Analysis of less-volatile products of poly-L-valine pyrolysis by gas chromatography/Fourier transform infrared spectroscopy/mass spectrometry

Less-volatile products of poly-L-valine pyrolysis at 500 degreesC under nitrogen atmosphere were analyzed by the coupled technique of gas chromatography/Fourier transform infrared spectroscopy/mass spectrometry (GC/FTIR/MS). Of 18 compounds identified, there were one isocyanate, one unsaturated carboxylic acid, two ketones, three unsaturated hydrocarbons, three nitriles, five amines, one linear and two cyclic amides (including valine diketopiperazine). Comparison with the composition of less-volatile products of poly-c;ly and poly-Ala pyrolysis, where majority of the compounds were cyclic amines and amides, shows that the differences between these cases is the presence of an isocyanate, unsaturated nitriles, ketones and hydrocarbons in the less-volatile fraction of poly-Val pyrolysate. For cyclic compounds, there is a general trend to form six-membered ring systems tin particular, substituted benzenes and pyridines) in the present case, whereas most cyclic products of poly-Gly and poly-Ala pyrolysis were five-membered mono-N-heterocycles (substituted pyrrolidines and pyrroles). (C) 2001 Elsevier Science B.V. All rights reserved.