Electron Spin Resonance Studies in Aqueous Solution: Fragmentation of Radical Intermediates Derived from β-Amino Alcohols

In acidic aqueous solution, oxidation of the β-amino alcohols [Formula: see text], I, and [Formula: see text], II, (R = H, alkyl) using the Ti(III)–H2O2 flow technique gave the radicals [Formula: see text], and [Formula: see text]. The spectrum of [Formula: see text] shows restricted rotation about the C1—C2 bond assigned to intramolecular hydrogen bonding.Under neutral conditions, oxidation of I gave the spectrum of •CH2CHO, and of II the acetonyl radical •CH2COCH3. It is proposed that elimination occurs by deprotonation of the abstraction radical in a hydrogen-bonded conformation, followed by rapid fragmentation to yield the α-carbonyl radical.