The Nuclear Magnetic Resonance Spectra of Three Unsymmetrical o-Dihalobenzenes

Smith, William B.; Cole, G. Mattney

doi:10.1021/j100782a511

Cited by 15 publications

(3 citation statements)

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“…It is then assumed that the shift of any proton can be found as the sum of two parameters D and one para parameter dp. This assumption is consistent with the fact that in a 1,2-disubstituted benzene the ortho interaction is not such as t o interfere with the additive effect at protons 4 and 5 (3,8). It is also consistent with the evidence (6) that in a 1-X-2-Y-benzene the shift of proton-4 is linearly related to the shift of proton-3 in the 1-Y-benzene.…”

Section: Spectral Analysissupporting

confidence: 85%

“…Some progress has been made in correlating the proton shifts in substituted benzenes with electron densities at the bonded carbon atoms (1)(2)(3) or with Hammett substituent constants (4,5). But there are also contributions2 to the shifts arising from substituent magnetic anisotropy, local van der Waals interactions, field effectsintroduced by substituent dipole moments, and from rather subtle ortho effects (7,8). Substituent-induced changes in ring currents also contribute (9).…”

Section: Introductionmentioning

confidence: 99%

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Proton chemical shifts of polyhalobenzenes in cyclohexane and carbon tetrachloride. An additivity scheme based on pairwise parameters

Richardson¹,

Schaefer²

1968

Can. J. Chem.

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An additivity scheme which takes into account the interactions between ortho substituents is applied to 39 proton shifts in 22 tri-, tetra-, and pentasubstitutcd halobenzenes as 3 mole % solutions in cyclohexane and carbon tetrachloride. The shift of any proton can be written as the sum of two parameters D ( X , Y ) and one parameter d,. D ( X , Y ) refers to a pair of substituents placed ortho ( X ) and meta ( Y )to the proton and d, refers to a substituent placed para to the proton. The mean deviation between observed and calculated shifts is found to be 0.010 p.p.m. for the cyclohexane solutions and 0.012 p.p.m. for the carbon tetrachloride solutions. The scheme also works reasonably well for mono and dihalobenzenes. The parameteris a measure of the stcric interaction between the X and Y substituents. It is also suggested that the steric environment of a proton is important in determining the shift in carbon tetrachloride solution.

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Section: Spectral Analysissupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Proton chemical shifts of polyhalobenzenes in cyclohexane and carbon tetrachloride. An additivity scheme based on pairwise parameters

Richardson¹,

Schaefer²

1968

Can. J. Chem.

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“…Considerable interest has been directed toward obtaining and interpreting the nmr parameters of the monosubstituted benzenes following the early work of Corio and Dailey.2 Because of difficulties inherent in the analysis of the spectral patterns of these systems, simplification by selective deuteration has been resorted to by some investigators.8-6 More recently, improvements in spectrometer performance and the availability of high-speed, iterative computer programs for nmr spectral analysis have greatly facilitated the study of these spectra.6-11 One point of widespread interest has been the question of additivity of substituent effects on the chemical shifts in polysubstituted benzenes. [10][11][12][13][14][15][16][17] Recently, the existence of additivity relations for the proton-proton coupling parameters in various halogen substituted benzenes has also been established. 10•17•18 This latter development has stemmed, in large part, from a series of precise analyses of the monohalobenzene spectra and of the 13CH satellite spectrum of benzene itself.8 •17,19 In this article we describe the results of nmr spectral analyses for phenol, benzoic acid, aniline, benzenethiol, and for 13 disubstituted benzenes derived from these compounds, all carried out under uniform experimental conditions.…”

Section: Introductionmentioning

confidence: 99%

Nuclear magnetic resonance spectra of mona- and disubstituted benzenes containing OH, SH, NH2, and COOH

Evans¹,

Tarpley²,

Goldstein³

1968

J. Phys. Chem.

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Nmr spectra have been analyzed for four monosubstituted benzenes (OH, SH, NH2, and COOH) and 13 disubstituted derivatives containing the same substituents. Substituent effects on the coupling parameters have been determined for all positions and have been found to be additive in the disubstituted compounds, the average deviation from additivity being 0.085 Hz for 62 couplings. A reasonably satisfactory additivity relation also holds for most of the chemical shifts. The effect of substituents on the coupling parameters, including previously obtained data, has been shown to correlate quite well with substituent (group) electronegativities. The results were also found to be useful in nmr spectral assignments and analysis for aromatic compounds.

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Protonenresonanz‐Spektroskopie Ungesättigter Ringsysteme—XIV: Zur Frage der Substituenten‐Einflüsse auf die Resonanzfrequenzen und Vicinalen Kopplungskonstanten von protonen in substituierten Benzolen

Bremser

Günther

1969

Org. Magn. Reson.

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The substituent effect on proton resonances and vicinal H,H-coupling constants in benzene derivatives is studied using linear regression analysis. The change in shielding observed on substitution, relative to the proton resonance in benzene, Au, can be expressed as AU = -1.04 X 10-l'Ez -1.08 X 10-18E2 + 9'17Ap + 0.18.This equation enables calculations of substituent effects on the basis of the dipolar and quadratic field effect (Ez, Ee) and the n-charge density changes on the neighbouring C-atom (Ap).The vicinal coupling constants show no correlation with the HMO-a-bond order. A linear regression using the well known dependence of the coupling constant on substituent electronegativity yieldswhere AE, and AEp are the changes in electronegativity caused by substitution in a-or /%position, respectively, to the HCCH-fragment considered.Zusammenfassung-Der EinfluD von Substituenten auf die Protonenresonanzen und die vicinalen H,H-Kopplungskonstanten in Benzolderivaten wird mit Hilfe h e a r e r Ausgleichsrechnungen untersucht. Fur die relativ zur Protonenresonanz des Benzols auftretende Abschirmungsanderung Ao bei der Substitution wird die Beziehung AU = -1,04 X 10-laEz -1,08 X 10-lsEa + 9,17Ap + 0,18 angegeben, die eine Berechnung der Substituenten-Effektes mit Hilfe des dipolaren und quadratischen Feldeffektes (Ez, E2) und der n-Ladungsdichte-hderung am benachbarten C-Atom (A,) erlaubt.Die vicinalen Kopplungskonstanten lassen sich mit der HMO-n-Bindungsordnung nicht korrelieren. Eine Ausgleichsrechnung unter Benutzung der bekannten Abhangigkeit der Kopplung von der Substituenten-Elektronegativitat liefert 'J = 7,63 + 0,508AE, -0,096AEp wobei AE, und AEg die durch Substitution bedingte h d e r u n g der Elektronegativitat in u-bzw. B-Stellung zum betrachteten HCCH-Fragment bedeuten. DIE UNTERSUCHUNGEN der Substituenten-Einflusse auf die NMR-Parameter von Protonen in Benzolderivaten lassen im wesentlichen zwei Zielsetzungen erkennen :(1) Die Ermittlung empirischer Substituenten-Konstanten S(8) und S(J), die eine Voraussage der Resonanzfrequenzen und Spin-Spin-Kopplungskonstanten fur beliebig substituierte Benzole ermoglichen.

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The Nuclear Magnetic Resonance Spectra of Three Unsymmetrical o-Dihalobenzenes

Cited by 15 publications

References 0 publications

Proton chemical shifts of polyhalobenzenes in cyclohexane and carbon tetrachloride. An additivity scheme based on pairwise parameters

Proton chemical shifts of polyhalobenzenes in cyclohexane and carbon tetrachloride. An additivity scheme based on pairwise parameters

Nuclear magnetic resonance spectra of mona- and disubstituted benzenes containing OH, SH, NH2, and COOH

Protonenresonanz‐Spektroskopie Ungesättigter Ringsysteme—XIV: Zur Frage der Substituenten‐Einflüsse auf die Resonanzfrequenzen und Vicinalen Kopplungskonstanten von protonen in substituierten Benzolen

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