Enones, 367. resonance forms

One of the resonant forms of tiiis carbocation with extended conjugation is an enone protonated on the oxygen. The deprotonation of this enone leads to the final compound. 

Spectra.—For compounds of low solubility in deuteriochloroform, the use of ASCI3-CDCI3 (2 1 v/v) may prove valuable as the chemical shift differences (excepting alcohols) between the two solvent systems is negligible (< 1 p.p.m.) on the n.m.r. scale. Titanium tetrachloride-induced shifts on the spectra of carbonyl compounds has been investigated. The carbonyl carbon atoms experience large down-field shifts, adjacent carbon atoms showed only small downfield shifts, and remote carbon atoms are scarcely perturbed. In a -unsaturated carbonyl compounds, large downfield shifts are observed for the P-carbon atoms, presumably because of the enhancement of the dipolar resonance form of the enone system consistent with this picture is the much smaller shift, in either direction, of the a-carbon atoms. Studies were extended to include ap-unsaturated acids and esters. ... 

Enolate A resonance-stabilized anion formed upon removal of the a-hydrogen from a carbonyl group. Enone An a, 3-unsaturated carbonyl group. 

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