Dependence of the Substituent Effect on Solvent Properties

Abstract

The influence of a solvent on the substituent effect (SE) in 1,4-disubstituted derivatives of benzene (BEN), cyclohexa-1,3-diene (CHD), and bicyclo[2.2.2]octane (BCO) is studied by the use of polarizable continuum model method. In all X-R-Y systems for the functional group Y (NO, COOH, OH, and NH), the following substituents X have been chosen: NO, CHO, H, OH, and NH. The substituent effect is characterized by the charge of the substituent active region (cSAR(X)), substituent effect stabilization energy (SESE), and substituent constants σ or F descriptors, the functional groups by cSAR(Y), whereas π-electron delocalization of transmitting moieties (BEN and CHD) is characterized by a geometry-based index, harmonic oscillator model of aromaticity. All computations were carried out by means of B3LYP/6-311++G(d,p) method. An application of quantum chemistry SE models (cSAR and SESE) allows to compare the SE in water solutions and in the gas phase. Results of performed analyses indicate an enhancement of the SE by water. The obtained Hammett-type relationships document different nature of interactions between Y and X in aromatic and olefinic systems (a coexistence of resonance and inductive effects) than in saturated ones (only the inductive effect). An increase of electric permittivity clearly enhances communications between X and Y for BEN and CHD systems.

Substituent effects of nitro group in cyclic compounds

“…21 Dependences of cSAR(NO 2 ) in water on these in the gas phase for X-R-NO 2 series. Reprinted with permission from J Phys Chem A 122:1896 (2018) [125]. Copyright 2018 American Chemical Society…”

“…The use of quantum chemistry SE models makes it possible to compare the strength of substituent effects in both phases (gas phase and water solution, using polarizable continuum model method, PCM). Studies of the electrostatic interactions between water and three different types of 1,4-disubstituted X-R-Y systems-aromatic, benzene (BEN); olefinic, cyclohexa-1,3-diene (CHD); and aliphatic, bicyclo[2.2.2]octane (BCO)-revealed the enhancement of the substituent effect by water [125]. This was documented by the results of the analysis of linear relationships between the values of the same SE parameter determined in the gas phase and water solution.…”

Changes in Electron Structure of the Triple Bond in Substituted Acetylene and Diacetylene Derivatives

“…Nevertheless, the assessment that a given X substituent is electron-acceptor or electron-donor is relative, as it also depends on the Y substituent and in general to the moiety to which it is attached. It has been shown that cSAR(X) values correlate well with Hammett substituent constants [12,13,[19][20][21][22] but its great advantage is that cSAR(X) values provide information about electronic state of the substituent X and its dependence on interactions with the substituted moiety. Substituent effects are also often described by means of many parameters associated with molecular electrostatic potential (MESP), [23][24][25][26][27] such as, e. g. V min and V C , [28][29][30][31][32][33] where the former parameter is the MESP minimum and the latter relates to the nucleus of para carbon.…”

Solvent influence on intramolecular interactions and aromaticity in meta and para nitroanilines

“…The acid-base equilibria of substituted benzoic acids are very sensitive to solvent: The reaction constant (slope) for the Hammett relation is for water equal 1.00 (by definition), but for dimethyl sulfoxide is 2.48 [17], whereas for the gas phase measurements is 5.6 [18], and for wider review, see [19]. Recently it was shown [20] that the substituent effect in olefinic (cyclohexa-1,3-diene) and aromatic (benzene) derivatives exhibits a substantially greater sensitivity in water represented by polarizable continuum model (PCM model) [21] than in the gas phase (GP). For saturated 2,2,2-bicyclooctane derivatives, the effect of solvent was significantly weaker [20].…”