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

Abstract

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.

Photolysis of Aqueous Solutions of Hydrogen Peroxide Containing β-Ammonio Alcohols

“…The experiments serve to coinplement and quantitatively affirm the conclusions of the e.p.r. spectroscopic studies (2). The clear-cut pattern that emerges permits extrapolation of the results to the y-radiolysis of the crystalline choline salts.…”

“…R H system show that the substrates, though less Products reactive than neutral alcohols (e.n. CH?CHOHCH, and At PH 1.0 (0.1 N HC1) ~h o t o l~s i s of the C H 3 C H 2 0 H ) , do provide spectra tha; indicate mider-auateriarv and tertiarv ammonium salts in 1.0 ately favorable attack relative to hydrogen peroxide (2). M H,O, solution gave less net reaction, and a…”

“…2-Hydroxypropyltrin~ethylamn~onium chloride (henceforth p-~nethq.1 choline) was prepared as previously described (2). The quaternary salts wcre purified by repeated recrystallization from ethanol-ether and vacuum desiccation until no trace of solvent remained (n.m.r.…”

“…data are presented in Table 1. Note that 1-(1V,hTdimethylamino)-2-propanone was available from the companion e.p.r, studies (2). The synthesis of 1-(N,N,Ntrimethy1amino)-2-propanone was carried out by treatment of I-(h5N-dimethylamino)-2-propanone with chloromethane in aqueous solution using the procedure adopted for the synthesis of p-n~ethylcholine chloride (2).…”

“…spectroscopy using the rapid flow system (Ti(II1)-H,O, reaction) (2). At p H 6.8 only fragmentation products are formed during photolysis.…”