The interaction of different rank coals with equimolar HNO3-Ac2O mixture has been studied. This process, proceeding fast at 15-30 degreesC for several hours. results in changes of spatial and chemical structures because of nitration of coal arenes. formation of oxygen functional groups and partial cleavage of C-C cross-links. As a result, structurally modified coals (SMCs) are obtained as new coal-derived substances. Properties of SMCs were investigated by X-ray diffraction method. DRIFT spectroscopy and thermogravimetry. The main reactions responsible for structural modification have been proposed, (C) 2002 Elsevier Science B.V. All rights reserved.