6-(5-chloro-2-pyridinyl)-7H-pyrrolo[3,4-b]pyrazin-5-one; 6-(5-Chloropyridin-2-yl)-6,7-dihydro-5H-pyrrolo[3,4-b]pyrazin-5-one; Zopiclone Impurity C (EP/BP); 6-(5-Chloro-2-pyridinyl)-6,7-dihydro-5H-pyrrolo[3,4-b]pyrazin-5-one;5H-Pyrrolo[3,4-b]pyrazin-5-one, 6-(5-chloro-2-pyridinyl)-6,7-dihydro