Sterically stabilized enols: a study employing the internal rotational barriers of the destabilized ketones

Substituent, Temperature and Solvent Effects on the Keto-Enol EQUILIBRIUM in <i>β</i>-Ketoamides: A Nuclear Magnetic Resonance Study

“…On the other hand, bulky phenyl groups in C-2 position increase the enolic content (compare compounds IX-XI with I-III and IV-VIII). This fact is in concorance with previous studies [20,21]. d…”

Enol and Enethiol Occurrence for Some Ketones and Thioketones. Mass Spectrometry and Theoretical Calculations

“…Although enols are thermodynamically unstable species in comparison with their carbonyl isomers, some of them have a long enough lifetime so as to be detected by conventional methods. They are dramatically stabilized by the introduction of bulky groups in the carbon α-to the carbonyl group [3][4][5] and, in some cases, the enol form can be the thermodynamically most stable [6,7].…”

Tautomerism of lactones and related compounds. Mass spectrometric data and theoretical calculations

“…This suggests that enols of carboxylic acids (and their derivatives) would have much lower intrinsic stability than enols of aldehydes and ketones. However, enols can be dramatically stabilized by the introduction of bulky groups onto the carbon α to the carbonyl group 5,6 and in some cases the enol may then be the thermodynamically stable tautomer, 7 although not kinetically. 8 The pentamethylphenyl group is an effective bulky substituent and provides the necessary stability for enediols (enol form of carboxylic acids and esters).…”