Time-of-flight (TOF) negative ion mass spectra have been obtained in collisions of 20-100 eV neutral potassium atoms with tetrahydrofuran (C4H8O), an analogue for the sugar unit in DNA/RNA. Major enhancements in O- and C2H3O- production were observed compared with earlier dissociative electron attachment (DEA) experiments. In further contrast with DEA, no evidence was observed for dehydrogenated parent anions, and three new fragment anions were detected: CH-, C-2(-), and C2H-. These contrasting results for potassium impact and DEA highlight significant differences in the reaction pathways initiated by the two electron delivery processes.