AbstractsChemistry

Isolated lignins, obtained by extraction with formic and acetic acids, which are normally insoluble in aqueous bisulphite solution, have been shown to yield water-soluble lignin sulphonic acids after a prior treatment of the lignin with ozone. The alkaline cleavage of these lignin sulphonic acids has given rise to vanillin and acetovanillone, both of which have hitherto evaded isolation from these lignins. The use of formic acid as an ozonization solvent has been developed, and its characteristics in this capacity demonstrated by experiments on organic compounds of known structure. For the first time direct chemical evidence has been demonstrated for the presence of a carbonyl group in the solubilization of lignin by aqueous bisulphites. A study of various lignins has produced evidence to show that the carbonyl group is associated with an hydroxyl group and that the presence of both these groups is necessary for the formation of lignin sulphonic acids. A new interpretation of the process of delignification by means of aqueous bisulphite solution has been postulated in view of these new experimental findings.