Equilibrium constants for reactions of the type trans-MeCH= CHCH2COX+ trans-EtCH= CHCOX, where X is H, OMe, and 0-t-Bu, have been determined in tert-butyl alcohol solution at various temperatures by using basic catalysts. These equilibrium constants for formation of the conjugated isomer, extrapolated to 25" C, are 24, 4.9, and 5.1 for the aldehyde, methyl ester, and tert-butyl ester, respectively. Possible explanations for the relative magnitudes ...