ALKALINE-HYDROLYSIS OF NONPHENOLIC ALPHA-CARBONYL BETA-0-4 LIGNIN DIMERS SUBSTITUTED ON THE LEAVING PHENOXIDE RING - COMPARISON WITH BENZYLIC HYDROXYL ANALOGS

Four a-carbonyl nonphenolic beta-0-4 lignin models [2-(2-methoxy-3-or imtedphenoxy)-1-(3,4-dimethoxyphenyl)-ethan-1-one] were synthesized an d the alkaline hydrolysis rates determined. The rates were then compar ed to rates for alpha-hydroxyl analogues run earlier. The unsubstitute d ketone hydrolyzed slightly slower, about 30 %, then the alcohol anal ogue. The 4'-CHO ketone hydrolyzed much faster than the unsubstituted ketone and had essentially the same hydrolysis rate as the alcohol ana logue. No definitive mechanistic conclusions could be made about the a lkaline hydrolysis reaction of the ketones. Unsubstituted and 4'-Me su bstituted alpha-carbonyl models appear to be susceptible, even at room temperature, to competing alkali-initiated oxidative degradation.