R(CH:CH)mCO(CH:CH)nR1 (R = thienyl, R1 = Ph, m = 0-3, n = 0-4, 6; R = R1 = Ph, m = 1-4, n = 0-2; R = R1 = thienyl, m = 1-4, n = 0-2) were prepared and their electronic absorption spectra in alcohol and cyclohexane determine A plot of scattered points was obtained in each case, indicating that there is no single conjugated system. Conjugative polarization on the mol. chain is blocked by the carbonyl bridge. The two branches on each side of the carbonyl bridge are in conjugative competition for the carbonyl group. When the wavelengths of absorption peaks for isomeric compounds are plotted against chain no. (m + n), a V-shaped curve with the lowest point at the middle was found.

Key words: CARBONYL COMPOUNDS, CONJUGATED DOUBLE BOND COMPOUNDS, STRUCTURAL EFFECT, BRIDGE COMPOUNDS