Further application of dual substituent parameter and dual substituent parameter–non-linear resonance methods in modelling<sup>13</sup>C substituent chemical shifts in β-substituted styrenes

Datta, Sumana; De, Asish; Bhattacharyya, S. P.; Medhi, C.; Chakravarty, Ajit K.; Brunskill, J. S. A.; Fadoujou, Solomon; Fish, Kenneth

doi:10.1039/p29880001599

Cited by 12 publications

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“…Second, we discuss the substitution of the b-proton by a methyl group in order to study the influence of coplanarity between the aromatic ring and the ethylenic double bond on the reduction of the nitro group. There are large amounts of work reported on correlation between spectroscopic observations and substituent effects in styrene derivatives [23][24][25][26][27]; however, despite the special electronic characteristics of this type of compound, no attempt has been made to find a correlation with the electrochemical parameters.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical study of β-nitrostyrene derivatives: steric and electronic effects on their electroreduction

Squella

Sturm

Weiss-López

et al. 1999

Journal of Electroanalytical Chemistry

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The electrochemical reduction of a series of b-nitrostyrene and b-methyl-b-nitrostyrene derivatives by tast and differential pulse polarography and cyclic voltammetry over a wide pH range was studied. The reduction potentials are sensitive to the electronic properties of the para-substituent and to the substitution at Cb. An increase in the electron-donor properties of the substituent at the para position makes the reduction potential more negative. On the other hand, the reduction potential shifts several tens of millivolts towards more negative potentials on going from b-nitrostyrene to b-methyl-b-nitrostyrene derivatives, due to the decrease in conjugation with the increase in the C1-Ca torsion angle. A linear correlation between the calculated electronic barrier and the half-wave potential was observed. Furthermore, a linear correlation between the Hammett | p substituent constant and the half-wave potential also was observed, demonstrating that the electrochemical behaviour of these derivatives depends primarily on molecular structure and electron density distribution in a way similar to rates and equilibrium of homogeneous chemical reaction. The b-nitrostyrenes studied illustrate nicely the effects of steric and electronic effects on electrochemical reactions.

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Section: Introductionmentioning

confidence: 99%

Electrochemical study of β-nitrostyrene derivatives: steric and electronic effects on their electroreduction

Squella

Sturm

Weiss-López

et al. 1999

Journal of Electroanalytical Chemistry

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“…Such an increase is, strictly speaking, due to a change in pI rather than q, but nevertheless the net effect is to make the former group behave as if it were at least 50% more electron attracting than the latter, i.e. 4-pyridyl behaves as if it had a oI ca. +0.8.…”

Section: Resultsmentioning

confidence: 99%

β-Substituent effects in the¹³C NMR chemical shifts of styrenes

Aun¹,

Clarkson²,

Happer³

1990

J. Chem. Soc., Perkin Trans. 2

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The effects of meta and para ring substituents on the 13C NMR chemical shifts of the P-carbon of a series of p-heteroaryl styrenes has been investigated. The results show that the contribution of the resonance effect of para substituents to the C-P chemical shift depends on both the polar and resonance effect of the P-substituent, and not, as was previously believed, on the resonance effect alone.

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“…Dual substituent parameter (DSP) treatments have also been employed for these nuclei with good success. , However, in view of the minimal number of substituents included in the present study, one cannot expect to get more than an approximate correlation with even a single-parameter, let alone a DSP, treatment. Average values of σ p , σ p + , and σ 13 for p -COT and p -COT 2- /2K + obtained by interpolation or extrapolation of the correlation lines for plots of δC 2 and δC 9 against the corresponding σ values for the p -phenyl substituents in 1a − c are given in Table .…”

Section: Discussionmentioning

confidence: 98%

Effect of Para Substituents on the Rate of Bond Shift in Arylcyclooctatetraenes

Staley

Kehlbeck

2001

J. Org. Chem.

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The rate constants for bond shift (k(BS)) in phenylcyclooctatetraene (1b) and its p-nitro and p-methoxy analogues (1a and 1c, respectively) in THF-d(8) were determined by dynamic NMR spectrometry to be identical, but k(BS) is eight times greater at 280 K relative to 1b when the para substituent is cyclooctatetraenyldipotassium (2(2-)/2K(+)). These results are discussed in the context of (a) possible intrinsically small substituent effects (as determined by (13)C chemical shifts in the ground state (GS)) for 1a-c and (b) differences in steric interactions and resonance stabilization between the ground and BS transition state (TS). The latter factor was modeled by employing HF/3-21G(*) ab initio molecular orbital calculations of the GS and ring inversion TS. It is concluded that k(BS) is unchanged in 1a-c because the potentially greater pi interaction in the BS TS is counterbalanced by a greater degree of twist between the aryl and COT rings resulting from increased steric hindrance relative to the GS. However, pi interaction assumes a greater importance in the TS of 2(2-)/2K(+) owing to a decreased HOMO-LUMO energy gap compared to 1a-c, particularly when the counterions are solvated. This causes a decrease in the inter-ring twist angle and, together, these changes are responsible for the observed increase in k(BS) in 2(2-)/2K(+). The effect of substituents on a possible contribution of heavy atom tunneling to the reaction mechanism is also discussed.

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Further application of dual substituent parameter and dual substituent parameter–non-linear resonance methods in modelling¹³C substituent chemical shifts in β-substituted styrenes

Cited by 12 publications

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Electrochemical study of β-nitrostyrene derivatives: steric and electronic effects on their electroreduction

Electrochemical study of β-nitrostyrene derivatives: steric and electronic effects on their electroreduction

β-Substituent effects in the¹³C NMR chemical shifts of styrenes

Effect of Para Substituents on the Rate of Bond Shift in Arylcyclooctatetraenes

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Further application of dual substituent parameter and dual substituent parameter–non-linear resonance methods in modelling13C substituent chemical shifts in β-substituted styrenes

Cited by 12 publications

References 0 publications

Electrochemical study of β-nitrostyrene derivatives: steric and electronic effects on their electroreduction

Electrochemical study of β-nitrostyrene derivatives: steric and electronic effects on their electroreduction

β-Substituent effects in the13C NMR chemical shifts of styrenes

Effect of Para Substituents on the Rate of Bond Shift in Arylcyclooctatetraenes

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Further application of dual substituent parameter and dual substituent parameter–non-linear resonance methods in modelling¹³C substituent chemical shifts in β-substituted styrenes

β-Substituent effects in the¹³C NMR chemical shifts of styrenes