ON THE COUPLING BETWEEN H1 AND F19 NUCLEI IN p-FLUOROTOLUENE. II

Schaefer, Ted; Schneider, W. G.

doi:10.1139/v59-302

Cited by 20 publications

(4 citation statements)

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“…This spectrum is an example of a n AzBzX system ( 2 4 ) but it appears t o be very nearly a first-order spectrum. In view of the known values of proton coupling constants in the cyclopropane ring (5)(6)(7)(8)(9)(10) and in view of our experience with first-order AzBzX spectra (3,4), this is very curious. I t can immediately be said t h a t the coupling between the A and B protons in the CHZCHZ moiety must be not more than a cycle or two in order t o give the observed spectrum (3,4).…”

Section: Introductionmentioning

confidence: 99%

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

Schaefer¹,

Hruska²,

Kotowycz³

1965

Can. J. Chem.

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The analysis of cyclopropyllithium allows estimates to be made of all proton coupling constants. The exceptionally small couplings across carbon atoms 2 and 3 are examined in the context of correlations of coupling constants with the electronegativities of substituents. I t is concluded that, although the couplings involving protons attached t o the same carbon a s the substituent decrease with increasing electronegativity of the substituent, the opposite is true for couplings involving the protons attached to carbons one bond removed from t h e substituent. Individual values are suggested for the coupling constants in cyclopropane itself and these agree with the observed 13C side bands in its proton spectrum.

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Section: Introductionmentioning

confidence: 99%

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

Schaefer¹,

Hruska²,

Kotowycz³

1965

Can. J. Chem.

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“…It has more precisely defined fine structure but the same general form as the typical A2B2X pattern (where A and B represent the protons ortho and meta, respectively, to the fluorine nucleus X) reported by Schaefer, for the case of small chemical shift between ortho and meta hydrogens, and splitting constants between the latter and the fluorine nucleus of 8.7 and 5.8 c.p.s., respectively. 26 The basic A2B2X pattern is complicated by long-range coupling with the methyl group protons which Schaefer has estimated to be 0.9 c.p.s. in this case.…”

Section: Resultsmentioning

confidence: 99%

Fluorine-19 Magnetic Resonance Study of Secondary Deuterium Isotope Effects of the Methyl Group¹

Traficante¹,

Maciel²

1965

J. Am. Chem. Soc.

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“…cis and trans coupling constants is, no doubt, an average value for reasons which are now well 1;nown (9).…”

Section: J C H~-c U~mentioning

confidence: 88%

THE PROTON MAGNETIC RESONANCE SPECTRA OF CHRYSANTHEMUM ETHYL ESTER AND THE RELATED cis- AND trans-CHRYSANTHEMUMIC ACIDS

Hutton¹,

Schaefer²

1962

Can. J. Chem.

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A B S T R A C T T h e high-resolution proton magnetic resonance spectra o f a mixture o f the cis and trans isomers o f chrysantheniuni monocarbosylic acid ethyl ester have been studied. T h e cischrysanthemumic and trans-chrysa~lthemumic acids spectra were obtained t o facilitate the interpretation o f the complex spectra o f t h e ester. T h e percentage o f the trans isomer in I N T R O D U C T I O NThere have been no unequivocal nleasure~nents of the cis and trans proton coupling constants in the cyclopropane ring. I n the present worli the analyses of the cis-and trans-chrysanthemum ester and the corresponding acids were used to obtain these values. The chrysanthemum ester sample was a mixture of both the cis and the trans isomers, making a conlplete assignment of spectra lines difficult. I t was found more convenient to analyze the cis-and trans-chrysanthen~un~ic acids separately in order to identify the resonance peaks. Since the two ring protons interact only with the isobutenyl proton the analysis was that of an ABX-type system.I t was necessary to use solvents which preferentially shifted the proton signals in such a manner that the resonance pealis of the ring protoils were not obscured by the other peaks. Carbon disulphide was used for the cis-cl~rysanthemuinic acid and benzene for the trans acid. E X P E R I M E N T A L T h e spectra were obtained on a Varian V4302 D P 60 M c / s spectrometer at room teniperat~~re. T h e line separations were measured b y t h e side-band technique, using a Hewlitt and Pacliard 521c frequency counter. T h e chrysanthemum ester (min. 95%), t h e cis-chrysanthemumic acid (99.9%), and the trans-chrysanthemumic acid (100%) were o f known purity as supplied b y Benzol Products Co., and were not purified further. Since the acids were o f limited solubility saturated solutions were used; the ester concentrations were approximate b y volume since t h e solvents were only used t o obtain preferential proton shifts. Internal benzene was used as the reference point in t h e measurement o f the shifts. A N A L Y S I S I. cis-Chrysanthemumic Acid in CS2The spectrum of the cis-chrysanthemulnic acid is shown in Fig. 1 together with the calculated spectrum for the ring protons corresponding to the AB part of an ABX system. The X part of the spectrum, a t 114 c.p.s. with respect t o internal benzene, consists of two doublets whose components are further split by the two isobutenyl methyl groups. The peaks of the latter occur a t 324 c.p.s. and 328 c.p.s. The methyl groups attached to the cyclopropane ring have the same shift and occur a t 357 c.p.s. The carboxyl proton peali is situated a t -287 c.p.s. and is not shown in Fig. 1. The results of the ABX analysis gave JAB (cis) = 8.7 c.p.s., JAX = 8.1 c.P.s., JBX = 0 C.P.S. The coupling constant of the X proton to the isobutenyl methyl group protons was about 1.4 c.p.s.

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ON THE COUPLING BETWEEN H¹ AND F¹⁹ NUCLEI IN p-FLUOROTOLUENE. II

Cited by 20 publications

References 1 publication

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

Fluorine-19 Magnetic Resonance Study of Secondary Deuterium Isotope Effects of the Methyl Group¹

THE PROTON MAGNETIC RESONANCE SPECTRA OF CHRYSANTHEMUM ETHYL ESTER AND THE RELATED cis- AND trans-CHRYSANTHEMUMIC ACIDS

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ON THE COUPLING BETWEEN H1 AND F19 NUCLEI IN p-FLUOROTOLUENE. II

Cited by 20 publications

References 1 publication

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

Correlations of Proton Coupling Constants in the Cyclopropane Ring With Electronegativity: Consideration of the Proton Resonance Spectrum of Cyclopropyllithium

Fluorine-19 Magnetic Resonance Study of Secondary Deuterium Isotope Effects of the Methyl Group1

THE PROTON MAGNETIC RESONANCE SPECTRA OF CHRYSANTHEMUM ETHYL ESTER AND THE RELATED cis- AND trans-CHRYSANTHEMUMIC ACIDS

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ON THE COUPLING BETWEEN H¹ AND F¹⁹ NUCLEI IN p-FLUOROTOLUENE. II

Fluorine-19 Magnetic Resonance Study of Secondary Deuterium Isotope Effects of the Methyl Group¹