Establishing lignin structure-upgradeability relationships using quantitative ¹ H– ¹³ C heteronuclear single quantum coherence nuclear magnetic resonance (HSQC-NMR) spectroscopy

can accurately quantify lignin functionalities in extracted lignin using several synthetic polymer models. We then prepared a range of isolated lignin samples with a wide range of ether contents (6-46%). By using a simple ether cleavage model, we were able to predict final depolymerization yields very accurately (<4% error), conclusively demonstrating the direct causal relationship between ether content and lignin activity. The accuracy of this model suggests that, unlike in native lignin, ether linkages no longer appear to be randomly distributed in isolated lignin.