The Influence of Anthrahydroquinone and Other Additives on the Condensation Reactions of Vanillyl Alcohol

Vanillyl alcohol, a simple lignin model, has been heated with alkali under a variety of conditions and in the presence of several additives. The level of condensed products, principally dimers and trimers, has been determined in each case. Some additives, such as sulfide and anthraquinone, showed few differences from the control. Other additives, such as anthrahydroquinone, dithionite and 3,5-dinitrobenzoic acid, greatly depressed the levels of condensation products. The detection of a minor product, a head-to-head dimer, suggests some radical intermediates are present under these reaction conditions. The degree of condensation and ratio of products was quite temperature dependent. The influence of selected additives on the condensation reactions of a dioxane lignin has also been studied.