Trapping of p-coumaryl and coniferyl alcohol during SODA/AQ treatment - A means of estimating uncondensed β-O-4 in native lignin

It was recently observed that ethylguaiacol (EG) is quite efficient at trapping coniferyl alcohol (CA) generated from the cleavage of uncondensed β-O-4 dimmers during soda-AQ or SAQ delignification of a hardwood. Some of the CA is transformed to vinylguaiacol (VG) and isoeugenol (IE) and the α-carbon atom in all three monomers condense to the C-5 position of EG. In the present research the feasibility of quantifying uncondensed β-O-4 structures where the ring that rearranges to the quinone methide is a guaiacyl (G) or p-hydroxyphenylpropane (H) unit was investigated. Central to this approach is the efficiency of EG trapping of CA, p-coumaryl alcohol (p-CMA) and their transformation products. The estimates of uncondensed β-O-4 structures in hardwood and bagasse lignin by this approach were in close agreement with traditional but more tedious methods such as permanganate oxidation and ³¹P NMR.