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 substituentsFile in questo prodotto:
Non ci sono file associati a questo prodotto.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
