Torsional barriers of 15 ortho-substituted biphenyls have been determined computationally using the B3LYP density functional and experimentally by variable-temperature (“dynamic”) nuclear magnetic resonance. Taking advantage of the 3’-isopropyldimethylsilyl group as a novel and superior diastereotopicity probe and tracking coalescence temperatures down to -173 °C (100 K), activation energies of aryl–aryl rotation as small as 5 kcal mol -1 can be assessed. The 2-X/2’-H repulsion increments thus derived are powerful parameters for rationalizing and predicting the conformational behavior of aromatic compounds carrying ortho substituents

B Values as a Sensitive Measure of steric Effects

RUZZICONI, Renzo;SPIZZICHINO, SARA;
2009

Abstract

Torsional barriers of 15 ortho-substituted biphenyls have been determined computationally using the B3LYP density functional and experimentally by variable-temperature (“dynamic”) nuclear magnetic resonance. Taking advantage of the 3’-isopropyldimethylsilyl group as a novel and superior diastereotopicity probe and tracking coalescence temperatures down to -173 °C (100 K), activation energies of aryl–aryl rotation as small as 5 kcal mol -1 can be assessed. The 2-X/2’-H repulsion increments thus derived are powerful parameters for rationalizing and predicting the conformational behavior of aromatic compounds carrying ortho substituents
2009
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11391/165130
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