethanementioning

confidence: 51%

Conformational preferences about both exocyclic carbon–carbon bonds in some phenyl derivatives of ethane, propene, and 4-picoline

Schaefer¹,

Kruczynski²,

Krawchuk³

et al. 1980

Can. J. Chem.

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The 1H nmr spectra in solution of 1-R-(3,5-dibromophenyl) ethanes (R = CH3, C2H5, n-C3H7 to n-C6H13, OH, F, Br), of 1-amino-2-(3,5-dichlorophenyl) ethane, of 3,5-dichloroallylbenzene, and of 4-(3,5-dibromobenzyl) pyridine are analyzed at 305 K. For the ethane derivatives, the populations of anti and gauche conformers are derived from the vicinal proton–proton coupling constants. The conformation about the C1—Cα bond in both gauche and anti forms is discussed in terms of long-range couplings to the ring protons and some approximate barriers about this bond are suggested for both conformers. Greater rigidity exists in the gauche than in the anti conformations. In some cases the measurements are compared with extensive molecular orbital calculations, for example, for phenethylamine. The low-energy conformations and the barriers about the C1—Cα bond are deduced for the allyl and pyridyl compounds.

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Section: I-bromo-(35-dibromophenyl) Ethanementioning

confidence: 51%

Conformational preferences about both exocyclic carbon–carbon bonds in some phenyl derivatives of ethane, propene, and 4-picoline

Schaefer¹,

Kruczynski²,

Krawchuk³

et al. 1980

Can. J. Chem.

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“…These relate to notational matters and are particularly directed at publications in chemical journals. In several places, we use different wording from the original reports and in some cases extended meanings: The nucleus giving rise to the spectrum concerned should always be explicitly stated in full or in abbreviation (e.g., 10 B NMR or boron-10 NMR). The isotopic mass number should be given except in cases without ambiguity.…”

Section: Recommendations Endorsedmentioning

confidence: 99%

“…δ X / ppm = 10 6 (Ξ X,sample -Ξ X,reference ) / Ξ X,reference (10) The widespread use of a 2 H lock for NMR measurements on isotropic samples suggests a modification of the substitution approach, since the relevant reference frequency should not vary with time. Thus, the chemical shifts of the X nuclei can, in principle, be determined on the unified (TMS-based) scale merely by measuring the resonance frequency of the sample and using a predetermined reference frequency for the nuclide in question.…”

Section: Practical Application Of the Unified Scalementioning

confidence: 99%

NMR nomenclature. Nuclear spin properties and conventions for chemical shifts(IUPAC Recommendations 2001)

Harris

Becker

Menezes

et al. 2001

Pure and Applied Chemistry

1,193

1,084

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Republication or reproduction of this report or its storage and/or dissemination by electronic means is permitted without the need for formal IUPAC permission on condition that an acknowledgmentAbstract: A unified scale is recommended for reporting the NMR chemical shifts of all nuclei relative to the 1 H resonance of tetramethylsilane (TMS). The unified scale is designed to provide a precise ratio, Ξ, of the resonance frequency of a given nuclide to that of the primary reference, the 1 H resonance of TMS in dilute solution (volume fraction, ϕ < 1%) in chloroform. Referencing procedures are discussed, including matters of practical application of the unified scale. Special attention is paid to recommended reference samples, and values of Ξ for secondary references on the unified scale are listed, many of which are the results of new measurements.Some earlier recommendations relating to the reporting of chemical shifts are endorsed. The chemical shift, δ, is redefined to avoid previous ambiguities but to leave practical usage unchanged. Relations between the unified scale and recently published recommendations for referencing in aqueous solutions (for specific use in biochemical work) are discussed, as well as the special effects of working in the solid state with magic-angle spinning. In all, nine new recommendations relating to chemical shifts are made.Standardized nuclear spin data are also presented in tabular form for the stable (and some unstable) isotopes of all elements with nonzero quantum numbers. The information given includes quantum numbers, isotopic abundances, magnetic moments, magnetogyric ratios and receptivities, together with quadrupole moments and line-width factors where appropriate.

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“…Based on somewhat complex referencing procedures (3,26), it was concluded that aromatic tritons resonate downfield from aromatic protons. The A values in Table 2 appear to confirm this conclusion because the 'H nmr shift of benzene in the appropriate solvent is used to calculate the A values (the shift of in [,HI-benzene relative to the shift of 'H in benzene is apparently unavailable).…”

Section: The Chemical Shifismentioning

confidence: 99%

¹H nuclear magnetic resonance spectral parameters of toluene. Implications for conformational analysis and isotope shifts

Schaefer¹,

Sebastian²,

Penner³

1985

Can. J. Chem.

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A precise analysis of the 'H nmr spectrum of toluene as a dilute solution in carbon disulfide yields a revised set of spectral parameters. The chemical shift of the para proton lies 12.6 ppb to low frequency of that of the ortho protons at 300 K. The ring proton chemical shifts are discussed and compared with 'H and 3H shifts observed in carbon tetrachloride. The long-range couplings between methyl and ring protons can be said to be quantitatively understood in terms of a and u-a electron transmitted mechanisms. The changes observed in these three couplings in phenylacetaldehyde can be quantitatively reproduced in terms of these mechanisms and also illustrate how these changes are direct measures of the conformational preferences in this molecule.TED SCHAEFER, RUDY SEBASTIAN et GLENN H. PENNER. Can. J. Chem. 63, 2597(1985.Une analyse prCcise des spectres rmn du 'H du tolukne, en solution diluCe dans le disulfure de carbone, a permis d'obtenir un nouvel ensemble de paramktres spectraux. A 300 K, le dCplacement chimique du proton para se situe ?I une frkquence de 12,6 ppb plus basse que celle des protons ortho. On discute des dCplacements chimiques des protons du cycle et on les compare avec les dCplacements des 'H et 3~ qui ont Ct C determinks en solution dans le tetrachlorure de carbone. On peut dire que I'on peut expliquer quantitativement les couplages ti longue distance entre les protons du cycle et ceux du groupement mCthyle en faisant appel ?I des mkcanismes impliquant que les Clectrons sont transmis par les liaisons u et u-a. On peut reproduire quantitativement les changements observks dans ces trois couplages du phCnylacCtaldChyde en faisant appel ?I ces mkcanismes; de plus, on peut illustrer comment ces changements sont des mesures directes des prCfCrences conformationnelles dans cette moltcule.[Traduit par le journal] !

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Tritium nuclear magnetic resonance spectroscopy. Part 11. Further consideration of referencing, isotope effects and coupling constants: Preparation of [³H]tetramethylsilane

Cited by 44 publications

References 18 publications

Conformational preferences about both exocyclic carbon–carbon bonds in some phenyl derivatives of ethane, propene, and 4-picoline

Conformational preferences about both exocyclic carbon–carbon bonds in some phenyl derivatives of ethane, propene, and 4-picoline

NMR nomenclature. Nuclear spin properties and conventions for chemical shifts(IUPAC Recommendations 2001)

¹H nuclear magnetic resonance spectral parameters of toluene. Implications for conformational analysis and isotope shifts

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Tritium nuclear magnetic resonance spectroscopy. Part 11. Further consideration of referencing, isotope effects and coupling constants: Preparation of [3H]tetramethylsilane

Cited by 44 publications

References 18 publications

Conformational preferences about both exocyclic carbon–carbon bonds in some phenyl derivatives of ethane, propene, and 4-picoline

Conformational preferences about both exocyclic carbon–carbon bonds in some phenyl derivatives of ethane, propene, and 4-picoline

NMR nomenclature. Nuclear spin properties and conventions for chemical shifts(IUPAC Recommendations 2001)

1H nuclear magnetic resonance spectral parameters of toluene. Implications for conformational analysis and isotope shifts

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Tritium nuclear magnetic resonance spectroscopy. Part 11. Further consideration of referencing, isotope effects and coupling constants: Preparation of [³H]tetramethylsilane

¹H nuclear magnetic resonance spectral parameters of toluene. Implications for conformational analysis and isotope shifts