ENTHALPIES OF FORMATION OF FREE RADICALS – REACTION INTERMEDIATES IN LIGNIN PYROLYSIS
D. A. PONOMAREV *
St. Petersburg Forest Technical University, Institutski Lane 5, 194021 St. Petersburg, Russia
H. D. METTEE
Youngstown State University, Youngstown, Ohio 44555, USA
*Author to whom correspondence should be addressed.
Abstract
It is demonstrated that enthalpies of formation for a number of carbon and oxygen centered aromatic free radicals related to lignin can be easily calculated arithmetically. The calculations are based on the assumption that enthalpy of formation for a given radical can be calculated from the experimental value for appropriate unsubstituted free radical taking into account i) the contribution in enthalpy of formation caused by substituent and ii) the correction term which reflects an electronic effect of substituent. The latter can be calculated from the data on relative free radical stability.
Keywords: lignin, pyrolysis, free radicals, enthalpies of formation