How intramolecular hydrogen bonding (IHB) controls the C-ON bond homolysis in alkoxyamines

Gerard Audran (1) , Raphael Bikanga (2) , Paul Bremond (1) , Mariya Edeleva (3) , Jean-Patrick Joly (1) , Sylvain R.A. Marque (1) , Paulin Nkolo (1) , Valerie Roubaud (1)

1 ICR - Institut de Chimie Radicalaire
2 LASNSOM - Laboratoire de Substances Naturelles et de Synthèses Organométalliques
3 N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry

Recent amazing results (Nkolo et al., Org. Biomol. Chem., 2017, 6167) on the effect of solvents and polarity on the C-ON bond homolysis rate constants kd of alkoxyamine R1R2NOR3 led us to re-investigate the antagonistic effect of intramolecular hydrogen-bonding (IHB) on kd. Here, IHB is investigated both in the nitroxyl fragment R1R2NO and in the alkyl fragment R-3, as well as between fragments, that is, the donating group on the alkyl fragment and the accepting group on the nitroxyl fragment, and conversely. It appears that IHB between fragments (inter IHB) strikingly decreases the homolysis rate constant kd, whereas IHB within the fragment (intra IHB) moderately increases kd. For one alkoxyamine, the simultaneous occurrence of IHB within the nitroxyl fragment and between fragments is reported. The protonation effect is weaker in the presence than in the absence of IHB. A moderate solvent effect is also observed.

Mots clés: chemistry; constants; derivatives; family; free-radical polymerization; nitroxyl fragment; polar

Domaines: Chimie organique

Gerard Audran, Raphael Bikanga, Paul Bremond, Mariya Edeleva, Jean-Patrick Joly, et al.. How intramolecular hydrogen bonding (IHB) controls the C-ON bond homolysis in alkoxyamines. Organic & Biomolecular Chemistry, 2017, 15 (39), pp.8425-8439. ⟨10.1039/c7ob02223a⟩. ⟨hal-01774244⟩