79784-63-7Relevant academic research and scientific papers
Deactivation of Triplet Phenyl Alkyl Ketones by Conjugatively Electron-Withdrawing Substituents
Wagner, Peter J.,Siebert, Elizabeth J.
, p. 7329 - 7335 (1981)
Para-cyano, -carbomethoxy, and -acyl substituents decrease the triplet reactivity of valerophenone (γ-hydrogen abstraction), whereas comparable meta substituents increase reactivity.Spectroscopic results are presented which indicate that para-(-R) substituents lower ?,?* triplet energies so much more than n,?* energies that the lowest triplets become largely ?,?* in nature.Meta-(-R) substituents do not stabilize ?,?* triplets enough to invert triplet levels.Both substitution patterns support a largely 1,4-biradical structure for the lowest ?,?* triplet of acylbenzenes.Ortho substituents show the usual steric anomalies: ortho cyano enhances valerophenone triplet reactivity by stabilizing the n,?* triplet; ortho carbomethoxy deactivates valerophenone by stabilizing the ?,?* triplet but not the n,?.*
