Abstract The 70 eV electron impact mass spectra of twelve 5-and 3-substituted thiophene-2- carboxamides are discussed with the aid of exact mass measurements and labelling experiments. All mass spectra exhibit pronounced molecular ions. Some isomeric 5-and 3- substituted title compounds can be differentiated by mass spectrometry. The fragmentation is influenced by a strong 'ortho-effect'which activates the NH 3 elimination. In the other cases ...
