Towards physical interpretation of Hammett constants: charge transferred between active regions of substituents and a functional group

Krygowski, Tadeusz M.; Sadlej-Sosnowska, Nina

doi:10.1007/s11224-010-9676-9

Cited by 58 publications

(67 citation statements)

References 62 publications

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“…Nevertheless, before going into detailed studies of SEs in meta-and para-substituted nitrobenzene derivatives by use of classical substituent constants (σ) and quantum chemistry based cSAR(X) [31][32][33] and SESE [29,30] characteristics we should determine their mutual interrelations.…”

Section: Resultsmentioning

confidence: 99%

Classical and reverse substituent effects in meta- and para-substituted nitrobenzene derivatives

et al. 2017

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Electron-accepting properties of the nitro group were studied in a series of meta-and para-X-substituted nitrobenzene derivatives (X = NMe 2 , NH 2 , OH, OMe, CH 3 , H, F, Cl, CF 3 , CN, CHO, COMe, CONH 2 , COOH, COCl, NO 2 , NO). For this purpose Hammett-like approaches were applied based on quantum chemistry modeling; the B3LYP/6-311++ G(d,p) method was used. The substituent effect (SE) was characterized by the mutually interrelated descriptors: the charge of the substituent active region, cSAR(X), and substituent effect stabilization energy, SESE, as well as substituent constants, σ. Classical SE is realized by dependences of the structural parameters of the nitro group (ONO angle and NO bond lengths) and cSAR(NO 2 ) on the above mentioned SE descriptors. The reverse substituent effect was clearly documented by a comparison of cSAR(X) values for monosubstituted benzenes, meta-and para-substituted nitrobenzenes as well as, additionally, for meta-and para-X-substituted anilines. For para-substituted systems the electron-accepting ability of the nitro group increases from cSAR(NO 2 ) = −0.170 up to −0.284 in dinitrobenzene and nitroaniline, respectively.

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Section: Resultsmentioning

confidence: 99%

Classical and reverse substituent effects in meta- and para-substituted nitrobenzene derivatives

et al. 2017

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“…By definition, cSAR(X) is a sum of atomic charges at all atoms of the substituent and the ipso carbon atom [7]. This descriptor correlates well with substituent constants [7][8][9][10]. It is important to stress that the cSAR(X) approach realized by the use of different atomic charge schemes leads to the results which are, as a rule, mutually well correlated [11].…”

Section: ) Is Alwaysmentioning

confidence: 99%

How OH and O– groups affect electronic structure of meta-substituted and para-substituted phenols and phenolates

2017

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An application of two independent quantum chemistry-based concepts, a substituent effect stabilization energy (SESE) and a charge of the substituent active region (cSAR), for describing substituent effects allows to investigate a nature of mutual interactions between substituents. The B3LYP/6-311++G(d,p) method is employed to examine changes in properties of a reaction center Y (Y = OH or O -groups) and a transmitting moiety (the benzene ring) due to substituent effects in a series of meta-X-substituted and para-X-substituted phenol and phenolate derivatives (X = NMe 2 , NH 2 , OH, OMe, CH 3 , H, F, Cl, CF 3 , CN, CHO, COCl, COMe, CONH 2 , COOH, NO 2 , NO). HOMA, NICS(1) and pEDA parameters are used to characterize π-electron delocalization of the transmitting moiety. Relations between cSAR(X) and σ constants show almost identical sensitivity of the substituent effect in meta-substituted phenol and phenolate derivatives, whereas in para-substituted analogs, different kinds of intramolecular interactions have been revealed. Due to electron attractive property of OH group in meta position, dependences of cSAR(X) on SESE show a dramatically different picture of interaction in meta-substituted phenols as compared to that found for all other series studied. Moreover, this group affects in a different way the electronattracting and electron-donating substituents in meta position. A clear substituent effect on π-electron delocalization of the benzene ring is observed only in para-substituted phenolate derivatives. The application of cSAR(X) parameter allows to estimate a difference between its value for a particular substituent in meta and para derivatives. In some cases, this difference amounts up to ∼53% of the range of cSAR(X) variability.Keywords substituent effects . electronic structure . molecular modeling . substituent effect stabilization energy . charge of the substituent active region

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“…It has been shown that also charges transferred between the active regions of a functional group and of substituents correlate with substituent constants. Namely, we found such correlations of calculated qSAR(X)-qSAR(NO) in p-and m-substituted nitrosobenzenes and the values of r p or r m [22], where qSAR(NO) means the charge of the active region of the NO functional group. Therefore, we aimed to investigate whether the amount of the transfer in the excited singlet state of the two series of compounds, p-substituted benzoic acids and p-substituted nitrosobenzenes, also correlates with the Hammett constants.…”

Section: Introductionmentioning

confidence: 64%

Excited state substituent constants: to Hammett or not?

Sadlej-Sosnowska

Kijak

2011

Struct Chem

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In this study, an answer has been sought to several questions: Can substituents' impact on the electronic properties of molecules in the excited singlet states be summed up by a set of substituent constants? Are the well known, ground state Hammett r constants practical for this purpose? To answer these questions, the potentials and charges on atoms of the functional groups in two classes of compounds, p-substituted benzoic acids and p-substituted nitrosobenzenes, were regressed against r p . It appeared that all correlations found in the ground state of the molecules also hold in the excited state, with lower correlation coefficients in the latter. An attempt has also been made to find a molecular characteristic which could be useful in a comparison of the acidic properties of benzoic acids (in gas phase) in the first excited and ground states.

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Towards physical interpretation of Hammett constants: charge transferred between active regions of substituents and a functional group

Cited by 58 publications

References 62 publications

Classical and reverse substituent effects in meta- and para-substituted nitrobenzene derivatives

Classical and reverse substituent effects in meta- and para-substituted nitrobenzene derivatives

How OH and O– groups affect electronic structure of meta-substituted and para-substituted phenols and phenolates

Excited state substituent constants: to Hammett or not?

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