Nonadditive carbon-13 nuclear magnetic resonance substituent shifts in 1,4-disubstituted benzenes. Nonlinear resonance and shift-charge ratio effects

Bromilow, John; Brownlee, Robert T. C.; Craik, David J.; Sadek, Maruse; Taft, Robert W.

doi:10.1021/jo01300a033

Cited by 160 publications

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“…Among these calculations, the latest results [24,25] indicate that the structure with lowest energy has C s symmetry with one hydrogen being out of the plane and the other two being out of plane in the opposite direction. This structure is supported by a recent ab initio study [26,27], There has been an interest in substituent resonance effects [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42], A major concern is the form of substituent response as the electron demand is altered in the attached pi-system [28][29][30][31][32][33][34][35][36][37],The aim of the present work is to utilize quantum chemical calculations to provide predictions of heat of formation, geometry, electron density distribution and stability of the cyclopropenyl system (cation, radical and anion) and to study the effect of the substituents O", OH, CH 3 , CHO, CN, N0 2 , F, and CF 3 on this system.The calculated heat of formation of monosubstituted cyclopropenyl system is obtained by the semiempirical MINDO-Forces MO method [43]. The 0932-0784 / 92 / 0600-784 $ 01.30/0.…”

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A Theoretical Study of Monosubstituted Cyclopropenyl System

Yahya

Khalil

1992

Zeitschrift Für Naturforschung A

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MONDO-Forces calculations have been performed, with complete optimization of geometry on X-cyclopropenyl system (cations, radicals and anions), where X is H, O", OH, CH 3 , CN, N0 2 , F and CF 3 . All substituents prefer planar structure when substituted on both cations and radicals, while they prefer pyramidal structure in the case of anions except CF 3 . The substituents O", OH and F act as electron releasing, while CHO, N0 2 and CF 3 act as electron withdrawing when substituted on cyclopropenyl system. CH 3 and CN show amphielectronic behaviour. They act as electron releasing on the cations and withdrawing on both radicals and anions depending on electron demand. In the case of cations and radicals, all substituents were found to increase the vicinal bonds and decrease the distal bonds and bond angles to which the substituent is attached. For anions the substitutents show no such regularity because the substituents are out of the three-membered ring plane. All substituents increase the stability of the cyclopropenyl system except CF 3 in the case of the cation.The cyclopropenyl cation is the smallest aromatic molecule which has two ^-electrons and satisfies the Hückel 4 n + 2 rule. The electronic structure is of great interset since the molecule is highly strained but despite of this the ion is stable in the form of salts, e. g. C 3 H 3 • SbCl^, and also in polar solvents [1]. D 3h configuration of the ion is indicated by its IR and NMR spectra [1], Allen has reported a structural analysis for two cyclopropenyl cation derivatives based upon Xray crystallographic data [2]. Clark carried out ab initio LCAO SCF MO Calculations on both C 3 H 3 + and C3H3 and discussed the aromaticitiy and antiaromaticity [3]. Ha et al. reported an ab initio LCAO SCF MO investigation on C 3 H 3 + , C 3 Hj and C 3 H 3~ and discussed the geometry and stability of these species [4j. Random et al. aiso carried out ab initio calculations on C3H3 using STO-3G and 6-31G and obtained the equilibrium structure of the ion [5]. Takada and Ohno also published an ab initio CI calculation on the electronic structure of C3H3 [6]. The most recent ab initio calculations on the molecular structure and vibrational spectrum of C3H3 were performed by Xie et al. [7], and Lee et al. [8], Cyclopropenyl free radical, the simplest member of the series of fully conjugated cyclic radicals, has been the subject of experimental [9-13] and theoretical studies [4,[14][15][16][17][18][19][20],The theoretical work by Chipman and Miller [20] predicts an ethylenic structure of C s symmetry as the lowest energy form. The hydrogen atom at the apex of the isoceles triangle is bent substantially out of the ring plane. The allylic structure, which satisfies the Jahn-Teller theorem, is predicted to be 5 kcal/mole higher in energy. Experimental work by Closs and Redwine [13] support the C s structure and rules out the allylic structure. There is no experimental information on the properties of the neutral radical, so it is necessary to resort to theoretical studies.The cyc...

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confidence: 64%

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A Theoretical Study of Monosubstituted Cyclopropenyl System

Yahya

Khalil

1992

Zeitschrift Für Naturforschung A

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“…It has become evident that in suitable systems the influence of substituents on these shifts is predominantly a consequence of their polar and resonance effects. The most widely used systems for this study have been the shifts of the para ring carbons in benzenes (4) and of the side-chain carbons of ring-substituted styrenes ( 5 , 6 ) . Considerably less attention has been paid to the aromatic carbonyl compounds, although the understanding of the ways in which substituents modify the electronic environment of this site is of great interest because of the importance of this group in organic chemistry.…”

Section: Introductionmentioning

confidence: 99%

Electronic effects of heterocyclic substituents. Spectroscopical and theoretical (AM1) study in a series of heterocyclic carboxaldehydes

Cativiela¹,

Garcı́a²

1990

Can. J. Chem.

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. The electronic effects of a series of 18 heterocyclic carboxaldehydes (furans, thiophenes, pyrroles, and pyridines) have been studied by means of the correlation existing between I3C chemical shifts of the carbonylic carbon and calculated total and T charges (AMI). The implications of this theoretical model to explain polar and resonance contributions to the total electronic effect are discussed.

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“…For a strongly interacting common substituent, a nonlinear resonance effect equation (14,15) would have been required to allow for the eiectron demand of the common group.…”

Section: Factor Analysis Of the Chemical Shiftsmentioning

confidence: 99%

“…Since Reynolds has recently shown that the inductive parameter, I, is more accurately described as a field parameter, F (13), this convention will be used throughout this paper. For 1,4-disubstituted benzenes with one fixed substituent, Bromilow and co-workers (14,15) have shown that the effect of substituents on para carbon chemical shifts is dependent on the electron demand exerted by the common group and can be analyzed with a dual snbstituent parameter nonlinear resonance effect (DSP-NLR) equation. The lack of statistical support (for example an F-test of the variance (14)) when applying a particular linear free-energy relationship has caused some concern (16,17).…”

Section: Introductionmentioning

confidence: 99%

Determination of substituent effects by factor analysis and multiple linear regression for the carbon-13 nuclear magnetic resonance chemical shifts in 4-substituted phenols and 2-nitrophenols

Hutton¹,

Kunz²,

Bozek³

et al. 1987

Can. J. Chem.

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. Can. J. Chem. 65, 1316Chem. 65, (1987. Carbon-13 nuclear magnetic resonance chemical shifts are reported for a series of 4-substituted phenols and 2-nitrophenols in dimethyl sulfoxide solution. For chemical shift correlations, it was found by factor analysis and iterative multiple linear regression that the para chemical shifts require two substituent factors whereas the ipso, ortho, and meta chemical shifts require three factors. Regression analyses were performed using the field and resonance parameters (uF, uRO) and the appropriate ipso, ortho, and meta parameters (I, 0, M) determined by Reynolds. Good correlations were obtained except for the three meta carbon analyses, where the correlation coefficients range from 0.877 to 0.963. On a dttermint les dCplacements chimiques, en rmn I3c, d'une strie de phtnols substituts en position 4 ainsi que de nitro-2 phtnols en solution dans le dimCthylsulfoxyde. Pour les corrtlations des dtplacements chimiques, on a trouvt par des analyses factorielles et par des rtgressions IinCaires multiples itCratives que les diplacements chimiques des positions para requikrent deux facteurs de substituants alors que les diplacements chimiques des positions ipso, ortho et me'trr requikrent trois facteurs. On a effectuk des analyses de regression en utilisant les paramktres de champ et de risonance (uF, uR0) ainsi que les paramktres ipso, ortho et me'ta appropriis (I, 0 et M) diterminCs par Reynolds. On a obtenu de bonnes corrilations, excepti pour trois analyses de carbones tnita pour lesquelles on a obtenu des coefficients de corrClation allant de 0,877 i 0,963.[Traduit par la revue]

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Nonadditive carbon-13 nuclear magnetic resonance substituent shifts in 1,4-disubstituted benzenes. Nonlinear resonance and shift-charge ratio effects

Cited by 160 publications

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A Theoretical Study of Monosubstituted Cyclopropenyl System

A Theoretical Study of Monosubstituted Cyclopropenyl System

Electronic effects of heterocyclic substituents. Spectroscopical and theoretical (AM1) study in a series of heterocyclic carboxaldehydes

Determination of substituent effects by factor analysis and multiple linear regression for the carbon-13 nuclear magnetic resonance chemical shifts in 4-substituted phenols and 2-nitrophenols

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