1444155-41-2Relevant academic research and scientific papers
Quantifying Through-Space Substituent Effects
Adam, Catherine,Burns, Rebecca J.,Cockroft, Scott L.,Mati, Ioulia K.,Muchowska, Kamila B.
, p. 16717 - 16724 (2020/07/24)
The description of substituents as electron donating or withdrawing leads to a perceived dominance of through-bond influences. The situation is compounded by the challenge of separating through-bond and through-space contributions. Here, we probe the experimental significance of through-space substituent effects in molecular interactions and reaction kinetics. Conformational equilibrium constants were transposed onto the Hammett substituent constant scale revealing dominant through-space substituent effects that cannot be described in classic terms. For example, NO2 groups positioned over a biaryl bond exhibited similar influences as resonant electron donors. Meanwhile, the electro-enhancing influence of OMe/OH groups could be switched off or inverted by conformational twisting. 267 conformational equilibrium constants measured across eleven solvents were found to be better predictors of reaction kinetics than calculated electrostatic potentials, suggesting utility in other contexts and for benchmarking theoretical solvation models.
Electrostatic modulation of aromatic rings via explicit solvation of substituents
Muchowska, Kamila B.,Adam, Catherine,Mati, Ioulia K.,Cockroft, Scott L.
, p. 9976 - 9979 (2013/07/26)
Solvent effects are implicated as playing a major role in modulating electrostatic interactions via through-space and polarization effects, but these phenomena are often hard to dissect. By using synthetic molecular torsion balances and a simple explicit solvation model, we demonstrate that the solvation of substituents substantially affects the electrostatic potential of aromatic rings. Although polarization effects are important, we show that a simple additive through-space model also provides a reasonable account of the experimental data. The results deliver insights into solvent structure and might contribute to the development of computationally inexpensive solvent models.
