The production of activated carbon fibres from commercial acrylic textile fibres was analysed in order to study the chemical transformations suffered by the precursor during the process. The thermal degradation of the precursor polymeric chain starts with the cyclisation of the structure with acetate ion from vinyl acetate acting as a catalyst. The chemical transformations continue with both cyclisation and dehydrogenation reactions which result in the formation of several functional groups. The groups identified for the carbonised fibre by FTIR were amines, amides, imides, lactones and -OH, whereas for the activated carbon fibre the groups that can be identified were pyrones, lactones, amines, amides and -OH. (c) 2005 Elsevier B.V. All rights reserved.