Resonance Effect in Hammett Relationship. III. The Modified Hammett Relationship for Electrophilic Reactions

Yukawa, Yasuhide; Tsuno, Yuho

doi:10.1246/bcsj.32.971

Cited by 287 publications

(55 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…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.…”

supporting

confidence: 57%

mentioning

confidence: 71%

See 1 more Smart Citation

A Theoretical Study of Monosubstituted Cyclopropenyl System

Yahya

Khalil

1992

Zeitschrift Für Naturforschung A

View full text Add to dashboard Cite

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...

show abstract

supporting

confidence: 57%

mentioning

confidence: 71%

A Theoretical Study of Monosubstituted Cyclopropenyl System

Yahya

Khalil

1992

Zeitschrift Für Naturforschung A

View full text Add to dashboard Cite

show abstract

“…The obtained substituent effects were analyzed using the extended Yukawa-Tsuno equation (2). All ring-substituted 3(X) anions had planar structures and gave an unexpectedly substantial r − value (0.59).…”

Section: Resultsmentioning

confidence: 99%

“…We have computationally determined the gas-phase stabilities of anionic benzene derivatives, and the obtained substituent effects were compared to reveal the electronic effects affecting the stabilities. As a result, we found three types of electronic effects that govern the stabilities of the anions, and proposed a 'three-term' extended Yukawa-Tsuno equation (2) [8]. …”

Section: Introductionmentioning

confidence: 95%

See 1 more Smart Citation

Computational study of the substituent effects on the gas-phase stabilities of phenylboranylmethyl anions

Nakata

Fujio

2017

Pure and Applied Chemistry

View full text Add to dashboard Cite

The relative gas-phase stabilities of ring-substituted phenylboranylmethyl anions were computationally determined using isodesmic reactions. The energies of species included in the reactions were calculated at the B3LYP/6-311+G(2d,p) level of theory. The obtained substituent effects were analyzed by the extended Yukawa-Tsuno equation, and unexpectedly substantial r − (0.59) and s (0.65) values were found for the fully-optimized planar anion. The substantial through-resonance effect quantified by the r − value was observed, although it is not possible to draw a canonical form in which the negative charge is delocalized on the benzene ring. Substituent effects were also analyzed for the anions in which the dihedral angle (φ) between the side chain plane and the benzene ring was fixed. The r − value decreased significantly by changing the φ from 0° to 90°, while the s value changed little. NBO analyses revealed that the r − value is proportional to the sum of the π-π* and σ-π* orbital interactions between the side chain and the benzene ring. This fact shows that the through-resonance effect quantified by the r − value is present at all φ, and therefore, the anion cannot become an ideal σ 0 -reference system. The constant saturation effect quantified by the s value can be explained by the constant charge distributed to the benzene ring. The combination of substituenteffect analysis and NBO analysis successfully revealed the nature of the anion.

show abstract

Linear free energy correlations in mass spectrometry

Harrison

1999

J. Mass Spectrom.

View full text Add to dashboard Cite

Resonance Effect in Hammett Relationship. III. The Modified Hammett Relationship for Electrophilic Reactions

Cited by 287 publications

References 43 publications

A Theoretical Study of Monosubstituted Cyclopropenyl System

A Theoretical Study of Monosubstituted Cyclopropenyl System

Computational study of the substituent effects on the gas-phase stabilities of phenylboranylmethyl anions

Linear free energy correlations in mass spectrometry

Contact Info

Product

Resources

About