THE DISTONIC ION (CH2CH2CH-C-CENTER-DOT, KETO ION CH3CH2CH=O-+CENTER-DOT, ENOL ION CH3CH=CHOH+CENTER-DOT, AND RELATED C3H6O+CENTER-DOT RADICAL CATIONS - STABILITIES AND ISOMERIZATION PROCLIVITIES STUDIED BY DISSOCIATION AND NEUTRALIZATION-REIONIZATION(OH))

Metastable ion decompositions, collision-activated dissociation (CAD), and neutralization-reionization mass spectrometry are utilized to stu dy the unimolecular chemistry of distonic ion (CH2CH2CH+OH)-C-.(2(+.)) and its enol-keto tautomers CH3CH=CHOH+. (1(+.)) and CH3CH2CH=O-+.(3( +.)). The major fragmentation of metastable 1(+.)-3(+.) is H-. loss to yield the propanoyl cation, CH3CH2C=O+. This reaction remains dominan t upon collisional activation, although now some isomeric CH2=CH-CH+OH is coproduced from all three precursors. The CAD and neutralization-r eionization ((+)NR(+)) spectra of keto ion 3(+.) are substantially dif ferent-from those of tautomers 2(+.) and 1(+.). Hence, 3(+.) without s ufficient energy for decomposition (i.e., ''stable'' 3(+.)) does not i somerize to the thermodynamically more stable ions 2(+.) or 1(+.), and the 1,4-H rearrangement H-CH2CH2CH=O-+.(3(+.)) --> (CH2CH2CH+O)-C-.-H (2(+.)) must require an appreciable critical energy. Although the frag ment ion abundances in the (+)NR(+) (and CAD) spectra of 1(+.) and 2(.) are similar, the relative and absolute intensities of the survivor ions (recovered C3H6O+. ions in the (+)NR(+) spectral are markedly dis tinct and independent of the internal energy of 1(+.) and 2(+.). Furth ermore, 1(+.) and 2(+.) show different MI spectra. Based on these data , distonic ion 2(+.) does not spontaneously rearrange to enol ion 1(+. ) (which is the most stable C3H6O+. of CCCO connectivity) and, therefo re, is separated from it by an appreciable barrier. In contrast, the m olecular ions of cyclopropanol (4(+.)) and allyl alcohol (5(+.)) isome rize readily to 2(+.), via ring opening and 1,2-H- shift, respectively . The sample found to generate the purest 2(+.) is alpha-hydroxy-gamma -butyrolactone. Several other precursors that would; yield 2(+.) by a least-motion reaction cogenerate detectable quantities of enol ion 1(.) or the enol ion of acetone (CH2=C(CH3)OH+. 6(+.)), or methyl vinyl ether ion (CH3OCH=CH2+., 7(+.)). Ion 6(+.) is coproduced from samples that contain the -CH2-CH(OH)-CH2- substructure, whereas 7(+.) is copro duced from compounds with methoxy substituents. Compared to CAD, metas table ion characteristics combined with neutralization-reionization al low for a superior differentiation of the ions studied.