Fluorine Nuclear Magnetic Resonance Shielding in p-Substituted Fluorobenzenes. The Influence of Structure and Solvent on Resonance Effects

Taft, Robert W.; Price, E.; Fox, Irwin; Lewis, I.C.; Andersen, Kell K.; Davis, George T.

doi:10.1021/ja00903a022

Cited by 301 publications

(70 citation statements)

References 13 publications

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“…The value = 0.98 was also computed from Exner's equation (39). The value 1.11 determined from the correlation [16] is close to the value computed from the data given by Taft et al (36,37) in Table 2 …”

Section: Resultssupporting

confidence: 85%

Kinetics of hydrolysis of aromatic mono- and disulfonyl chlorides

Sanecki¹,

Rokaszewski²

1987

Can. J. Chem.

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PRZEMYSLAW SANECKI and EDWARD ROKASZEWSKI. Can. J. Chem. 65, 2263 (1 987).A continuous polarographic method of recording instantaneous concentrations of -S02C1 groups in an aqueous acetic acid system containing CH3C02Na has been elaborated. Ten model monosulfonyl chlorides underwent hydrolysis according to pseudo-first order kinetics (20% H20, 80% V.V. CH3C02H, 0.5 mol x dm-3 CH3C02Na). Plots of hydrolysis for seven disulfonyl dichlorides with different number of -CH3 groups have been determined. Pseudo-first order rate constants for two consecutive reactions of hydrolysis (k, and k2) have been computed and the influence of -S02C1 and -SO; groups on the reactivity of the second group -S02CI has been discussed. The mechanism of nucleophilic substitution has also been discussed.PRZEMYSLAW SANECKI et EDWARD ROKASZEWSKI. Can. J. Chem. 65, 2263 (1987.On a dtveloppt une mtthode polarographique continue qui permet d'enregistrer instantantment la prtsence de groupements -S02C1 dans des systkmes aqueux d'acide acCtique contenant du CH3C02Na. Dix chlorures modkles de monosulfonyles ont subi une hydrolyse suivant une cinttique de pseudo-premier ordre (20% H20, 80% v/v de CH3C02H et 0,5 mol x dm-3 de CH3C02Na). On a determint les courbes d'hydrolyse de sept dichlomres de disulfonyles qui diffkrent par le nombre de groupements CH3. On a calcult les constantes de pseudo-premier ordre pour les deux reactions d'hydrolyse constcutives (k, et kZ) et on discute de l'influence des groupements -S02C1 et -SO; sur la rtactivitt du deuxikme groupement -S02C1. On discute aussi du mtcanisme de la substitution nucltophile.[Traduit par la revue] IntroductionThe solvolysis and hydrolysis of sulfonyl halogenides are subject of many papers (refs. 1-23 and references therein). The character of the investigations is closely linked with advances in knowledge on reaction mechanism as reported by Arrhenius, Bodenstein, Ingold, Winstein, Bronsted, and Hammett and co-workers. The titrimetric or conductometric methods were used in the determination of instantaneous concentrations of reagents or products, and spectral uv was used only in two cases.It has been found that monosulfonyl chlorides hydrolyze according to the SN2 mechanism (e.g. refs. 9, 10):

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Section: Resultssupporting

confidence: 85%

Kinetics of hydrolysis of aromatic mono- and disulfonyl chlorides

Sanecki¹,

Rokaszewski²

1987

Can. J. Chem.

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“…Substituent σ constant for the twisted p-dimethylamino substituent in this compound is equal to -0.24 [28]. 19 F-NMR chemical shifts of 4-amino-3,5-dimethylfluorobenzene and of its N,N-dimethyl derivative were interpreted in terms of a strong steric inhibition to resonance in their molecules but they are insufficient to push these amino groups out of conjugation with the benzene ring [44].…”

Section: Resultsmentioning

confidence: 99%

“…[19][20][21]. σ p values for the NMe 2 and NH 2 [8] as well as these for other non-amine substituents [22] are known [8] σ value based on reactivity measurements is -0.52 [28].…”

Section: Resultsmentioning

confidence: 99%

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13C-NMR Based Evaluation of the Electronic and Steric Interactions in Aromatic Amines

Zakrzewska¹,

Gawinecki²,

Kolehmainen

et al. 2005

IJMS

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Chemical shifts of the para carbon atoms, δ( 13 C-4), in a series of aromatic amines were used to calculate the σ p , σ R and O R σ substituent constants for different amino groups. N, and N,N-diethylamino groups were found to be the most strong electron-donors. ortho-Substitution decreases the donor properties of the amino group. The amino groups in 2,6-di-i-propylaniline and N,N-2,6-tetramethylaniline have very weak electron-donor properties. The nitrogen atom in benzoquinuclidine and N,N-dimethyl-2,6-di-i-propylaniline have an electron-acceptor character. The calculated substituent constants of the amino groups studied are consistent with the spectral and reactivity data available in literature. Values of δ( 15 N) cannot be used as a direct measure of electronic effects of the N atom in anilines.

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“…Yet Wittstruck and Trachtenberg examined the shifts in a series of cinnamic and dihydrocinnamic acids and concluded that both field and anisotropy effects of the substituent were negligible (10). Taft has shown that aromatic fluorine shifts correlate well with o: values (14) and that these parameters can be related by theoretical calculations to the excess n: charge density introduced by a substituent (1 5). While the sensitivity of fluorine and proton nuclei to substituent effects is different, many similarities in their correlations do exist.…”

mentioning

confidence: 99%

Effect of substituents on the chemical shift of benzylic protons

Fraser¹,

Gurudata²,

Renaud³

et al. 1969

Can. J. Chem.

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The chemical shift of the benzylic protons in fifteen series of para-substituted toluenes bearing different groups in the alpha position are reported. In each series a plot of the chemical shift in tau units of the benzylic protons against the Hammett o value of thepara substituent is linear. The slopes of these plots vary from -0.20 to +0.01 p.p.m./o. The variation of slopes appears to be conformationally dependent, an observation at odds with current theory. In two rigid systems having the same geometry the slope has been found to vary from -0.12 to -0.18 indicating a dependence on other factors as well. The effect of solvent on the slopes has been determined, and shows no correlation with solvent dielectric properties.

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Fluorine Nuclear Magnetic Resonance Shielding in p-Substituted Fluorobenzenes. The Influence of Structure and Solvent on Resonance Effects

Cited by 301 publications

References 13 publications

Kinetics of hydrolysis of aromatic mono- and disulfonyl chlorides

Kinetics of hydrolysis of aromatic mono- and disulfonyl chlorides

13C-NMR Based Evaluation of the Electronic and Steric Interactions in Aromatic Amines

Effect of substituents on the chemical shift of benzylic protons

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