The mechanism of methylpyrazine ammoxidation on a vanadia-titania catalyst has been studied by in situ FTIR spectroscopy. The structure of surface intermediates has been identified and the sequence of their transformation in the temperature range of 150-230 degrees C has been ascertained. The interaction of methylpyrazine with catalyst surface includes a consecutive transformation of coordinatively bound methylpyrazine into oxygenated surface compounds, viz., an aldehyde-like complex and an asymmetrical carboxylate. The main reaction product, amidopyrazine, is formed through the interaction of the surface oxyintermediates with adsorbed ammonia species. (c) 2007 Elsevier B.V. All rights reserved.