Abstract: The stable free radical I1 (BIP), mp 155-156", scavenges short-lived free radicals by direct addition, as does galvinoxyl; the products from t-butoxy and cyanoisopropyl radicals have been characterized. BIP agrees with other good scavengers in indicating cage effects of 38-44% for the decomposition of azobisisobutyronitrile (AIBN) in benzene at 34- 62", and of less than 3% for di-t-butyl diperoxyoxalate (DBPO) at 25". ...